[PATCH v6 0/9] Introduce the Counter subsystem

[PATCH v6 0/9] Introduce the Counter subsystem

[William Breathitt Gray]

This revision is primarily a code refactor and formatting cleanup -- the
interface has remained essentially the same as revision 5, with some
minor additions.

Here's a brief summary of the Generic Counter interface and related code
changes in this revision:

    * checkpatch.pl formatting suggestions implemented (parameters line
      up with opening round bracket, etc.)
    * Implement struct counter_ops to enable const structure for
      driver callbacks
    * Provide const string array for count_direction and count_mode
      options to help maintain a consistent interface
    * Reduce local variables by inlining where appropriate
    * Bring memory cleanup code closer to respective allocations for
      clarity and easier debugging
    * Implement counter_name_attribute_create function to reduce
      repeated code for various "name" attributes
    * Implement counter_global_attr_register function to organize global
      counter attribute registration together
    * Implement prepare_counter_device_groups_list and
      prepare_counter_device_groups functions to organize sysfs
      attribute configuration into logical groups (this makes the
      counter_register function logic much easier to follow)

Furthermore, the following additions have been made:

    * The "ceiling" and "floor" attributes are defined to represent the
      upper limit and lower limit respectively for a Count
    * The following attributes are now part of the main Generic Counter
      interface: count_mode, direction, enable, preset, preset_enable,
      and error_noise
    * The "Quadrature x1" and "Quadrature x2" function modes are now
      known as "Quadrature x1 A" and "Quadrature x2 A" respectively
    * The following new function modes are defined in order to support
      the STM32 LP Timer quadrature modes: Quadrature x1 B, Quadrature
      x2 B, Quadrature x2 Rising, and Quadrature x2 Falling
    * The "num_counts" and "num_signals" attributes are defined to
      represent the total number of Counts and total number of Signals
      respectively

The 104-QUAD-8 counter driver has been updated to make use of the
Generic Counter API changes ("ceiling" and "floor" attributes, constant
counter_ops structure, count_mode and direction string arrays, etc.).

The STM32 Timer counter driver has been updated to make use of the
Generic Counter API changes ("ceiling" attribute, constant counter_ops
structure, etc.). In addition, Fabrice Gasnier added support for a
missing encoder mode (see STM32_COUNT_ENCODER_MODE_2).

Proper Generic Counter interface support for the STM32 LP Timer has been
added to its respective counter driver. This is the last in-tree Linux
kernel driver using the deprecated IIO Counter interface, so we can
safely remove that interface in the future now.

I've added deprecation notices to the IIO Counter attributes to
encourage the switch to the Generic Counter interface. I didn't mention
a removal date for the relevant code, but perhaps before the next
longterm kernel release would be a good idea -- this should prevent the
IIO Counter API from persisting longer than necessary.

William Breathitt Gray

Benjamin Gaignard (2):
  dt-bindings: counter: Document stm32 quadrature encoder
  counter: Add STM32 Timer quadrature encoder

Fabrice Gasnier (1):
  counter: stm32-lptimer: add counter device

William Breathitt Gray (6):
  counter: Introduce the Generic Counter interface
  counter: Documentation: Add Generic Counter sysfs documentation
  docs: Add Generic Counter interface documentation
  counter: 104-quad-8: Add Generic Counter interface support
  counter: 104-quad-8: Documentation: Add Generic Counter sysfs
    documentation
  iio: counter: Remove IIO counter subdirectory

 Documentation/ABI/testing/sysfs-bus-counter   |  241 +++
 .../ABI/testing/sysfs-bus-counter-104-quad-8  |   36 +
 Documentation/ABI/testing/sysfs-bus-iio       |    8 +
 .../testing/sysfs-bus-iio-counter-104-quad-8  |   16 +
 .../{iio => }/counter/stm32-lptimer-cnt.txt   |    0
 .../bindings/counter/stm32-timer-cnt.txt      |   26 +
 .../devicetree/bindings/mfd/stm32-lptimer.txt |    2 +-
 .../devicetree/bindings/mfd/stm32-timers.txt  |    7 +
 Documentation/driver-api/generic-counter.rst  |  336 ++++
 Documentation/driver-api/index.rst            |    1 +
 MAINTAINERS                                   |   14 +-
 drivers/Kconfig                               |    2 +
 drivers/Makefile                              |    1 +
 drivers/counter/104-quad-8.c                  | 1335 ++++++++++++++
 drivers/counter/Kconfig                       |   59 +
 drivers/{iio => }/counter/Makefile            |    6 +-
 drivers/counter/generic-counter.c             | 1541 +++++++++++++++++
 drivers/counter/stm32-lptimer-cnt.c           |  722 ++++++++
 drivers/counter/stm32-timer-cnt.c             |  390 +++++
 drivers/iio/Kconfig                           |    1 -
 drivers/iio/Makefile                          |    1 -
 drivers/iio/counter/104-quad-8.c              |  596 -------
 drivers/iio/counter/Kconfig                   |   34 -
 drivers/iio/counter/stm32-lptimer-cnt.c       |  382 ----
 include/linux/counter.h                       |  554 ++++++
 25 files changed, 5293 insertions(+), 1018 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-bus-counter
 create mode 100644 Documentation/ABI/testing/sysfs-bus-counter-104-quad-8
 rename Documentation/devicetree/bindings/{iio => }/counter/stm32-lptimer-cnt.txt (100%)
 create mode 100644 Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt
 create mode 100644 Documentation/driver-api/generic-counter.rst
 create mode 100644 drivers/counter/104-quad-8.c
 create mode 100644 drivers/counter/Kconfig
 rename drivers/{iio => }/counter/Makefile (52%)
 create mode 100644 drivers/counter/generic-counter.c
 create mode 100644 drivers/counter/stm32-lptimer-cnt.c
 create mode 100644 drivers/counter/stm32-timer-cnt.c
 delete mode 100644 drivers/iio/counter/104-quad-8.c
 delete mode 100644 drivers/iio/counter/Kconfig
 delete mode 100644 drivers/iio/counter/stm32-lptimer-cnt.c
 create mode 100644 include/linux/counter.h

-- 
2.17.0

[PATCH v6 1/9] counter: Introduce the Generic Counter interface

[William Breathitt Gray]

This patch introduces the Generic Counter interface for supporting
counter devices.

In the context of the Generic Counter interface, a counter is defined as
a device that reports one or more "counts" based on the state changes of
one or more "signals" as evaluated by a defined "count function."

Driver callbacks should be provided to communicate with the device: to
read and write various Signals and Counts, and to set and get the
"action mode" and "count function" for various Synapses and Counts
respectively.

To support a counter device, a driver must first allocate the available
Counter Signals via counter_signal structures. These Signals should
be stored as an array and set to the signals array member of an
allocated counter_device structure before the Counter is registered to
the system.

Counter Counts may be allocated via counter_count structures, and
respective Counter Signal associations (Synapses) made via
counter_synapse structures. Associated counter_synapse structures are
stored as an array and set to the the synapses array member of the
respective counter_count structure. These counter_count structures are
set to the counts array member of an allocated counter_device structure
before the Counter is registered to the system.

A counter device is registered to the system by passing the respective
initialized counter_device structure to the counter_register function;
similarly, the counter_unregister function unregisters the respective
Counter. The devm_counter_register and devm_counter_unregister functions
serve as device memory-managed versions of the counter_register and
counter_unregister functions respectively.

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
---
 MAINTAINERS                       |    7 +
 drivers/Kconfig                   |    2 +
 drivers/Makefile                  |    1 +
 drivers/counter/Kconfig           |   18 +
 drivers/counter/Makefile          |    8 +
 drivers/counter/generic-counter.c | 1541 +++++++++++++++++++++++++++++
 include/linux/counter.h           |  554 +++++++++++
 7 files changed, 2131 insertions(+)
 create mode 100644 drivers/counter/Kconfig
 create mode 100644 drivers/counter/Makefile
 create mode 100644 drivers/counter/generic-counter.c
 create mode 100644 include/linux/counter.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 4b65225d443a..2a016d73ab72 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3669,6 +3669,13 @@ W:	http://www.fi.muni.cz/~kas/cosa/
 S:	Maintained
 F:	drivers/net/wan/cosa*
 
+COUNTER SUBSYSTEM
+M:	William Breathitt Gray <vilhelm.gray@gmail.com>
+L:	linux-iio@vger.kernel.org
+S:	Maintained
+F:	drivers/counter/
+F:	include/linux/counter.h
+
 CPMAC ETHERNET DRIVER
 M:	Florian Fainelli <f.fainelli@gmail.com>
 L:	netdev@vger.kernel.org
diff --git a/drivers/Kconfig b/drivers/Kconfig
index 95b9ccc08165..70b3cc88dc0b 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -165,6 +165,8 @@ source "drivers/memory/Kconfig"
 
 source "drivers/iio/Kconfig"
 
+source "drivers/counter/Kconfig"
+
 source "drivers/ntb/Kconfig"
 
 source "drivers/vme/Kconfig"
diff --git a/drivers/Makefile b/drivers/Makefile
index 24cd47014657..5914c78688c3 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -165,6 +165,7 @@ obj-$(CONFIG_PM_DEVFREQ)	+= devfreq/
 obj-$(CONFIG_EXTCON)		+= extcon/
 obj-$(CONFIG_MEMORY)		+= memory/
 obj-$(CONFIG_IIO)		+= iio/
+obj-$(CONFIG_COUNTER)		+= counter/
 obj-$(CONFIG_VME_BUS)		+= vme/
 obj-$(CONFIG_IPACK_BUS)		+= ipack/
 obj-$(CONFIG_NTB)		+= ntb/
diff --git a/drivers/counter/Kconfig b/drivers/counter/Kconfig
new file mode 100644
index 000000000000..65fa92abd5a4
--- /dev/null
+++ b/drivers/counter/Kconfig
@@ -0,0 +1,18 @@
+#
+# Counter devices
+#
+# When adding new entries keep the list in alphabetical order
+
+menuconfig COUNTER
+	tristate "Counter support"
+	help
+	  Provides Generic Counter interface support for counter devices.
+
+	  Counter devices are prevalent within a diverse spectrum of industries.
+	  The ubiquitous presence of these devices necessitates a common
+	  interface and standard of interaction and exposure. This driver API
+	  attempts to resolve the issue of duplicate code found among existing
+	  counter device drivers by providing a generic counter interface for
+	  consumption. The Generic Counter interface enables drivers to support
+	  and expose a common set of components and functionality present in
+	  counter devices.
diff --git a/drivers/counter/Makefile b/drivers/counter/Makefile
new file mode 100644
index 000000000000..ad1ba7109cdc
--- /dev/null
+++ b/drivers/counter/Makefile
@@ -0,0 +1,8 @@
+#
+# Makefile for Counter devices
+#
+
+# When adding new entries keep the list in alphabetical order
+
+obj-$(CONFIG_COUNTER) += counter.o
+counter-y := generic-counter.o
diff --git a/drivers/counter/generic-counter.c b/drivers/counter/generic-counter.c
new file mode 100644
index 000000000000..0d83b862453f
--- /dev/null
+++ b/drivers/counter/generic-counter.c
@@ -0,0 +1,1541 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Generic Counter interface
+ * Copyright (C) 2017 William Breathitt Gray
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2, as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/export.h>
+#include <linux/fs.h>
+#include <linux/gfp.h>
+#include <linux/idr.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/printk.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/sysfs.h>
+#include <linux/types.h>
+
+#include <linux/counter.h>
+
+const char *const count_direction_str[2] = {
+	[COUNT_DIRECTION_FORWARD] = "forward",
+	[COUNT_DIRECTION_BACKWARD] = "backward"
+};
+EXPORT_SYMBOL(count_direction_str);
+
+const char *const count_mode_str[4] = {
+	[COUNT_MODE_NORMAL] = "normal",
+	[COUNT_MODE_RANGE_LIMIT] = "range limit",
+	[COUNT_MODE_NON_RECYCLE] = "non-recycle",
+	[COUNT_MODE_MODULO_N] = "modulo-n"
+};
+EXPORT_SYMBOL(count_mode_str);
+
+ssize_t counter_signal_enum_read(struct counter_device *counter,
+				 struct counter_signal *signal, void *priv,
+				 char *buf)
+{
+	const struct counter_signal_enum_ext *const e = priv;
+	int err;
+	size_t index;
+
+	if (!e->get)
+		return -EINVAL;
+
+	err = e->get(counter, signal, &index);
+	if (err)
+		return err;
+
+	if (index >= e->num_items)
+		return -EINVAL;
+
+	return scnprintf(buf, PAGE_SIZE, "%s\n", e->items[index]);
+}
+EXPORT_SYMBOL(counter_signal_enum_read);
+
+ssize_t counter_signal_enum_write(struct counter_device *counter,
+				  struct counter_signal *signal, void *priv,
+				  const char *buf, size_t len)
+{
+	const struct counter_signal_enum_ext *const e = priv;
+	ssize_t index;
+	int err;
+
+	if (!e->set)
+		return -EINVAL;
+
+	index = __sysfs_match_string(e->items, e->num_items, buf);
+	if (index < 0)
+		return index;
+
+	err = e->set(counter, signal, index);
+	if (err)
+		return err;
+
+	return len;
+}
+EXPORT_SYMBOL(counter_signal_enum_write);
+
+ssize_t counter_signal_enum_available_read(struct counter_device *counter,
+					   struct counter_signal *signal,
+					   void *priv, char *buf)
+{
+	const struct counter_signal_enum_ext *const e = priv;
+	size_t i;
+	size_t len = 0;
+
+	if (!e->num_items)
+		return 0;
+
+	for (i = 0; i < e->num_items; i++)
+		len += scnprintf(buf + len, PAGE_SIZE - len, "%s\n",
+			e->items[i]);
+
+	return len;
+}
+EXPORT_SYMBOL(counter_signal_enum_available_read);
+
+ssize_t counter_count_enum_read(struct counter_device *counter,
+				struct counter_count *count, void *priv,
+				char *buf)
+{
+	const struct counter_count_enum_ext *const e = priv;
+	int err;
+	size_t index;
+
+	if (!e->get)
+		return -EINVAL;
+
+	err = e->get(counter, count, &index);
+	if (err)
+		return err;
+
+	if (index >= e->num_items)
+		return -EINVAL;
+
+	return scnprintf(buf, PAGE_SIZE, "%s\n", e->items[index]);
+}
+EXPORT_SYMBOL(counter_count_enum_read);
+
+ssize_t counter_count_enum_write(struct counter_device *counter,
+				 struct counter_count *count, void *priv,
+				 const char *buf, size_t len)
+{
+	const struct counter_count_enum_ext *const e = priv;
+	ssize_t index;
+	int err;
+
+	if (!e->set)
+		return -EINVAL;
+
+	index = __sysfs_match_string(e->items, e->num_items, buf);
+	if (index < 0)
+		return index;
+
+	err = e->set(counter, count, index);
+	if (err)
+		return err;
+
+	return len;
+}
+EXPORT_SYMBOL(counter_count_enum_write);
+
+ssize_t counter_count_enum_available_read(struct counter_device *counter,
+					  struct counter_count *count,
+					  void *priv, char *buf)
+{
+	const struct counter_count_enum_ext *const e = priv;
+	size_t i;
+	size_t len = 0;
+
+	if (!e->num_items)
+		return 0;
+
+	for (i = 0; i < e->num_items; i++)
+		len += scnprintf(buf + len, PAGE_SIZE - len, "%s\n",
+			e->items[i]);
+
+	return len;
+}
+EXPORT_SYMBOL(counter_count_enum_available_read);
+
+ssize_t counter_device_enum_read(struct counter_device *counter, void *priv,
+				 char *buf)
+{
+	const struct counter_device_enum_ext *const e = priv;
+	int err;
+	size_t index;
+
+	if (!e->get)
+		return -EINVAL;
+
+	err = e->get(counter, &index);
+	if (err)
+		return err;
+
+	if (index >= e->num_items)
+		return -EINVAL;
+
+	return scnprintf(buf, PAGE_SIZE, "%s\n", e->items[index]);
+}
+EXPORT_SYMBOL(counter_device_enum_read);
+
+ssize_t counter_device_enum_write(struct counter_device *counter, void *priv,
+				  const char *buf, size_t len)
+{
+	const struct counter_device_enum_ext *const e = priv;
+	ssize_t index;
+	int err;
+
+	if (!e->set)
+		return -EINVAL;
+
+	index = __sysfs_match_string(e->items, e->num_items, buf);
+	if (index < 0)
+		return index;
+
+	err = e->set(counter, index);
+	if (err)
+		return err;
+
+	return len;
+}
+EXPORT_SYMBOL(counter_device_enum_write);
+
+ssize_t counter_device_enum_available_read(struct counter_device *counter,
+					   void *priv, char *buf)
+{
+	const struct counter_device_enum_ext *const e = priv;
+	size_t i;
+	size_t len = 0;
+
+	if (!e->num_items)
+		return 0;
+
+	for (i = 0; i < e->num_items; i++)
+		len += scnprintf(buf + len, PAGE_SIZE - len, "%s\n",
+			e->items[i]);
+
+	return len;
+}
+EXPORT_SYMBOL(counter_device_enum_available_read);
+
+static const char *const signal_level_str[] = {
+	[SIGNAL_LEVEL_LOW] = "low",
+	[SIGNAL_LEVEL_HIGH] = "high"
+};
+
+/**
+ * set_signal_read_value - set signal_read_value data
+ * @val:	signal_read_value structure to set
+ * @type:	property Signal data represents
+ * @data:	Signal data
+ *
+ * This function sets an opaque signal_read_value structure with the provided
+ * Signal data.
+ */
+void set_signal_read_value(struct signal_read_value *const val,
+			   const enum signal_value_type type, void *const data)
+{
+	if (type == SIGNAL_LEVEL)
+		val->len = scnprintf(val->buf, PAGE_SIZE, "%s\n",
+			signal_level_str[*(enum signal_level *)data]);
+	else
+		val->len = 0;
+}
+EXPORT_SYMBOL(set_signal_read_value);
+
+/**
+ * set_count_read_value - set count_read_value data
+ * @val:	count_read_value structure to set
+ * @type:	property Count data represents
+ * @data:	Count data
+ *
+ * This function sets an opaque count_read_value structure with the provided
+ * Count data.
+ */
+void set_count_read_value(struct count_read_value *const val,
+			  const enum count_value_type type, void *const data)
+{
+	switch (type) {
+	case COUNT_POSITION_UNSIGNED:
+		val->len = scnprintf(val->buf, PAGE_SIZE, "%lu\n",
+				     *(unsigned long *)data);
+		break;
+	case COUNT_POSITION_SIGNED:
+		val->len = scnprintf(val->buf, PAGE_SIZE, "%ld\n",
+				     *(long *)data);
+		break;
+	default:
+		val->len = 0;
+	}
+}
+EXPORT_SYMBOL(set_count_read_value);
+
+/**
+ * get_count_write_value - get count_write_value data
+ * @data:	Count data
+ * @type:	property Count data represents
+ * @val:	count_write_value structure containing data
+ *
+ * This function extracts Count data from the provided opaque count_write_value
+ * structure and stores it at the address provided by @data.
+ *
+ * RETURNS:
+ * 0 on success, negative error number on failure.
+ */
+int get_count_write_value(void *const data, const enum count_value_type type,
+			  const struct count_write_value *const val)
+{
+	int err;
+
+	switch (type) {
+	case COUNT_POSITION_UNSIGNED:
+		err = kstrtoul(val->buf, 0, data);
+		if (err)
+			return err;
+		break;
+	case COUNT_POSITION_SIGNED:
+		err = kstrtol(val->buf, 0, data);
+		if (err)
+			return err;
+		break;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(get_count_write_value);
+
+struct counter_device_attr {
+	struct device_attribute		dev_attr;
+	struct list_head		l;
+	void				*component;
+};
+
+static int counter_attribute_create(
+	struct counter_device_attr_group *const group,
+	const char *const prefix,
+	const char *const name,
+	ssize_t (*show)(struct device *dev, struct device_attribute *attr,
+			char *buf),
+	ssize_t (*store)(struct device *dev, struct device_attribute *attr,
+			 const char *buf, size_t len),
+	void *const component)
+{
+	struct counter_device_attr *counter_attr;
+	struct device_attribute *dev_attr;
+	int err;
+	struct list_head *const attr_list = &group->attr_list;
+
+	/* Allocate a Counter device attribute */
+	counter_attr = kzalloc(sizeof(*counter_attr), GFP_KERNEL);
+	if (!counter_attr)
+		return -ENOMEM;
+	dev_attr = &counter_attr->dev_attr;
+
+	sysfs_attr_init(&dev_attr->attr);
+
+	/* Configure device attribute */
+	dev_attr->attr.name = kasprintf(GFP_KERNEL, "%s%s", prefix, name);
+	if (!dev_attr->attr.name) {
+		err = -ENOMEM;
+		goto err_free_counter_attr;
+	}
+	if (show) {
+		dev_attr->attr.mode |= 0444;
+		dev_attr->show = show;
+	}
+	if (store) {
+		dev_attr->attr.mode |= 0200;
+		dev_attr->store = store;
+	}
+
+	/* Store associated Counter component with attribute */
+	counter_attr->component = component;
+
+	/* Keep track of the attribute for later cleanup */
+	list_add(&counter_attr->l, attr_list);
+	group->num_attr++;
+
+	return 0;
+
+err_free_counter_attr:
+	kfree(counter_attr);
+	return err;
+}
+
+#define to_counter_attr(_dev_attr) \
+	container_of(_dev_attr, struct counter_device_attr, dev_attr)
+
+struct signal_comp_t {
+	struct counter_signal	*signal;
+};
+
+static ssize_t counter_signal_show(struct device *dev,
+				   struct device_attribute *attr, char *buf)
+{
+	struct counter_device *const counter = dev_get_drvdata(dev);
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct signal_comp_t *const component = devattr->component;
+	struct counter_signal *const signal = component->signal;
+	int err;
+	struct signal_read_value val = { .buf = buf };
+
+	err = counter->ops->signal_read(counter, signal, &val);
+	if (err)
+		return err;
+
+	return val.len;
+}
+
+struct name_comp_t {
+	const char	*name;
+};
+
+static ssize_t counter_device_attr_name_show(struct device *dev,
+					     struct device_attribute *attr,
+					     char *buf)
+{
+	const struct name_comp_t *const comp = to_counter_attr(attr)->component;
+
+	return scnprintf(buf, PAGE_SIZE, "%s\n", comp->name);
+}
+
+static int counter_name_attribute_create(
+	struct counter_device_attr_group *const group,
+	const char *const name)
+{
+	struct name_comp_t *name_comp;
+	int err;
+
+	/* Skip if no name */
+	if (!name)
+		return 0;
+
+	/* Allocate name attribute component */
+	name_comp = kmalloc(sizeof(*name_comp), GFP_KERNEL);
+	if (!name_comp)
+		return -ENOMEM;
+	name_comp->name = name;
+
+	/* Allocate Signal name attribute */
+	err = counter_attribute_create(group, "", "name",
+				       counter_device_attr_name_show, NULL,
+				       name_comp);
+	if (err)
+		goto err_free_name_comp;
+
+	return 0;
+
+err_free_name_comp:
+	kfree(name_comp);
+	return err;
+}
+
+struct signal_ext_comp_t {
+	struct counter_signal		*signal;
+	const struct counter_signal_ext	*ext;
+};
+
+static ssize_t counter_signal_ext_show(struct device *dev,
+				       struct device_attribute *attr, char *buf)
+{
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct signal_ext_comp_t *const comp = devattr->component;
+	const struct counter_signal_ext *const ext = comp->ext;
+
+	return ext->read(dev_get_drvdata(dev), comp->signal, ext->priv, buf);
+}
+
+static ssize_t counter_signal_ext_store(struct device *dev,
+					struct device_attribute *attr,
+					const char *buf, size_t len)
+{
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct signal_ext_comp_t *const comp = devattr->component;
+	const struct counter_signal_ext *const ext = comp->ext;
+
+	return ext->write(dev_get_drvdata(dev), comp->signal, ext->priv, buf,
+		len);
+}
+
+static void free_counter_device_attr_list(struct list_head *attr_list)
+{
+	struct counter_device_attr *p, *n;
+
+	list_for_each_entry_safe(p, n, attr_list, l) {
+		kfree(p->dev_attr.attr.name);
+		kfree(p->component);
+		list_del(&p->l);
+		kfree(p);
+	}
+}
+
+static int counter_signal_ext_register(
+	struct counter_device_attr_group *const group,
+	struct counter_signal *const signal)
+{
+	const size_t num_ext = signal->num_ext;
+	size_t i;
+	const struct counter_signal_ext *ext;
+	struct signal_ext_comp_t *signal_ext_comp;
+	int err;
+
+	/* Create an attribute for each extension */
+	for (i = 0 ; i < num_ext; i++) {
+		ext = signal->ext + i;
+
+		/* Allocate signal_ext attribute component */
+		signal_ext_comp = kmalloc(sizeof(*signal_ext_comp), GFP_KERNEL);
+		if (!signal_ext_comp) {
+			err = -ENOMEM;
+			goto err_free_attr_list;
+		}
+		signal_ext_comp->signal = signal;
+		signal_ext_comp->ext = ext;
+
+		/* Allocate a Counter device attribute */
+		err = counter_attribute_create(group, "", ext->name,
+			(ext->read) ? counter_signal_ext_show : NULL,
+			(ext->write) ? counter_signal_ext_store : NULL,
+			signal_ext_comp);
+		if (err) {
+			kfree(signal_ext_comp);
+			goto err_free_attr_list;
+		}
+	}
+
+	return 0;
+
+err_free_attr_list:
+	free_counter_device_attr_list(&group->attr_list);
+	return err;
+}
+
+static int counter_signal_attributes_create(
+	struct counter_device_attr_group *const group,
+	const struct counter_device *const counter,
+	struct counter_signal *const signal)
+{
+	struct signal_comp_t *signal_comp;
+	int err;
+
+	/* Allocate Signal attribute component */
+	signal_comp = kmalloc(sizeof(*signal_comp), GFP_KERNEL);
+	if (!signal_comp)
+		return -ENOMEM;
+	signal_comp->signal = signal;
+
+	/* Create main Signal attribute */
+	err = counter_attribute_create(group, "", "signal",
+		(counter->ops->signal_read) ? counter_signal_show : NULL, NULL,
+		signal_comp);
+	if (err) {
+		kfree(signal_comp);
+		return err;
+	}
+
+	/* Create Signal name attribute */
+	err = counter_name_attribute_create(group, signal->name);
+	if (err)
+		goto err_free_attr_list;
+
+	/* Register Signal extension attributes */
+	err = counter_signal_ext_register(group, signal);
+	if (err)
+		goto err_free_attr_list;
+
+	return 0;
+
+err_free_attr_list:
+	free_counter_device_attr_list(&group->attr_list);
+	return err;
+}
+
+static int counter_signals_register(
+	struct counter_device_attr_group *const groups_list,
+	const struct counter_device *const counter)
+{
+	const size_t num_signals = counter->num_signals;
+	size_t i;
+	struct counter_signal *signal;
+	const char *name;
+	int err;
+
+	/* Register each Signal */
+	for (i = 0; i < num_signals; i++) {
+		signal = counter->signals + i;
+
+		/* Generate Signal attribute directory name */
+		name = kasprintf(GFP_KERNEL, "signal%d", signal->id);
+		if (!name) {
+			err = -ENOMEM;
+			goto err_free_attr_groups;
+		}
+		groups_list[i].attr_group.name = name;
+
+		/* Create all attributes associated with Signal */
+		err = counter_signal_attributes_create(groups_list + i, counter,
+						       signal);
+		if (err)
+			goto err_free_attr_groups;
+	}
+
+	return 0;
+
+err_free_attr_groups:
+	do {
+		kfree(groups_list[i].attr_group.name);
+		free_counter_device_attr_list(&groups_list[i].attr_list);
+	} while (i--);
+	return err;
+}
+
+static const char *const synapse_action_str[] = {
+	[SYNAPSE_ACTION_NONE] = "none",
+	[SYNAPSE_ACTION_RISING_EDGE] = "rising edge",
+	[SYNAPSE_ACTION_FALLING_EDGE] = "falling edge",
+	[SYNAPSE_ACTION_BOTH_EDGES] = "both edges"
+};
+
+struct action_comp_t {
+	struct counter_synapse	*synapse;
+	struct counter_count	*count;
+};
+
+static ssize_t counter_action_show(struct device *dev,
+				   struct device_attribute *attr, char *buf)
+{
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	int err;
+	struct counter_device *const counter = dev_get_drvdata(dev);
+	const struct action_comp_t *const component = devattr->component;
+	struct counter_count *const count = component->count;
+	struct counter_synapse *const synapse = component->synapse;
+	size_t action_index;
+	enum synapse_action action;
+
+	err = counter->ops->action_get(counter, count, synapse, &action_index);
+	if (err)
+		return err;
+
+	synapse->action = action_index;
+
+	action = synapse->actions_list[action_index];
+	return scnprintf(buf, PAGE_SIZE, "%s\n", synapse_action_str[action]);
+}
+
+static ssize_t counter_action_store(struct device *dev,
+				    struct device_attribute *attr,
+				    const char *buf, size_t len)
+{
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct action_comp_t *const component = devattr->component;
+	struct counter_synapse *const synapse = component->synapse;
+	size_t action_index;
+	const size_t num_actions = synapse->num_actions;
+	enum synapse_action action;
+	int err;
+	struct counter_device *const counter = dev_get_drvdata(dev);
+	struct counter_count *const count = component->count;
+
+	/* Find requested action mode */
+	for (action_index = 0; action_index < num_actions; action_index++) {
+		action = synapse->actions_list[action_index];
+		if (sysfs_streq(buf, synapse_action_str[action]))
+			break;
+	}
+	/* If requested action mode not found */
+	if (action_index >= num_actions)
+		return -EINVAL;
+
+	err = counter->ops->action_set(counter, count, synapse, action_index);
+	if (err)
+		return err;
+
+	synapse->action = action_index;
+
+	return len;
+}
+
+struct action_avail_comp_t {
+	const enum synapse_action	*actions_list;
+	size_t				num_actions;
+};
+
+static ssize_t counter_synapse_action_available_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct action_avail_comp_t *const component = devattr->component;
+	const enum synapse_action *const actions_list = component->actions_list;
+	const size_t num_actions = component->num_actions;
+	size_t i;
+	enum synapse_action action;
+	ssize_t len = 0;
+
+	for (i = 0; i < num_actions; i++) {
+		action = actions_list[i];
+		len += scnprintf(buf + len, PAGE_SIZE - len, "%s\n",
+			synapse_action_str[action]);
+	}
+
+	return len;
+}
+
+static int counter_synapses_register(
+	struct counter_device_attr_group *const group,
+	const struct counter_device *const counter,
+	struct counter_count *const count, const char *const count_attr_name)
+{
+	const size_t num_synapses = count->num_synapses;
+	size_t i;
+	struct counter_synapse *synapse;
+	const char *prefix;
+	struct action_comp_t *action_comp;
+	int err;
+	struct action_avail_comp_t *avail_comp;
+
+	/* Register each Synapse */
+	for (i = 0; i < num_synapses; i++) {
+		synapse = count->synapses + i;
+
+		/* Generate attribute prefix */
+		prefix = kasprintf(GFP_KERNEL, "signal%d_",
+				   synapse->signal->id);
+		if (!prefix) {
+			err = -ENOMEM;
+			goto err_free_attr_list;
+		}
+
+		/* Allocate action attribute component */
+		action_comp = kmalloc(sizeof(*action_comp), GFP_KERNEL);
+		if (!action_comp) {
+			err = -ENOMEM;
+			goto err_free_prefix;
+		}
+		action_comp->synapse = synapse;
+		action_comp->count = count;
+
+		/* Create action attribute */
+		err = counter_attribute_create(group, prefix, "action",
+			(counter->ops->action_get) ? counter_action_show : NULL,
+			(counter->ops->action_set) ? counter_action_store : NULL,
+			action_comp);
+		if (err) {
+			kfree(action_comp);
+			goto err_free_prefix;
+		}
+
+		/* Allocate action available attribute component */
+		avail_comp = kmalloc(sizeof(*avail_comp), GFP_KERNEL);
+		if (!avail_comp) {
+			err = -ENOMEM;
+			goto err_free_prefix;
+		}
+		avail_comp->actions_list = synapse->actions_list;
+		avail_comp->num_actions = synapse->num_actions;
+
+		/* Create action_available attribute */
+		err = counter_attribute_create(group, prefix,
+			"action_available",
+			counter_synapse_action_available_show, NULL,
+			avail_comp);
+		if (err) {
+			kfree(avail_comp);
+			goto err_free_prefix;
+		}
+
+		kfree(prefix);
+	}
+
+	return 0;
+
+err_free_prefix:
+	kfree(prefix);
+err_free_attr_list:
+	free_counter_device_attr_list(&group->attr_list);
+	return err;
+}
+
+struct count_comp_t {
+	struct counter_count	*count;
+};
+
+static ssize_t counter_count_show(struct device *dev,
+				  struct device_attribute *attr,
+				  char *buf)
+{
+	struct counter_device *const counter = dev_get_drvdata(dev);
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct count_comp_t *const component = devattr->component;
+	struct counter_count *const count = component->count;
+	int err;
+	struct count_read_value val = { .buf = buf };
+
+	err = counter->ops->count_read(counter, count, &val);
+	if (err)
+		return err;
+
+	return val.len;
+}
+
+static ssize_t counter_count_store(struct device *dev,
+				   struct device_attribute *attr,
+				   const char *buf, size_t len)
+{
+	struct counter_device *const counter = dev_get_drvdata(dev);
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct count_comp_t *const component = devattr->component;
+	struct counter_count *const count = component->count;
+	int err;
+	struct count_write_value val = { .buf = buf };
+
+	err = counter->ops->count_write(counter, count, &val);
+	if (err)
+		return err;
+
+	return len;
+}
+
+static const char *const count_function_str[] = {
+	[COUNT_FUNCTION_INCREASE] = "increase",
+	[COUNT_FUNCTION_DECREASE] = "decrease",
+	[COUNT_FUNCTION_PULSE_DIRECTION] = "pulse-direction",
+	[COUNT_FUNCTION_QUADRATURE_X1_A] = "quadrature x1 a",
+	[COUNT_FUNCTION_QUADRATURE_X1_B] = "quadrature x1 b",
+	[COUNT_FUNCTION_QUADRATURE_X2_A] = "quadrature x2 a",
+	[COUNT_FUNCTION_QUADRATURE_X2_B] = "quadrature x2 b",
+	[COUNT_FUNCTION_QUADRATURE_X2_RISING] = "quadrature x2 rising",
+	[COUNT_FUNCTION_QUADRATURE_X2_FALLING] = "quadrature x2 falling",
+	[COUNT_FUNCTION_QUADRATURE_X4] = "quadrature x4"
+};
+
+static ssize_t counter_function_show(struct device *dev,
+				     struct device_attribute *attr, char *buf)
+{
+	int err;
+	struct counter_device *const counter = dev_get_drvdata(dev);
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct count_comp_t *const component = devattr->component;
+	struct counter_count *const count = component->count;
+	size_t func_index;
+	enum count_function function;
+
+	err = counter->ops->function_get(counter, count, &func_index);
+	if (err)
+		return err;
+
+	count->function = func_index;
+
+	function = count->functions_list[func_index];
+	return scnprintf(buf, PAGE_SIZE, "%s\n", count_function_str[function]);
+}
+
+static ssize_t counter_function_store(struct device *dev,
+				      struct device_attribute *attr,
+				      const char *buf, size_t len)
+{
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct count_comp_t *const component = devattr->component;
+	struct counter_count *const count = component->count;
+	const size_t num_functions = count->num_functions;
+	size_t func_index;
+	enum count_function function;
+	int err;
+	struct counter_device *const counter = dev_get_drvdata(dev);
+
+	/* Find requested Count function mode */
+	for (func_index = 0; func_index < num_functions; func_index++) {
+		function = count->functions_list[func_index];
+		if (sysfs_streq(buf, count_function_str[function]))
+			break;
+	}
+	/* Return error if requested Count function mode not found */
+	if (func_index >= num_functions)
+		return -EINVAL;
+
+	err = counter->ops->function_set(counter, count, func_index);
+	if (err)
+		return err;
+
+	count->function = func_index;
+
+	return len;
+}
+
+struct count_ext_comp_t {
+	struct counter_count		*count;
+	const struct counter_count_ext	*ext;
+};
+
+static ssize_t counter_count_ext_show(struct device *dev,
+				      struct device_attribute *attr, char *buf)
+{
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct count_ext_comp_t *const comp = devattr->component;
+	const struct counter_count_ext *const ext = comp->ext;
+
+	return ext->read(dev_get_drvdata(dev), comp->count, ext->priv, buf);
+}
+
+static ssize_t counter_count_ext_store(struct device *dev,
+				       struct device_attribute *attr,
+				       const char *buf, size_t len)
+{
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct count_ext_comp_t *const comp = devattr->component;
+	const struct counter_count_ext *const ext = comp->ext;
+
+	return ext->write(dev_get_drvdata(dev), comp->count, ext->priv, buf,
+		len);
+}
+
+static int counter_count_ext_register(
+	struct counter_device_attr_group *const group,
+	struct counter_count *const count)
+{
+	const size_t num_ext = count->num_ext;
+	size_t i;
+	const struct counter_count_ext *ext;
+	struct count_ext_comp_t *count_ext_comp;
+	int err;
+
+	/* Create an attribute for each extension */
+	for (i = 0 ; i < num_ext; i++) {
+		ext = count->ext + i;
+
+		/* Allocate count_ext attribute component */
+		count_ext_comp = kmalloc(sizeof(*count_ext_comp), GFP_KERNEL);
+		if (!count_ext_comp) {
+			err = -ENOMEM;
+			goto err_free_attr_list;
+		}
+		count_ext_comp->count = count;
+		count_ext_comp->ext = ext;
+
+		/* Allocate count_ext attribute */
+		err = counter_attribute_create(group, "", ext->name,
+			(ext->read) ? counter_count_ext_show : NULL,
+			(ext->write) ? counter_count_ext_store : NULL,
+			count_ext_comp);
+		if (err) {
+			kfree(count_ext_comp);
+			goto err_free_attr_list;
+		}
+	}
+
+	return 0;
+
+err_free_attr_list:
+	free_counter_device_attr_list(&group->attr_list);
+	return err;
+}
+
+struct func_avail_comp_t {
+	const enum count_function	*functions_list;
+	size_t				num_functions;
+};
+
+static ssize_t counter_count_function_available_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct func_avail_comp_t *const component = devattr->component;
+	const enum count_function *const func_list = component->functions_list;
+	const size_t num_functions = component->num_functions;
+	size_t i;
+	enum count_function function;
+	ssize_t len = 0;
+
+	for (i = 0; i < num_functions; i++) {
+		function = func_list[i];
+		len += scnprintf(buf + len, PAGE_SIZE - len, "%s\n",
+			count_function_str[function]);
+	}
+
+	return len;
+}
+
+static int counter_count_attributes_create(
+	struct counter_device_attr_group *const group,
+	const struct counter_device *const counter,
+	struct counter_count *const count)
+{
+	struct count_comp_t *count_comp;
+	int err;
+	struct count_comp_t *func_comp;
+	struct func_avail_comp_t *avail_comp;
+
+	/* Allocate count attribute component */
+	count_comp = kmalloc(sizeof(*count_comp), GFP_KERNEL);
+	if (!count_comp)
+		return -ENOMEM;
+	count_comp->count = count;
+
+	/* Create main Count attribute */
+	err = counter_attribute_create(group, "", "count",
+		(counter->ops->count_read) ? counter_count_show : NULL,
+		(counter->ops->count_write) ? counter_count_store : NULL,
+		count_comp);
+	if (err) {
+		kfree(count_comp);
+		return err;
+	}
+
+	/* Allocate function attribute component */
+	func_comp = kmalloc(sizeof(*func_comp), GFP_KERNEL);
+	if (!func_comp) {
+		err = -ENOMEM;
+		goto err_free_attr_list;
+	}
+	func_comp->count = count;
+
+	/* Create Count function attribute */
+	err = counter_attribute_create(group, "", "function",
+		(counter->ops->function_get) ? counter_function_show : NULL,
+		(counter->ops->function_set) ? counter_function_store : NULL,
+		func_comp);
+	if (err) {
+		kfree(func_comp);
+		goto err_free_attr_list;
+	}
+
+	/* Allocate function available attribute component */
+	avail_comp = kmalloc(sizeof(*avail_comp), GFP_KERNEL);
+	if (!avail_comp) {
+		err = -ENOMEM;
+		goto err_free_attr_list;
+	}
+	avail_comp->functions_list = count->functions_list;
+	avail_comp->num_functions = count->num_functions;
+
+	/* Create Count function_available attribute */
+	err = counter_attribute_create(group, "", "function_available",
+				       counter_count_function_available_show,
+				       NULL, avail_comp);
+	if (err) {
+		kfree(avail_comp);
+		goto err_free_attr_list;
+	}
+
+	/* Create Count name attribute */
+	err = counter_name_attribute_create(group, count->name);
+	if (err)
+		goto err_free_attr_list;
+
+	/* Register Count extension attributes */
+	err = counter_count_ext_register(group, count);
+	if (err)
+		goto err_free_attr_list;
+
+	return 0;
+
+err_free_attr_list:
+	free_counter_device_attr_list(&group->attr_list);
+	return err;
+}
+
+static int counter_counts_register(
+	struct counter_device_attr_group *const groups_list,
+	const struct counter_device *const counter)
+{
+	const size_t num_counts = counter->num_counts;
+	size_t i;
+	struct counter_count *count;
+	const char *name;
+	int err;
+
+	/* Register each Count */
+	for (i = 0; i < num_counts; i++) {
+		count = counter->counts + i;
+
+		/* Generate Count attribute directory name */
+		name = kasprintf(GFP_KERNEL, "count%d", count->id);
+		if (!name) {
+			err = -ENOMEM;
+			goto err_free_attr_groups;
+		}
+		groups_list[i].attr_group.name = name;
+
+		/* Register the Synapses associated with each Count */
+		err = counter_synapses_register(groups_list + i, counter, count,
+						name);
+		if (err)
+			goto err_free_attr_groups;
+
+		/* Create all attributes associated with Count */
+		err = counter_count_attributes_create(groups_list + i, counter,
+						      count);
+		if (err)
+			goto err_free_attr_groups;
+	}
+
+	return 0;
+
+err_free_attr_groups:
+	do {
+		kfree(groups_list[i].attr_group.name);
+		free_counter_device_attr_list(&groups_list[i].attr_list);
+	} while (i--);
+	return err;
+}
+
+struct size_comp_t {
+	size_t size;
+};
+
+static ssize_t counter_device_attr_size_show(struct device *dev,
+					     struct device_attribute *attr,
+					     char *buf)
+{
+	const struct size_comp_t *const comp = to_counter_attr(attr)->component;
+
+	return scnprintf(buf, PAGE_SIZE, "%zu\n", comp->size);
+}
+
+static int counter_size_attribute_create(
+	struct counter_device_attr_group *const group,
+	const size_t size, const char *const name)
+{
+	struct size_comp_t *size_comp;
+	int err;
+
+	/* Allocate size attribute component */
+	size_comp = kmalloc(sizeof(*size_comp), GFP_KERNEL);
+	if (!size_comp)
+		return -ENOMEM;
+	size_comp->size = size;
+
+	err = counter_attribute_create(group, "", name,
+				       counter_device_attr_size_show, NULL,
+				       size_comp);
+	if (err)
+		goto err_free_size_comp;
+
+	return 0;
+
+err_free_size_comp:
+	kfree(size_comp);
+	return err;
+}
+
+struct ext_comp_t {
+	const struct counter_device_ext	*ext;
+};
+
+static ssize_t counter_device_ext_show(struct device *dev,
+				       struct device_attribute *attr, char *buf)
+{
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct ext_comp_t *const component = devattr->component;
+	const struct counter_device_ext *const ext = component->ext;
+
+	return ext->read(dev_get_drvdata(dev), ext->priv, buf);
+}
+
+static ssize_t counter_device_ext_store(struct device *dev,
+					struct device_attribute *attr,
+					const char *buf, size_t len)
+{
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct ext_comp_t *const component = devattr->component;
+	const struct counter_device_ext *const ext = component->ext;
+
+	return ext->write(dev_get_drvdata(dev), ext->priv, buf, len);
+}
+
+static int counter_device_ext_register(
+	struct counter_device_attr_group *const group,
+	struct counter_device *const counter)
+{
+	const size_t num_ext = counter->num_ext;
+	struct ext_comp_t *ext_comp;
+	size_t i;
+	const struct counter_device_ext *ext;
+	int err;
+
+	/* Create an attribute for each extension */
+	for (i = 0 ; i < num_ext; i++) {
+		ext = counter->ext + i;
+
+		/* Allocate extension attribute component */
+		ext_comp = kmalloc(sizeof(*ext_comp), GFP_KERNEL);
+		if (!ext_comp) {
+			err = -ENOMEM;
+			goto err_free_attr_list;
+		}
+
+		ext_comp->ext = ext;
+
+		/* Allocate extension attribute */
+		err = counter_attribute_create(group, "", ext->name,
+			(ext->read) ? counter_device_ext_show : NULL,
+			(ext->write) ? counter_device_ext_store : NULL,
+			ext_comp);
+		if (err) {
+			kfree(ext_comp);
+			goto err_free_attr_list;
+		}
+	}
+
+	return 0;
+
+err_free_attr_list:
+	free_counter_device_attr_list(&group->attr_list);
+	return err;
+}
+
+static int counter_global_attr_register(
+	struct counter_device_attr_group *const group,
+	struct counter_device *const counter)
+{
+	int err;
+
+	/* Create name attribute */
+	err = counter_name_attribute_create(group, counter->name);
+	if (err)
+		return err;
+
+	/* Create num_counts attribute */
+	err = counter_size_attribute_create(group, counter->num_counts,
+					    "num_counts");
+	if (err)
+		goto err_free_attr_list;
+
+	/* Create num_signals attribute */
+	err = counter_size_attribute_create(group, counter->num_signals,
+					    "num_signals");
+	if (err)
+		goto err_free_attr_list;
+
+	/* Register Counter device extension attributes */
+	err = counter_device_ext_register(group, counter);
+	if (err)
+		goto err_free_attr_list;
+
+	return 0;
+
+err_free_attr_list:
+	free_counter_device_attr_list(&group->attr_list);
+	return err;
+}
+
+static void free_counter_device_groups_list(
+	struct counter_device_attr_group *const groups_list,
+	const size_t num_groups)
+{
+	struct counter_device_attr_group *group;
+	size_t i;
+
+	for (i = 0; i < num_groups; i++) {
+		group = groups_list + i;
+
+		kfree(group->attr_group.name);
+		kfree(group->attr_group.attrs);
+		free_counter_device_attr_list(&group->attr_list);
+	}
+
+	kfree(groups_list);
+}
+
+static int prepare_counter_device_groups_list(
+	struct counter_device *const counter)
+{
+	const size_t total_num_groups =
+		counter->num_signals + counter->num_counts + 1;
+	struct counter_device_attr_group *groups_list;
+	size_t i;
+	int err;
+	size_t num_groups = 0;
+
+	/* Allocate space for attribute groups (signals. counts, and ext) */
+	groups_list = kcalloc(total_num_groups, sizeof(*groups_list),
+			      GFP_KERNEL);
+	if (!groups_list)
+		return -ENOMEM;
+
+	/* Initialize attribute lists */
+	for (i = 0; i < total_num_groups; i++)
+		INIT_LIST_HEAD(&groups_list[i].attr_list);
+
+	/* Register Signals */
+	err = counter_signals_register(groups_list, counter);
+	if (err)
+		goto err_free_groups_list;
+	num_groups += counter->num_signals;
+
+	/* Register Counts and respective Synapses */
+	err = counter_counts_register(groups_list + num_groups, counter);
+	if (err)
+		goto err_free_groups_list;
+	num_groups += counter->num_counts;
+
+	/* Register Counter global attributes */
+	err = counter_global_attr_register(groups_list + num_groups, counter);
+	if (err)
+		goto err_free_groups_list;
+	num_groups++;
+
+	/* Store groups_list in device_state */
+	counter->device_state->groups_list = groups_list;
+	counter->device_state->num_groups = num_groups;
+
+	return 0;
+
+err_free_groups_list:
+	free_counter_device_groups_list(groups_list, num_groups);
+	return err;
+}
+
+static int prepare_counter_device_groups(
+	struct counter_device_state *const device_state)
+{
+	size_t i;
+	struct counter_device_attr_group *group;
+	int err;
+	size_t j;
+	struct counter_device_attr *p;
+
+	/* Allocate attribute groups for association with device */
+	device_state->groups = kcalloc(device_state->num_groups + 1,
+				       sizeof(*device_state->groups),
+				       GFP_KERNEL);
+	if (!device_state->groups)
+		return -ENOMEM;
+
+	/* Prepare each group of attributes for association */
+	for (i = 0; i < device_state->num_groups; i++) {
+		group = device_state->groups_list + i;
+
+		/* Allocate space for attribute pointers in attribute group */
+		group->attr_group.attrs = kcalloc(group->num_attr + 1,
+			sizeof(*group->attr_group.attrs), GFP_KERNEL);
+		if (!group->attr_group.attrs) {
+			err = -ENOMEM;
+			goto err_free_groups;
+		}
+
+		/* Add attribute pointers to attribute group */
+		j = 0;
+		list_for_each_entry(p, &group->attr_list, l)
+			group->attr_group.attrs[j++] = &p->dev_attr.attr;
+
+		/* Group attributes in attribute group */
+		device_state->groups[i] = &group->attr_group;
+	}
+	/* Associate attributes with device */
+	device_state->dev.groups = device_state->groups;
+
+	return 0;
+
+err_free_groups:
+	kfree(device_state->groups);
+	return err;
+}
+
+/* Provides a unique ID for each counter device */
+static DEFINE_IDA(counter_ida);
+
+static void counter_device_release(struct device *dev)
+{
+	struct counter_device *const counter = dev_get_drvdata(dev);
+	struct counter_device_state *const device_state = counter->device_state;
+
+	kfree(device_state->groups);
+	free_counter_device_groups_list(device_state->groups_list,
+					device_state->num_groups);
+	ida_simple_remove(&counter_ida, device_state->id);
+	kfree(device_state);
+}
+
+static struct device_type counter_device_type = {
+	.name = "counter_device",
+	.release = counter_device_release
+};
+
+static struct bus_type counter_bus_type = {
+	.name = "counter"
+};
+
+/**
+ * counter_register - register Counter to the system
+ * @counter:	pointer to Counter to register
+ *
+ * This function registers a Counter to the system. A sysfs "counter" directory
+ * will be created and populated with sysfs attributes correlating with the
+ * Counter Signals, Synapses, and Counts respectively.
+ */
+int counter_register(struct counter_device *const counter)
+{
+	struct counter_device_state *device_state;
+	int err;
+
+	/* Allocate internal state container for Counter device */
+	device_state = kzalloc(sizeof(*device_state), GFP_KERNEL);
+	if (!device_state)
+		return -ENOMEM;
+	counter->device_state = device_state;
+
+	/* Acquire unique ID */
+	device_state->id = ida_simple_get(&counter_ida, 0, 0, GFP_KERNEL);
+	if (device_state->id < 0) {
+		err = device_state->id;
+		goto err_free_device_state;
+	}
+
+	/* Configure device structure for Counter */
+	device_state->dev.type = &counter_device_type;
+	device_state->dev.bus = &counter_bus_type;
+	if (counter->parent) {
+		device_state->dev.parent = counter->parent;
+		device_state->dev.of_node = counter->parent->of_node;
+	}
+	dev_set_name(&device_state->dev, "counter%d", device_state->id);
+	device_initialize(&device_state->dev);
+	dev_set_drvdata(&device_state->dev, counter);
+
+	/* Prepare device attributes */
+	err = prepare_counter_device_groups_list(counter);
+	if (err)
+		goto err_free_id;
+
+	/* Organize device attributes to groups and match to device */
+	err = prepare_counter_device_groups(device_state);
+	if (err)
+		goto err_free_groups_list;
+
+	/* Add device to system */
+	err = device_add(&device_state->dev);
+	if (err)
+		goto err_free_groups;
+
+	return 0;
+
+err_free_groups:
+	kfree(device_state->groups);
+err_free_groups_list:
+	free_counter_device_groups_list(device_state->groups_list,
+					device_state->num_groups);
+err_free_id:
+	ida_simple_remove(&counter_ida, device_state->id);
+err_free_device_state:
+	kfree(device_state);
+	return err;
+}
+EXPORT_SYMBOL(counter_register);
+
+/**
+ * counter_unregister - unregister Counter from the system
+ * @counter:	pointer to Counter to unregister
+ *
+ * The Counter is unregistered from the system; all allocated memory is freed.
+ */
+void counter_unregister(struct counter_device *const counter)
+{
+	if (counter)
+		device_del(&counter->device_state->dev);
+}
+EXPORT_SYMBOL(counter_unregister);
+
+static void devm_counter_unreg(struct device *dev, void *res)
+{
+	counter_unregister(*(struct counter_device **)res);
+}
+
+/**
+ * devm_counter_register - Resource-managed counter_register
+ * @dev:	device to allocate counter_device for
+ * @counter:	pointer to Counter to register
+ *
+ * Managed counter_register. The Counter registered with this function is
+ * automatically unregistered on driver detach. This function calls
+ * counter_register internally. Refer to that function for more information.
+ *
+ * If an Counter registered with this function needs to be unregistered
+ * separately, devm_counter_unregister must be used.
+ *
+ * RETURNS:
+ * 0 on success, negative error number on failure.
+ */
+int devm_counter_register(struct device *dev,
+			  struct counter_device *const counter)
+{
+	struct counter_device **ptr;
+	int ret;
+
+	ptr = devres_alloc(devm_counter_unreg, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return -ENOMEM;
+
+	ret = counter_register(counter);
+	if (!ret) {
+		*ptr = counter;
+		devres_add(dev, ptr);
+	} else {
+		devres_free(ptr);
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(devm_counter_register);
+
+static int devm_counter_match(struct device *dev, void *res, void *data)
+{
+	struct counter_device **r = res;
+
+	if (!r || !*r) {
+		WARN_ON(!r || !*r);
+		return 0;
+	}
+
+	return *r == data;
+}
+
+/**
+ * devm_counter_unregister - Resource-managed counter_unregister
+ * @dev:	device this counter_device belongs to
+ * @counter:	pointer to Counter associated with the device
+ *
+ * Unregister Counter registered with devm_counter_register.
+ */
+void devm_counter_unregister(struct device *dev,
+			     struct counter_device *const counter)
+{
+	int rc;
+
+	rc = devres_release(dev, devm_counter_unreg, devm_counter_match,
+			    counter);
+	WARN_ON(rc);
+}
+EXPORT_SYMBOL(devm_counter_unregister);
+
+static int __init counter_init(void)
+{
+	return bus_register(&counter_bus_type);
+}
+
+static void __exit counter_exit(void)
+{
+	bus_unregister(&counter_bus_type);
+}
+
+subsys_initcall(counter_init);
+module_exit(counter_exit);
+
+MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
+MODULE_DESCRIPTION("Generic Counter interface");
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/counter.h b/include/linux/counter.h
new file mode 100644
index 000000000000..a0b0349d098a
--- /dev/null
+++ b/include/linux/counter.h
@@ -0,0 +1,554 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Counter interface
+ * Copyright (C) 2017 William Breathitt Gray
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2, as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+#ifndef _COUNTER_H_
+#define _COUNTER_H_
+
+#include <linux/device.h>
+#include <linux/types.h>
+
+enum count_direction {
+	COUNT_DIRECTION_FORWARD = 0,
+	COUNT_DIRECTION_BACKWARD
+};
+extern const char *const count_direction_str[2];
+
+enum count_mode {
+	COUNT_MODE_NORMAL = 0,
+	COUNT_MODE_RANGE_LIMIT,
+	COUNT_MODE_NON_RECYCLE,
+	COUNT_MODE_MODULO_N
+};
+extern const char *const count_mode_str[4];
+
+struct counter_device;
+struct counter_signal;
+
+/**
+ * struct counter_signal_ext - Counter Signal extensions
+ * @name:	attribute name
+ * @read:	read callback for this attribute; may be NULL
+ * @write:	write callback for this attribute; may be NULL
+ * @priv:	data private to the driver
+ */
+struct counter_signal_ext {
+	const char	*name;
+	ssize_t		(*read)(struct counter_device *counter,
+				struct counter_signal *signal, void *priv,
+				char *buf);
+	ssize_t		(*write)(struct counter_device *counter,
+				 struct counter_signal *signal, void *priv,
+				 const char *buf, size_t len);
+	void		*priv;
+};
+
+/**
+ * struct counter_signal - Counter Signal node
+ * @id:		unique ID used to identify signal
+ * @name:	device-specific Signal name; ideally, this should match the name
+ *		as it appears in the datasheet documentation
+ * @ext:	optional array of Counter Signal extensions
+ * @num_ext:	number of Counter Signal extensions specified in @ext
+ * @priv:	optional private data supplied by driver
+ */
+struct counter_signal {
+	int		id;
+	const char	*name;
+
+	const struct counter_signal_ext	*ext;
+	size_t				num_ext;
+
+	void	*priv;
+};
+
+/**
+ * struct counter_signal_enum_ext - Signal enum extension attribute
+ * @items:	Array of strings
+ * @num_items:	Number of items specified in @items
+ * @set:	Set callback function; may be NULL
+ * @get:	Get callback function; may be NULL
+ *
+ * The counter_signal_enum_ext structure can be used to implement enum style
+ * Signal extension attributes. Enum style attributes are those which have a set
+ * of strings that map to unsigned integer values. The Generic Counter Signal
+ * enum extension helper code takes care of mapping between value and string, as
+ * well as generating a "_available" file which contains a list of all available
+ * items. The get callback is used to query the currently active item; the index
+ * of the item within the respective items array is returned via the 'item'
+ * parameter. The set callback is called when the attribute is updated; the
+ * 'item' parameter contains the index of the newly activated item within the
+ * respective items array.
+ */
+struct counter_signal_enum_ext {
+	const char * const	*items;
+	size_t			num_items;
+	int			(*get)(struct counter_device *counter,
+				       struct counter_signal *signal,
+				       size_t *item);
+	int			(*set)(struct counter_device *counter,
+				       struct counter_signal *signal,
+				       size_t item);
+};
+
+ssize_t counter_signal_enum_read(struct counter_device *counter,
+				 struct counter_signal *signal, void *priv,
+				 char *buf);
+ssize_t counter_signal_enum_write(struct counter_device *counter,
+				  struct counter_signal *signal, void *priv,
+				  const char *buf, size_t len);
+
+/**
+ * COUNTER_SIGNAL_ENUM() - Initialize Signal enum extension
+ * @_name:	Attribute name
+ * @_e:		Pointer to a counter_count_enum structure
+ *
+ * This should usually be used together with COUNTER_SIGNAL_ENUM_AVAILABLE()
+ */
+#define COUNTER_SIGNAL_ENUM(_name, _e) \
+{ \
+	.name = (_name), \
+	.read = counter_signal_enum_read, \
+	.write = counter_signal_enum_write, \
+	.priv = (_e) \
+}
+
+ssize_t counter_signal_enum_available_read(struct counter_device *counter,
+					   struct counter_signal *signal,
+					   void *priv, char *buf);
+
+/**
+ * COUNTER_SIGNAL_ENUM_AVAILABLE() - Initialize Signal enum available extension
+ * @_name:	Attribute name ("_available" will be appended to the name)
+ * @_e:		Pointer to a counter_signal_enum structure
+ *
+ * Creates a read only attribute that lists all the available enum items in a
+ * newline separated list. This should usually be used together with
+ * COUNTER_SIGNAL_ENUM()
+ */
+#define COUNTER_SIGNAL_ENUM_AVAILABLE(_name, _e) \
+{ \
+	.name = (_name "_available"), \
+	.read = counter_signal_enum_available_read, \
+	.priv = (_e) \
+}
+
+enum synapse_action {
+	SYNAPSE_ACTION_NONE = 0,
+	SYNAPSE_ACTION_RISING_EDGE,
+	SYNAPSE_ACTION_FALLING_EDGE,
+	SYNAPSE_ACTION_BOTH_EDGES
+};
+
+/**
+ * struct counter_synapse - Counter Synapse node
+ * @action:		index of current action mode
+ * @actions_list:	array of available action modes
+ * @num_actions:	number of action modes specified in @actions_list
+ * @signal:		pointer to associated signal
+ */
+struct counter_synapse {
+	size_t					action;
+	const enum synapse_action		*actions_list;
+	size_t					num_actions;
+
+	struct counter_signal			*signal;
+};
+
+struct counter_count;
+
+/**
+ * struct counter_count_ext - Counter Count extension
+ * @name:	attribute name
+ * @read:	read callback for this attribute; may be NULL
+ * @write:	write callback for this attribute; may be NULL
+ * @priv:	data private to the driver
+ */
+struct counter_count_ext {
+	const char	*name;
+	ssize_t		(*read)(struct counter_device *counter,
+				struct counter_count *count, void *priv,
+				char *buf);
+	ssize_t		(*write)(struct counter_device *counter,
+				 struct counter_count *count, void *priv,
+				 const char *buf, size_t len);
+	void		*priv;
+};
+
+enum count_function {
+	COUNT_FUNCTION_INCREASE = 0,
+	COUNT_FUNCTION_DECREASE,
+	COUNT_FUNCTION_PULSE_DIRECTION,
+	COUNT_FUNCTION_QUADRATURE_X1_A,
+	COUNT_FUNCTION_QUADRATURE_X1_B,
+	COUNT_FUNCTION_QUADRATURE_X2_A,
+	COUNT_FUNCTION_QUADRATURE_X2_B,
+	COUNT_FUNCTION_QUADRATURE_X2_RISING,
+	COUNT_FUNCTION_QUADRATURE_X2_FALLING,
+	COUNT_FUNCTION_QUADRATURE_X4
+};
+
+/**
+ * struct counter_count - Counter Count node
+ * @id:			unique ID used to identify Count
+ * @name:		device-specific Count name; ideally, this should match
+ *			the name as it appears in the datasheet documentation
+ * @function:		index of current function mode
+ * @functions_list:	array available function modes
+ * @num_functions:	number of function modes specified in @functions_list
+ * @synapses:		array of synapses for initialization
+ * @num_synapses:	number of synapses specified in @synapses
+ * @ext:		optional array of Counter Count extensions
+ * @num_ext:		number of Counter Count extensions specified in @ext
+ * @priv:		optional private data supplied by driver
+ */
+struct counter_count {
+	int			id;
+	const char		*name;
+
+	size_t					function;
+	const enum count_function		*functions_list;
+	size_t					num_functions;
+
+	struct counter_synapse	*synapses;
+	size_t			num_synapses;
+
+	const struct counter_count_ext	*ext;
+	size_t				num_ext;
+
+	void	*priv;
+};
+
+/**
+ * struct counter_count_enum_ext - Count enum extension attribute
+ * @items:	Array of strings
+ * @num_items:	Number of items specified in @items
+ * @set:	Set callback function; may be NULL
+ * @get:	Get callback function; may be NULL
+ *
+ * The counter_count_enum_ext structure can be used to implement enum style
+ * Count extension attributes. Enum style attributes are those which have a set
+ * of strings that map to unsigned integer values. The Generic Counter Count
+ * enum extension helper code takes care of mapping between value and string, as
+ * well as generating a "_available" file which contains a list of all available
+ * items. The get callback is used to query the currently active item; the index
+ * of the item within the respective items array is returned via the 'item'
+ * parameter. The set callback is called when the attribute is updated; the
+ * 'item' parameter contains the index of the newly activated item within the
+ * respective items array.
+ */
+struct counter_count_enum_ext {
+	const char * const	*items;
+	size_t			num_items;
+	int			(*get)(struct counter_device *counter,
+				       struct counter_count *count,
+				       size_t *item);
+	int			(*set)(struct counter_device *counter,
+				       struct counter_count *count,
+				       size_t item);
+};
+
+ssize_t counter_count_enum_read(struct counter_device *counter,
+				struct counter_count *count, void *priv,
+				char *buf);
+ssize_t counter_count_enum_write(struct counter_device *counter,
+				 struct counter_count *count, void *priv,
+				 const char *buf, size_t len);
+
+/**
+ * COUNTER_COUNT_ENUM() - Initialize Count enum extension
+ * @_name:	Attribute name
+ * @_e:		Pointer to a counter_count_enum structure
+ *
+ * This should usually be used together with COUNTER_COUNT_ENUM_AVAILABLE()
+ */
+#define COUNTER_COUNT_ENUM(_name, _e) \
+{ \
+	.name = (_name), \
+	.read = counter_count_enum_read, \
+	.write = counter_count_enum_write, \
+	.priv = (_e) \
+}
+
+ssize_t counter_count_enum_available_read(struct counter_device *counter,
+					  struct counter_count *count,
+					  void *priv, char *buf);
+
+/**
+ * COUNTER_COUNT_ENUM_AVAILABLE() - Initialize Count enum available extension
+ * @_name:	Attribute name ("_available" will be appended to the name)
+ * @_e:		Pointer to a counter_count_enum structure
+ *
+ * Creates a read only attribute that lists all the available enum items in a
+ * newline separated list. This should usually be used together with
+ * COUNTER_COUNT_ENUM()
+ */
+#define COUNTER_COUNT_ENUM_AVAILABLE(_name, _e) \
+{ \
+	.name = (_name "_available"), \
+	.read = counter_count_enum_available_read, \
+	.priv = (_e) \
+}
+
+/**
+ * struct counter_device_attr_group - internal container for attribute group
+ * @attr_group:	Counter sysfs attributes group
+ * @attr_list:	list to keep track of created Counter sysfs attributes
+ * @num_attr:	number of Counter sysfs attributes
+ */
+struct counter_device_attr_group {
+	struct attribute_group	attr_group;
+	struct list_head	attr_list;
+	size_t			num_attr;
+};
+
+/**
+ * struct counter_device_state - internal state container for a Counter device
+ * @id:		unique ID used to identify the Counter
+ * @dev:	internal device structure
+ * @groups_list	attribute groups list (groups for Signals, Counts, and ext)
+ * @num_groups	number of attribute groups containers
+ * @groups:	Counter sysfs attribute groups (used to populate @dev.groups)
+ */
+struct counter_device_state {
+	int					id;
+	struct device				dev;
+	struct counter_device_attr_group	*groups_list;
+	size_t					num_groups;
+	const struct attribute_group		**groups;
+};
+
+/**
+ * struct signal_read_value - Opaque Signal read value
+ * @buf:	string representation of Signal read value
+ * @len:	length of string in @buf
+ */
+struct signal_read_value {
+	char	*buf;
+	size_t	len;
+};
+
+/**
+ * struct count_read_value - Opaque Count read value
+ * @buf:	string representation of Count read value
+ * @len:	length of string in @buf
+ */
+struct count_read_value {
+	char	*buf;
+	size_t	len;
+};
+
+/**
+ * struct count_write_value - Opaque Count write value
+ * @buf:	string representation of Count write value
+ */
+struct count_write_value {
+	const char	*buf;
+};
+
+/**
+ * struct counter_ops - Callbacks from driver
+ * @signal_read:	optional read callback for Signal attribute. The read
+ *			value of the respective Signal should be passed back via
+ *			the val parameter. val points to an opaque type which
+ *			should be set only via the set_signal_read_value
+ *			function.
+ * @count_read:		optional read callback for Count attribute. The read
+ *			value of the respective Count should be passed back via
+ *			the val parameter. val points to an opaque type which
+ *			should be set only via the set_count_read_value
+ *			function.
+ * @count_write:	optional write callback for Count attribute. The write
+ *			value for the respective Count is passed in via the val
+ *			parameter. val points to an opaque type which should be
+ *			access only via the get_count_write_value function.
+ * @function_get:	function to get the current count function mode. Returns
+ *			0 on success and negative error code on error. The index
+ *			of the respective Count's returned function mode should
+ *			be passed back via the function parameter.
+ * @function_set:	function to set the count function mode. function is the
+ *			index of the requested function mode from the respective
+ *			Count's functions_list array.
+ * @action_get:		function to get the current action mode. Returns 0 on
+ *			success and negative error code on error. The index of
+ *			the respective Signal's returned action mode should be
+ *			passed back via the action parameter.
+ * @action_set:		function to set the action mode. action is the index of
+ *			the requested action mode from the respective Synapse's
+ *			actions_list array.
+ */
+struct counter_ops {
+	int	(*signal_read)(struct counter_device *counter,
+			       struct counter_signal *signal,
+			       struct signal_read_value *val);
+	int	(*count_read)(struct counter_device *counter,
+			      struct counter_count *count,
+			      struct count_read_value *val);
+	int	(*count_write)(struct counter_device *counter,
+			       struct counter_count *count,
+			       struct count_write_value *val);
+	int	(*function_get)(struct counter_device *counter,
+				struct counter_count *count, size_t *function);
+	int	(*function_set)(struct counter_device *counter,
+				struct counter_count *count, size_t function);
+	int	(*action_get)(struct counter_device *counter,
+			      struct counter_count *count,
+			      struct counter_synapse *synapse, size_t *action);
+	int	(*action_set)(struct counter_device *counter,
+			      struct counter_count *count,
+			      struct counter_synapse *synapse, size_t action);
+};
+
+/**
+ * struct counter_device_ext - Counter device extension
+ * @name:	attribute name
+ * @read:	read callback for this attribute; may be NULL
+ * @write:	write callback for this attribute; may be NULL
+ * @priv:	data private to the driver
+ */
+struct counter_device_ext {
+	const char	*name;
+	ssize_t		(*read)(struct counter_device *counter, void *priv,
+				char *buf);
+	ssize_t		(*write)(struct counter_device *counter, void *priv,
+				 const char *buf, size_t len);
+	void		*priv;
+};
+
+/**
+ * struct counter_device_enum_ext - Counter enum extension attribute
+ * @items:	Array of strings
+ * @num_items:	Number of items specified in @items
+ * @set:	Set callback function; may be NULL
+ * @get:	Get callback function; may be NULL
+ *
+ * The counter_device_enum_ext structure can be used to implement enum style
+ * Counter extension attributes. Enum style attributes are those which have a
+ * set of strings that map to unsigned integer values. The Generic Counter enum
+ * extension helper code takes care of mapping between value and string, as well
+ * as generating a "_available" file which contains a list of all available
+ * items. The get callback is used to query the currently active item; the index
+ * of the item within the respective items array is returned via the 'item'
+ * parameter. The set callback is called when the attribute is updated; the
+ * 'item' parameter contains the index of the newly activated item within the
+ * respective items array.
+ */
+struct counter_device_enum_ext {
+	const char * const	*items;
+	size_t			num_items;
+	int			(*get)(struct counter_device *counter,
+				       size_t *item);
+	int			(*set)(struct counter_device *counter,
+				       size_t item);
+};
+
+ssize_t counter_device_enum_read(struct counter_device *counter, void *priv,
+				 char *buf);
+ssize_t counter_device_enum_write(struct counter_device *counter, void *priv,
+				  const char *buf, size_t len);
+
+/**
+ * COUNTER_DEVICE_ENUM() - Initialize Counter enum extension
+ * @_name:	Attribute name
+ * @_e:		Pointer to a counter_device_enum structure
+ *
+ * This should usually be used together with COUNTER_DEVICE_ENUM_AVAILABLE()
+ */
+#define COUNTER_DEVICE_ENUM(_name, _e) \
+{ \
+	.name = (_name), \
+	.read = counter_device_enum_read, \
+	.write = counter_device_enum_write, \
+	.priv = (_e) \
+}
+
+ssize_t counter_device_enum_available_read(struct counter_device *counter,
+					   void *priv, char *buf);
+
+/**
+ * COUNTER_DEVICE_ENUM_AVAILABLE() - Initialize Counter enum available extension
+ * @_name:	Attribute name ("_available" will be appended to the name)
+ * @_e:		Pointer to a counter_device_enum structure
+ *
+ * Creates a read only attribute that lists all the available enum items in a
+ * newline separated list. This should usually be used together with
+ * COUNTER_DEVICE_ENUM()
+ */
+#define COUNTER_DEVICE_ENUM_AVAILABLE(_name, _e) \
+{ \
+	.name = (_name "_available"), \
+	.read = counter_device_enum_available_read, \
+	.priv = (_e) \
+}
+
+/**
+ * struct counter_device - Counter data structure
+ * @name:		name of the device as it appears in the datasheet
+ * @parent:		optional parent device providing the counters
+ * @device_state:	internal device state container
+ * @ops:		callbacks from driver
+ * @signals:		array of Signals
+ * @num_signals:	number of Signals specified in @signals
+ * @counts:		array of Counts
+ * @num_counts:		number of Counts specified in @counts
+ * @ext:		optional array of Counter device extensions
+ * @num_ext:		number of Counter device extensions specified in @ext
+ * @priv:		optional private data supplied by driver
+ */
+struct counter_device {
+	const char			*name;
+	struct device			*parent;
+	struct counter_device_state	*device_state;
+
+	const struct counter_ops	*ops;
+
+	struct counter_signal	*signals;
+	size_t			num_signals;
+	struct counter_count	*counts;
+	size_t			num_counts;
+
+	const struct counter_device_ext	*ext;
+	size_t				num_ext;
+
+	void	*priv;
+};
+
+enum signal_level {
+	SIGNAL_LEVEL_LOW = 0,
+	SIGNAL_LEVEL_HIGH
+};
+
+enum signal_value_type {
+	SIGNAL_LEVEL = 0
+};
+
+enum count_value_type {
+	COUNT_POSITION_UNSIGNED = 0,
+	COUNT_POSITION_SIGNED
+};
+
+void set_signal_read_value(struct signal_read_value *const val,
+			   const enum signal_value_type type, void *const data);
+void set_count_read_value(struct count_read_value *const val,
+			  const enum count_value_type type, void *const data);
+int get_count_write_value(void *const data, const enum count_value_type type,
+			  const struct count_write_value *const val);
+
+int counter_register(struct counter_device *const counter);
+void counter_unregister(struct counter_device *const counter);
+int devm_counter_register(struct device *dev,
+			  struct counter_device *const counter);
+void devm_counter_unregister(struct device *dev,
+			     struct counter_device *const counter);
+
+#endif /* _COUNTER_H_ */
-- 
2.17.0

[PATCH v6 2/9] counter: Documentation: Add Generic Counter sysfs documentation

[William Breathitt Gray]

This patch adds standard documentation for the userspace sysfs
attributes of the Generic Counter interface.

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
---
 Documentation/ABI/testing/sysfs-bus-counter | 241 ++++++++++++++++++++
 MAINTAINERS                                 |   1 +
 2 files changed, 242 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-bus-counter

diff --git a/Documentation/ABI/testing/sysfs-bus-counter b/Documentation/ABI/testing/sysfs-bus-counter
new file mode 100644
index 000000000000..e4a45d231b4f
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-counter
@@ -0,0 +1,241 @@
+What:		/sys/bus/counter/devices/counterX/countY/count
+KernelVersion:	4.18
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Count data of Count Y represented as a string.
+
+What:		/sys/bus/counter/devices/counterX/countY/ceiling
+KernelVersion:	4.18
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Count value ceiling for Count Y. This is the upper limit for the
+		respective counter.
+
+What:		/sys/bus/counter/devices/counterX/countY/floor
+KernelVersion:	4.18
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Count value floor for Count Y. This is the lower limit for the
+		respective counter.
+
+What:		/sys/bus/counter/devices/counterX/countY/count_mode
+KernelVersion:	4.18
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Count mode for channel Y. The ceiling and floor values for
+		Count Y are used by the count mode where required. The following
+		count modes are available:
+
+		Normal:
+			Counting is continuous in either direction.
+
+		Range Limit:
+			An upper or lower limit is set, mimicking limit switches
+			in the mechanical counterpart. The upper limit is set to
+			the Count Y ceiling value, while the lower limit is set
+			to the Count Y floor value. The counter freezes at
+			count = ceiling when counting up, and at count = floor
+			when counting down. At either of these limits, the
+			counting is resumed only when the count direction is
+			reversed.
+
+		Non-Recycle:
+			The counter is disabled whenever a counter overflow or
+			underflow takes place. The counter is re-enabled when a
+			new count value is loaded to the counter via a preset
+			operation or direct write.
+
+		Modulo-N:
+			A count value boundary is set between the Count Y floor
+			value and the Count Y ceiling value. The counter is
+			reset to the Cunt Y floor value at count = ceiling when
+			counting up, while the counter is set to the Count Y
+			ceiling value at count = floor when counting down; the
+			counter does not freeze at the boundary points, but
+			counts continuously throughout.
+
+What:		/sys/bus/counter/devices/counterX/countY/count_mode_available
+What:		/sys/bus/counter/devices/counterX/countY/error_noise_available
+What:		/sys/bus/counter/devices/counterX/countY/function_available
+What:		/sys/bus/counter/devices/counterX/countY/signalZ_action_available
+KernelVersion:	4.18
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Discrete set of available values for the respective Count Y
+		configuration are listed in this file. Values are delineated by
+		newline characters.
+
+What:		/sys/bus/counter/devices/counterX/countY/direction
+KernelVersion:	4.18
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Read-only attribute that indicates the count direction of Count
+		Y. Two count directions are available: forward and backward.
+
+		Some counter devices are able to determine the direction of
+		their counting. For example, quadrature encoding counters can
+		determine the direction of movement by evaluating the leading
+		phase of the respective A and B quadrature encoding signals.
+		This attribute exposes such count directions.
+
+What:		/sys/bus/counter/devices/counterX/countY/enable
+KernelVersion:	4.18
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Whether channel Y counter is enabled. Valid attribute values are
+		boolean.
+
+		This attribute is intended to serve as a pause/unpause mechanism
+		for Count Y. Suppose a counter device is used to count the total
+		movement of a conveyor belt: this attribute allows an operator
+		to temporarily pause the counter, service the conveyor belt,
+		and then finally unpause the counter to continue where it had
+		left off.
+
+What:		/sys/bus/counter/devices/counterX/countY/error_noise
+KernelVersion:	4.18
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Read-only attribute that indicates whether excessive noise is
+		present at the channel Y counter inputs.
+
+What:		/sys/bus/counter/devices/counterX/countY/function
+KernelVersion:	4.18
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Count function mode of Count Y; count function evaluation is
+		triggered by conditions specified by the Count Y signalZ_action
+		attributes. The following count functions are available:
+
+		Increase:
+			Accumulated count is incremented.
+
+		Decrease:
+			Accumulated count is decremented.
+
+		Pulse-Direction:
+			Rising edges on quadrature pair signal A updates the
+			respective count. The input level of quadrature pair
+			signal B determines direction.
+
+		Quadrature x1 A:
+			If direction is forward, rising edges on quadrature pair
+			signal A updates the respective count; if the direction
+			is backward, falling edges on quadrature pair signal A
+			updates the respective count. Quadrature encoding
+			determines the direction.
+
+		Quadrature x1 B:
+			If direction is forward, rising edges on quadrature pair
+			signal B updates the respective count; if the direction
+			is backward, falling edges on quadrature pair signal B
+			updates the respective count. Quadrature encoding
+			determines the direction.
+
+		Quadrature x2 A:
+			Any state transition on quadrature pair signal A updates
+			the respective count. Quadrature encoding determines the
+			direction.
+
+		Quadrature x2 B:
+			Any state transition on quadrature pair signal B updates
+			the respective count. Quadrature encoding determines the
+			direction.
+
+		Quadrature x2 Rising:
+			Rising edges on either quadrature pair signals updates
+			the respective count. Quadrature encoding determines the
+			direction.
+
+		Quadrature x2 Falling:
+			Falling edges on either quadrature pair signals updates
+			the respective count. Quadrature encoding determines the
+			direction.
+
+		Quadrature x4:
+			Any state transition on either quadrature pair signals
+			updates	the respective count. Quadrature encoding
+			determines the direction.
+
+What:		/sys/bus/counter/devices/counterX/countY/name
+KernelVersion:	4.18
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Read-only attribute that indicates the device-specific name of
+		Count Y. If possible, this should match the name of the
+		respective channel as it appears in the device datasheet
+		documentation text.
+
+What:		/sys/bus/counter/devices/counterX/countY/preset
+KernelVersion:	4.18
+Contact:	linux-iio@vger.kernel.org
+Description:
+		If the counter device supports preset registers, the preset
+		count for channel Y is provided by this attribute.
+
+What:		/sys/bus/counter/devices/counterX/countY/preset_enable
+KernelVersion:	4.18
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Whether channel Y counter preset operation is enabled. Valid
+		attribute values are boolean.
+
+What:		/sys/bus/counter/devices/counterX/countY/signalZ_action
+KernelVersion:	4.18
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Action mode of Count Y for Signal Z. This attribute indicates
+		the condition of Signal Z that triggers the count function
+		evaluation for Count Y. The following action modes are
+		available:
+
+		None:
+			Signal does not trigger the count function. In
+			Pulse-Direction count function mode, this Signal is
+			evaluated as Direction.
+
+		Rising Edge:
+			Low state transitions to high state.
+
+		Falling Edge:
+			High state transitions to low state.
+
+		Both Edges:
+			Any state transition.
+
+What:		/sys/bus/counter/devices/counterX/name
+KernelVersion:	4.18
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Read-only attribute that indicates the device-specific name of
+		the Counter. This should match the name of the device as it
+		appears in its respective datasheet documentation text.
+
+What:		/sys/bus/counter/devices/counterX/num_counts
+KernelVersion:	4.18
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Read-only attribute that indicates the total number of Counts
+		belonging to the Counter.
+
+What:		/sys/bus/counter/devices/counterX/num_signals
+KernelVersion:	4.18
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Read-only attribute that indicates the total number of Signals
+		belonging to the Counter.
+
+What:		/sys/bus/counter/devices/counterX/signalY/signal
+KernelVersion:	4.18
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Signal data of Signal Y represented as a string.
+
+What:		/sys/bus/counter/devices/counterX/signalY/name
+KernelVersion:	4.18
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Read-only attribute that indicates the device-specific name of
+		Signal Y. If possible, this should match the name of the
+		respective signal as it appears in the device datasheet
+		documentation text.
diff --git a/MAINTAINERS b/MAINTAINERS
index 2a016d73ab72..1413e3eb49e5 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3673,6 +3673,7 @@ COUNTER SUBSYSTEM
 M:	William Breathitt Gray <vilhelm.gray@gmail.com>
 L:	linux-iio@vger.kernel.org
 S:	Maintained
+F:	Documentation/ABI/testing/sysfs-bus-counter*
 F:	drivers/counter/
 F:	include/linux/counter.h
 
-- 
2.17.0

[PATCH v6 3/9] docs: Add Generic Counter interface documentation

[William Breathitt Gray]

This patch adds high-level documentation about the Generic Counter
interface.

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
---
 Documentation/driver-api/generic-counter.rst | 336 +++++++++++++++++++
 Documentation/driver-api/index.rst           |   1 +
 MAINTAINERS                                  |   1 +
 3 files changed, 338 insertions(+)
 create mode 100644 Documentation/driver-api/generic-counter.rst

diff --git a/Documentation/driver-api/generic-counter.rst b/Documentation/driver-api/generic-counter.rst
new file mode 100644
index 000000000000..5c6b9c008c06
--- /dev/null
+++ b/Documentation/driver-api/generic-counter.rst
@@ -0,0 +1,336 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=========================
+Generic Counter Interface
+=========================
+
+Introduction
+============
+
+Counter devices are prevalent within a diverse spectrum of industries.
+The ubiquitous presence of these devices necessitates a common interface
+and standard of interaction and exposure. This driver API attempts to
+resolve the issue of duplicate code found among existing counter device
+drivers by introducing a generic counter interface for consumption. The
+Generic Counter interface enables drivers to support and expose a common
+set of components and functionality present in counter devices.
+
+Theory
+======
+
+Counter devices can vary greatly in design, but regardless of whether
+some devices are quadrature encoder counters or tally counters, all
+counter devices consist of a core set of components. This core set of
+components, shared by all counter devices, is what forms the essence of
+the Generic Counter interface.
+
+There are three core components to a counter:
+
+COUNT
+-----
+A Count represents the count data for a set of Signals. The Generic
+Counter interface provides the following available count data types:
+
+* COUNT_POSITION_UNSIGNED:
+  Unsigned integer value representing position.
+
+* COUNT_POSITION_SIGNED:
+  Signed integer value representing position.
+
+A Count has a count function mode which represents the update behavior
+for the count data. The Generic Counter interface provides the following
+available count function modes:
+
+* Increase:
+  Accumulated count is incremented.
+
+* Decrease:
+  Accumulated count is decremented.
+
+* Pulse-Direction:
+  Rising edges on quadrature pair signal A updates the respective count.
+  The input level of quadrature pair signal B determines direction.
+
+* Quadrature x1 A:
+  If direction is forward, rising edges on quadrature pair signal A
+  updates the respective count; if the direction is backward, falling
+  edges on quadrature pair signal A updates the respective count.
+  Quadrature encoding determines the direction.
+
+* Quadrature x1 B:
+  If direction is forward, rising edges on quadrature pair signal B
+  updates the respective count; if the direction is backward, falling
+  edges on quadrature pair signal B updates the respective count.
+  Quadrature encoding determines the direction.
+
+* Quadrature x2 A:
+  Any state transition on quadrature pair signal A updates the
+  respective count. Quadrature encoding determines the direction.
+
+* Quadrature x2 B:
+  Any state transition on quadrature pair signal B updates the
+  respective count. Quadrature encoding determines the direction.
+
+* Quadrature x2 Rising:
+  Rising edges on either quadrature pair signals updates the respective
+  count. Quadrature encoding determines the direction.
+
+* Quadrature x2 Falling:
+  Falling edges on either quadrature pair signals updates the respective
+  count. Quadrature encoding determines the direction.
+
+* Quadrature x4:
+  Any state transition on either quadrature pair signals updates the
+  respective count. Quadrature encoding determines the direction.
+
+A Count has a set of one or more associated Signals.
+
+SIGNAL
+------
+A Signal represents a counter input data; this is the input data that is
+analyzed by the counter to determine the count data; e.g. a quadrature
+signal output line of a rotary encoder. Not all counter devices provide
+user access to the Signal data.
+
+The Generic Counter interface provides the following available signal
+data types for when the Signal data is available for user access:
+
+* SIGNAL_LEVEL_LOW:
+  Signal line is in a low state.
+
+* SIGNAL_LEVEL_HIGH:
+  Signal line is in a high state.
+
+A Signal may be associated with one or more Counts.
+
+SYNAPSE
+-------
+A Synapse represents the association of a Signal with a respective
+Count. Signal data affects respective Count data, and the Synapse
+represents this relationship.
+
+The Synapse action mode specifies the Signal data condition which
+triggers the respective Count's count function evaluation to update the
+count data. The Generic Counter interface provides the following
+available action modes:
+
+* None:
+  Signal does not trigger the count function. In Pulse-Direction count
+  function mode, this Signal is evaluated as Direction.
+
+* Rising Edge:
+  Low state transitions to high state.
+
+* Falling Edge:
+  High state transitions to low state.
+
+* Both Edges:
+  Any state transition.
+
+A counter is defined as a set of input signals associated with count
+data that are generated by the evaluation of the state of the associated
+input signals as defined by the respective count functions. Within the
+context of the Generic Counter interface, a counter consists of Counts
+each associated with a set of Signals, whose respective Synapse
+instances represent the count function update conditions for the
+associated Counts.
+
+Paradigm
+========
+
+The most basic counter device may be expressed as a single Count
+associated with a single Signal via a single Synapse. Take for example
+a counter device which simply accumulates a count of rising edges on a
+source input line::
+
+                Count                Synapse        Signal
+                -----                -------        ------
+        +---------------------+
+        | Data: Count         |    Rising Edge     ________
+        | Function: Increase  |  <-------------   / Source \
+        |                     |                  ____________
+        +---------------------+
+
+In this example, the Signal is a source input line with a pulsing
+voltage, while the Count is a persistent count value which is repeatedly
+incremented. The Signal is associated with the respective Count via a
+Synapse. The increase function is triggered by the Signal data condition
+specified by the Synapse -- in this case a rising edge condition on the
+voltage input line. In summary, the counter device existence and
+behavior is aptly represented by respective Count, Signal, and Synapse
+components: a rising edge condition triggers an increase function on an
+accumulating count datum.
+
+A counter device is not limited to a single Signal; in fact, in theory
+many Signals may be associated with even a single Count. For example, a
+quadrature encoder counter device can keep track of position based on
+the states of two input lines::
+
+                   Count                 Synapse     Signal
+                   -----                 -------     ------
+        +-------------------------+
+        | Data: Position          |    Both Edges     ___
+        | Function: Quadrature x4 |  <------------   / A \
+        |                         |                 _______
+        |                         |
+        |                         |    Both Edges     ___
+        |                         |  <------------   / B \
+        |                         |                 _______
+        +-------------------------+
+
+In this example, two Signals (quadrature encoder lines A and B) are
+associated with a single Count: a rising or falling edge on either A or
+B triggers the "Quadrature x4" function which determines the direction
+of movement and updates the respective position data. The "Quadrature
+x4" function is likely implemented in the hardware of the quadrature
+encoder counter device; the Count, Signals, and Synapses simply
+represent this hardware behavior and functionality.
+
+Signals associated with the same Count can have differing Synapse action
+mode conditions. For example, a quadrature encoder counter device
+operating in a non-quadrature Pulse-Direction mode could have one input
+line dedicated for movement and a second input line dedicated for
+direction::
+
+                   Count                   Synapse      Signal
+                   -----                   -------      ------
+        +---------------------------+
+        | Data: Position            |    Rising Edge     ___
+        | Function: Pulse-Direction |  <-------------   / A \ (Movement)
+        |                           |                  _______
+        |                           |
+        |                           |       None         ___
+        |                           |  <-------------   / B \ (Direction)
+        |                           |                  _______
+        +---------------------------+
+
+Only Signal A triggers the "Pulse-Direction" update function, but the
+instantaneous state of Signal B is still required in order to know the
+direction so that the position data may be properly updated. Ultimately,
+both Signals are associated with the same Count via two respective
+Synapses, but only one Synapse has an active action mode condition which
+triggers the respective count function while the other is left with a
+"None" condition action mode to indicate its respective Signal's
+availability for state evaluation despite its non-triggering mode.
+
+Keep in mind that the Signal, Synapse, and Count are abstract
+representations which do not need to be closely married to their
+respective physical sources. This allows the user of a counter to
+divorce themselves from the nuances of physical components (such as
+whether an input line is differential or single-ended) and instead focus
+on the core idea of what the data and process represent (e.g. position
+as interpreted from quadrature encoding data).
+
+Userspace Interface
+===================
+
+Several sysfs attributes are generated by the Generic Counter interface,
+and reside under the /sys/bus/counter/devices/counterX directory, where
+counterX refers to the respective counter device. Please see
+Documentation/ABI/testing/sys-bus-counter-generic-sysfs for detailed
+information on each Generic Counter interface sysfs attribute.
+
+Through these sysfs attributes, programs and scripts may interact with
+the Generic Counter paradigm Counts, Signals, and Synapses of respective
+counter devices.
+
+Driver API
+==========
+
+Driver authors may utilize the Generic Counter interface in their code
+by including the include/linux/iio/counter.h header file. This header
+file provides several core data structures, function prototypes, and
+macros for defining a counter device.
+
+.. kernel-doc:: include/linux/counter.h
+   :internal:
+
+.. kernel-doc:: drivers/counter/generic-counter.c
+   :export:
+
+Implementation
+==============
+
+To support a counter device, a driver must first allocate the available
+Counter Signals via counter_signal structures. These Signals should
+be stored as an array and set to the signals array member of an
+allocated counter_device structure before the Counter is registered to
+the system.
+
+Counter Counts may be allocated via counter_count structures, and
+respective Counter Signal associations (Synapses) made via
+counter_synapse structures. Associated counter_synapse structures are
+stored as an array and set to the the synapses array member of the
+respective counter_count structure. These counter_count structures are
+set to the counts array member of an allocated counter_device structure
+before the Counter is registered to the system.
+
+Driver callbacks should be provided to the counter_device structure via
+a constant counter_ops structure in order to communicate with the
+device: to read and write various Signals and Counts, and to set and get
+the "action mode" and "function mode" for various Synapses and Counts
+respectively.
+
+A defined counter_device structure may be registered to the system by
+passing it to the counter_register function, and unregistered by passing
+it to the counter_unregister function. Similarly, the
+devm_counter_register and devm_counter_unregister functions may be used
+if device memory-managed registration is desired.
+
+Extension sysfs attributes can be created for auxiliary functionality
+and data by passing in defined counter_device_ext, counter_count_ext,
+and counter_signal_ext structures. In these cases, the
+counter_device_ext structure is used for global configuration of the
+respective Counter device, while the counter_count_ext and
+counter_signal_ext structures allow for auxiliary exposure and
+configuration of a specific Count or Signal respectively.
+
+Architecture
+============
+
+When the Generic Counter interface counter module is loaded, the
+counter_init function is called which registers a bus_type named
+"counter" to the system. Subsequently, when the module is unloaded, the
+counter_exit function is called which unregisters the bus_type named
+"counter" from the system.
+
+Counter devices are registered to the system via the counter_register
+function, and later removed via the counter_unregister function. The
+counter_register function establishes a unique ID for the Counter
+device and creates a respective sysfs directory, where X is the
+mentioned unique ID:
+
+    /sys/bus/counter/devices/counterX
+
+Sysfs attributes are created within the counterX directory to expose
+functionality, configurations, and data relating to the Counts, Signals,
+and Synapses of the Counter device, as well as options and information
+for the Counter device itself.
+
+Each Signal has a directory created to house its relevant sysfs
+attributes, where Y is the unique ID of the respective Signal:
+
+    /sys/bus/counter/devices/counterX/signalY
+
+Similarly, each Count has a directory created to house its relevant
+sysfs attributes, where Y is the unique ID of the respective Count:
+
+    /sys/bus/counter/devices/counterX/countY
+
+For a more detailed breakdown of the available Generic Counter interface
+sysfs attributes, please refer to the
+Documentation/ABI/testing/sys-bus-counter file.
+
+The Signals and Counts associated with the Counter device are registered
+to the system as well by the counter_register function. The
+signal_read/signal_write driver callbacks are associated with their
+respective Signal attributes, while the count_read/count_write and
+function_get/function_set driver callbacks are associated with their
+respective Count attributes; similarly, the same is true for the
+action_get/action_set driver callbacks and their respective Synapse
+attributes. If a driver callback is left undefined, then the respective
+read/write permission is left disabled for the relevant attributes.
+
+Similarly, extension sysfs attributes are created for the defined
+counter_device_ext, counter_count_ext, and counter_signal_ext
+structures that are passed in.
diff --git a/Documentation/driver-api/index.rst b/Documentation/driver-api/index.rst
index 6d8352c0f354..5fd747c4f2ce 100644
--- a/Documentation/driver-api/index.rst
+++ b/Documentation/driver-api/index.rst
@@ -25,6 +25,7 @@ available subsections can be seen below.
    frame-buffer
    regulator
    iio/index
+   generic-counter
    input
    usb/index
    pci
diff --git a/MAINTAINERS b/MAINTAINERS
index 1413e3eb49e5..7a01aa63fb33 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3674,6 +3674,7 @@ M:	William Breathitt Gray <vilhelm.gray@gmail.com>
 L:	linux-iio@vger.kernel.org
 S:	Maintained
 F:	Documentation/ABI/testing/sysfs-bus-counter*
+F:	Documentation/driver-api/generic-counter.rst
 F:	drivers/counter/
 F:	include/linux/counter.h
 
-- 
2.17.0

[PATCH v6 4/9] counter: 104-quad-8: Add Generic Counter interface support

[William Breathitt Gray]

This patch adds support for the Generic Counter interface to the
104-QUAD-8 driver. The existing 104-QUAD-8 device interface should not
be affected by this patch; all changes are intended as supplemental
additions as perceived by the user.

Generic Counter Counts are created for the eight quadrature channel
counts, as well as their respective quadrature A and B Signals (which
are associated via respective Synapse structures) and respective index
Signals.

The new Generic Counter interface sysfs attributes are intended to
expose the same functionality and data available via the existing
104-QUAD-8 IIO device interface; the Generic Counter interface serves
to provide the respective functionality and data in a standard way
expected of counter devices.

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
---
 MAINTAINERS                      |    4 +-
 drivers/counter/104-quad-8.c     | 1335 ++++++++++++++++++++++++++++++
 drivers/counter/Kconfig          |   21 +
 drivers/counter/Makefile         |    2 +
 drivers/iio/counter/104-quad-8.c |  596 -------------
 drivers/iio/counter/Kconfig      |   17 -
 drivers/iio/counter/Makefile     |    1 -
 7 files changed, 1360 insertions(+), 616 deletions(-)
 create mode 100644 drivers/counter/104-quad-8.c
 delete mode 100644 drivers/iio/counter/104-quad-8.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 7a01aa63fb33..f11bf7885aeb 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -266,12 +266,12 @@ L:	linux-gpio@vger.kernel.org
 S:	Maintained
 F:	drivers/gpio/gpio-104-idio-16.c
 
-ACCES 104-QUAD-8 IIO DRIVER
+ACCES 104-QUAD-8 DRIVER
 M:	William Breathitt Gray <vilhelm.gray@gmail.com>
 L:	linux-iio@vger.kernel.org
 S:	Maintained
 F:	Documentation/ABI/testing/sysfs-bus-iio-counter-104-quad-8
-F:	drivers/iio/counter/104-quad-8.c
+F:	drivers/counter/104-quad-8.c
 
 ACCES PCI-IDIO-16 GPIO DRIVER
 M:	William Breathitt Gray <vilhelm.gray@gmail.com>
diff --git a/drivers/counter/104-quad-8.c b/drivers/counter/104-quad-8.c
new file mode 100644
index 000000000000..7c72fb72d660
--- /dev/null
+++ b/drivers/counter/104-quad-8.c
@@ -0,0 +1,1335 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * IIO driver for the ACCES 104-QUAD-8
+ * Copyright (C) 2016 William Breathitt Gray
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2, as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * This driver supports the ACCES 104-QUAD-8 and ACCES 104-QUAD-4.
+ */
+#include <linux/bitops.h>
+#include <linux/counter.h>
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/types.h>
+#include <linux/io.h>
+#include <linux/ioport.h>
+#include <linux/isa.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/types.h>
+
+#define QUAD8_EXTENT 32
+
+static unsigned int base[max_num_isa_dev(QUAD8_EXTENT)];
+static unsigned int num_quad8;
+module_param_array(base, uint, &num_quad8, 0);
+MODULE_PARM_DESC(base, "ACCES 104-QUAD-8 base addresses");
+
+#define QUAD8_NUM_COUNTERS 8
+
+/**
+ * struct quad8_iio - IIO device private data structure
+ * @counter:		instance of the counter_device
+ * @preset:		array of preset values
+ * @count_mode:		array of count mode configurations
+ * @quadrature_mode:	array of quadrature mode configurations
+ * @quadrature_scale:	array of quadrature mode scale configurations
+ * @ab_enable:		array of A and B inputs enable configurations
+ * @preset_enable:	array of set_to_preset_on_index attribute configurations
+ * @synchronous_mode:	array of index function synchronous mode configurations
+ * @index_polarity:	array of index function polarity configurations
+ * @base:		base port address of the IIO device
+ */
+struct quad8_iio {
+	struct counter_device counter;
+	unsigned int preset[QUAD8_NUM_COUNTERS];
+	unsigned int count_mode[QUAD8_NUM_COUNTERS];
+	unsigned int quadrature_mode[QUAD8_NUM_COUNTERS];
+	unsigned int quadrature_scale[QUAD8_NUM_COUNTERS];
+	unsigned int ab_enable[QUAD8_NUM_COUNTERS];
+	unsigned int preset_enable[QUAD8_NUM_COUNTERS];
+	unsigned int synchronous_mode[QUAD8_NUM_COUNTERS];
+	unsigned int index_polarity[QUAD8_NUM_COUNTERS];
+	unsigned int base;
+};
+
+static int quad8_read_raw(struct iio_dev *indio_dev,
+	struct iio_chan_spec const *chan, int *val, int *val2, long mask)
+{
+	struct quad8_iio *const priv = iio_priv(indio_dev);
+	const int base_offset = priv->base + 2 * chan->channel;
+	unsigned int flags;
+	unsigned int borrow;
+	unsigned int carry;
+	int i;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		if (chan->type == IIO_INDEX) {
+			*val = !!(inb(priv->base + 0x16) & BIT(chan->channel));
+			return IIO_VAL_INT;
+		}
+
+		flags = inb(base_offset + 1);
+		borrow = flags & BIT(0);
+		carry = !!(flags & BIT(1));
+
+		/* Borrow XOR Carry effectively doubles count range */
+		*val = (borrow ^ carry) << 24;
+
+		/* Reset Byte Pointer; transfer Counter to Output Latch */
+		outb(0x11, base_offset + 1);
+
+		for (i = 0; i < 3; i++)
+			*val |= (unsigned int)inb(base_offset) << (8 * i);
+
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_ENABLE:
+		*val = priv->ab_enable[chan->channel];
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		*val = 1;
+		*val2 = priv->quadrature_scale[chan->channel];
+		return IIO_VAL_FRACTIONAL_LOG2;
+	}
+
+	return -EINVAL;
+}
+
+static int quad8_write_raw(struct iio_dev *indio_dev,
+	struct iio_chan_spec const *chan, int val, int val2, long mask)
+{
+	struct quad8_iio *const priv = iio_priv(indio_dev);
+	const int base_offset = priv->base + 2 * chan->channel;
+	int i;
+	unsigned int ior_cfg;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		if (chan->type == IIO_INDEX)
+			return -EINVAL;
+
+		/* Only 24-bit values are supported */
+		if ((unsigned int)val > 0xFFFFFF)
+			return -EINVAL;
+
+		/* Reset Byte Pointer */
+		outb(0x01, base_offset + 1);
+
+		/* Counter can only be set via Preset Register */
+		for (i = 0; i < 3; i++)
+			outb(val >> (8 * i), base_offset);
+
+		/* Transfer Preset Register to Counter */
+		outb(0x08, base_offset + 1);
+
+		/* Reset Byte Pointer */
+		outb(0x01, base_offset + 1);
+
+		/* Set Preset Register back to original value */
+		val = priv->preset[chan->channel];
+		for (i = 0; i < 3; i++)
+			outb(val >> (8 * i), base_offset);
+
+		/* Reset Borrow, Carry, Compare, and Sign flags */
+		outb(0x02, base_offset + 1);
+		/* Reset Error flag */
+		outb(0x06, base_offset + 1);
+
+		return 0;
+	case IIO_CHAN_INFO_ENABLE:
+		/* only boolean values accepted */
+		if (val < 0 || val > 1)
+			return -EINVAL;
+
+		priv->ab_enable[chan->channel] = val;
+
+		ior_cfg = val | priv->preset_enable[chan->channel] << 1;
+
+		/* Load I/O control configuration */
+		outb(0x40 | ior_cfg, base_offset + 1);
+
+		return 0;
+	case IIO_CHAN_INFO_SCALE:
+		/* Quadrature scaling only available in quadrature mode */
+		if (!priv->quadrature_mode[chan->channel] && (val2 || val != 1))
+			return -EINVAL;
+
+		/* Only three gain states (1, 0.5, 0.25) */
+		if (val == 1 && !val2)
+			priv->quadrature_scale[chan->channel] = 0;
+		else if (!val)
+			switch (val2) {
+			case 500000:
+				priv->quadrature_scale[chan->channel] = 1;
+				break;
+			case 250000:
+				priv->quadrature_scale[chan->channel] = 2;
+				break;
+			default:
+				return -EINVAL;
+			}
+		else
+			return -EINVAL;
+
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
+static const struct iio_info quad8_info = {
+	.read_raw = quad8_read_raw,
+	.write_raw = quad8_write_raw
+};
+
+static ssize_t quad8_read_preset(struct iio_dev *indio_dev, uintptr_t private,
+	const struct iio_chan_spec *chan, char *buf)
+{
+	const struct quad8_iio *const priv = iio_priv(indio_dev);
+
+	return snprintf(buf, PAGE_SIZE, "%u\n", priv->preset[chan->channel]);
+}
+
+static ssize_t quad8_write_preset(struct iio_dev *indio_dev, uintptr_t private,
+	const struct iio_chan_spec *chan, const char *buf, size_t len)
+{
+	struct quad8_iio *const priv = iio_priv(indio_dev);
+	const int base_offset = priv->base + 2 * chan->channel;
+	unsigned int preset;
+	int ret;
+	int i;
+
+	ret = kstrtouint(buf, 0, &preset);
+	if (ret)
+		return ret;
+
+	/* Only 24-bit values are supported */
+	if (preset > 0xFFFFFF)
+		return -EINVAL;
+
+	priv->preset[chan->channel] = preset;
+
+	/* Reset Byte Pointer */
+	outb(0x01, base_offset + 1);
+
+	/* Set Preset Register */
+	for (i = 0; i < 3; i++)
+		outb(preset >> (8 * i), base_offset);
+
+	return len;
+}
+
+static ssize_t quad8_read_set_to_preset_on_index(struct iio_dev *indio_dev,
+	uintptr_t private, const struct iio_chan_spec *chan, char *buf)
+{
+	const struct quad8_iio *const priv = iio_priv(indio_dev);
+
+	return snprintf(buf, PAGE_SIZE, "%u\n",
+		!priv->preset_enable[chan->channel]);
+}
+
+static ssize_t quad8_write_set_to_preset_on_index(struct iio_dev *indio_dev,
+	uintptr_t private, const struct iio_chan_spec *chan, const char *buf,
+	size_t len)
+{
+	struct quad8_iio *const priv = iio_priv(indio_dev);
+	const int base_offset = priv->base + 2 * chan->channel + 1;
+	bool preset_enable;
+	int ret;
+	unsigned int ior_cfg;
+
+	ret = kstrtobool(buf, &preset_enable);
+	if (ret)
+		return ret;
+
+	/* Preset enable is active low in Input/Output Control register */
+	preset_enable = !preset_enable;
+
+	priv->preset_enable[chan->channel] = preset_enable;
+
+	ior_cfg = priv->ab_enable[chan->channel] |
+		(unsigned int)preset_enable << 1;
+
+	/* Load I/O control configuration to Input / Output Control Register */
+	outb(0x40 | ior_cfg, base_offset);
+
+	return len;
+}
+
+static const char *const quad8_noise_error_states[] = {
+	"No excessive noise is present at the count inputs",
+	"Excessive noise is present at the count inputs"
+};
+
+static int quad8_get_noise_error(struct iio_dev *indio_dev,
+	const struct iio_chan_spec *chan)
+{
+	struct quad8_iio *const priv = iio_priv(indio_dev);
+	const int base_offset = priv->base + 2 * chan->channel + 1;
+
+	return !!(inb(base_offset) & BIT(4));
+}
+
+static const struct iio_enum quad8_noise_error_enum = {
+	.items = quad8_noise_error_states,
+	.num_items = ARRAY_SIZE(quad8_noise_error_states),
+	.get = quad8_get_noise_error
+};
+
+static const char *const quad8_count_direction_states[] = {
+	"down",
+	"up"
+};
+
+static int quad8_get_count_direction(struct iio_dev *indio_dev,
+	const struct iio_chan_spec *chan)
+{
+	struct quad8_iio *const priv = iio_priv(indio_dev);
+	const int base_offset = priv->base + 2 * chan->channel + 1;
+
+	return !!(inb(base_offset) & BIT(5));
+}
+
+static const struct iio_enum quad8_count_direction_enum = {
+	.items = quad8_count_direction_states,
+	.num_items = ARRAY_SIZE(quad8_count_direction_states),
+	.get = quad8_get_count_direction
+};
+
+static const char *const quad8_count_modes[] = {
+	"normal",
+	"range limit",
+	"non-recycle",
+	"modulo-n"
+};
+
+static int quad8_set_count_mode(struct iio_dev *indio_dev,
+	const struct iio_chan_spec *chan, unsigned int cnt_mode)
+{
+	struct quad8_iio *const priv = iio_priv(indio_dev);
+	unsigned int mode_cfg = cnt_mode << 1;
+	const int base_offset = priv->base + 2 * chan->channel + 1;
+
+	priv->count_mode[chan->channel] = cnt_mode;
+
+	/* Add quadrature mode configuration */
+	if (priv->quadrature_mode[chan->channel])
+		mode_cfg |= (priv->quadrature_scale[chan->channel] + 1) << 3;
+
+	/* Load mode configuration to Counter Mode Register */
+	outb(0x20 | mode_cfg, base_offset);
+
+	return 0;
+}
+
+static int quad8_get_count_mode(struct iio_dev *indio_dev,
+	const struct iio_chan_spec *chan)
+{
+	const struct quad8_iio *const priv = iio_priv(indio_dev);
+
+	return priv->count_mode[chan->channel];
+}
+
+static const struct iio_enum quad8_count_mode_enum = {
+	.items = quad8_count_modes,
+	.num_items = ARRAY_SIZE(quad8_count_modes),
+	.set = quad8_set_count_mode,
+	.get = quad8_get_count_mode
+};
+
+static const char *const quad8_synchronous_modes[] = {
+	"non-synchronous",
+	"synchronous"
+};
+
+static int quad8_set_synchronous_mode(struct iio_dev *indio_dev,
+	const struct iio_chan_spec *chan, unsigned int synchronous_mode)
+{
+	struct quad8_iio *const priv = iio_priv(indio_dev);
+	const unsigned int idr_cfg = synchronous_mode |
+		priv->index_polarity[chan->channel] << 1;
+	const int base_offset = priv->base + 2 * chan->channel + 1;
+
+	/* Index function must be non-synchronous in non-quadrature mode */
+	if (synchronous_mode && !priv->quadrature_mode[chan->channel])
+		return -EINVAL;
+
+	priv->synchronous_mode[chan->channel] = synchronous_mode;
+
+	/* Load Index Control configuration to Index Control Register */
+	outb(0x60 | idr_cfg, base_offset);
+
+	return 0;
+}
+
+static int quad8_get_synchronous_mode(struct iio_dev *indio_dev,
+	const struct iio_chan_spec *chan)
+{
+	const struct quad8_iio *const priv = iio_priv(indio_dev);
+
+	return priv->synchronous_mode[chan->channel];
+}
+
+static const struct iio_enum quad8_synchronous_mode_enum = {
+	.items = quad8_synchronous_modes,
+	.num_items = ARRAY_SIZE(quad8_synchronous_modes),
+	.set = quad8_set_synchronous_mode,
+	.get = quad8_get_synchronous_mode
+};
+
+static const char *const quad8_quadrature_modes[] = {
+	"non-quadrature",
+	"quadrature"
+};
+
+static int quad8_set_quadrature_mode(struct iio_dev *indio_dev,
+	const struct iio_chan_spec *chan, unsigned int quadrature_mode)
+{
+	struct quad8_iio *const priv = iio_priv(indio_dev);
+	unsigned int mode_cfg = priv->count_mode[chan->channel] << 1;
+	const int base_offset = priv->base + 2 * chan->channel + 1;
+
+	if (quadrature_mode)
+		mode_cfg |= (priv->quadrature_scale[chan->channel] + 1) << 3;
+	else {
+		/* Quadrature scaling only available in quadrature mode */
+		priv->quadrature_scale[chan->channel] = 0;
+
+		/* Synchronous function not supported in non-quadrature mode */
+		if (priv->synchronous_mode[chan->channel])
+			quad8_set_synchronous_mode(indio_dev, chan, 0);
+	}
+
+	priv->quadrature_mode[chan->channel] = quadrature_mode;
+
+	/* Load mode configuration to Counter Mode Register */
+	outb(0x20 | mode_cfg, base_offset);
+
+	return 0;
+}
+
+static int quad8_get_quadrature_mode(struct iio_dev *indio_dev,
+	const struct iio_chan_spec *chan)
+{
+	const struct quad8_iio *const priv = iio_priv(indio_dev);
+
+	return priv->quadrature_mode[chan->channel];
+}
+
+static const struct iio_enum quad8_quadrature_mode_enum = {
+	.items = quad8_quadrature_modes,
+	.num_items = ARRAY_SIZE(quad8_quadrature_modes),
+	.set = quad8_set_quadrature_mode,
+	.get = quad8_get_quadrature_mode
+};
+
+static const char *const quad8_index_polarity_modes[] = {
+	"negative",
+	"positive"
+};
+
+static int quad8_set_index_polarity(struct iio_dev *indio_dev,
+	const struct iio_chan_spec *chan, unsigned int index_polarity)
+{
+	struct quad8_iio *const priv = iio_priv(indio_dev);
+	const unsigned int idr_cfg = priv->synchronous_mode[chan->channel] |
+		index_polarity << 1;
+	const int base_offset = priv->base + 2 * chan->channel + 1;
+
+	priv->index_polarity[chan->channel] = index_polarity;
+
+	/* Load Index Control configuration to Index Control Register */
+	outb(0x60 | idr_cfg, base_offset);
+
+	return 0;
+}
+
+static int quad8_get_index_polarity(struct iio_dev *indio_dev,
+	const struct iio_chan_spec *chan)
+{
+	const struct quad8_iio *const priv = iio_priv(indio_dev);
+
+	return priv->index_polarity[chan->channel];
+}
+
+static const struct iio_enum quad8_index_polarity_enum = {
+	.items = quad8_index_polarity_modes,
+	.num_items = ARRAY_SIZE(quad8_index_polarity_modes),
+	.set = quad8_set_index_polarity,
+	.get = quad8_get_index_polarity
+};
+
+static const struct iio_chan_spec_ext_info quad8_count_ext_info[] = {
+	{
+		.name = "preset",
+		.shared = IIO_SEPARATE,
+		.read = quad8_read_preset,
+		.write = quad8_write_preset
+	},
+	{
+		.name = "set_to_preset_on_index",
+		.shared = IIO_SEPARATE,
+		.read = quad8_read_set_to_preset_on_index,
+		.write = quad8_write_set_to_preset_on_index
+	},
+	IIO_ENUM("noise_error", IIO_SEPARATE, &quad8_noise_error_enum),
+	IIO_ENUM_AVAILABLE("noise_error", &quad8_noise_error_enum),
+	IIO_ENUM("count_direction", IIO_SEPARATE, &quad8_count_direction_enum),
+	IIO_ENUM_AVAILABLE("count_direction", &quad8_count_direction_enum),
+	IIO_ENUM("count_mode", IIO_SEPARATE, &quad8_count_mode_enum),
+	IIO_ENUM_AVAILABLE("count_mode", &quad8_count_mode_enum),
+	IIO_ENUM("quadrature_mode", IIO_SEPARATE, &quad8_quadrature_mode_enum),
+	IIO_ENUM_AVAILABLE("quadrature_mode", &quad8_quadrature_mode_enum),
+	{}
+};
+
+static const struct iio_chan_spec_ext_info quad8_index_ext_info[] = {
+	IIO_ENUM("synchronous_mode", IIO_SEPARATE,
+		&quad8_synchronous_mode_enum),
+	IIO_ENUM_AVAILABLE("synchronous_mode", &quad8_synchronous_mode_enum),
+	IIO_ENUM("index_polarity", IIO_SEPARATE, &quad8_index_polarity_enum),
+	IIO_ENUM_AVAILABLE("index_polarity", &quad8_index_polarity_enum),
+	{}
+};
+
+#define QUAD8_COUNT_CHAN(_chan) {					\
+	.type = IIO_COUNT,						\
+	.channel = (_chan),						\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |			\
+		BIT(IIO_CHAN_INFO_ENABLE) | BIT(IIO_CHAN_INFO_SCALE),	\
+	.ext_info = quad8_count_ext_info,				\
+	.indexed = 1							\
+}
+
+#define QUAD8_INDEX_CHAN(_chan) {			\
+	.type = IIO_INDEX,				\
+	.channel = (_chan),				\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),	\
+	.ext_info = quad8_index_ext_info,		\
+	.indexed = 1					\
+}
+
+static const struct iio_chan_spec quad8_channels[] = {
+	QUAD8_COUNT_CHAN(0), QUAD8_INDEX_CHAN(0),
+	QUAD8_COUNT_CHAN(1), QUAD8_INDEX_CHAN(1),
+	QUAD8_COUNT_CHAN(2), QUAD8_INDEX_CHAN(2),
+	QUAD8_COUNT_CHAN(3), QUAD8_INDEX_CHAN(3),
+	QUAD8_COUNT_CHAN(4), QUAD8_INDEX_CHAN(4),
+	QUAD8_COUNT_CHAN(5), QUAD8_INDEX_CHAN(5),
+	QUAD8_COUNT_CHAN(6), QUAD8_INDEX_CHAN(6),
+	QUAD8_COUNT_CHAN(7), QUAD8_INDEX_CHAN(7)
+};
+
+static int quad8_signal_read(struct counter_device *counter,
+	struct counter_signal *signal, struct signal_read_value *val)
+{
+	const struct quad8_iio *const priv = counter->priv;
+	unsigned int state;
+	enum signal_level level;
+
+	/* Only Index signal levels can be read */
+	if (signal->id < 16)
+		return -EINVAL;
+
+	state = inb(priv->base + 0x16) & BIT(signal->id - 16);
+
+	level = (state) ? SIGNAL_LEVEL_HIGH : SIGNAL_LEVEL_LOW;
+
+	set_signal_read_value(val, SIGNAL_LEVEL, &level);
+
+	return 0;
+}
+
+static int quad8_count_read(struct counter_device *counter,
+	struct counter_count *count, struct count_read_value *val)
+{
+	const struct quad8_iio *const priv = counter->priv;
+	const int base_offset = priv->base + 2 * count->id;
+	unsigned int flags;
+	unsigned int borrow;
+	unsigned int carry;
+	unsigned long position;
+	int i;
+
+	flags = inb(base_offset + 1);
+	borrow = flags & BIT(0);
+	carry = !!(flags & BIT(1));
+
+	/* Borrow XOR Carry effectively doubles count range */
+	position = (unsigned long)(borrow ^ carry) << 24;
+
+	/* Reset Byte Pointer; transfer Counter to Output Latch */
+	outb(0x11, base_offset + 1);
+
+	for (i = 0; i < 3; i++)
+		position |= (unsigned long)inb(base_offset) << (8 * i);
+
+	set_count_read_value(val, COUNT_POSITION_UNSIGNED, &position);
+
+	return 0;
+}
+
+static int quad8_count_write(struct counter_device *counter,
+	struct counter_count *count, struct count_write_value *val)
+{
+	const struct quad8_iio *const priv = counter->priv;
+	const int base_offset = priv->base + 2 * count->id;
+	int err;
+	unsigned long position;
+	int i;
+
+	err = get_count_write_value(&position, COUNT_POSITION_UNSIGNED, val);
+	if (err)
+		return err;
+
+	/* Only 24-bit values are supported */
+	if (position > 0xFFFFFF)
+		return -EINVAL;
+
+	/* Reset Byte Pointer */
+	outb(0x01, base_offset + 1);
+
+	/* Counter can only be set via Preset Register */
+	for (i = 0; i < 3; i++)
+		outb(position >> (8 * i), base_offset);
+
+	/* Transfer Preset Register to Counter */
+	outb(0x08, base_offset + 1);
+
+	/* Reset Byte Pointer */
+	outb(0x01, base_offset + 1);
+
+	/* Set Preset Register back to original value */
+	position = priv->preset[count->id];
+	for (i = 0; i < 3; i++)
+		outb(position >> (8 * i), base_offset);
+
+	/* Reset Borrow, Carry, Compare, and Sign flags */
+	outb(0x02, base_offset + 1);
+	/* Reset Error flag */
+	outb(0x06, base_offset + 1);
+
+	return 0;
+}
+
+enum quad8_count_function {
+	QUAD8_COUNT_FUNCTION_PULSE_DIRECTION = 0,
+	QUAD8_COUNT_FUNCTION_QUADRATURE_X1,
+	QUAD8_COUNT_FUNCTION_QUADRATURE_X2,
+	QUAD8_COUNT_FUNCTION_QUADRATURE_X4
+};
+
+static enum count_function quad8_count_functions_list[] = {
+	[QUAD8_COUNT_FUNCTION_PULSE_DIRECTION] = COUNT_FUNCTION_PULSE_DIRECTION,
+	[QUAD8_COUNT_FUNCTION_QUADRATURE_X1] = COUNT_FUNCTION_QUADRATURE_X1_A,
+	[QUAD8_COUNT_FUNCTION_QUADRATURE_X2] = COUNT_FUNCTION_QUADRATURE_X2_A,
+	[QUAD8_COUNT_FUNCTION_QUADRATURE_X4] = COUNT_FUNCTION_QUADRATURE_X4
+};
+
+static int quad8_function_get(struct counter_device *counter,
+	struct counter_count *count, size_t *function)
+{
+	const struct quad8_iio *const priv = counter->priv;
+	const int id = count->id;
+	const unsigned int quadrature_mode = priv->quadrature_mode[id];
+	const unsigned int scale = priv->quadrature_scale[id];
+
+	if (quadrature_mode)
+		switch (scale) {
+		case 0:
+			*function = QUAD8_COUNT_FUNCTION_QUADRATURE_X1;
+			break;
+		case 1:
+			*function = QUAD8_COUNT_FUNCTION_QUADRATURE_X2;
+			break;
+		case 2:
+			*function = QUAD8_COUNT_FUNCTION_QUADRATURE_X4;
+			break;
+		}
+	else
+		*function = QUAD8_COUNT_FUNCTION_PULSE_DIRECTION;
+
+	return 0;
+}
+
+static int quad8_function_set(struct counter_device *counter,
+	struct counter_count *count, size_t function)
+{
+	struct quad8_iio *const priv = counter->priv;
+	const int id = count->id;
+	unsigned int *const quadrature_mode = priv->quadrature_mode + id;
+	unsigned int *const scale = priv->quadrature_scale + id;
+	unsigned int mode_cfg = priv->count_mode[id] << 1;
+	unsigned int *const synchronous_mode = priv->synchronous_mode + id;
+	const unsigned int idr_cfg = priv->index_polarity[id] << 1;
+	const int base_offset = priv->base + 2 * id + 1;
+
+	if (function == QUAD8_COUNT_FUNCTION_PULSE_DIRECTION) {
+		*quadrature_mode = 0;
+
+		/* Quadrature scaling only available in quadrature mode */
+		*scale = 0;
+
+		/* Synchronous function not supported in non-quadrature mode */
+		if (*synchronous_mode) {
+			*synchronous_mode = 0;
+			/* Disable synchronous function mode */
+			outb(0x60 | idr_cfg, base_offset);
+		}
+	} else {
+		*quadrature_mode = 1;
+
+		switch (function) {
+		case QUAD8_COUNT_FUNCTION_QUADRATURE_X1:
+			*scale = 0;
+			mode_cfg |= 0x8;
+			break;
+		case QUAD8_COUNT_FUNCTION_QUADRATURE_X2:
+			*scale = 1;
+			mode_cfg |= 0x10;
+			break;
+		case QUAD8_COUNT_FUNCTION_QUADRATURE_X4:
+			*scale = 2;
+			mode_cfg |= 0x18;
+			break;
+		}
+	}
+
+	/* Load mode configuration to Counter Mode Register */
+	outb(0x20 | mode_cfg, base_offset);
+
+	return 0;
+}
+
+static void quad8_direction_get(struct counter_device *counter,
+	struct counter_count *count, enum count_direction *direction)
+{
+	const struct quad8_iio *const priv = counter->priv;
+	unsigned int ud_flag;
+	const unsigned int flag_addr = priv->base + 2 * count->id + 1;
+
+	/* U/D flag: nonzero = up, zero = down */
+	ud_flag = inb(flag_addr) & BIT(5);
+
+	*direction = (ud_flag) ? COUNT_DIRECTION_FORWARD :
+		COUNT_DIRECTION_BACKWARD;
+}
+
+enum quad8_synapse_action {
+	QUAD8_SYNAPSE_ACTION_NONE = 0,
+	QUAD8_SYNAPSE_ACTION_RISING_EDGE,
+	QUAD8_SYNAPSE_ACTION_FALLING_EDGE,
+	QUAD8_SYNAPSE_ACTION_BOTH_EDGES
+};
+
+static enum synapse_action quad8_index_actions_list[] = {
+	[QUAD8_SYNAPSE_ACTION_NONE] = SYNAPSE_ACTION_NONE,
+	[QUAD8_SYNAPSE_ACTION_RISING_EDGE] = SYNAPSE_ACTION_RISING_EDGE
+};
+
+static enum synapse_action quad8_synapse_actions_list[] = {
+	[QUAD8_SYNAPSE_ACTION_NONE] = SYNAPSE_ACTION_NONE,
+	[QUAD8_SYNAPSE_ACTION_RISING_EDGE] = SYNAPSE_ACTION_RISING_EDGE,
+	[QUAD8_SYNAPSE_ACTION_FALLING_EDGE] = SYNAPSE_ACTION_FALLING_EDGE,
+	[QUAD8_SYNAPSE_ACTION_BOTH_EDGES] = SYNAPSE_ACTION_BOTH_EDGES
+};
+
+static int quad8_action_get(struct counter_device *counter,
+	struct counter_count *count, struct counter_synapse *synapse,
+	size_t *action)
+{
+	struct quad8_iio *const priv = counter->priv;
+	int err;
+	size_t function = 0;
+	const size_t signal_a_id = count->synapses[0].signal->id;
+	enum count_direction direction;
+
+	/* Handle Index signals */
+	if (synapse->signal->id >= 16) {
+		if (priv->preset_enable[count->id])
+			*action = QUAD8_SYNAPSE_ACTION_RISING_EDGE;
+		else
+			*action = QUAD8_SYNAPSE_ACTION_NONE;
+
+		return 0;
+	}
+
+	err = quad8_function_get(counter, count, &function);
+	if (err)
+		return err;
+
+	/* Default action mode */
+	*action = QUAD8_SYNAPSE_ACTION_NONE;
+
+	/* Determine action mode based on current count function mode */
+	switch (function) {
+	case QUAD8_COUNT_FUNCTION_PULSE_DIRECTION:
+		if (synapse->signal->id == signal_a_id)
+			*action = QUAD8_SYNAPSE_ACTION_RISING_EDGE;
+		break;
+	case QUAD8_COUNT_FUNCTION_QUADRATURE_X1:
+		if (synapse->signal->id == signal_a_id) {
+			quad8_direction_get(counter, count, &direction);
+
+			if (direction == COUNT_DIRECTION_FORWARD)
+				*action = QUAD8_SYNAPSE_ACTION_RISING_EDGE;
+			else
+				*action = QUAD8_SYNAPSE_ACTION_FALLING_EDGE;
+		}
+		break;
+	case QUAD8_COUNT_FUNCTION_QUADRATURE_X2:
+		if (synapse->signal->id == signal_a_id)
+			*action = QUAD8_SYNAPSE_ACTION_BOTH_EDGES;
+		break;
+	case QUAD8_COUNT_FUNCTION_QUADRATURE_X4:
+		*action = QUAD8_SYNAPSE_ACTION_BOTH_EDGES;
+		break;
+	}
+
+	return 0;
+}
+
+const struct counter_ops quad8_ops = {
+	.signal_read = quad8_signal_read,
+	.count_read = quad8_count_read,
+	.count_write = quad8_count_write,
+	.function_get = quad8_function_get,
+	.function_set = quad8_function_set,
+	.action_get = quad8_action_get
+};
+
+static int quad8_index_polarity_get(struct counter_device *counter,
+	struct counter_signal *signal, size_t *index_polarity)
+{
+	const struct quad8_iio *const priv = counter->priv;
+	const size_t channel_id = signal->id - 16;
+
+	*index_polarity = priv->index_polarity[channel_id];
+
+	return 0;
+}
+
+static int quad8_index_polarity_set(struct counter_device *counter,
+	struct counter_signal *signal, size_t index_polarity)
+{
+	struct quad8_iio *const priv = counter->priv;
+	const size_t channel_id = signal->id - 16;
+	const unsigned int idr_cfg = priv->synchronous_mode[channel_id] |
+		index_polarity << 1;
+	const int base_offset = priv->base + 2 * channel_id + 1;
+
+	priv->index_polarity[channel_id] = index_polarity;
+
+	/* Load Index Control configuration to Index Control Register */
+	outb(0x60 | idr_cfg, base_offset);
+
+	return 0;
+}
+
+static struct counter_signal_enum_ext quad8_index_pol_enum = {
+	.items = quad8_index_polarity_modes,
+	.num_items = ARRAY_SIZE(quad8_index_polarity_modes),
+	.get = quad8_index_polarity_get,
+	.set = quad8_index_polarity_set
+};
+
+static int quad8_synchronous_mode_get(struct counter_device *counter,
+	struct counter_signal *signal, size_t *synchronous_mode)
+{
+	const struct quad8_iio *const priv = counter->priv;
+	const size_t channel_id = signal->id - 16;
+
+	*synchronous_mode = priv->synchronous_mode[channel_id];
+
+	return 0;
+}
+
+static int quad8_synchronous_mode_set(struct counter_device *counter,
+	struct counter_signal *signal, size_t synchronous_mode)
+{
+	struct quad8_iio *const priv = counter->priv;
+	const size_t channel_id = signal->id - 16;
+	const unsigned int idr_cfg = synchronous_mode |
+		priv->index_polarity[channel_id] << 1;
+	const int base_offset = priv->base + 2 * channel_id + 1;
+
+	/* Index function must be non-synchronous in non-quadrature mode */
+	if (synchronous_mode && !priv->quadrature_mode[channel_id])
+		return -EINVAL;
+
+	priv->synchronous_mode[channel_id] = synchronous_mode;
+
+	/* Load Index Control configuration to Index Control Register */
+	outb(0x60 | idr_cfg, base_offset);
+
+	return 0;
+}
+
+static struct counter_signal_enum_ext quad8_syn_mode_enum = {
+	.items = quad8_synchronous_modes,
+	.num_items = ARRAY_SIZE(quad8_synchronous_modes),
+	.get = quad8_synchronous_mode_get,
+	.set = quad8_synchronous_mode_set
+};
+
+static ssize_t quad8_count_floor_read(struct counter_device *counter,
+	struct counter_count *count, void *private, char *buf)
+{
+	/* Only a floor of 0 is supported */
+	return snprintf(buf, PAGE_SIZE, "0\n");
+}
+
+static int quad8_count_mode_get(struct counter_device *counter,
+	struct counter_count *count, size_t *cnt_mode)
+{
+	const struct quad8_iio *const priv = counter->priv;
+
+	/* Map 104-QUAD-8 count mode to Generic Counter count mode */
+	switch (priv->count_mode[count->id]) {
+	case 0:
+		*cnt_mode = COUNT_MODE_NORMAL;
+		break;
+	case 1:
+		*cnt_mode = COUNT_MODE_RANGE_LIMIT;
+		break;
+	case 2:
+		*cnt_mode = COUNT_MODE_NON_RECYCLE;
+		break;
+	case 3:
+		*cnt_mode = COUNT_MODE_MODULO_N;
+		break;
+	}
+
+	return 0;
+}
+
+static int quad8_count_mode_set(struct counter_device *counter,
+	struct counter_count *count, size_t cnt_mode)
+{
+	struct quad8_iio *const priv = counter->priv;
+	unsigned int mode_cfg;
+	const int base_offset = priv->base + 2 * count->id + 1;
+
+	/* Map Generic Counter count mode to 104-QUAD-8 count mode */
+	switch (cnt_mode) {
+	case COUNT_MODE_NORMAL:
+		cnt_mode = 0;
+		break;
+	case COUNT_MODE_RANGE_LIMIT:
+		cnt_mode = 1;
+		break;
+	case COUNT_MODE_NON_RECYCLE:
+		cnt_mode = 2;
+		break;
+	case COUNT_MODE_MODULO_N:
+		cnt_mode = 3;
+		break;
+	}
+
+	priv->count_mode[count->id] = cnt_mode;
+
+	/* Set count mode configuration value */
+	mode_cfg = cnt_mode << 1;
+
+	/* Add quadrature mode configuration */
+	if (priv->quadrature_mode[count->id])
+		mode_cfg |= (priv->quadrature_scale[count->id] + 1) << 3;
+
+	/* Load mode configuration to Counter Mode Register */
+	outb(0x20 | mode_cfg, base_offset);
+
+	return 0;
+}
+
+static struct counter_count_enum_ext quad8_cnt_mode_enum = {
+	.items = count_mode_str,
+	.num_items = ARRAY_SIZE(count_mode_str),
+	.get = quad8_count_mode_get,
+	.set = quad8_count_mode_set
+};
+
+static ssize_t quad8_count_direction_read(struct counter_device *counter,
+	struct counter_count *count, void *priv, char *buf)
+{
+	enum count_direction dir;
+
+	quad8_direction_get(counter, count, &dir);
+
+	return scnprintf(buf, PAGE_SIZE, "%s\n", count_direction_str[dir]);
+}
+
+static ssize_t quad8_count_enable_read(struct counter_device *counter,
+	struct counter_count *count, void *private, char *buf)
+{
+	const struct quad8_iio *const priv = counter->priv;
+
+	return scnprintf(buf, PAGE_SIZE, "%u\n", priv->ab_enable[count->id]);
+}
+
+static ssize_t quad8_count_enable_write(struct counter_device *counter,
+	struct counter_count *count, void *private, const char *buf, size_t len)
+{
+	struct quad8_iio *const priv = counter->priv;
+	const int base_offset = priv->base + 2 * count->id;
+	int err;
+	bool ab_enable;
+	unsigned int ior_cfg;
+
+	err = kstrtobool(buf, &ab_enable);
+	if (err)
+		return err;
+
+	priv->ab_enable[count->id] = ab_enable;
+
+	ior_cfg = ab_enable | priv->preset_enable[count->id] << 1;
+
+	/* Load I/O control configuration */
+	outb(0x40 | ior_cfg, base_offset + 1);
+
+	return len;
+}
+
+static int quad8_error_noise_get(struct counter_device *counter,
+	struct counter_count *count, size_t *noise_error)
+{
+	const struct quad8_iio *const priv = counter->priv;
+	const int base_offset = priv->base + 2 * count->id + 1;
+
+	*noise_error = !!(inb(base_offset) & BIT(4));
+
+	return 0;
+}
+
+static struct counter_count_enum_ext quad8_error_noise_enum = {
+	.items = quad8_noise_error_states,
+	.num_items = ARRAY_SIZE(quad8_noise_error_states),
+	.get = quad8_error_noise_get
+};
+
+static ssize_t quad8_count_preset_read(struct counter_device *counter,
+	struct counter_count *count, void *private, char *buf)
+{
+	const struct quad8_iio *const priv = counter->priv;
+
+	return snprintf(buf, PAGE_SIZE, "%u\n", priv->preset[count->id]);
+}
+
+static ssize_t quad8_count_preset_write(struct counter_device *counter,
+	struct counter_count *count, void *private, const char *buf, size_t len)
+{
+	struct quad8_iio *const priv = counter->priv;
+	const int base_offset = priv->base + 2 * count->id;
+	unsigned int preset;
+	int ret;
+	int i;
+
+	ret = kstrtouint(buf, 0, &preset);
+	if (ret)
+		return ret;
+
+	/* Only 24-bit values are supported */
+	if (preset > 0xFFFFFF)
+		return -EINVAL;
+
+	priv->preset[count->id] = preset;
+
+	/* Reset Byte Pointer */
+	outb(0x01, base_offset + 1);
+
+	/* Set Preset Register */
+	for (i = 0; i < 3; i++)
+		outb(preset >> (8 * i), base_offset);
+
+	return len;
+}
+
+static ssize_t quad8_count_ceiling_read(struct counter_device *counter,
+	struct counter_count *count, void *private, char *buf)
+{
+	const struct quad8_iio *const priv = counter->priv;
+
+	/* Range Limit and Modulo-N count modes use preset value as ceiling */
+	switch (priv->count_mode[count->id]) {
+	case 1:
+	case 3:
+		return quad8_count_preset_read(counter, count, private, buf);
+	}
+
+	/* By default 0x1FFFFFF (25 bits unsigned) is maximum count */
+	return snprintf(buf, PAGE_SIZE, "33554431\n");
+}
+
+static ssize_t quad8_count_ceiling_write(struct counter_device *counter,
+	struct counter_count *count, void *private, const char *buf, size_t len)
+{
+	struct quad8_iio *const priv = counter->priv;
+
+	/* Range Limit and Modulo-N count modes use preset value as ceiling */
+	switch (priv->count_mode[count->id]) {
+	case 1:
+	case 3:
+		return quad8_count_preset_write(counter, count, private, buf,
+						len);
+	}
+
+	return len;
+}
+
+static ssize_t quad8_count_preset_enable_read(struct counter_device *counter,
+	struct counter_count *count, void *private, char *buf)
+{
+	const struct quad8_iio *const priv = counter->priv;
+
+	return snprintf(buf, PAGE_SIZE, "%u\n",
+		!priv->preset_enable[count->id]);
+}
+
+static ssize_t quad8_count_preset_enable_write(struct counter_device *counter,
+	struct counter_count *count, void *private, const char *buf, size_t len)
+{
+	struct quad8_iio *const priv = counter->priv;
+	const int base_offset = priv->base + 2 * count->id + 1;
+	bool preset_enable;
+	int ret;
+	unsigned int ior_cfg;
+
+	ret = kstrtobool(buf, &preset_enable);
+	if (ret)
+		return ret;
+
+	/* Preset enable is active low in Input/Output Control register */
+	preset_enable = !preset_enable;
+
+	priv->preset_enable[count->id] = preset_enable;
+
+	ior_cfg = priv->ab_enable[count->id] | (unsigned int)preset_enable << 1;
+
+	/* Load I/O control configuration to Input / Output Control Register */
+	outb(0x40 | ior_cfg, base_offset);
+
+	return len;
+}
+
+static const struct counter_signal_ext quad8_index_ext[] = {
+	COUNTER_SIGNAL_ENUM("index_polarity", &quad8_index_pol_enum),
+	COUNTER_SIGNAL_ENUM_AVAILABLE("index_polarity",	&quad8_index_pol_enum),
+	COUNTER_SIGNAL_ENUM("synchronous_mode", &quad8_syn_mode_enum),
+	COUNTER_SIGNAL_ENUM_AVAILABLE("synchronous_mode", &quad8_syn_mode_enum)
+};
+
+#define	QUAD8_QUAD_SIGNAL(_id, _name) {	\
+	.id = (_id),			\
+	.name = (_name)			\
+}
+
+#define	QUAD8_INDEX_SIGNAL(_id, _name) {	\
+	.id = (_id),				\
+	.name = (_name),			\
+	.ext = quad8_index_ext,			\
+	.num_ext = ARRAY_SIZE(quad8_index_ext)	\
+}
+
+static struct counter_signal quad8_signals[] = {
+	QUAD8_QUAD_SIGNAL(0, "Channel 1 Quadrature A"),
+	QUAD8_QUAD_SIGNAL(1, "Channel 1 Quadrature B"),
+	QUAD8_QUAD_SIGNAL(2, "Channel 2 Quadrature A"),
+	QUAD8_QUAD_SIGNAL(3, "Channel 2 Quadrature B"),
+	QUAD8_QUAD_SIGNAL(4, "Channel 3 Quadrature A"),
+	QUAD8_QUAD_SIGNAL(5, "Channel 3 Quadrature B"),
+	QUAD8_QUAD_SIGNAL(6, "Channel 4 Quadrature A"),
+	QUAD8_QUAD_SIGNAL(7, "Channel 4 Quadrature B"),
+	QUAD8_QUAD_SIGNAL(8, "Channel 5 Quadrature A"),
+	QUAD8_QUAD_SIGNAL(9, "Channel 5 Quadrature B"),
+	QUAD8_QUAD_SIGNAL(10, "Channel 6 Quadrature A"),
+	QUAD8_QUAD_SIGNAL(11, "Channel 6 Quadrature B"),
+	QUAD8_QUAD_SIGNAL(12, "Channel 7 Quadrature A"),
+	QUAD8_QUAD_SIGNAL(13, "Channel 7 Quadrature B"),
+	QUAD8_QUAD_SIGNAL(14, "Channel 8 Quadrature A"),
+	QUAD8_QUAD_SIGNAL(15, "Channel 8 Quadrature B"),
+	QUAD8_INDEX_SIGNAL(16, "Channel 1 Index"),
+	QUAD8_INDEX_SIGNAL(17, "Channel 2 Index"),
+	QUAD8_INDEX_SIGNAL(18, "Channel 3 Index"),
+	QUAD8_INDEX_SIGNAL(19, "Channel 4 Index"),
+	QUAD8_INDEX_SIGNAL(20, "Channel 5 Index"),
+	QUAD8_INDEX_SIGNAL(21, "Channel 6 Index"),
+	QUAD8_INDEX_SIGNAL(22, "Channel 7 Index"),
+	QUAD8_INDEX_SIGNAL(23, "Channel 8 Index")
+};
+
+#define QUAD8_COUNT_SYNAPSES(_id) {					\
+	{								\
+		.actions_list = quad8_synapse_actions_list,		\
+		.num_actions = ARRAY_SIZE(quad8_synapse_actions_list),	\
+		.signal = quad8_signals + 2 * (_id)			\
+	},								\
+	{								\
+		.actions_list = quad8_synapse_actions_list,		\
+		.num_actions = ARRAY_SIZE(quad8_synapse_actions_list),	\
+		.signal = quad8_signals + 2 * (_id) + 1			\
+	},								\
+	{								\
+		.actions_list = quad8_index_actions_list,		\
+		.num_actions = ARRAY_SIZE(quad8_index_actions_list),	\
+		.signal = quad8_signals + 2 * (_id) + 16		\
+	}								\
+}
+
+static struct counter_synapse quad8_count_synapses[][3] = {
+	QUAD8_COUNT_SYNAPSES(0), QUAD8_COUNT_SYNAPSES(1),
+	QUAD8_COUNT_SYNAPSES(2), QUAD8_COUNT_SYNAPSES(3),
+	QUAD8_COUNT_SYNAPSES(4), QUAD8_COUNT_SYNAPSES(5),
+	QUAD8_COUNT_SYNAPSES(6), QUAD8_COUNT_SYNAPSES(7)
+};
+
+static const struct counter_count_ext quad8_count_ext[] = {
+	{
+		.name = "ceiling",
+		.read = quad8_count_ceiling_read,
+		.write = quad8_count_ceiling_write
+	},
+	{
+		.name = "floor",
+		.read = quad8_count_floor_read
+	},
+	COUNTER_COUNT_ENUM("count_mode", &quad8_cnt_mode_enum),
+	COUNTER_COUNT_ENUM_AVAILABLE("count_mode", &quad8_cnt_mode_enum),
+	{
+		.name = "direction",
+		.read = quad8_count_direction_read
+	},
+	{
+		.name = "enable",
+		.read = quad8_count_enable_read,
+		.write = quad8_count_enable_write
+	},
+	COUNTER_COUNT_ENUM("error_noise", &quad8_error_noise_enum),
+	COUNTER_COUNT_ENUM_AVAILABLE("error_noise", &quad8_error_noise_enum),
+	{
+		.name = "preset",
+		.read = quad8_count_preset_read,
+		.write = quad8_count_preset_write
+	},
+	{
+		.name = "preset_enable",
+		.read = quad8_count_preset_enable_read,
+		.write = quad8_count_preset_enable_write
+	}
+};
+
+#define QUAD8_COUNT(_id, _cntname) {					\
+	.id = (_id),							\
+	.name = (_cntname),						\
+	.functions_list = quad8_count_functions_list,			\
+	.num_functions = ARRAY_SIZE(quad8_count_functions_list),	\
+	.synapses = quad8_count_synapses[(_id)],			\
+	.num_synapses =	2,						\
+	.ext = quad8_count_ext,						\
+	.num_ext = ARRAY_SIZE(quad8_count_ext)				\
+}
+
+static struct counter_count quad8_counts[] = {
+	QUAD8_COUNT(0, "Channel 1 Count"),
+	QUAD8_COUNT(1, "Channel 2 Count"),
+	QUAD8_COUNT(2, "Channel 3 Count"),
+	QUAD8_COUNT(3, "Channel 4 Count"),
+	QUAD8_COUNT(4, "Channel 5 Count"),
+	QUAD8_COUNT(5, "Channel 6 Count"),
+	QUAD8_COUNT(6, "Channel 7 Count"),
+	QUAD8_COUNT(7, "Channel 8 Count")
+};
+
+static int quad8_probe(struct device *dev, unsigned int id)
+{
+	struct iio_dev *indio_dev;
+	struct quad8_iio *quad8iio;
+	int i, j;
+	unsigned int base_offset;
+	int err;
+
+	if (!devm_request_region(dev, base[id], QUAD8_EXTENT, dev_name(dev))) {
+		dev_err(dev, "Unable to lock port addresses (0x%X-0x%X)\n",
+			base[id], base[id] + QUAD8_EXTENT);
+		return -EBUSY;
+	}
+
+	/* Allocate IIO device; this also allocates driver data structure */
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*quad8iio));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	/* Initialize IIO device */
+	indio_dev->info = &quad8_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->num_channels = ARRAY_SIZE(quad8_channels);
+	indio_dev->channels = quad8_channels;
+	indio_dev->name = dev_name(dev);
+	indio_dev->dev.parent = dev;
+
+	/* Initialize Counter device and driver data */
+	quad8iio = iio_priv(indio_dev);
+	quad8iio->counter.name = dev_name(dev);
+	quad8iio->counter.parent = dev;
+	quad8iio->counter.ops = &quad8_ops;
+	quad8iio->counter.counts = quad8_counts;
+	quad8iio->counter.num_counts = ARRAY_SIZE(quad8_counts);
+	quad8iio->counter.signals = quad8_signals;
+	quad8iio->counter.num_signals = ARRAY_SIZE(quad8_signals);
+	quad8iio->counter.priv = quad8iio;
+	quad8iio->base = base[id];
+
+	/* Reset all counters and disable interrupt function */
+	outb(0x01, base[id] + 0x11);
+	/* Set initial configuration for all counters */
+	for (i = 0; i < QUAD8_NUM_COUNTERS; i++) {
+		base_offset = base[id] + 2 * i;
+		/* Reset Byte Pointer */
+		outb(0x01, base_offset + 1);
+		/* Reset Preset Register */
+		for (j = 0; j < 3; j++)
+			outb(0x00, base_offset);
+		/* Reset Borrow, Carry, Compare, and Sign flags */
+		outb(0x04, base_offset + 1);
+		/* Reset Error flag */
+		outb(0x06, base_offset + 1);
+		/* Binary encoding; Normal count; non-quadrature mode */
+		outb(0x20, base_offset + 1);
+		/* Disable A and B inputs; preset on index; FLG1 as Carry */
+		outb(0x40, base_offset + 1);
+		/* Disable index function; negative index polarity */
+		outb(0x60, base_offset + 1);
+	}
+	/* Enable all counters */
+	outb(0x00, base[id] + 0x11);
+
+	/* Register IIO device */
+	err = devm_iio_device_register(dev, indio_dev);
+	if (err)
+		return err;
+
+	/* Register Counter device */
+	return devm_counter_register(dev, &quad8iio->counter);
+}
+
+static struct isa_driver quad8_driver = {
+	.probe = quad8_probe,
+	.driver = {
+		.name = "104-quad-8"
+	}
+};
+
+module_isa_driver(quad8_driver, num_quad8);
+
+MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
+MODULE_DESCRIPTION("ACCES 104-QUAD-8 IIO driver");
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/counter/Kconfig b/drivers/counter/Kconfig
index 65fa92abd5a4..73f03372484f 100644
--- a/drivers/counter/Kconfig
+++ b/drivers/counter/Kconfig
@@ -16,3 +16,24 @@ menuconfig COUNTER
 	  consumption. The Generic Counter interface enables drivers to support
 	  and expose a common set of components and functionality present in
 	  counter devices.
+
+if COUNTER
+
+config 104_QUAD_8
+	tristate "ACCES 104-QUAD-8 driver"
+	depends on PC104 && X86 && IIO
+	select ISA_BUS_API
+	help
+	  Say yes here to build support for the ACCES 104-QUAD-8 quadrature
+	  encoder counter/interface device family (104-QUAD-8, 104-QUAD-4).
+
+	  Performing a write to a counter's IIO_CHAN_INFO_RAW sets the counter and
+	  also clears the counter's respective error flag. Although the counters
+	  have a 25-bit range, only the lower 24 bits may be set, either directly
+	  or via a counter's preset attribute. Interrupts are not supported by
+	  this driver.
+
+	  The base port addresses for the devices may be configured via the base
+	  array module parameter.
+
+endif # COUNTER
diff --git a/drivers/counter/Makefile b/drivers/counter/Makefile
index ad1ba7109cdc..23a4f6263e45 100644
--- a/drivers/counter/Makefile
+++ b/drivers/counter/Makefile
@@ -6,3 +6,5 @@
 
 obj-$(CONFIG_COUNTER) += counter.o
 counter-y := generic-counter.o
+
+obj-$(CONFIG_104_QUAD_8)	+= 104-quad-8.o
diff --git a/drivers/iio/counter/104-quad-8.c b/drivers/iio/counter/104-quad-8.c
deleted file mode 100644
index b56985078d8c..000000000000
--- a/drivers/iio/counter/104-quad-8.c
+++ /dev/null
@@ -1,596 +0,0 @@
-/*
- * IIO driver for the ACCES 104-QUAD-8
- * Copyright (C) 2016 William Breathitt Gray
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License, version 2, as
- * published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful, but
- * WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * General Public License for more details.
- *
- * This driver supports the ACCES 104-QUAD-8 and ACCES 104-QUAD-4.
- */
-#include <linux/bitops.h>
-#include <linux/device.h>
-#include <linux/errno.h>
-#include <linux/iio/iio.h>
-#include <linux/iio/types.h>
-#include <linux/io.h>
-#include <linux/ioport.h>
-#include <linux/isa.h>
-#include <linux/kernel.h>
-#include <linux/module.h>
-#include <linux/moduleparam.h>
-#include <linux/types.h>
-
-#define QUAD8_EXTENT 32
-
-static unsigned int base[max_num_isa_dev(QUAD8_EXTENT)];
-static unsigned int num_quad8;
-module_param_array(base, uint, &num_quad8, 0);
-MODULE_PARM_DESC(base, "ACCES 104-QUAD-8 base addresses");
-
-#define QUAD8_NUM_COUNTERS 8
-
-/**
- * struct quad8_iio - IIO device private data structure
- * @preset:		array of preset values
- * @count_mode:		array of count mode configurations
- * @quadrature_mode:	array of quadrature mode configurations
- * @quadrature_scale:	array of quadrature mode scale configurations
- * @ab_enable:		array of A and B inputs enable configurations
- * @preset_enable:	array of set_to_preset_on_index attribute configurations
- * @synchronous_mode:	array of index function synchronous mode configurations
- * @index_polarity:	array of index function polarity configurations
- * @base:		base port address of the IIO device
- */
-struct quad8_iio {
-	unsigned int preset[QUAD8_NUM_COUNTERS];
-	unsigned int count_mode[QUAD8_NUM_COUNTERS];
-	unsigned int quadrature_mode[QUAD8_NUM_COUNTERS];
-	unsigned int quadrature_scale[QUAD8_NUM_COUNTERS];
-	unsigned int ab_enable[QUAD8_NUM_COUNTERS];
-	unsigned int preset_enable[QUAD8_NUM_COUNTERS];
-	unsigned int synchronous_mode[QUAD8_NUM_COUNTERS];
-	unsigned int index_polarity[QUAD8_NUM_COUNTERS];
-	unsigned int base;
-};
-
-static int quad8_read_raw(struct iio_dev *indio_dev,
-	struct iio_chan_spec const *chan, int *val, int *val2, long mask)
-{
-	struct quad8_iio *const priv = iio_priv(indio_dev);
-	const int base_offset = priv->base + 2 * chan->channel;
-	unsigned int flags;
-	unsigned int borrow;
-	unsigned int carry;
-	int i;
-
-	switch (mask) {
-	case IIO_CHAN_INFO_RAW:
-		if (chan->type == IIO_INDEX) {
-			*val = !!(inb(priv->base + 0x16) & BIT(chan->channel));
-			return IIO_VAL_INT;
-		}
-
-		flags = inb(base_offset + 1);
-		borrow = flags & BIT(0);
-		carry = !!(flags & BIT(1));
-
-		/* Borrow XOR Carry effectively doubles count range */
-		*val = (borrow ^ carry) << 24;
-
-		/* Reset Byte Pointer; transfer Counter to Output Latch */
-		outb(0x11, base_offset + 1);
-
-		for (i = 0; i < 3; i++)
-			*val |= (unsigned int)inb(base_offset) << (8 * i);
-
-		return IIO_VAL_INT;
-	case IIO_CHAN_INFO_ENABLE:
-		*val = priv->ab_enable[chan->channel];
-		return IIO_VAL_INT;
-	case IIO_CHAN_INFO_SCALE:
-		*val = 1;
-		*val2 = priv->quadrature_scale[chan->channel];
-		return IIO_VAL_FRACTIONAL_LOG2;
-	}
-
-	return -EINVAL;
-}
-
-static int quad8_write_raw(struct iio_dev *indio_dev,
-	struct iio_chan_spec const *chan, int val, int val2, long mask)
-{
-	struct quad8_iio *const priv = iio_priv(indio_dev);
-	const int base_offset = priv->base + 2 * chan->channel;
-	int i;
-	unsigned int ior_cfg;
-
-	switch (mask) {
-	case IIO_CHAN_INFO_RAW:
-		if (chan->type == IIO_INDEX)
-			return -EINVAL;
-
-		/* Only 24-bit values are supported */
-		if ((unsigned int)val > 0xFFFFFF)
-			return -EINVAL;
-
-		/* Reset Byte Pointer */
-		outb(0x01, base_offset + 1);
-
-		/* Counter can only be set via Preset Register */
-		for (i = 0; i < 3; i++)
-			outb(val >> (8 * i), base_offset);
-
-		/* Transfer Preset Register to Counter */
-		outb(0x08, base_offset + 1);
-
-		/* Reset Byte Pointer */
-		outb(0x01, base_offset + 1);
-
-		/* Set Preset Register back to original value */
-		val = priv->preset[chan->channel];
-		for (i = 0; i < 3; i++)
-			outb(val >> (8 * i), base_offset);
-
-		/* Reset Borrow, Carry, Compare, and Sign flags */
-		outb(0x02, base_offset + 1);
-		/* Reset Error flag */
-		outb(0x06, base_offset + 1);
-
-		return 0;
-	case IIO_CHAN_INFO_ENABLE:
-		/* only boolean values accepted */
-		if (val < 0 || val > 1)
-			return -EINVAL;
-
-		priv->ab_enable[chan->channel] = val;
-
-		ior_cfg = val | priv->preset_enable[chan->channel] << 1;
-
-		/* Load I/O control configuration */
-		outb(0x40 | ior_cfg, base_offset + 1);
-
-		return 0;
-	case IIO_CHAN_INFO_SCALE:
-		/* Quadrature scaling only available in quadrature mode */
-		if (!priv->quadrature_mode[chan->channel] && (val2 || val != 1))
-			return -EINVAL;
-
-		/* Only three gain states (1, 0.5, 0.25) */
-		if (val == 1 && !val2)
-			priv->quadrature_scale[chan->channel] = 0;
-		else if (!val)
-			switch (val2) {
-			case 500000:
-				priv->quadrature_scale[chan->channel] = 1;
-				break;
-			case 250000:
-				priv->quadrature_scale[chan->channel] = 2;
-				break;
-			default:
-				return -EINVAL;
-			}
-		else
-			return -EINVAL;
-
-		return 0;
-	}
-
-	return -EINVAL;
-}
-
-static const struct iio_info quad8_info = {
-	.read_raw = quad8_read_raw,
-	.write_raw = quad8_write_raw
-};
-
-static ssize_t quad8_read_preset(struct iio_dev *indio_dev, uintptr_t private,
-	const struct iio_chan_spec *chan, char *buf)
-{
-	const struct quad8_iio *const priv = iio_priv(indio_dev);
-
-	return snprintf(buf, PAGE_SIZE, "%u\n", priv->preset[chan->channel]);
-}
-
-static ssize_t quad8_write_preset(struct iio_dev *indio_dev, uintptr_t private,
-	const struct iio_chan_spec *chan, const char *buf, size_t len)
-{
-	struct quad8_iio *const priv = iio_priv(indio_dev);
-	const int base_offset = priv->base + 2 * chan->channel;
-	unsigned int preset;
-	int ret;
-	int i;
-
-	ret = kstrtouint(buf, 0, &preset);
-	if (ret)
-		return ret;
-
-	/* Only 24-bit values are supported */
-	if (preset > 0xFFFFFF)
-		return -EINVAL;
-
-	priv->preset[chan->channel] = preset;
-
-	/* Reset Byte Pointer */
-	outb(0x01, base_offset + 1);
-
-	/* Set Preset Register */
-	for (i = 0; i < 3; i++)
-		outb(preset >> (8 * i), base_offset);
-
-	return len;
-}
-
-static ssize_t quad8_read_set_to_preset_on_index(struct iio_dev *indio_dev,
-	uintptr_t private, const struct iio_chan_spec *chan, char *buf)
-{
-	const struct quad8_iio *const priv = iio_priv(indio_dev);
-
-	return snprintf(buf, PAGE_SIZE, "%u\n",
-		!priv->preset_enable[chan->channel]);
-}
-
-static ssize_t quad8_write_set_to_preset_on_index(struct iio_dev *indio_dev,
-	uintptr_t private, const struct iio_chan_spec *chan, const char *buf,
-	size_t len)
-{
-	struct quad8_iio *const priv = iio_priv(indio_dev);
-	const int base_offset = priv->base + 2 * chan->channel + 1;
-	bool preset_enable;
-	int ret;
-	unsigned int ior_cfg;
-
-	ret = kstrtobool(buf, &preset_enable);
-	if (ret)
-		return ret;
-
-	/* Preset enable is active low in Input/Output Control register */
-	preset_enable = !preset_enable;
-
-	priv->preset_enable[chan->channel] = preset_enable;
-
-	ior_cfg = priv->ab_enable[chan->channel] |
-		(unsigned int)preset_enable << 1;
-
-	/* Load I/O control configuration to Input / Output Control Register */
-	outb(0x40 | ior_cfg, base_offset);
-
-	return len;
-}
-
-static const char *const quad8_noise_error_states[] = {
-	"No excessive noise is present at the count inputs",
-	"Excessive noise is present at the count inputs"
-};
-
-static int quad8_get_noise_error(struct iio_dev *indio_dev,
-	const struct iio_chan_spec *chan)
-{
-	struct quad8_iio *const priv = iio_priv(indio_dev);
-	const int base_offset = priv->base + 2 * chan->channel + 1;
-
-	return !!(inb(base_offset) & BIT(4));
-}
-
-static const struct iio_enum quad8_noise_error_enum = {
-	.items = quad8_noise_error_states,
-	.num_items = ARRAY_SIZE(quad8_noise_error_states),
-	.get = quad8_get_noise_error
-};
-
-static const char *const quad8_count_direction_states[] = {
-	"down",
-	"up"
-};
-
-static int quad8_get_count_direction(struct iio_dev *indio_dev,
-	const struct iio_chan_spec *chan)
-{
-	struct quad8_iio *const priv = iio_priv(indio_dev);
-	const int base_offset = priv->base + 2 * chan->channel + 1;
-
-	return !!(inb(base_offset) & BIT(5));
-}
-
-static const struct iio_enum quad8_count_direction_enum = {
-	.items = quad8_count_direction_states,
-	.num_items = ARRAY_SIZE(quad8_count_direction_states),
-	.get = quad8_get_count_direction
-};
-
-static const char *const quad8_count_modes[] = {
-	"normal",
-	"range limit",
-	"non-recycle",
-	"modulo-n"
-};
-
-static int quad8_set_count_mode(struct iio_dev *indio_dev,
-	const struct iio_chan_spec *chan, unsigned int count_mode)
-{
-	struct quad8_iio *const priv = iio_priv(indio_dev);
-	unsigned int mode_cfg = count_mode << 1;
-	const int base_offset = priv->base + 2 * chan->channel + 1;
-
-	priv->count_mode[chan->channel] = count_mode;
-
-	/* Add quadrature mode configuration */
-	if (priv->quadrature_mode[chan->channel])
-		mode_cfg |= (priv->quadrature_scale[chan->channel] + 1) << 3;
-
-	/* Load mode configuration to Counter Mode Register */
-	outb(0x20 | mode_cfg, base_offset);
-
-	return 0;
-}
-
-static int quad8_get_count_mode(struct iio_dev *indio_dev,
-	const struct iio_chan_spec *chan)
-{
-	const struct quad8_iio *const priv = iio_priv(indio_dev);
-
-	return priv->count_mode[chan->channel];
-}
-
-static const struct iio_enum quad8_count_mode_enum = {
-	.items = quad8_count_modes,
-	.num_items = ARRAY_SIZE(quad8_count_modes),
-	.set = quad8_set_count_mode,
-	.get = quad8_get_count_mode
-};
-
-static const char *const quad8_synchronous_modes[] = {
-	"non-synchronous",
-	"synchronous"
-};
-
-static int quad8_set_synchronous_mode(struct iio_dev *indio_dev,
-	const struct iio_chan_spec *chan, unsigned int synchronous_mode)
-{
-	struct quad8_iio *const priv = iio_priv(indio_dev);
-	const unsigned int idr_cfg = synchronous_mode |
-		priv->index_polarity[chan->channel] << 1;
-	const int base_offset = priv->base + 2 * chan->channel + 1;
-
-	/* Index function must be non-synchronous in non-quadrature mode */
-	if (synchronous_mode && !priv->quadrature_mode[chan->channel])
-		return -EINVAL;
-
-	priv->synchronous_mode[chan->channel] = synchronous_mode;
-
-	/* Load Index Control configuration to Index Control Register */
-	outb(0x60 | idr_cfg, base_offset);
-
-	return 0;
-}
-
-static int quad8_get_synchronous_mode(struct iio_dev *indio_dev,
-	const struct iio_chan_spec *chan)
-{
-	const struct quad8_iio *const priv = iio_priv(indio_dev);
-
-	return priv->synchronous_mode[chan->channel];
-}
-
-static const struct iio_enum quad8_synchronous_mode_enum = {
-	.items = quad8_synchronous_modes,
-	.num_items = ARRAY_SIZE(quad8_synchronous_modes),
-	.set = quad8_set_synchronous_mode,
-	.get = quad8_get_synchronous_mode
-};
-
-static const char *const quad8_quadrature_modes[] = {
-	"non-quadrature",
-	"quadrature"
-};
-
-static int quad8_set_quadrature_mode(struct iio_dev *indio_dev,
-	const struct iio_chan_spec *chan, unsigned int quadrature_mode)
-{
-	struct quad8_iio *const priv = iio_priv(indio_dev);
-	unsigned int mode_cfg = priv->count_mode[chan->channel] << 1;
-	const int base_offset = priv->base + 2 * chan->channel + 1;
-
-	if (quadrature_mode)
-		mode_cfg |= (priv->quadrature_scale[chan->channel] + 1) << 3;
-	else {
-		/* Quadrature scaling only available in quadrature mode */
-		priv->quadrature_scale[chan->channel] = 0;
-
-		/* Synchronous function not supported in non-quadrature mode */
-		if (priv->synchronous_mode[chan->channel])
-			quad8_set_synchronous_mode(indio_dev, chan, 0);
-	}
-
-	priv->quadrature_mode[chan->channel] = quadrature_mode;
-
-	/* Load mode configuration to Counter Mode Register */
-	outb(0x20 | mode_cfg, base_offset);
-
-	return 0;
-}
-
-static int quad8_get_quadrature_mode(struct iio_dev *indio_dev,
-	const struct iio_chan_spec *chan)
-{
-	const struct quad8_iio *const priv = iio_priv(indio_dev);
-
-	return priv->quadrature_mode[chan->channel];
-}
-
-static const struct iio_enum quad8_quadrature_mode_enum = {
-	.items = quad8_quadrature_modes,
-	.num_items = ARRAY_SIZE(quad8_quadrature_modes),
-	.set = quad8_set_quadrature_mode,
-	.get = quad8_get_quadrature_mode
-};
-
-static const char *const quad8_index_polarity_modes[] = {
-	"negative",
-	"positive"
-};
-
-static int quad8_set_index_polarity(struct iio_dev *indio_dev,
-	const struct iio_chan_spec *chan, unsigned int index_polarity)
-{
-	struct quad8_iio *const priv = iio_priv(indio_dev);
-	const unsigned int idr_cfg = priv->synchronous_mode[chan->channel] |
-		index_polarity << 1;
-	const int base_offset = priv->base + 2 * chan->channel + 1;
-
-	priv->index_polarity[chan->channel] = index_polarity;
-
-	/* Load Index Control configuration to Index Control Register */
-	outb(0x60 | idr_cfg, base_offset);
-
-	return 0;
-}
-
-static int quad8_get_index_polarity(struct iio_dev *indio_dev,
-	const struct iio_chan_spec *chan)
-{
-	const struct quad8_iio *const priv = iio_priv(indio_dev);
-
-	return priv->index_polarity[chan->channel];
-}
-
-static const struct iio_enum quad8_index_polarity_enum = {
-	.items = quad8_index_polarity_modes,
-	.num_items = ARRAY_SIZE(quad8_index_polarity_modes),
-	.set = quad8_set_index_polarity,
-	.get = quad8_get_index_polarity
-};
-
-static const struct iio_chan_spec_ext_info quad8_count_ext_info[] = {
-	{
-		.name = "preset",
-		.shared = IIO_SEPARATE,
-		.read = quad8_read_preset,
-		.write = quad8_write_preset
-	},
-	{
-		.name = "set_to_preset_on_index",
-		.shared = IIO_SEPARATE,
-		.read = quad8_read_set_to_preset_on_index,
-		.write = quad8_write_set_to_preset_on_index
-	},
-	IIO_ENUM("noise_error", IIO_SEPARATE, &quad8_noise_error_enum),
-	IIO_ENUM_AVAILABLE("noise_error", &quad8_noise_error_enum),
-	IIO_ENUM("count_direction", IIO_SEPARATE, &quad8_count_direction_enum),
-	IIO_ENUM_AVAILABLE("count_direction", &quad8_count_direction_enum),
-	IIO_ENUM("count_mode", IIO_SEPARATE, &quad8_count_mode_enum),
-	IIO_ENUM_AVAILABLE("count_mode", &quad8_count_mode_enum),
-	IIO_ENUM("quadrature_mode", IIO_SEPARATE, &quad8_quadrature_mode_enum),
-	IIO_ENUM_AVAILABLE("quadrature_mode", &quad8_quadrature_mode_enum),
-	{}
-};
-
-static const struct iio_chan_spec_ext_info quad8_index_ext_info[] = {
-	IIO_ENUM("synchronous_mode", IIO_SEPARATE,
-		&quad8_synchronous_mode_enum),
-	IIO_ENUM_AVAILABLE("synchronous_mode", &quad8_synchronous_mode_enum),
-	IIO_ENUM("index_polarity", IIO_SEPARATE, &quad8_index_polarity_enum),
-	IIO_ENUM_AVAILABLE("index_polarity", &quad8_index_polarity_enum),
-	{}
-};
-
-#define QUAD8_COUNT_CHAN(_chan) {					\
-	.type = IIO_COUNT,						\
-	.channel = (_chan),						\
-	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |			\
-		BIT(IIO_CHAN_INFO_ENABLE) | BIT(IIO_CHAN_INFO_SCALE),	\
-	.ext_info = quad8_count_ext_info,				\
-	.indexed = 1							\
-}
-
-#define QUAD8_INDEX_CHAN(_chan) {			\
-	.type = IIO_INDEX,				\
-	.channel = (_chan),				\
-	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),	\
-	.ext_info = quad8_index_ext_info,		\
-	.indexed = 1					\
-}
-
-static const struct iio_chan_spec quad8_channels[] = {
-	QUAD8_COUNT_CHAN(0), QUAD8_INDEX_CHAN(0),
-	QUAD8_COUNT_CHAN(1), QUAD8_INDEX_CHAN(1),
-	QUAD8_COUNT_CHAN(2), QUAD8_INDEX_CHAN(2),
-	QUAD8_COUNT_CHAN(3), QUAD8_INDEX_CHAN(3),
-	QUAD8_COUNT_CHAN(4), QUAD8_INDEX_CHAN(4),
-	QUAD8_COUNT_CHAN(5), QUAD8_INDEX_CHAN(5),
-	QUAD8_COUNT_CHAN(6), QUAD8_INDEX_CHAN(6),
-	QUAD8_COUNT_CHAN(7), QUAD8_INDEX_CHAN(7)
-};
-
-static int quad8_probe(struct device *dev, unsigned int id)
-{
-	struct iio_dev *indio_dev;
-	struct quad8_iio *priv;
-	int i, j;
-	unsigned int base_offset;
-
-	indio_dev = devm_iio_device_alloc(dev, sizeof(*priv));
-	if (!indio_dev)
-		return -ENOMEM;
-
-	if (!devm_request_region(dev, base[id], QUAD8_EXTENT,
-		dev_name(dev))) {
-		dev_err(dev, "Unable to lock port addresses (0x%X-0x%X)\n",
-			base[id], base[id] + QUAD8_EXTENT);
-		return -EBUSY;
-	}
-
-	indio_dev->info = &quad8_info;
-	indio_dev->modes = INDIO_DIRECT_MODE;
-	indio_dev->num_channels = ARRAY_SIZE(quad8_channels);
-	indio_dev->channels = quad8_channels;
-	indio_dev->name = dev_name(dev);
-	indio_dev->dev.parent = dev;
-
-	priv = iio_priv(indio_dev);
-	priv->base = base[id];
-
-	/* Reset all counters and disable interrupt function */
-	outb(0x01, base[id] + 0x11);
-	/* Set initial configuration for all counters */
-	for (i = 0; i < QUAD8_NUM_COUNTERS; i++) {
-		base_offset = base[id] + 2 * i;
-		/* Reset Byte Pointer */
-		outb(0x01, base_offset + 1);
-		/* Reset Preset Register */
-		for (j = 0; j < 3; j++)
-			outb(0x00, base_offset);
-		/* Reset Borrow, Carry, Compare, and Sign flags */
-		outb(0x04, base_offset + 1);
-		/* Reset Error flag */
-		outb(0x06, base_offset + 1);
-		/* Binary encoding; Normal count; non-quadrature mode */
-		outb(0x20, base_offset + 1);
-		/* Disable A and B inputs; preset on index; FLG1 as Carry */
-		outb(0x40, base_offset + 1);
-		/* Disable index function; negative index polarity */
-		outb(0x60, base_offset + 1);
-	}
-	/* Enable all counters */
-	outb(0x00, base[id] + 0x11);
-
-	return devm_iio_device_register(dev, indio_dev);
-}
-
-static struct isa_driver quad8_driver = {
-	.probe = quad8_probe,
-	.driver = {
-		.name = "104-quad-8"
-	}
-};
-
-module_isa_driver(quad8_driver, num_quad8);
-
-MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
-MODULE_DESCRIPTION("ACCES 104-QUAD-8 IIO driver");
-MODULE_LICENSE("GPL v2");
diff --git a/drivers/iio/counter/Kconfig b/drivers/iio/counter/Kconfig
index bf1e559ad7cd..eeb358122cbe 100644
--- a/drivers/iio/counter/Kconfig
+++ b/drivers/iio/counter/Kconfig
@@ -5,23 +5,6 @@
 
 menu "Counters"
 
-config 104_QUAD_8
-	tristate "ACCES 104-QUAD-8 driver"
-	depends on PC104 && X86
-	select ISA_BUS_API
-	help
-	  Say yes here to build support for the ACCES 104-QUAD-8 quadrature
-	  encoder counter/interface device family (104-QUAD-8, 104-QUAD-4).
-
-	  Performing a write to a counter's IIO_CHAN_INFO_RAW sets the counter and
-	  also clears the counter's respective error flag. Although the counters
-	  have a 25-bit range, only the lower 24 bits may be set, either directly
-	  or via a counter's preset attribute. Interrupts are not supported by
-	  this driver.
-
-	  The base port addresses for the devices may be configured via the base
-	  array module parameter.
-
 config STM32_LPTIMER_CNT
 	tristate "STM32 LP Timer encoder counter driver"
 	depends on MFD_STM32_LPTIMER || COMPILE_TEST
diff --git a/drivers/iio/counter/Makefile b/drivers/iio/counter/Makefile
index 1b9a896eb488..93933ba49280 100644
--- a/drivers/iio/counter/Makefile
+++ b/drivers/iio/counter/Makefile
@@ -4,5 +4,4 @@
 
 # When adding new entries keep the list in alphabetical order
 
-obj-$(CONFIG_104_QUAD_8)	+= 104-quad-8.o
 obj-$(CONFIG_STM32_LPTIMER_CNT)	+= stm32-lptimer-cnt.o
-- 
2.17.0

[PATCH v6 5/9] counter: 104-quad-8: Documentation: Add Generic Counter sysfs documentation

[William Breathitt Gray]

This patch adds standard documentation for the Generic Counter interface
userspace sysfs attributes of the 104-QUAD-8 driver.

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
---
 .../ABI/testing/sysfs-bus-counter-104-quad-8  | 36 +++++++++++++++++++
 MAINTAINERS                                   |  1 +
 2 files changed, 37 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-bus-counter-104-quad-8

diff --git a/Documentation/ABI/testing/sysfs-bus-counter-104-quad-8 b/Documentation/ABI/testing/sysfs-bus-counter-104-quad-8
new file mode 100644
index 000000000000..274df6768b97
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-counter-104-quad-8
@@ -0,0 +1,36 @@
+What:		/sys/bus/counter/devices/counterX/signalY/index_polarity
+KernelVersion:	4.18
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Active level of index input Signal Y; irrelevant in
+		non-synchronous load mode.
+
+What:		/sys/bus/counter/devices/counterX/signalY/index_polarity_available
+What:		/sys/bus/counter/devices/counterX/signalY/synchronous_mode_available
+KernelVersion:	4.18
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Discrete set of available values for the respective Signal Y
+		configuration are listed in this file.
+
+What:		/sys/bus/counter/devices/counterX/signalY/synchronous_mode
+KernelVersion:	4.18
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Configure the counter associated with Signal Y for
+		non-synchronous or synchronous load mode. Synchronous load mode
+		cannot be selected in non-quadrature (Pulse-Direction) clock
+		mode.
+
+		Non-synchronous:
+			A logic low level is the active level at this index
+			input. The index function (as enabled via preset_enable)
+			is performed directly on the active level of the index
+			input.
+
+		Synchronous:
+			Intended for interfacing with encoder Index output in
+			quadrature clock mode. The active level is configured
+			via index_polarity. The index function (as enabled via
+			preset_enable) is performed synchronously with the
+			quadrature clock on the active level of the index input.
diff --git a/MAINTAINERS b/MAINTAINERS
index f11bf7885aeb..8e27b49e8d5e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -270,6 +270,7 @@ ACCES 104-QUAD-8 DRIVER
 M:	William Breathitt Gray <vilhelm.gray@gmail.com>
 L:	linux-iio@vger.kernel.org
 S:	Maintained
+F:	Documentation/ABI/testing/sysfs-bus-counter-104-quad-8
 F:	Documentation/ABI/testing/sysfs-bus-iio-counter-104-quad-8
 F:	drivers/counter/104-quad-8.c
 
-- 
2.17.0

[PATCH v6 6/9] dt-bindings: counter: Document stm32 quadrature encoder

[William Breathitt Gray]

From: Benjamin Gaignard <benjamin.gaignard@st.com>

Add bindings for STM32 Timer quadrature encoder.
It is a sub-node of STM32 Timer which implement the
counter part of the hardware.

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
---
 .../bindings/counter/stm32-timer-cnt.txt      | 26 +++++++++++++++++++
 .../devicetree/bindings/mfd/stm32-timers.txt  |  7 +++++
 2 files changed, 33 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt

diff --git a/Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt b/Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt
new file mode 100644
index 000000000000..377728128bef
--- /dev/null
+++ b/Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt
@@ -0,0 +1,26 @@
+STMicroelectronics STM32 Timer quadrature encoder
+
+STM32 Timer provides quadrature encoder counter mode to detect
+angular position and direction of rotary elements,
+from IN1 and IN2 input signals.
+
+Must be a sub-node of an STM32 Timer device tree node.
+See ../mfd/stm32-timers.txt for details about the parent node.
+
+Required properties:
+- compatible:		Must be "st,stm32-timer-counter".
+- pinctrl-names: 	Set to "default".
+- pinctrl-0: 		List of phandles pointing to pin configuration nodes,
+			to set IN1/IN2 pins in mode of operation for Low-Power
+			Timer input on external pin.
+
+Example:
+	timers@40010000  {
+		compatible = "st,stm32-timers";
+		...
+		counter {
+			compatible = "st,stm32-timer-counter";
+			pinctrl-names = "default";
+			pinctrl-0 = <&tim1_in_pins>;
+		};
+	};
diff --git a/Documentation/devicetree/bindings/mfd/stm32-timers.txt b/Documentation/devicetree/bindings/mfd/stm32-timers.txt
index 1db6e0057a63..ff9c14ada30b 100644
--- a/Documentation/devicetree/bindings/mfd/stm32-timers.txt
+++ b/Documentation/devicetree/bindings/mfd/stm32-timers.txt
@@ -23,6 +23,7 @@ Optional parameters:
 Optional subnodes:
 - pwm:			See ../pwm/pwm-stm32.txt
 - timer:		See ../iio/timer/stm32-timer-trigger.txt
+- counter:		See ../counter/stm32-timer-cnt.txt
 
 Example:
 	timers@40010000 {
@@ -43,4 +44,10 @@ Example:
 			compatible = "st,stm32-timer-trigger";
 			reg = <0>;
 		};
+
+		counter {
+			compatible = "st,stm32-timer-counter";
+			pinctrl-names = "default";
+			pinctrl-0 = <&tim1_in_pins>;
+		};
 	};
-- 
2.17.0

[PATCH v6 7/9] counter: Add STM32 Timer quadrature encoder

[William Breathitt Gray]

From: Benjamin Gaignard <benjamin.gaignard@st.com>

Implement counter part of the STM32 timer hardware block by using
counter API. Hardware only supports X2 and X4 quadrature modes. A
ceiling value can be set to define the maximum value reachable by the
counter.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
Co-authored-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
---
 drivers/counter/Kconfig           |  10 +
 drivers/counter/Makefile          |   1 +
 drivers/counter/stm32-timer-cnt.c | 390 ++++++++++++++++++++++++++++++
 3 files changed, 401 insertions(+)
 create mode 100644 drivers/counter/stm32-timer-cnt.c

diff --git a/drivers/counter/Kconfig b/drivers/counter/Kconfig
index 73f03372484f..90b698aa52cf 100644
--- a/drivers/counter/Kconfig
+++ b/drivers/counter/Kconfig
@@ -36,4 +36,14 @@ config 104_QUAD_8
 	  The base port addresses for the devices may be configured via the base
 	  array module parameter.
 
+config STM32_TIMER_CNT
+	tristate "STM32 Timer encoder counter driver"
+	depends on MFD_STM32_TIMERS || COMPILE_TEST
+	help
+	  Select this option to enable STM32 Timer quadrature encoder
+	  and counter driver.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called stm32-timer-cnt.
+
 endif # COUNTER
diff --git a/drivers/counter/Makefile b/drivers/counter/Makefile
index 23a4f6263e45..ff024259fb46 100644
--- a/drivers/counter/Makefile
+++ b/drivers/counter/Makefile
@@ -8,3 +8,4 @@ obj-$(CONFIG_COUNTER) += counter.o
 counter-y := generic-counter.o
 
 obj-$(CONFIG_104_QUAD_8)	+= 104-quad-8.o
+obj-$(CONFIG_STM32_TIMER_CNT)	+= stm32-timer-cnt.o
diff --git a/drivers/counter/stm32-timer-cnt.c b/drivers/counter/stm32-timer-cnt.c
new file mode 100644
index 000000000000..8fc6f74751b0
--- /dev/null
+++ b/drivers/counter/stm32-timer-cnt.c
@@ -0,0 +1,390 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * STM32 Timer Encoder and Counter driver
+ *
+ * Copyright (C) STMicroelectronics 2018
+ *
+ * Author: Benjamin Gaignard <benjamin.gaignard@st.com>
+ *
+ */
+#include <linux/counter.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/types.h>
+#include <linux/mfd/stm32-timers.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+#define TIM_CCMR_CCXS	(BIT(8) | BIT(0))
+#define TIM_CCMR_MASK	(TIM_CCMR_CC1S | TIM_CCMR_CC2S | \
+			 TIM_CCMR_IC1F | TIM_CCMR_IC2F)
+#define TIM_CCER_MASK	(TIM_CCER_CC1P | TIM_CCER_CC1NP | \
+			 TIM_CCER_CC2P | TIM_CCER_CC2NP)
+
+struct stm32_timer_cnt {
+	struct counter_device counter;
+	struct regmap *regmap;
+	struct clk *clk;
+	u32 ceiling;
+};
+
+/**
+ * stm32_count_function - enumerates stm32 timer counter encoder modes
+ * @STM32_COUNT_SLAVE_MODE_DISABLED: counts on internal clock when CEN=1
+ * @STM32_COUNT_ENCODER_MODE_1: counts TI1FP1 edges, depending on TI2FP2 level
+ * @STM32_COUNT_ENCODER_MODE_2: counts TI2FP2 edges, depending on TI1FP1 level
+ * @STM32_COUNT_ENCODER_MODE_3: counts on both TI1FP1 and TI2FP2 edges
+ */
+enum stm32_count_function {
+	STM32_COUNT_SLAVE_MODE_DISABLED = -1,
+	STM32_COUNT_ENCODER_MODE_1,
+	STM32_COUNT_ENCODER_MODE_2,
+	STM32_COUNT_ENCODER_MODE_3,
+};
+
+static enum count_function stm32_count_functions[] = {
+	[STM32_COUNT_ENCODER_MODE_1] = COUNT_FUNCTION_QUADRATURE_X2_A,
+	[STM32_COUNT_ENCODER_MODE_2] = COUNT_FUNCTION_QUADRATURE_X2_B,
+	[STM32_COUNT_ENCODER_MODE_3] = COUNT_FUNCTION_QUADRATURE_X4,
+};
+
+static int stm32_count_read(struct counter_device *counter,
+			    struct counter_count *count,
+			    struct count_read_value *val)
+{
+	struct stm32_timer_cnt *const priv = counter->priv;
+	u32 cnt;
+
+	regmap_read(priv->regmap, TIM_CNT, &cnt);
+	set_count_read_value(val, COUNT_POSITION_UNSIGNED, &cnt);
+
+	return 0;
+}
+
+static int stm32_count_write(struct counter_device *counter,
+			     struct counter_count *count,
+			     struct count_write_value *val)
+{
+	struct stm32_timer_cnt *const priv = counter->priv;
+	u32 cnt;
+	int err;
+
+	err = get_count_write_value(&cnt, COUNT_POSITION_UNSIGNED, val);
+	if (err)
+		return err;
+
+	if (cnt > priv->ceiling)
+		return -EINVAL;
+
+	return regmap_write(priv->regmap, TIM_CNT, cnt);
+}
+
+static int stm32_count_function_get(struct counter_device *counter,
+				    struct counter_count *count,
+				    size_t *function)
+{
+	struct stm32_timer_cnt *const priv = counter->priv;
+	u32 smcr;
+
+	regmap_read(priv->regmap, TIM_SMCR, &smcr);
+
+	switch (smcr & TIM_SMCR_SMS) {
+	case 1:
+		*function = STM32_COUNT_ENCODER_MODE_1;
+		return 0;
+	case 2:
+		*function = STM32_COUNT_ENCODER_MODE_2;
+		return 0;
+	case 3:
+		*function = STM32_COUNT_ENCODER_MODE_3;
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
+static int stm32_count_function_set(struct counter_device *counter,
+				    struct counter_count *count,
+				    size_t function)
+{
+	struct stm32_timer_cnt *const priv = counter->priv;
+	u32 cr1, sms;
+
+	switch (function) {
+	case STM32_COUNT_ENCODER_MODE_1:
+		sms = 1;
+		break;
+	case STM32_COUNT_ENCODER_MODE_2:
+		sms = 2;
+		break;
+	case STM32_COUNT_ENCODER_MODE_3:
+		sms = 3;
+		break;
+	default:
+		sms = 0;
+		break;
+	}
+
+	/* Store enable status */
+	regmap_read(priv->regmap, TIM_CR1, &cr1);
+
+	regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_CEN, 0);
+
+	/* TIMx_ARR register shouldn't be buffered (ARPE=0) */
+	regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_ARPE, 0);
+	regmap_write(priv->regmap, TIM_ARR, priv->ceiling);
+
+	regmap_update_bits(priv->regmap, TIM_SMCR, TIM_SMCR_SMS, sms);
+
+	/* Make sure that registers are updated */
+	regmap_update_bits(priv->regmap, TIM_EGR, TIM_EGR_UG, TIM_EGR_UG);
+
+	/* Restore the enable status */
+	regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_CEN, cr1);
+
+	return 0;
+}
+
+static ssize_t stm32_count_direction_read(struct counter_device *counter,
+				      struct counter_count *count,
+				      void *private, char *buf)
+{
+	struct stm32_timer_cnt *const priv = counter->priv;
+	const char *direction;
+	u32 cr1;
+
+	regmap_read(priv->regmap, TIM_CR1, &cr1);
+	direction = (cr1 & TIM_CR1_DIR) ? "backward" : "forward";
+
+	return scnprintf(buf, PAGE_SIZE, "%s\n", direction);
+}
+
+static ssize_t stm32_count_ceiling_read(struct counter_device *counter,
+					struct counter_count *count,
+					void *private, char *buf)
+{
+	struct stm32_timer_cnt *const priv = counter->priv;
+	u32 arr;
+
+	regmap_read(priv->regmap, TIM_ARR, &arr);
+
+	return snprintf(buf, PAGE_SIZE, "%u\n", arr);
+}
+
+static ssize_t stm32_count_ceiling_write(struct counter_device *counter,
+					 struct counter_count *count,
+					 void *private,
+					 const char *buf, size_t len)
+{
+	struct stm32_timer_cnt *const priv = counter->priv;
+	unsigned int ceiling;
+	int ret;
+
+	ret = kstrtouint(buf, 0, &ceiling);
+	if (ret)
+		return ret;
+
+	/* TIMx_ARR register shouldn't be buffered (ARPE=0) */
+	regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_ARPE, 0);
+	regmap_write(priv->regmap, TIM_ARR, ceiling);
+
+	priv->ceiling = ceiling;
+	return len;
+}
+
+static ssize_t stm32_count_enable_read(struct counter_device *counter,
+				       struct counter_count *count,
+				       void *private, char *buf)
+{
+	struct stm32_timer_cnt *const priv = counter->priv;
+	u32 cr1;
+
+	regmap_read(priv->regmap, TIM_CR1, &cr1);
+
+	return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)(cr1 & TIM_CR1_CEN));
+}
+
+static ssize_t stm32_count_enable_write(struct counter_device *counter,
+					struct counter_count *count,
+					void *private,
+					const char *buf, size_t len)
+{
+	struct stm32_timer_cnt *const priv = counter->priv;
+	int err;
+	u32 cr1;
+	bool enable;
+
+	err = kstrtobool(buf, &enable);
+	if (err)
+		return err;
+
+	if (enable) {
+		regmap_read(priv->regmap, TIM_CR1, &cr1);
+			if (!(cr1 & TIM_CR1_CEN))
+				clk_enable(priv->clk);
+
+		regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_CEN,
+				   TIM_CR1_CEN);
+	} else {
+		regmap_read(priv->regmap, TIM_CR1, &cr1);
+		regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_CEN, 0);
+		if (cr1 & TIM_CR1_CEN)
+			clk_disable(priv->clk);
+	}
+
+	return len;
+}
+
+static const struct counter_count_ext stm32_count_ext[] = {
+	{
+		.name = "direction",
+		.read = stm32_count_direction_read,
+	},
+	{
+		.name = "enable",
+		.read = stm32_count_enable_read,
+		.write = stm32_count_enable_write
+	},
+	{
+		.name = "ceiling",
+		.read = stm32_count_ceiling_read,
+		.write = stm32_count_ceiling_write
+	},
+};
+
+enum stm32_synapse_action {
+	STM32_SYNAPSE_ACTION_NONE,
+	STM32_SYNAPSE_ACTION_BOTH_EDGES
+};
+
+static enum synapse_action stm32_synapse_actions[] = {
+	[STM32_SYNAPSE_ACTION_NONE] = SYNAPSE_ACTION_NONE,
+	[STM32_SYNAPSE_ACTION_BOTH_EDGES] = SYNAPSE_ACTION_BOTH_EDGES
+};
+
+static int stm32_action_get(struct counter_device *counter,
+			    struct counter_count *count,
+			    struct counter_synapse *synapse,
+			    size_t *action)
+{
+	size_t function;
+	int err;
+
+	/* Default action mode (e.g. STM32_COUNT_SLAVE_MODE_DISABLED) */
+	*action = STM32_SYNAPSE_ACTION_NONE;
+
+	err = stm32_count_function_get(counter, count, &function);
+	if (err)
+		return 0;
+
+	switch (function) {
+	case STM32_COUNT_ENCODER_MODE_1:
+		/* counts up/down on TI1FP1 edge depending on TI2FP2 level */
+		if (synapse->signal->id == count->synapses[0].signal->id)
+			*action = STM32_SYNAPSE_ACTION_BOTH_EDGES;
+		break;
+	case STM32_COUNT_ENCODER_MODE_2:
+		/* counts up/down on TI2FP2 edge depending on TI1FP1 level */
+		if (synapse->signal->id == count->synapses[1].signal->id)
+			*action = STM32_SYNAPSE_ACTION_BOTH_EDGES;
+		break;
+	case STM32_COUNT_ENCODER_MODE_3:
+		/* counts up/down on both TI1FP1 and TI2FP2 edges */
+		*action = STM32_SYNAPSE_ACTION_BOTH_EDGES;
+		break;
+	}
+
+	return 0;
+}
+
+static const struct counter_ops stm32_timer_cnt_ops = {
+	.count_read = stm32_count_read,
+	.count_write = stm32_count_write,
+	.function_get = stm32_count_function_get,
+	.function_set = stm32_count_function_set,
+	.action_get = stm32_action_get,
+};
+
+static struct counter_signal stm32_signals[] = {
+	{
+		.id = 0,
+		.name = "Channel 1 Quadrature A"
+	},
+	{
+		.id = 1,
+		.name = "Channel 1 Quadrature B"
+	}
+};
+
+static struct counter_synapse stm32_count_synapses[] = {
+	{
+		.actions_list = stm32_synapse_actions,
+		.num_actions = ARRAY_SIZE(stm32_synapse_actions),
+		.signal = &stm32_signals[0]
+	},
+	{
+		.actions_list = stm32_synapse_actions,
+		.num_actions = ARRAY_SIZE(stm32_synapse_actions),
+		.signal = &stm32_signals[1]
+	}
+};
+
+static struct counter_count stm32_counts = {
+	.id = 0,
+	.name = "Channel 1 Count",
+	.functions_list = stm32_count_functions,
+	.num_functions = ARRAY_SIZE(stm32_count_functions),
+	.synapses = stm32_count_synapses,
+	.num_synapses = ARRAY_SIZE(stm32_count_synapses),
+	.ext = stm32_count_ext,
+	.num_ext = ARRAY_SIZE(stm32_count_ext)
+};
+
+static int stm32_timer_cnt_probe(struct platform_device *pdev)
+{
+	struct stm32_timers *ddata = dev_get_drvdata(pdev->dev.parent);
+	struct device *dev = &pdev->dev;
+	struct stm32_timer_cnt *priv;
+
+	if (IS_ERR_OR_NULL(ddata))
+		return -EINVAL;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->regmap = ddata->regmap;
+	priv->clk = ddata->clk;
+	priv->ceiling = ddata->max_arr;
+
+	priv->counter.name = dev_name(dev);
+	priv->counter.parent = dev;
+	priv->counter.ops = &stm32_timer_cnt_ops;
+	priv->counter.counts = &stm32_counts;
+	priv->counter.num_counts = 1;
+	priv->counter.signals = stm32_signals;
+	priv->counter.num_signals = ARRAY_SIZE(stm32_signals);
+	priv->counter.priv = priv;
+
+	/* Register Counter device */
+	return devm_counter_register(dev, &priv->counter);
+}
+
+static const struct of_device_id stm32_timer_cnt_of_match[] = {
+	{ .compatible = "st,stm32-timer-counter", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, stm32_timer_cnt_of_match);
+
+static struct platform_driver stm32_timer_cnt_driver = {
+	.probe = stm32_timer_cnt_probe,
+	.driver = {
+		.name = "stm32-timer-counter",
+		.of_match_table = stm32_timer_cnt_of_match,
+	},
+};
+module_platform_driver(stm32_timer_cnt_driver);
+
+MODULE_AUTHOR("Benjamin Gaignard <benjamin.gaignard@st.com>");
+MODULE_ALIAS("platform:stm32-timer-counter");
+MODULE_DESCRIPTION("STMicroelectronics STM32 TIMER counter driver");
+MODULE_LICENSE("GPL v2");
-- 
2.17.0

[PATCH v6 8/9] counter: stm32-lptimer: add counter device

[William Breathitt Gray]

From: Fabrice Gasnier <fabrice.gasnier@st.com>

Add support for new counter device to stm32-lptimer.

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
---
 .../{iio => }/counter/stm32-lptimer-cnt.txt   |   0
 .../devicetree/bindings/mfd/stm32-lptimer.txt |   2 +-
 drivers/counter/Kconfig                       |  10 +
 drivers/counter/Makefile                      |   1 +
 drivers/counter/stm32-lptimer-cnt.c           | 722 ++++++++++++++++++
 drivers/iio/counter/Kconfig                   |   9 -
 drivers/iio/counter/Makefile                  |   2 -
 drivers/iio/counter/stm32-lptimer-cnt.c       | 382 ---------
 8 files changed, 734 insertions(+), 394 deletions(-)
 rename Documentation/devicetree/bindings/{iio => }/counter/stm32-lptimer-cnt.txt (100%)
 create mode 100644 drivers/counter/stm32-lptimer-cnt.c
 delete mode 100644 drivers/iio/counter/stm32-lptimer-cnt.c

diff --git a/Documentation/devicetree/bindings/iio/counter/stm32-lptimer-cnt.txt b/Documentation/devicetree/bindings/counter/stm32-lptimer-cnt.txt
similarity index 100%
rename from Documentation/devicetree/bindings/iio/counter/stm32-lptimer-cnt.txt
rename to Documentation/devicetree/bindings/counter/stm32-lptimer-cnt.txt
diff --git a/Documentation/devicetree/bindings/mfd/stm32-lptimer.txt b/Documentation/devicetree/bindings/mfd/stm32-lptimer.txt
index 2a9ff29db9c9..fb54e4dad5b3 100644
--- a/Documentation/devicetree/bindings/mfd/stm32-lptimer.txt
+++ b/Documentation/devicetree/bindings/mfd/stm32-lptimer.txt
@@ -16,7 +16,7 @@ Required properties:
 
 Optional subnodes:
 - pwm:			See ../pwm/pwm-stm32-lp.txt
-- counter:		See ../iio/timer/stm32-lptimer-cnt.txt
+- counter:		See ../counter/stm32-lptimer-cnt.txt
 - trigger:		See ../iio/timer/stm32-lptimer-trigger.txt
 
 Example:
diff --git a/drivers/counter/Kconfig b/drivers/counter/Kconfig
index 90b698aa52cf..196d210d4e19 100644
--- a/drivers/counter/Kconfig
+++ b/drivers/counter/Kconfig
@@ -46,4 +46,14 @@ config STM32_TIMER_CNT
 	  To compile this driver as a module, choose M here: the
 	  module will be called stm32-timer-cnt.
 
+config STM32_LPTIMER_CNT
+	tristate "STM32 LP Timer encoder counter driver"
+	depends on (MFD_STM32_LPTIMER || COMPILE_TEST) && IIO
+	help
+	  Select this option to enable STM32 Low-Power Timer quadrature encoder
+	  and counter driver.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called stm32-lptimer-cnt.
+
 endif # COUNTER
diff --git a/drivers/counter/Makefile b/drivers/counter/Makefile
index ff024259fb46..8ff19b32022b 100644
--- a/drivers/counter/Makefile
+++ b/drivers/counter/Makefile
@@ -9,3 +9,4 @@ counter-y := generic-counter.o
 
 obj-$(CONFIG_104_QUAD_8)	+= 104-quad-8.o
 obj-$(CONFIG_STM32_TIMER_CNT)	+= stm32-timer-cnt.o
+obj-$(CONFIG_STM32_LPTIMER_CNT)	+= stm32-lptimer-cnt.o
diff --git a/drivers/counter/stm32-lptimer-cnt.c b/drivers/counter/stm32-lptimer-cnt.c
new file mode 100644
index 000000000000..c2c0b19320cf
--- /dev/null
+++ b/drivers/counter/stm32-lptimer-cnt.c
@@ -0,0 +1,722 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * STM32 Low-Power Timer Encoder and Counter driver
+ *
+ * Copyright (C) STMicroelectronics 2017
+ *
+ * Author: Fabrice Gasnier <fabrice.gasnier@st.com>
+ *
+ * Inspired by 104-quad-8 and stm32-timer-trigger drivers.
+ *
+ */
+
+#include <linux/bitfield.h>
+#include <linux/counter.h>
+#include <linux/iio/iio.h>
+#include <linux/mfd/stm32-lptimer.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+struct stm32_lptim_cnt {
+	struct counter_device counter;
+	struct device *dev;
+	struct regmap *regmap;
+	struct clk *clk;
+	u32 ceiling;
+	u32 polarity;
+	u32 quadrature_mode;
+};
+
+static int stm32_lptim_is_enabled(struct stm32_lptim_cnt *priv)
+{
+	u32 val;
+	int ret;
+
+	ret = regmap_read(priv->regmap, STM32_LPTIM_CR, &val);
+	if (ret)
+		return ret;
+
+	return FIELD_GET(STM32_LPTIM_ENABLE, val);
+}
+
+static int stm32_lptim_set_enable_state(struct stm32_lptim_cnt *priv,
+					int enable)
+{
+	int ret;
+	u32 val;
+
+	val = FIELD_PREP(STM32_LPTIM_ENABLE, enable);
+	ret = regmap_write(priv->regmap, STM32_LPTIM_CR, val);
+	if (ret)
+		return ret;
+
+	if (!enable) {
+		clk_disable(priv->clk);
+		return 0;
+	}
+
+	/* LP timer must be enabled before writing CMP & ARR */
+	ret = regmap_write(priv->regmap, STM32_LPTIM_ARR, priv->ceiling);
+	if (ret)
+		return ret;
+
+	ret = regmap_write(priv->regmap, STM32_LPTIM_CMP, 0);
+	if (ret)
+		return ret;
+
+	/* ensure CMP & ARR registers are properly written */
+	ret = regmap_read_poll_timeout(priv->regmap, STM32_LPTIM_ISR, val,
+				       (val & STM32_LPTIM_CMPOK_ARROK),
+				       100, 1000);
+	if (ret)
+		return ret;
+
+	ret = regmap_write(priv->regmap, STM32_LPTIM_ICR,
+			   STM32_LPTIM_CMPOKCF_ARROKCF);
+	if (ret)
+		return ret;
+
+	ret = clk_enable(priv->clk);
+	if (ret) {
+		regmap_write(priv->regmap, STM32_LPTIM_CR, 0);
+		return ret;
+	}
+
+	/* Start LP timer in continuous mode */
+	return regmap_update_bits(priv->regmap, STM32_LPTIM_CR,
+				  STM32_LPTIM_CNTSTRT, STM32_LPTIM_CNTSTRT);
+}
+
+static int stm32_lptim_setup(struct stm32_lptim_cnt *priv, int enable)
+{
+	u32 mask = STM32_LPTIM_ENC | STM32_LPTIM_COUNTMODE |
+		   STM32_LPTIM_CKPOL | STM32_LPTIM_PRESC;
+	u32 val;
+
+	/* Setup LP timer encoder/counter and polarity, without prescaler */
+	if (priv->quadrature_mode)
+		val = enable ? STM32_LPTIM_ENC : 0;
+	else
+		val = enable ? STM32_LPTIM_COUNTMODE : 0;
+	val |= FIELD_PREP(STM32_LPTIM_CKPOL, enable ? priv->polarity : 0);
+
+	return regmap_update_bits(priv->regmap, STM32_LPTIM_CFGR, mask, val);
+}
+
+static int stm32_lptim_write_raw(struct iio_dev *indio_dev,
+				 struct iio_chan_spec const *chan,
+				 int val, int val2, long mask)
+{
+	struct stm32_lptim_cnt *priv = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_ENABLE:
+		if (val < 0 || val > 1)
+			return -EINVAL;
+
+		/* Check nobody uses the timer, or already disabled/enabled */
+		ret = stm32_lptim_is_enabled(priv);
+		if ((ret < 0) || (!ret && !val))
+			return ret;
+		if (val && ret)
+			return -EBUSY;
+
+		ret = stm32_lptim_setup(priv, val);
+		if (ret)
+			return ret;
+		return stm32_lptim_set_enable_state(priv, val);
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static int stm32_lptim_read_raw(struct iio_dev *indio_dev,
+				struct iio_chan_spec const *chan,
+				int *val, int *val2, long mask)
+{
+	struct stm32_lptim_cnt *priv = iio_priv(indio_dev);
+	u32 dat;
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = regmap_read(priv->regmap, STM32_LPTIM_CNT, &dat);
+		if (ret)
+			return ret;
+		*val = dat;
+		return IIO_VAL_INT;
+
+	case IIO_CHAN_INFO_ENABLE:
+		ret = stm32_lptim_is_enabled(priv);
+		if (ret < 0)
+			return ret;
+		*val = ret;
+		return IIO_VAL_INT;
+
+	case IIO_CHAN_INFO_SCALE:
+		/* Non-quadrature mode: scale = 1 */
+		*val = 1;
+		*val2 = 0;
+		if (priv->quadrature_mode) {
+			/*
+			 * Quadrature encoder mode:
+			 * - both edges, quarter cycle, scale is 0.25
+			 * - either rising/falling edge scale is 0.5
+			 */
+			if (priv->polarity > 1)
+				*val2 = 2;
+			else
+				*val2 = 1;
+		}
+		return IIO_VAL_FRACTIONAL_LOG2;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info stm32_lptim_cnt_iio_info = {
+	.read_raw = stm32_lptim_read_raw,
+	.write_raw = stm32_lptim_write_raw,
+};
+
+static const char *const stm32_lptim_quadrature_modes[] = {
+	"non-quadrature",
+	"quadrature",
+};
+
+static int stm32_lptim_get_quadrature_mode(struct iio_dev *indio_dev,
+					   const struct iio_chan_spec *chan)
+{
+	struct stm32_lptim_cnt *priv = iio_priv(indio_dev);
+
+	return priv->quadrature_mode;
+}
+
+static int stm32_lptim_set_quadrature_mode(struct iio_dev *indio_dev,
+					   const struct iio_chan_spec *chan,
+					   unsigned int type)
+{
+	struct stm32_lptim_cnt *priv = iio_priv(indio_dev);
+
+	if (stm32_lptim_is_enabled(priv))
+		return -EBUSY;
+
+	priv->quadrature_mode = type;
+
+	return 0;
+}
+
+static const struct iio_enum stm32_lptim_quadrature_mode_en = {
+	.items = stm32_lptim_quadrature_modes,
+	.num_items = ARRAY_SIZE(stm32_lptim_quadrature_modes),
+	.get = stm32_lptim_get_quadrature_mode,
+	.set = stm32_lptim_set_quadrature_mode,
+};
+
+static const char * const stm32_lptim_cnt_polarity[] = {
+	"rising-edge", "falling-edge", "both-edges",
+};
+
+static int stm32_lptim_cnt_get_polarity(struct iio_dev *indio_dev,
+					const struct iio_chan_spec *chan)
+{
+	struct stm32_lptim_cnt *priv = iio_priv(indio_dev);
+
+	return priv->polarity;
+}
+
+static int stm32_lptim_cnt_set_polarity(struct iio_dev *indio_dev,
+					const struct iio_chan_spec *chan,
+					unsigned int type)
+{
+	struct stm32_lptim_cnt *priv = iio_priv(indio_dev);
+
+	if (stm32_lptim_is_enabled(priv))
+		return -EBUSY;
+
+	priv->polarity = type;
+
+	return 0;
+}
+
+static const struct iio_enum stm32_lptim_cnt_polarity_en = {
+	.items = stm32_lptim_cnt_polarity,
+	.num_items = ARRAY_SIZE(stm32_lptim_cnt_polarity),
+	.get = stm32_lptim_cnt_get_polarity,
+	.set = stm32_lptim_cnt_set_polarity,
+};
+
+static ssize_t stm32_lptim_cnt_get_ceiling(struct stm32_lptim_cnt *priv,
+					   char *buf)
+{
+	return snprintf(buf, PAGE_SIZE, "%u\n", priv->ceiling);
+}
+
+static ssize_t stm32_lptim_cnt_set_ceiling(struct stm32_lptim_cnt *priv,
+					   const char *buf, size_t len)
+{
+	int ret;
+
+	if (stm32_lptim_is_enabled(priv))
+		return -EBUSY;
+
+	ret = kstrtouint(buf, 0, &priv->ceiling);
+	if (ret)
+		return ret;
+
+	if (priv->ceiling > STM32_LPTIM_MAX_ARR)
+		return -EINVAL;
+
+	return len;
+}
+
+static ssize_t stm32_lptim_cnt_get_preset_iio(struct iio_dev *indio_dev,
+					      uintptr_t private,
+					      const struct iio_chan_spec *chan,
+					      char *buf)
+{
+	struct stm32_lptim_cnt *priv = iio_priv(indio_dev);
+
+	return stm32_lptim_cnt_get_ceiling(priv, buf);
+}
+
+static ssize_t stm32_lptim_cnt_set_preset_iio(struct iio_dev *indio_dev,
+					      uintptr_t private,
+					      const struct iio_chan_spec *chan,
+					      const char *buf, size_t len)
+{
+	struct stm32_lptim_cnt *priv = iio_priv(indio_dev);
+
+	return stm32_lptim_cnt_set_ceiling(priv, buf, len);
+}
+
+/* LP timer with encoder */
+static const struct iio_chan_spec_ext_info stm32_lptim_enc_ext_info[] = {
+	{
+		.name = "preset",
+		.shared = IIO_SEPARATE,
+		.read = stm32_lptim_cnt_get_preset_iio,
+		.write = stm32_lptim_cnt_set_preset_iio,
+	},
+	IIO_ENUM("polarity", IIO_SEPARATE, &stm32_lptim_cnt_polarity_en),
+	IIO_ENUM_AVAILABLE("polarity", &stm32_lptim_cnt_polarity_en),
+	IIO_ENUM("quadrature_mode", IIO_SEPARATE,
+		 &stm32_lptim_quadrature_mode_en),
+	IIO_ENUM_AVAILABLE("quadrature_mode", &stm32_lptim_quadrature_mode_en),
+	{}
+};
+
+static const struct iio_chan_spec stm32_lptim_enc_channels = {
+	.type = IIO_COUNT,
+	.channel = 0,
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+			      BIT(IIO_CHAN_INFO_ENABLE) |
+			      BIT(IIO_CHAN_INFO_SCALE),
+	.ext_info = stm32_lptim_enc_ext_info,
+	.indexed = 1,
+};
+
+/* LP timer without encoder (counter only) */
+static const struct iio_chan_spec_ext_info stm32_lptim_cnt_ext_info[] = {
+	{
+		.name = "preset",
+		.shared = IIO_SEPARATE,
+		.read = stm32_lptim_cnt_get_preset_iio,
+		.write = stm32_lptim_cnt_set_preset_iio,
+	},
+	IIO_ENUM("polarity", IIO_SEPARATE, &stm32_lptim_cnt_polarity_en),
+	IIO_ENUM_AVAILABLE("polarity", &stm32_lptim_cnt_polarity_en),
+	{}
+};
+
+static const struct iio_chan_spec stm32_lptim_cnt_channels = {
+	.type = IIO_COUNT,
+	.channel = 0,
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+			      BIT(IIO_CHAN_INFO_ENABLE) |
+			      BIT(IIO_CHAN_INFO_SCALE),
+	.ext_info = stm32_lptim_cnt_ext_info,
+	.indexed = 1,
+};
+
+/**
+ * stm32_lptim_cnt_function - enumerates stm32 LPTimer counter & encoder modes
+ * @STM32_LPTIM_COUNTER_INCREASE: up count on IN1 rising, falling or both edges
+ * @STM32_LPTIM_ENCODER_RISING: count on rising edge (IN1 & IN2 quadrature)
+ * @STM32_LPTIM_ENCODER_FALLING: count on falling edge (IN1 & IN2 quadrature)
+ * @STM32_LPTIM_ENCODER_BOTH_EDGE: count on both edges (IN1 & IN2 quadrature)
+ */
+enum stm32_lptim_cnt_function {
+	STM32_LPTIM_COUNTER_INCREASE,
+	STM32_LPTIM_ENCODER_RISING,
+	STM32_LPTIM_ENCODER_FALLING,
+	STM32_LPTIM_ENCODER_BOTH_EDGE,
+};
+
+static enum count_function stm32_lptim_cnt_functions[] = {
+	[STM32_LPTIM_COUNTER_INCREASE] = COUNT_FUNCTION_INCREASE,
+	[STM32_LPTIM_ENCODER_RISING] = COUNT_FUNCTION_QUADRATURE_X2_RISING,
+	[STM32_LPTIM_ENCODER_FALLING] = COUNT_FUNCTION_QUADRATURE_X2_FALLING,
+	[STM32_LPTIM_ENCODER_BOTH_EDGE] = COUNT_FUNCTION_QUADRATURE_X4,
+};
+
+enum stm32_lptim_synapse_action {
+	STM32_LPTIM_SYNAPSE_ACTION_RISING_EDGE,
+	STM32_LPTIM_SYNAPSE_ACTION_FALLING_EDGE,
+	STM32_LPTIM_SYNAPSE_ACTION_BOTH_EDGES,
+	STM32_LPTIM_SYNAPSE_ACTION_NONE,
+};
+
+static enum synapse_action stm32_lptim_cnt_synapse_actions[] = {
+	/* Index must match with stm32_lptim_cnt_polarity[] (priv->polarity) */
+	[STM32_LPTIM_SYNAPSE_ACTION_RISING_EDGE] = SYNAPSE_ACTION_RISING_EDGE,
+	[STM32_LPTIM_SYNAPSE_ACTION_FALLING_EDGE] = SYNAPSE_ACTION_FALLING_EDGE,
+	[STM32_LPTIM_SYNAPSE_ACTION_BOTH_EDGES] = SYNAPSE_ACTION_BOTH_EDGES,
+	[STM32_LPTIM_SYNAPSE_ACTION_NONE] = SYNAPSE_ACTION_NONE,
+};
+
+static int stm32_lptim_cnt_read(struct counter_device *counter,
+				struct counter_count *count,
+				struct count_read_value *val)
+{
+	struct stm32_lptim_cnt *const priv = counter->priv;
+	u32 cnt;
+	int ret;
+
+	ret = regmap_read(priv->regmap, STM32_LPTIM_CNT, &cnt);
+	if (ret)
+		return ret;
+
+	set_count_read_value(val, COUNT_POSITION_UNSIGNED, &cnt);
+
+	return 0;
+}
+
+static int stm32_lptim_cnt_function_get(struct counter_device *counter,
+					struct counter_count *count,
+					size_t *function)
+{
+	struct stm32_lptim_cnt *const priv = counter->priv;
+
+	if (!priv->quadrature_mode) {
+		*function = STM32_LPTIM_COUNTER_INCREASE;
+		return 0;
+	}
+
+	switch (priv->polarity) {
+	case STM32_LPTIM_SYNAPSE_ACTION_RISING_EDGE:
+		*function = STM32_LPTIM_ENCODER_RISING;
+		return 0;
+	case STM32_LPTIM_SYNAPSE_ACTION_FALLING_EDGE:
+		*function = STM32_LPTIM_ENCODER_FALLING;
+		return 0;
+	case STM32_LPTIM_SYNAPSE_ACTION_BOTH_EDGES:
+		*function = STM32_LPTIM_ENCODER_BOTH_EDGE;
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
+static int stm32_lptim_cnt_function_set(struct counter_device *counter,
+					struct counter_count *count,
+					size_t function)
+{
+	struct stm32_lptim_cnt *const priv = counter->priv;
+
+	if (stm32_lptim_is_enabled(priv))
+		return -EBUSY;
+
+	switch (function) {
+	case STM32_LPTIM_COUNTER_INCREASE:
+		priv->quadrature_mode = 0;
+		return 0;
+	case STM32_LPTIM_ENCODER_RISING:
+		priv->quadrature_mode = 1;
+		priv->polarity = STM32_LPTIM_SYNAPSE_ACTION_RISING_EDGE;
+		return 0;
+	case STM32_LPTIM_ENCODER_FALLING:
+		priv->quadrature_mode = 1;
+		priv->polarity = STM32_LPTIM_SYNAPSE_ACTION_FALLING_EDGE;
+		return 0;
+	case STM32_LPTIM_ENCODER_BOTH_EDGE:
+		priv->quadrature_mode = 1;
+		priv->polarity = STM32_LPTIM_SYNAPSE_ACTION_BOTH_EDGES;
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
+static ssize_t stm32_lptim_cnt_enable_read(struct counter_device *counter,
+					   struct counter_count *count,
+					   void *private, char *buf)
+{
+	struct stm32_lptim_cnt *const priv = counter->priv;
+	int ret;
+
+	ret = stm32_lptim_is_enabled(priv);
+	if (ret < 0)
+		return ret;
+
+	return scnprintf(buf, PAGE_SIZE, "%u\n", ret);
+}
+
+static ssize_t stm32_lptim_cnt_enable_write(struct counter_device *counter,
+					    struct counter_count *count,
+					    void *private,
+					    const char *buf, size_t len)
+{
+	struct stm32_lptim_cnt *const priv = counter->priv;
+	bool enable;
+	int ret;
+
+	ret = kstrtobool(buf, &enable);
+	if (ret)
+		return ret;
+
+	/* Check nobody uses the timer, or already disabled/enabled */
+	ret = stm32_lptim_is_enabled(priv);
+	if ((ret < 0) || (!ret && !enable))
+		return ret;
+	if (enable && ret)
+		return -EBUSY;
+
+	ret = stm32_lptim_setup(priv, enable);
+	if (ret)
+		return ret;
+
+	ret = stm32_lptim_set_enable_state(priv, enable);
+	if (ret)
+		return ret;
+
+	return len;
+}
+
+static ssize_t stm32_lptim_cnt_ceiling_read(struct counter_device *counter,
+					    struct counter_count *count,
+					    void *private, char *buf)
+{
+	struct stm32_lptim_cnt *const priv = counter->priv;
+
+	return stm32_lptim_cnt_get_ceiling(priv, buf);
+}
+
+static ssize_t stm32_lptim_cnt_ceiling_write(struct counter_device *counter,
+					     struct counter_count *count,
+					     void *private,
+					     const char *buf, size_t len)
+{
+	struct stm32_lptim_cnt *const priv = counter->priv;
+
+	return stm32_lptim_cnt_set_ceiling(priv, buf, len);
+}
+
+static const struct counter_count_ext stm32_lptim_cnt_ext[] = {
+	{
+		.name = "enable",
+		.read = stm32_lptim_cnt_enable_read,
+		.write = stm32_lptim_cnt_enable_write
+	},
+	{
+		.name = "ceiling",
+		.read = stm32_lptim_cnt_ceiling_read,
+		.write = stm32_lptim_cnt_ceiling_write
+	},
+};
+
+static int stm32_lptim_cnt_action_get(struct counter_device *counter,
+				      struct counter_count *count,
+				      struct counter_synapse *synapse,
+				      size_t *action)
+{
+	struct stm32_lptim_cnt *const priv = counter->priv;
+	size_t function;
+	int err;
+
+	err = stm32_lptim_cnt_function_get(counter, count, &function);
+	if (err)
+		return err;
+
+	switch (function) {
+	case STM32_LPTIM_COUNTER_INCREASE:
+		/* LP Timer acts as up-counter on input 1 */
+		if (synapse->signal->id == count->synapses[0].signal->id)
+			*action = priv->polarity;
+		else
+			*action = STM32_LPTIM_SYNAPSE_ACTION_NONE;
+		return 0;
+	case STM32_LPTIM_ENCODER_RISING:
+	case STM32_LPTIM_ENCODER_FALLING:
+	case STM32_LPTIM_ENCODER_BOTH_EDGE:
+		*action = priv->polarity;
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
+static int stm32_lptim_cnt_action_set(struct counter_device *counter,
+				      struct counter_count *count,
+				      struct counter_synapse *synapse,
+				      size_t action)
+{
+	struct stm32_lptim_cnt *const priv = counter->priv;
+	size_t function;
+	int err;
+
+	if (stm32_lptim_is_enabled(priv))
+		return -EBUSY;
+
+	err = stm32_lptim_cnt_function_get(counter, count, &function);
+	if (err)
+		return err;
+
+	/* only set polarity when in counter mode (on input 1) */
+	if (function == STM32_LPTIM_COUNTER_INCREASE
+	    && synapse->signal->id == count->synapses[0].signal->id) {
+		switch (action) {
+		case STM32_LPTIM_SYNAPSE_ACTION_RISING_EDGE:
+		case STM32_LPTIM_SYNAPSE_ACTION_FALLING_EDGE:
+		case STM32_LPTIM_SYNAPSE_ACTION_BOTH_EDGES:
+			priv->polarity = action;
+			return 0;
+		}
+	}
+
+	return -EINVAL;
+}
+
+static const struct counter_ops stm32_lptim_cnt_ops = {
+	.count_read = stm32_lptim_cnt_read,
+	.function_get = stm32_lptim_cnt_function_get,
+	.function_set = stm32_lptim_cnt_function_set,
+	.action_get = stm32_lptim_cnt_action_get,
+	.action_set = stm32_lptim_cnt_action_set,
+};
+
+static struct counter_signal stm32_lptim_cnt_signals[] = {
+	{
+		.id = 0,
+		.name = "Channel 1 Quadrature A"
+	},
+	{
+		.id = 1,
+		.name = "Channel 1 Quadrature B"
+	}
+};
+
+static struct counter_synapse stm32_lptim_cnt_synapses[] = {
+	{
+		.actions_list = stm32_lptim_cnt_synapse_actions,
+		.num_actions = ARRAY_SIZE(stm32_lptim_cnt_synapse_actions),
+		.signal = &stm32_lptim_cnt_signals[0]
+	},
+	{
+		.actions_list = stm32_lptim_cnt_synapse_actions,
+		.num_actions = ARRAY_SIZE(stm32_lptim_cnt_synapse_actions),
+		.signal = &stm32_lptim_cnt_signals[1]
+	}
+};
+
+/* LP timer with encoder */
+static struct counter_count stm32_lptim_enc_counts = {
+	.id = 0,
+	.name = "LPTimer Count",
+	.functions_list = stm32_lptim_cnt_functions,
+	.num_functions = ARRAY_SIZE(stm32_lptim_cnt_functions),
+	.synapses = stm32_lptim_cnt_synapses,
+	.num_synapses = ARRAY_SIZE(stm32_lptim_cnt_synapses),
+	.ext = stm32_lptim_cnt_ext,
+	.num_ext = ARRAY_SIZE(stm32_lptim_cnt_ext)
+};
+
+/* LP timer without encoder (counter only) */
+static struct counter_count stm32_lptim_in1_counts = {
+	.id = 0,
+	.name = "LPTimer Count",
+	.functions_list = stm32_lptim_cnt_functions,
+	.num_functions = 1,
+	.synapses = stm32_lptim_cnt_synapses,
+	.num_synapses = 1,
+	.ext = stm32_lptim_cnt_ext,
+	.num_ext = ARRAY_SIZE(stm32_lptim_cnt_ext)
+};
+
+static int stm32_lptim_cnt_probe(struct platform_device *pdev)
+{
+	struct stm32_lptimer *ddata = dev_get_drvdata(pdev->dev.parent);
+	struct stm32_lptim_cnt *priv;
+	struct iio_dev *indio_dev;
+	int ret;
+
+	if (IS_ERR_OR_NULL(ddata))
+		return -EINVAL;
+
+	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*priv));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	priv = iio_priv(indio_dev);
+	priv->dev = &pdev->dev;
+	priv->regmap = ddata->regmap;
+	priv->clk = ddata->clk;
+	priv->ceiling = STM32_LPTIM_MAX_ARR;
+
+	/* Initialize IIO device */
+	indio_dev->name = dev_name(&pdev->dev);
+	indio_dev->dev.parent = &pdev->dev;
+	indio_dev->dev.of_node = pdev->dev.of_node;
+	indio_dev->info = &stm32_lptim_cnt_iio_info;
+	if (ddata->has_encoder)
+		indio_dev->channels = &stm32_lptim_enc_channels;
+	else
+		indio_dev->channels = &stm32_lptim_cnt_channels;
+	indio_dev->num_channels = 1;
+
+	/* Initialize Counter device */
+	priv->counter.name = dev_name(&pdev->dev);
+	priv->counter.parent = &pdev->dev;
+	priv->counter.ops = &stm32_lptim_cnt_ops;
+	if (ddata->has_encoder) {
+		priv->counter.counts = &stm32_lptim_enc_counts;
+		priv->counter.num_signals = ARRAY_SIZE(stm32_lptim_cnt_signals);
+	} else {
+		priv->counter.counts = &stm32_lptim_in1_counts;
+		priv->counter.num_signals = 1;
+	}
+	priv->counter.num_counts = 1;
+	priv->counter.signals = stm32_lptim_cnt_signals;
+	priv->counter.priv = priv;
+
+	platform_set_drvdata(pdev, priv);
+
+	ret = devm_iio_device_register(&pdev->dev, indio_dev);
+	if (ret)
+		return ret;
+
+	return devm_counter_register(&pdev->dev, &priv->counter);
+}
+
+static const struct of_device_id stm32_lptim_cnt_of_match[] = {
+	{ .compatible = "st,stm32-lptimer-counter", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, stm32_lptim_cnt_of_match);
+
+static struct platform_driver stm32_lptim_cnt_driver = {
+	.probe = stm32_lptim_cnt_probe,
+	.driver = {
+		.name = "stm32-lptimer-counter",
+		.of_match_table = stm32_lptim_cnt_of_match,
+	},
+};
+module_platform_driver(stm32_lptim_cnt_driver);
+
+MODULE_AUTHOR("Fabrice Gasnier <fabrice.gasnier@st.com>");
+MODULE_ALIAS("platform:stm32-lptimer-counter");
+MODULE_DESCRIPTION("STMicroelectronics STM32 LPTIM counter driver");
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/iio/counter/Kconfig b/drivers/iio/counter/Kconfig
index eeb358122cbe..95a7a0df6cac 100644
--- a/drivers/iio/counter/Kconfig
+++ b/drivers/iio/counter/Kconfig
@@ -5,13 +5,4 @@
 
 menu "Counters"
 
-config STM32_LPTIMER_CNT
-	tristate "STM32 LP Timer encoder counter driver"
-	depends on MFD_STM32_LPTIMER || COMPILE_TEST
-	help
-	  Select this option to enable STM32 Low-Power Timer quadrature encoder
-	  and counter driver.
-
-	  To compile this driver as a module, choose M here: the
-	  module will be called stm32-lptimer-cnt.
 endmenu
diff --git a/drivers/iio/counter/Makefile b/drivers/iio/counter/Makefile
index 93933ba49280..8fd3d954775a 100644
--- a/drivers/iio/counter/Makefile
+++ b/drivers/iio/counter/Makefile
@@ -3,5 +3,3 @@
 #
 
 # When adding new entries keep the list in alphabetical order
-
-obj-$(CONFIG_STM32_LPTIMER_CNT)	+= stm32-lptimer-cnt.o
diff --git a/drivers/iio/counter/stm32-lptimer-cnt.c b/drivers/iio/counter/stm32-lptimer-cnt.c
deleted file mode 100644
index 42fb8ba67090..000000000000
--- a/drivers/iio/counter/stm32-lptimer-cnt.c
+++ /dev/null
@@ -1,382 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- * STM32 Low-Power Timer Encoder and Counter driver
- *
- * Copyright (C) STMicroelectronics 2017
- *
- * Author: Fabrice Gasnier <fabrice.gasnier@st.com>
- *
- * Inspired by 104-quad-8 and stm32-timer-trigger drivers.
- *
- */
-
-#include <linux/bitfield.h>
-#include <linux/iio/iio.h>
-#include <linux/mfd/stm32-lptimer.h>
-#include <linux/module.h>
-#include <linux/platform_device.h>
-
-struct stm32_lptim_cnt {
-	struct device *dev;
-	struct regmap *regmap;
-	struct clk *clk;
-	u32 preset;
-	u32 polarity;
-	u32 quadrature_mode;
-};
-
-static int stm32_lptim_is_enabled(struct stm32_lptim_cnt *priv)
-{
-	u32 val;
-	int ret;
-
-	ret = regmap_read(priv->regmap, STM32_LPTIM_CR, &val);
-	if (ret)
-		return ret;
-
-	return FIELD_GET(STM32_LPTIM_ENABLE, val);
-}
-
-static int stm32_lptim_set_enable_state(struct stm32_lptim_cnt *priv,
-					int enable)
-{
-	int ret;
-	u32 val;
-
-	val = FIELD_PREP(STM32_LPTIM_ENABLE, enable);
-	ret = regmap_write(priv->regmap, STM32_LPTIM_CR, val);
-	if (ret)
-		return ret;
-
-	if (!enable) {
-		clk_disable(priv->clk);
-		return 0;
-	}
-
-	/* LP timer must be enabled before writing CMP & ARR */
-	ret = regmap_write(priv->regmap, STM32_LPTIM_ARR, priv->preset);
-	if (ret)
-		return ret;
-
-	ret = regmap_write(priv->regmap, STM32_LPTIM_CMP, 0);
-	if (ret)
-		return ret;
-
-	/* ensure CMP & ARR registers are properly written */
-	ret = regmap_read_poll_timeout(priv->regmap, STM32_LPTIM_ISR, val,
-				       (val & STM32_LPTIM_CMPOK_ARROK),
-				       100, 1000);
-	if (ret)
-		return ret;
-
-	ret = regmap_write(priv->regmap, STM32_LPTIM_ICR,
-			   STM32_LPTIM_CMPOKCF_ARROKCF);
-	if (ret)
-		return ret;
-
-	ret = clk_enable(priv->clk);
-	if (ret) {
-		regmap_write(priv->regmap, STM32_LPTIM_CR, 0);
-		return ret;
-	}
-
-	/* Start LP timer in continuous mode */
-	return regmap_update_bits(priv->regmap, STM32_LPTIM_CR,
-				  STM32_LPTIM_CNTSTRT, STM32_LPTIM_CNTSTRT);
-}
-
-static int stm32_lptim_setup(struct stm32_lptim_cnt *priv, int enable)
-{
-	u32 mask = STM32_LPTIM_ENC | STM32_LPTIM_COUNTMODE |
-		   STM32_LPTIM_CKPOL | STM32_LPTIM_PRESC;
-	u32 val;
-
-	/* Setup LP timer encoder/counter and polarity, without prescaler */
-	if (priv->quadrature_mode)
-		val = enable ? STM32_LPTIM_ENC : 0;
-	else
-		val = enable ? STM32_LPTIM_COUNTMODE : 0;
-	val |= FIELD_PREP(STM32_LPTIM_CKPOL, enable ? priv->polarity : 0);
-
-	return regmap_update_bits(priv->regmap, STM32_LPTIM_CFGR, mask, val);
-}
-
-static int stm32_lptim_write_raw(struct iio_dev *indio_dev,
-				 struct iio_chan_spec const *chan,
-				 int val, int val2, long mask)
-{
-	struct stm32_lptim_cnt *priv = iio_priv(indio_dev);
-	int ret;
-
-	switch (mask) {
-	case IIO_CHAN_INFO_ENABLE:
-		if (val < 0 || val > 1)
-			return -EINVAL;
-
-		/* Check nobody uses the timer, or already disabled/enabled */
-		ret = stm32_lptim_is_enabled(priv);
-		if ((ret < 0) || (!ret && !val))
-			return ret;
-		if (val && ret)
-			return -EBUSY;
-
-		ret = stm32_lptim_setup(priv, val);
-		if (ret)
-			return ret;
-		return stm32_lptim_set_enable_state(priv, val);
-
-	default:
-		return -EINVAL;
-	}
-}
-
-static int stm32_lptim_read_raw(struct iio_dev *indio_dev,
-				struct iio_chan_spec const *chan,
-				int *val, int *val2, long mask)
-{
-	struct stm32_lptim_cnt *priv = iio_priv(indio_dev);
-	u32 dat;
-	int ret;
-
-	switch (mask) {
-	case IIO_CHAN_INFO_RAW:
-		ret = regmap_read(priv->regmap, STM32_LPTIM_CNT, &dat);
-		if (ret)
-			return ret;
-		*val = dat;
-		return IIO_VAL_INT;
-
-	case IIO_CHAN_INFO_ENABLE:
-		ret = stm32_lptim_is_enabled(priv);
-		if (ret < 0)
-			return ret;
-		*val = ret;
-		return IIO_VAL_INT;
-
-	case IIO_CHAN_INFO_SCALE:
-		/* Non-quadrature mode: scale = 1 */
-		*val = 1;
-		*val2 = 0;
-		if (priv->quadrature_mode) {
-			/*
-			 * Quadrature encoder mode:
-			 * - both edges, quarter cycle, scale is 0.25
-			 * - either rising/falling edge scale is 0.5
-			 */
-			if (priv->polarity > 1)
-				*val2 = 2;
-			else
-				*val2 = 1;
-		}
-		return IIO_VAL_FRACTIONAL_LOG2;
-
-	default:
-		return -EINVAL;
-	}
-}
-
-static const struct iio_info stm32_lptim_cnt_iio_info = {
-	.read_raw = stm32_lptim_read_raw,
-	.write_raw = stm32_lptim_write_raw,
-};
-
-static const char *const stm32_lptim_quadrature_modes[] = {
-	"non-quadrature",
-	"quadrature",
-};
-
-static int stm32_lptim_get_quadrature_mode(struct iio_dev *indio_dev,
-					   const struct iio_chan_spec *chan)
-{
-	struct stm32_lptim_cnt *priv = iio_priv(indio_dev);
-
-	return priv->quadrature_mode;
-}
-
-static int stm32_lptim_set_quadrature_mode(struct iio_dev *indio_dev,
-					   const struct iio_chan_spec *chan,
-					   unsigned int type)
-{
-	struct stm32_lptim_cnt *priv = iio_priv(indio_dev);
-
-	if (stm32_lptim_is_enabled(priv))
-		return -EBUSY;
-
-	priv->quadrature_mode = type;
-
-	return 0;
-}
-
-static const struct iio_enum stm32_lptim_quadrature_mode_en = {
-	.items = stm32_lptim_quadrature_modes,
-	.num_items = ARRAY_SIZE(stm32_lptim_quadrature_modes),
-	.get = stm32_lptim_get_quadrature_mode,
-	.set = stm32_lptim_set_quadrature_mode,
-};
-
-static const char * const stm32_lptim_cnt_polarity[] = {
-	"rising-edge", "falling-edge", "both-edges",
-};
-
-static int stm32_lptim_cnt_get_polarity(struct iio_dev *indio_dev,
-					const struct iio_chan_spec *chan)
-{
-	struct stm32_lptim_cnt *priv = iio_priv(indio_dev);
-
-	return priv->polarity;
-}
-
-static int stm32_lptim_cnt_set_polarity(struct iio_dev *indio_dev,
-					const struct iio_chan_spec *chan,
-					unsigned int type)
-{
-	struct stm32_lptim_cnt *priv = iio_priv(indio_dev);
-
-	if (stm32_lptim_is_enabled(priv))
-		return -EBUSY;
-
-	priv->polarity = type;
-
-	return 0;
-}
-
-static const struct iio_enum stm32_lptim_cnt_polarity_en = {
-	.items = stm32_lptim_cnt_polarity,
-	.num_items = ARRAY_SIZE(stm32_lptim_cnt_polarity),
-	.get = stm32_lptim_cnt_get_polarity,
-	.set = stm32_lptim_cnt_set_polarity,
-};
-
-static ssize_t stm32_lptim_cnt_get_preset(struct iio_dev *indio_dev,
-					  uintptr_t private,
-					  const struct iio_chan_spec *chan,
-					  char *buf)
-{
-	struct stm32_lptim_cnt *priv = iio_priv(indio_dev);
-
-	return snprintf(buf, PAGE_SIZE, "%u\n", priv->preset);
-}
-
-static ssize_t stm32_lptim_cnt_set_preset(struct iio_dev *indio_dev,
-					  uintptr_t private,
-					  const struct iio_chan_spec *chan,
-					  const char *buf, size_t len)
-{
-	struct stm32_lptim_cnt *priv = iio_priv(indio_dev);
-	int ret;
-
-	if (stm32_lptim_is_enabled(priv))
-		return -EBUSY;
-
-	ret = kstrtouint(buf, 0, &priv->preset);
-	if (ret)
-		return ret;
-
-	if (priv->preset > STM32_LPTIM_MAX_ARR)
-		return -EINVAL;
-
-	return len;
-}
-
-/* LP timer with encoder */
-static const struct iio_chan_spec_ext_info stm32_lptim_enc_ext_info[] = {
-	{
-		.name = "preset",
-		.shared = IIO_SEPARATE,
-		.read = stm32_lptim_cnt_get_preset,
-		.write = stm32_lptim_cnt_set_preset,
-	},
-	IIO_ENUM("polarity", IIO_SEPARATE, &stm32_lptim_cnt_polarity_en),
-	IIO_ENUM_AVAILABLE("polarity", &stm32_lptim_cnt_polarity_en),
-	IIO_ENUM("quadrature_mode", IIO_SEPARATE,
-		 &stm32_lptim_quadrature_mode_en),
-	IIO_ENUM_AVAILABLE("quadrature_mode", &stm32_lptim_quadrature_mode_en),
-	{}
-};
-
-static const struct iio_chan_spec stm32_lptim_enc_channels = {
-	.type = IIO_COUNT,
-	.channel = 0,
-	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
-			      BIT(IIO_CHAN_INFO_ENABLE) |
-			      BIT(IIO_CHAN_INFO_SCALE),
-	.ext_info = stm32_lptim_enc_ext_info,
-	.indexed = 1,
-};
-
-/* LP timer without encoder (counter only) */
-static const struct iio_chan_spec_ext_info stm32_lptim_cnt_ext_info[] = {
-	{
-		.name = "preset",
-		.shared = IIO_SEPARATE,
-		.read = stm32_lptim_cnt_get_preset,
-		.write = stm32_lptim_cnt_set_preset,
-	},
-	IIO_ENUM("polarity", IIO_SEPARATE, &stm32_lptim_cnt_polarity_en),
-	IIO_ENUM_AVAILABLE("polarity", &stm32_lptim_cnt_polarity_en),
-	{}
-};
-
-static const struct iio_chan_spec stm32_lptim_cnt_channels = {
-	.type = IIO_COUNT,
-	.channel = 0,
-	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
-			      BIT(IIO_CHAN_INFO_ENABLE) |
-			      BIT(IIO_CHAN_INFO_SCALE),
-	.ext_info = stm32_lptim_cnt_ext_info,
-	.indexed = 1,
-};
-
-static int stm32_lptim_cnt_probe(struct platform_device *pdev)
-{
-	struct stm32_lptimer *ddata = dev_get_drvdata(pdev->dev.parent);
-	struct stm32_lptim_cnt *priv;
-	struct iio_dev *indio_dev;
-
-	if (IS_ERR_OR_NULL(ddata))
-		return -EINVAL;
-
-	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*priv));
-	if (!indio_dev)
-		return -ENOMEM;
-
-	priv = iio_priv(indio_dev);
-	priv->dev = &pdev->dev;
-	priv->regmap = ddata->regmap;
-	priv->clk = ddata->clk;
-	priv->preset = STM32_LPTIM_MAX_ARR;
-
-	indio_dev->name = dev_name(&pdev->dev);
-	indio_dev->dev.parent = &pdev->dev;
-	indio_dev->dev.of_node = pdev->dev.of_node;
-	indio_dev->info = &stm32_lptim_cnt_iio_info;
-	if (ddata->has_encoder)
-		indio_dev->channels = &stm32_lptim_enc_channels;
-	else
-		indio_dev->channels = &stm32_lptim_cnt_channels;
-	indio_dev->num_channels = 1;
-
-	platform_set_drvdata(pdev, priv);
-
-	return devm_iio_device_register(&pdev->dev, indio_dev);
-}
-
-static const struct of_device_id stm32_lptim_cnt_of_match[] = {
-	{ .compatible = "st,stm32-lptimer-counter", },
-	{},
-};
-MODULE_DEVICE_TABLE(of, stm32_lptim_cnt_of_match);
-
-static struct platform_driver stm32_lptim_cnt_driver = {
-	.probe = stm32_lptim_cnt_probe,
-	.driver = {
-		.name = "stm32-lptimer-counter",
-		.of_match_table = stm32_lptim_cnt_of_match,
-	},
-};
-module_platform_driver(stm32_lptim_cnt_driver);
-
-MODULE_AUTHOR("Fabrice Gasnier <fabrice.gasnier@st.com>");
-MODULE_ALIAS("platform:stm32-lptimer-counter");
-MODULE_DESCRIPTION("STMicroelectronics STM32 LPTIM counter driver");
-MODULE_LICENSE("GPL v2");
-- 
2.17.0

[PATCH v6 9/9] iio: counter: Remove IIO counter subdirectory

[William Breathitt Gray]

This patch removes the IIO counter subdirectory which is now superceded
by the Counter subsystem. Deprecation warnings are added to the
documentation of the relevant IIO counter sysfs attributes.

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
---
 Documentation/ABI/testing/sysfs-bus-iio          |  8 ++++++++
 .../ABI/testing/sysfs-bus-iio-counter-104-quad-8 | 16 ++++++++++++++++
 drivers/iio/Kconfig                              |  1 -
 drivers/iio/Makefile                             |  1 -
 drivers/iio/counter/Kconfig                      |  8 --------
 drivers/iio/counter/Makefile                     |  5 -----
 6 files changed, 24 insertions(+), 15 deletions(-)
 delete mode 100644 drivers/iio/counter/Kconfig
 delete mode 100644 drivers/iio/counter/Makefile

diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
index 731146c3b138..6115d97b075e 100644
--- a/Documentation/ABI/testing/sysfs-bus-iio
+++ b/Documentation/ABI/testing/sysfs-bus-iio
@@ -1637,6 +1637,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_raw
 KernelVersion:	4.10
 Contact:	linux-iio@vger.kernel.org
 Description:
+		This interface is deprecated; please use the Counter subsystem.
+
 		Raw counter device counts from channel Y. For quadrature
 		counters, multiplication by an available [Y]_scale results in
 		the counts of a single quadrature signal phase from channel Y.
@@ -1645,6 +1647,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_indexY_raw
 KernelVersion:	4.10
 Contact:	linux-iio@vger.kernel.org
 Description:
+		This interface is deprecated; please use the Counter subsystem.
+
 		Raw counter device index value from channel Y. This attribute
 		provides an absolute positional reference (e.g. a pulse once per
 		revolution) which may be used to home positional systems as
@@ -1654,6 +1658,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_count_count_direction_available
 KernelVersion:	4.12
 Contact:	linux-iio@vger.kernel.org
 Description:
+		This interface is deprecated; please use the Counter subsystem.
+
 		A list of possible counting directions which are:
 		- "up"	: counter device is increasing.
 		- "down": counter device is decreasing.
@@ -1662,4 +1668,6 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_count_direction
 KernelVersion:	4.12
 Contact:	linux-iio@vger.kernel.org
 Description:
+		This interface is deprecated; please use the Counter subsystem.
+
 		Raw counter device counters direction for channel Y.
diff --git a/Documentation/ABI/testing/sysfs-bus-iio-counter-104-quad-8 b/Documentation/ABI/testing/sysfs-bus-iio-counter-104-quad-8
index 7fac2c268d9a..bac3d0d48b7b 100644
--- a/Documentation/ABI/testing/sysfs-bus-iio-counter-104-quad-8
+++ b/Documentation/ABI/testing/sysfs-bus-iio-counter-104-quad-8
@@ -6,6 +6,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_index_synchronous_mode_available
 KernelVersion:	4.10
 Contact:	linux-iio@vger.kernel.org
 Description:
+		This interface is deprecated; please use the Counter subsystem.
+
 		Discrete set of available values for the respective counter
 		configuration are listed in this file.
 
@@ -13,6 +15,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_count_mode
 KernelVersion:	4.10
 Contact:	linux-iio@vger.kernel.org
 Description:
+		This interface is deprecated; please use the Counter subsystem.
+
 		Count mode for channel Y. Four count modes are available:
 		normal, range limit, non-recycle, and modulo-n. The preset value
 		for channel Y is used by the count mode where required.
@@ -47,6 +51,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_noise_error
 KernelVersion:	4.10
 Contact:	linux-iio@vger.kernel.org
 Description:
+		This interface is deprecated; please use the Counter subsystem.
+
 		Read-only attribute that indicates whether excessive noise is
 		present at the channel Y count inputs in quadrature clock mode;
 		irrelevant in non-quadrature clock mode.
@@ -55,6 +61,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_preset
 KernelVersion:	4.10
 Contact:	linux-iio@vger.kernel.org
 Description:
+		This interface is deprecated; please use the Counter subsystem.
+
 		If the counter device supports preset registers, the preset
 		count for channel Y is provided by this attribute.
 
@@ -62,6 +70,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_quadrature_mode
 KernelVersion:	4.10
 Contact:	linux-iio@vger.kernel.org
 Description:
+		This interface is deprecated; please use the Counter subsystem.
+
 		Configure channel Y counter for non-quadrature or quadrature
 		clock mode. Selecting non-quadrature clock mode will disable
 		synchronous load mode. In quadrature clock mode, the channel Y
@@ -83,6 +93,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_set_to_preset_on_index
 KernelVersion:	4.10
 Contact:	linux-iio@vger.kernel.org
 Description:
+		This interface is deprecated; please use the Counter subsystem.
+
 		Whether to set channel Y counter with channel Y preset value
 		when channel Y index input is active, or continuously count.
 		Valid attribute values are boolean.
@@ -91,6 +103,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_indexY_index_polarity
 KernelVersion:	4.10
 Contact:	linux-iio@vger.kernel.org
 Description:
+		This interface is deprecated; please use the Counter subsystem.
+
 		Active level of channel Y index input; irrelevant in
 		non-synchronous load mode.
 
@@ -98,6 +112,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_indexY_synchronous_mode
 KernelVersion:	4.10
 Contact:	linux-iio@vger.kernel.org
 Description:
+		This interface is deprecated; please use the Counter subsystem.
+
 		Configure channel Y counter for non-synchronous or synchronous
 		load mode. Synchronous load mode cannot be selected in
 		non-quadrature clock mode.
diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
index d69e85a8bdc3..1152efad91a1 100644
--- a/drivers/iio/Kconfig
+++ b/drivers/iio/Kconfig
@@ -74,7 +74,6 @@ source "drivers/iio/afe/Kconfig"
 source "drivers/iio/amplifiers/Kconfig"
 source "drivers/iio/chemical/Kconfig"
 source "drivers/iio/common/Kconfig"
-source "drivers/iio/counter/Kconfig"
 source "drivers/iio/dac/Kconfig"
 source "drivers/iio/dummy/Kconfig"
 source "drivers/iio/frequency/Kconfig"
diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile
index d8cba9c229c0..7bdd31f1b88f 100644
--- a/drivers/iio/Makefile
+++ b/drivers/iio/Makefile
@@ -20,7 +20,6 @@ obj-y += amplifiers/
 obj-y += buffer/
 obj-y += chemical/
 obj-y += common/
-obj-y += counter/
 obj-y += dac/
 obj-y += dummy/
 obj-y += gyro/
diff --git a/drivers/iio/counter/Kconfig b/drivers/iio/counter/Kconfig
deleted file mode 100644
index 95a7a0df6cac..000000000000
--- a/drivers/iio/counter/Kconfig
+++ /dev/null
@@ -1,8 +0,0 @@
-#
-# Counter devices
-#
-# When adding new entries keep the list in alphabetical order
-
-menu "Counters"
-
-endmenu
diff --git a/drivers/iio/counter/Makefile b/drivers/iio/counter/Makefile
deleted file mode 100644
index 8fd3d954775a..000000000000
--- a/drivers/iio/counter/Makefile
+++ /dev/null
@@ -1,5 +0,0 @@
-#
-# Makefile for IIO counter devices
-#
-
-# When adding new entries keep the list in alphabetical order
-- 
2.17.0

Re: [PATCH v6 6/9] dt-bindings: counter: Document stm32 quadrature encoder

[Rob Herring]

On Wed, May 16, 2018 at 12:51 PM, William Breathitt Gray
<vilhelm.gray@gmail.com> wrote:
> From: Benjamin Gaignard <benjamin.gaignard@st.com>

v6? Where's v1-v5?

> Add bindings for STM32 Timer quadrature encoder.
> It is a sub-node of STM32 Timer which implement the
> counter part of the hardware.
>
> Cc: Rob Herring <robh+dt@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
> ---
>  .../bindings/counter/stm32-timer-cnt.txt      | 26 +++++++++++++++++++
>  .../devicetree/bindings/mfd/stm32-timers.txt  |  7 +++++
>  2 files changed, 33 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt
>
> diff --git a/Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt b/Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt
> new file mode 100644
> index 000000000000..377728128bef
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt
> @@ -0,0 +1,26 @@
> +STMicroelectronics STM32 Timer quadrature encoder
> +
> +STM32 Timer provides quadrature encoder counter mode to detect

'mode' does not sound like a sub-block of the timers block.

> +angular position and direction of rotary elements,
> +from IN1 and IN2 input signals.
> +
> +Must be a sub-node of an STM32 Timer device tree node.
> +See ../mfd/stm32-timers.txt for details about the parent node.
> +
> +Required properties:
> +- compatible:          Must be "st,stm32-timer-counter".
> +- pinctrl-names:       Set to "default".
> +- pinctrl-0:           List of phandles pointing to pin configuration nodes,
> +                       to set IN1/IN2 pins in mode of operation for Low-Power
> +                       Timer input on external pin.
> +
> +Example:
> +       timers@40010000  {
> +               compatible = "st,stm32-timers";
> +               ...
> +               counter {
> +                       compatible = "st,stm32-timer-counter";

Is there only 1? How is the counter addressed?

> +                       pinctrl-names = "default";
> +                       pinctrl-0 = <&tim1_in_pins>;
> +               };
> +       };

Re: [PATCH v6 6/9] dt-bindings: counter: Document stm32 quadrature encoder

[William Breathitt Gray]

On Thu, May 17, 2018 at 11:23:22AM -0500, Rob Herring wrote:
>On Wed, May 16, 2018 at 12:51 PM, William Breathitt Gray
><vilhelm.gray@gmail.com> wrote:
>> From: Benjamin Gaignard <benjamin.gaignard@st.com>
>
>v6? Where's v1-v5?

Hi Rob,

I apologize, I should have CC you on the rest of the patchset to give
you a better idea of the context of this particular patch. Benjamin
Gaignard authored this particular patch, so I'll leave it up to him to
respond to your inline comments, but I can at least provide a brief
history of the revisions of this patchset as a whole.

This patchset introduces a "Generic Counter" interface for drivers to
support various counter devices (tally counters, rotary encoders, etc.).
The v1 revision was submitted on 31 July 2017
(https://lkml.org/lkml/2017/7/31/514) as a wrapper over existing
IIO functionality. This implementation design was unsuitable for the
needs of Generic Counter API, so the v4 revision submitted on 14
December 2017 reimplemented the Generic Counter API as its own Counter
subsystem (https://lkml.org/lkml/2017/12/14/778).

The v5 revision was submitted on 9 March 2018
(https://lkml.org/lkml/2018/3/9/728) and introduced the STM32 Timer
quadrature encoder driver with Generic Counter interface support. I
should have CC you in that revision to comment on the dt-bindings patch,
but I overlooked it, so I made sure to CC you on this v6 revision.

William Breathitt Gray

>
>> Add bindings for STM32 Timer quadrature encoder.
>> It is a sub-node of STM32 Timer which implement the
>> counter part of the hardware.
>>
>> Cc: Rob Herring <robh+dt@kernel.org>
>> Cc: Mark Rutland <mark.rutland@arm.com>
>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
>> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
>> ---
>>  .../bindings/counter/stm32-timer-cnt.txt      | 26 +++++++++++++++++++
>>  .../devicetree/bindings/mfd/stm32-timers.txt  |  7 +++++
>>  2 files changed, 33 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt
>>
>> diff --git a/Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt b/Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt
>> new file mode 100644
>> index 000000000000..377728128bef
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt
>> @@ -0,0 +1,26 @@
>> +STMicroelectronics STM32 Timer quadrature encoder
>> +
>> +STM32 Timer provides quadrature encoder counter mode to detect
>
>'mode' does not sound like a sub-block of the timers block.
>
>> +angular position and direction of rotary elements,
>> +from IN1 and IN2 input signals.
>> +
>> +Must be a sub-node of an STM32 Timer device tree node.
>> +See ../mfd/stm32-timers.txt for details about the parent node.
>> +
>> +Required properties:
>> +- compatible:          Must be "st,stm32-timer-counter".
>> +- pinctrl-names:       Set to "default".
>> +- pinctrl-0:           List of phandles pointing to pin configuration nodes,
>> +                       to set IN1/IN2 pins in mode of operation for Low-Power
>> +                       Timer input on external pin.
>> +
>> +Example:
>> +       timers@40010000  {
>> +               compatible = "st,stm32-timers";
>> +               ...
>> +               counter {
>> +                       compatible = "st,stm32-timer-counter";
>
>Is there only 1? How is the counter addressed?
>
>> +                       pinctrl-names = "default";
>> +                       pinctrl-0 = <&tim1_in_pins>;
>> +               };
>> +       };

Re: [PATCH v6 6/9] dt-bindings: counter: Document stm32 quadrature encoder

[Benjamin Gaignard]

2018-05-17 18:23 GMT+02:00 Rob Herring <robh+dt@kernel.org>:
> On Wed, May 16, 2018 at 12:51 PM, William Breathitt Gray
> <vilhelm.gray@gmail.com> wrote:
>> From: Benjamin Gaignard <benjamin.gaignard@st.com>
>
> v6? Where's v1-v5?
>
>> Add bindings for STM32 Timer quadrature encoder.
>> It is a sub-node of STM32 Timer which implement the
>> counter part of the hardware.
>>
>> Cc: Rob Herring <robh+dt@kernel.org>
>> Cc: Mark Rutland <mark.rutland@arm.com>
>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
>> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
>> ---
>>  .../bindings/counter/stm32-timer-cnt.txt      | 26 +++++++++++++++++++
>>  .../devicetree/bindings/mfd/stm32-timers.txt  |  7 +++++
>>  2 files changed, 33 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt
>>
>> diff --git a/Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt b/Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt
>> new file mode 100644
>> index 000000000000..377728128bef
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt
>> @@ -0,0 +1,26 @@
>> +STMicroelectronics STM32 Timer quadrature encoder
>> +
>> +STM32 Timer provides quadrature encoder counter mode to detect
>
> 'mode' does not sound like a sub-block of the timers block.

quadrature encoding is one of the counting modes of this hardware
block which is enable to count on other signals/triggers

>
>> +angular position and direction of rotary elements,
>> +from IN1 and IN2 input signals.
>> +
>> +Must be a sub-node of an STM32 Timer device tree node.
>> +See ../mfd/stm32-timers.txt for details about the parent node.
>> +
>> +Required properties:
>> +- compatible:          Must be "st,stm32-timer-counter".
>> +- pinctrl-names:       Set to "default".
>> +- pinctrl-0:           List of phandles pointing to pin configuration nodes,
>> +                       to set IN1/IN2 pins in mode of operation for Low-Power
>> +                       Timer input on external pin.
>> +
>> +Example:
>> +       timers@40010000  {
>> +               compatible = "st,stm32-timers";
>> +               ...
>> +               counter {
>> +                       compatible = "st,stm32-timer-counter";
>
> Is there only 1? How is the counter addressed?

Yes there is only one counter per hardware block.
Counter is addressed like the two others sub-nodes and the details
about parent mode are describe in stm32-timers.txt
Should I add them here too ? so example will be like that:
timers@40010000  {
  #address-cells = <1>;
  #size-cells = <0>;
  compatible = "st,stm32-timers";
  reg = <0x40010000 0x400>;
  clocks = <&rcc 0 160>;
  clock-names = "int";
  counter {
    compatible = "st,stm32-timer-counter";
    pinctrl-names = "default";
    pinctrl-0 = <&tim1_in_pins>;
    };
 };

Benjamin
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH v6 6/9] dt-bindings: counter: Document stm32 quadrature encoder

[Rob Herring]

On Thu, May 17, 2018 at 08:59:40PM +0200, Benjamin Gaignard wrote:
> 2018-05-17 18:23 GMT+02:00 Rob Herring <robh+dt@kernel.org>:
> > On Wed, May 16, 2018 at 12:51 PM, William Breathitt Gray
> > <vilhelm.gray@gmail.com> wrote:
> >> From: Benjamin Gaignard <benjamin.gaignard@st.com>
> >
> > v6? Where's v1-v5?
> >
> >> Add bindings for STM32 Timer quadrature encoder.
> >> It is a sub-node of STM32 Timer which implement the
> >> counter part of the hardware.
> >>
> >> Cc: Rob Herring <robh+dt@kernel.org>
> >> Cc: Mark Rutland <mark.rutland@arm.com>
> >> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
> >> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
> >> ---
> >>  .../bindings/counter/stm32-timer-cnt.txt      | 26 +++++++++++++++++++
> >>  .../devicetree/bindings/mfd/stm32-timers.txt  |  7 +++++
> >>  2 files changed, 33 insertions(+)
> >>  create mode 100644 Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt
> >>
> >> diff --git a/Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt b/Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt
> >> new file mode 100644
> >> index 000000000000..377728128bef
> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt
> >> @@ -0,0 +1,26 @@
> >> +STMicroelectronics STM32 Timer quadrature encoder
> >> +
> >> +STM32 Timer provides quadrature encoder counter mode to detect
> >
> > 'mode' does not sound like a sub-block of the timers block.
> 
> quadrature encoding is one of the counting modes of this hardware
> block which is enable to count on other signals/triggers

You don't need a child node and compatible to set a mode.

> >> +angular position and direction of rotary elements,
> >> +from IN1 and IN2 input signals.
> >> +
> >> +Must be a sub-node of an STM32 Timer device tree node.
> >> +See ../mfd/stm32-timers.txt for details about the parent node.
> >> +
> >> +Required properties:
> >> +- compatible:          Must be "st,stm32-timer-counter".
> >> +- pinctrl-names:       Set to "default".
> >> +- pinctrl-0:           List of phandles pointing to pin configuration nodes,
> >> +                       to set IN1/IN2 pins in mode of operation for Low-Power
> >> +                       Timer input on external pin.
> >> +
> >> +Example:
> >> +       timers@40010000  {
> >> +               compatible = "st,stm32-timers";
> >> +               ...
> >> +               counter {
> >> +                       compatible = "st,stm32-timer-counter";
> >
> > Is there only 1? How is the counter addressed?
> 
> Yes there is only one counter per hardware block.
> Counter is addressed like the two others sub-nodes and the details
> about parent mode are describe in stm32-timers.txt
> Should I add them here too ? so example will be like that:

No, you should drop the child node and add pinctrl to the parent.

Any other functions this block has that you plan on adding? Please make 
bindings as complete as possible, not what you currently have drivers 
for.

> timers@40010000  {
>   #address-cells = <1>;
>   #size-cells = <0>;
>   compatible = "st,stm32-timers";
>   reg = <0x40010000 0x400>;
>   clocks = <&rcc 0 160>;
>   clock-names = "int";
>   counter {
>     compatible = "st,stm32-timer-counter";
>     pinctrl-names = "default";
>     pinctrl-0 = <&tim1_in_pins>;
>     };
>  };
> 
> Benjamin
> >
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH v6 8/9] counter: stm32-lptimer: add counter device

[Rob Herring]

On Wed, May 16, 2018 at 01:52:27PM -0400, William Breathitt Gray wrote:
> From: Fabrice Gasnier <fabrice.gasnier@st.com>
> 
> Add support for new counter device to stm32-lptimer.
> 
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
> ---
>  .../{iio => }/counter/stm32-lptimer-cnt.txt   |   0
>  .../devicetree/bindings/mfd/stm32-lptimer.txt |   2 +-

Please split bindings to separate patch.

>  drivers/counter/Kconfig                       |  10 +
>  drivers/counter/Makefile                      |   1 +
>  drivers/counter/stm32-lptimer-cnt.c           | 722 ++++++++++++++++++
>  drivers/iio/counter/Kconfig                   |   9 -
>  drivers/iio/counter/Makefile                  |   2 -
>  drivers/iio/counter/stm32-lptimer-cnt.c       | 382 ---------
>  8 files changed, 734 insertions(+), 394 deletions(-)
>  rename Documentation/devicetree/bindings/{iio => }/counter/stm32-lptimer-cnt.txt (100%)
>  create mode 100644 drivers/counter/stm32-lptimer-cnt.c
>  delete mode 100644 drivers/iio/counter/stm32-lptimer-cnt.c

[RFC PATCH] counter: 104-quad-8: quad8_ops can be static

[kbuild test robot]

Fixes: b3822048aa0b ("counter: 104-quad-8: Add Generic Counter interface support")
Signed-off-by: kbuild test robot <fengguang.wu@intel.com>
---
 104-quad-8.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/counter/104-quad-8.c b/drivers/counter/104-quad-8.c
index 7c72fb7..8696a512 100644
--- a/drivers/counter/104-quad-8.c
+++ b/drivers/counter/104-quad-8.c
@@ -800,7 +800,7 @@ static int quad8_action_get(struct counter_device *counter,
 	return 0;
 }
 
-const struct counter_ops quad8_ops = {
+static const struct counter_ops quad8_ops = {
 	.signal_read = quad8_signal_read,
 	.count_read = quad8_count_read,
 	.count_write = quad8_count_write,

Re: [PATCH v6 4/9] counter: 104-quad-8: Add Generic Counter interface support

[kbuild test robot]

Hi William,

I love your patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v4.17-rc5 next-20180517]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/William-Breathitt-Gray/Introduce-the-Counter-subsystem/20180519-151353
reproduce:
        # apt-get install sparse
        make ARCH=x86_64 allmodconfig
        make C=1 CF=-D__CHECK_ENDIAN__


sparse warnings: (new ones prefixed by >>)

>> drivers/counter/104-quad-8.c:803:26: sparse: symbol 'quad8_ops' was not declared. Should it be static?

Please review and possibly fold the followup patch.

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

Re: [PATCH v6 4/9] counter: 104-quad-8: Add Generic Counter interface support

[William Breathitt Gray]

On Sat, May 19, 2018 at 09:16:55PM +0800, kbuild test robot wrote:
>Hi William,
>
>I love your patch! Perhaps something to improve:
>
>[auto build test WARNING on linus/master]
>[also build test WARNING on v4.17-rc5 next-20180517]
>[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
>
>url:    https://github.com/0day-ci/linux/commits/William-Breathitt-Gray/Introduce-the-Counter-subsystem/20180519-151353
>reproduce:
>        # apt-get install sparse
>        make ARCH=x86_64 allmodconfig
>        make C=1 CF=-D__CHECK_ENDIAN__
>
>
>sparse warnings: (new ones prefixed by >>)
>
>>> drivers/counter/104-quad-8.c:803:26: sparse: symbol 'quad8_ops' was not declared. Should it be static?
>
>Please review and possibly fold the followup patch.

Ah, yes it should be static -- looks like I made a minor mistake. I'll
squash the fix into the next revision of this patchset.

Thank you,

William Breathitt Gray

>
>---
>0-DAY kernel test infrastructure                Open Source Technology Center
>https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

Re: [PATCH v6 3/9] docs: Add Generic Counter interface documentation

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 20388 bytes --]

Hi William,

I love your patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v4.17-rc5 next-20180517]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/William-Breathitt-Gray/Introduce-the-Counter-subsystem/20180519-151353
reproduce: make htmldocs

All warnings (new ones prefixed by >>):

   WARNING: convert(1) not found, for SVG to PDF conversion install ImageMagick (https://www.imagemagick.org)
   include/net/cfg80211.h:4216: warning: Function parameter or member 'wext.ibss' not described in 'wireless_dev'
   include/net/cfg80211.h:4216: warning: Function parameter or member 'wext.connect' not described in 'wireless_dev'
   include/net/cfg80211.h:4216: warning: Function parameter or member 'wext.keys' not described in 'wireless_dev'
   include/net/cfg80211.h:4216: warning: Function parameter or member 'wext.ie' not described in 'wireless_dev'
   include/net/cfg80211.h:4216: warning: Function parameter or member 'wext.ie_len' not described in 'wireless_dev'
   include/net/cfg80211.h:4216: warning: Function parameter or member 'wext.bssid' not described in 'wireless_dev'
   include/net/cfg80211.h:4216: warning: Function parameter or member 'wext.ssid' not described in 'wireless_dev'
   include/net/cfg80211.h:4216: warning: Function parameter or member 'wext.default_key' not described in 'wireless_dev'
   include/net/cfg80211.h:4216: warning: Function parameter or member 'wext.default_mgmt_key' not described in 'wireless_dev'
   include/net/cfg80211.h:4216: warning: Function parameter or member 'wext.prev_bssid_valid' not described in 'wireless_dev'
   include/net/mac80211.h:2282: warning: Function parameter or member 'radiotap_timestamp.units_pos' not described in 'ieee80211_hw'
   include/net/mac80211.h:2282: warning: Function parameter or member 'radiotap_timestamp.accuracy' not described in 'ieee80211_hw'
   include/net/mac80211.h:955: warning: Function parameter or member 'control.rates' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:955: warning: Function parameter or member 'control.rts_cts_rate_idx' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:955: warning: Function parameter or member 'control.use_rts' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:955: warning: Function parameter or member 'control.use_cts_prot' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:955: warning: Function parameter or member 'control.short_preamble' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:955: warning: Function parameter or member 'control.skip_table' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:955: warning: Function parameter or member 'control.jiffies' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:955: warning: Function parameter or member 'control.vif' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:955: warning: Function parameter or member 'control.hw_key' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:955: warning: Function parameter or member 'control.flags' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:955: warning: Function parameter or member 'control.enqueue_time' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:955: warning: Function parameter or member 'ack' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:955: warning: Function parameter or member 'ack.cookie' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:955: warning: Function parameter or member 'status.rates' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:955: warning: Function parameter or member 'status.ack_signal' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:955: warning: Function parameter or member 'status.ampdu_ack_len' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:955: warning: Function parameter or member 'status.ampdu_len' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:955: warning: Function parameter or member 'status.antenna' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:955: warning: Function parameter or member 'status.tx_time' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:955: warning: Function parameter or member 'status.is_valid_ack_signal' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:955: warning: Function parameter or member 'status.status_driver_data' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:955: warning: Function parameter or member 'driver_rates' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:955: warning: Function parameter or member 'pad' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:955: warning: Function parameter or member 'rate_driver_data' not described in 'ieee80211_tx_info'
   net/mac80211/sta_info.h:586: warning: Function parameter or member 'rx_stats_avg' not described in 'sta_info'
   net/mac80211/sta_info.h:586: warning: Function parameter or member 'rx_stats_avg.signal' not described in 'sta_info'
   net/mac80211/sta_info.h:586: warning: Function parameter or member 'rx_stats_avg.chain_signal' not described in 'sta_info'
   net/mac80211/sta_info.h:586: warning: Function parameter or member 'status_stats.filtered' not described in 'sta_info'
   net/mac80211/sta_info.h:586: warning: Function parameter or member 'status_stats.retry_failed' not described in 'sta_info'
   net/mac80211/sta_info.h:586: warning: Function parameter or member 'status_stats.retry_count' not described in 'sta_info'
   net/mac80211/sta_info.h:586: warning: Function parameter or member 'status_stats.lost_packets' not described in 'sta_info'
   net/mac80211/sta_info.h:586: warning: Function parameter or member 'status_stats.last_tdls_pkt_time' not described in 'sta_info'
   net/mac80211/sta_info.h:586: warning: Function parameter or member 'status_stats.msdu_retries' not described in 'sta_info'
   net/mac80211/sta_info.h:586: warning: Function parameter or member 'status_stats.msdu_failed' not described in 'sta_info'
   net/mac80211/sta_info.h:586: warning: Function parameter or member 'status_stats.last_ack' not described in 'sta_info'
   net/mac80211/sta_info.h:586: warning: Function parameter or member 'status_stats.last_ack_signal' not described in 'sta_info'
   net/mac80211/sta_info.h:586: warning: Function parameter or member 'status_stats.ack_signal_filled' not described in 'sta_info'
   net/mac80211/sta_info.h:586: warning: Function parameter or member 'tx_stats.packets' not described in 'sta_info'
   net/mac80211/sta_info.h:586: warning: Function parameter or member 'tx_stats.bytes' not described in 'sta_info'
   net/mac80211/sta_info.h:586: warning: Function parameter or member 'tx_stats.last_rate' not described in 'sta_info'
   net/mac80211/sta_info.h:586: warning: Function parameter or member 'tx_stats.msdu' not described in 'sta_info'
   kernel/sched/fair.c:3719: warning: Function parameter or member 'flags' not described in 'attach_entity_load_avg'
   include/linux/dma-buf.h:307: warning: Function parameter or member 'cb_excl.cb' not described in 'dma_buf'
   include/linux/dma-buf.h:307: warning: Function parameter or member 'cb_excl.poll' not described in 'dma_buf'
   include/linux/dma-buf.h:307: warning: Function parameter or member 'cb_excl.active' not described in 'dma_buf'
   include/linux/dma-buf.h:307: warning: Function parameter or member 'cb_shared.cb' not described in 'dma_buf'
   include/linux/dma-buf.h:307: warning: Function parameter or member 'cb_shared.poll' not described in 'dma_buf'
   include/linux/dma-buf.h:307: warning: Function parameter or member 'cb_shared.active' not described in 'dma_buf'
   include/linux/dma-fence-array.h:54: warning: Function parameter or member 'work' not described in 'dma_fence_array'
>> include/linux/counter.h:330: warning: Function parameter or member 'groups_list' not described in 'counter_device_state'
>> include/linux/counter.h:330: warning: Function parameter or member 'num_groups' not described in 'counter_device_state'
   include/linux/gpio/driver.h:142: warning: Function parameter or member 'request_key' not described in 'gpio_irq_chip'
   include/linux/iio/iio.h:270: warning: Function parameter or member 'scan_type.sign' not described in 'iio_chan_spec'
   include/linux/iio/iio.h:270: warning: Function parameter or member 'scan_type.realbits' not described in 'iio_chan_spec'
   include/linux/iio/iio.h:270: warning: Function parameter or member 'scan_type.storagebits' not described in 'iio_chan_spec'
   include/linux/iio/iio.h:270: warning: Function parameter or member 'scan_type.shift' not described in 'iio_chan_spec'
   include/linux/iio/iio.h:270: warning: Function parameter or member 'scan_type.repeat' not described in 'iio_chan_spec'
   include/linux/iio/iio.h:270: warning: Function parameter or member 'scan_type.endianness' not described in 'iio_chan_spec'
   include/linux/iio/hw-consumer.h:1: warning: no structured comments found
   include/linux/input/sparse-keymap.h:46: warning: Function parameter or member 'sw' not described in 'key_entry'
   include/linux/mtd/rawnand.h:752: warning: Function parameter or member 'timings.sdr' not described in 'nand_data_interface'
   include/linux/mtd/rawnand.h:817: warning: Function parameter or member 'buf' not described in 'nand_op_data_instr'
   include/linux/mtd/rawnand.h:817: warning: Function parameter or member 'buf.in' not described in 'nand_op_data_instr'
   include/linux/mtd/rawnand.h:817: warning: Function parameter or member 'buf.out' not described in 'nand_op_data_instr'
   include/linux/mtd/rawnand.h:863: warning: Function parameter or member 'ctx' not described in 'nand_op_instr'
   include/linux/mtd/rawnand.h:863: warning: Function parameter or member 'ctx.cmd' not described in 'nand_op_instr'
   include/linux/mtd/rawnand.h:863: warning: Function parameter or member 'ctx.addr' not described in 'nand_op_instr'
   include/linux/mtd/rawnand.h:863: warning: Function parameter or member 'ctx.data' not described in 'nand_op_instr'
   include/linux/mtd/rawnand.h:863: warning: Function parameter or member 'ctx.waitrdy' not described in 'nand_op_instr'
   include/linux/mtd/rawnand.h:1010: warning: Function parameter or member 'ctx' not described in 'nand_op_parser_pattern_elem'
   include/linux/mtd/rawnand.h:1010: warning: Function parameter or member 'ctx.addr' not described in 'nand_op_parser_pattern_elem'
   include/linux/mtd/rawnand.h:1010: warning: Function parameter or member 'ctx.data' not described in 'nand_op_parser_pattern_elem'
   include/linux/mtd/rawnand.h:1313: warning: Function parameter or member 'manufacturer.desc' not described in 'nand_chip'
   include/linux/mtd/rawnand.h:1313: warning: Function parameter or member 'manufacturer.priv' not described in 'nand_chip'
   include/linux/regulator/driver.h:222: warning: Function parameter or member 'resume_early' not described in 'regulator_ops'
   drivers/regulator/core.c:4306: warning: Excess function parameter 'state' description in 'regulator_suspend_late'
   arch/s390/include/asm/cio.h:245: warning: Function parameter or member 'esw.esw0' not described in 'irb'
   arch/s390/include/asm/cio.h:245: warning: Function parameter or member 'esw.esw1' not described in 'irb'
   arch/s390/include/asm/cio.h:245: warning: Function parameter or member 'esw.esw2' not described in 'irb'
   arch/s390/include/asm/cio.h:245: warning: Function parameter or member 'esw.esw3' not described in 'irb'
   arch/s390/include/asm/cio.h:245: warning: Function parameter or member 'esw.eadm' not described in 'irb'
   drivers/usb/typec/mux.c:186: warning: Function parameter or member 'mux' not described in 'typec_mux_unregister'
   drivers/usb/typec/mux.c:186: warning: Excess function parameter 'sw' description in 'typec_mux_unregister'
   include/drm/drm_drv.h:610: warning: Function parameter or member 'gem_prime_pin' not described in 'drm_driver'
   include/drm/drm_drv.h:610: warning: Function parameter or member 'gem_prime_unpin' not described in 'drm_driver'
   include/drm/drm_drv.h:610: warning: Function parameter or member 'gem_prime_res_obj' not described in 'drm_driver'
   include/drm/drm_drv.h:610: warning: Function parameter or member 'gem_prime_get_sg_table' not described in 'drm_driver'
   include/drm/drm_drv.h:610: warning: Function parameter or member 'gem_prime_import_sg_table' not described in 'drm_driver'
   include/drm/drm_drv.h:610: warning: Function parameter or member 'gem_prime_vmap' not described in 'drm_driver'
   include/drm/drm_drv.h:610: warning: Function parameter or member 'gem_prime_vunmap' not described in 'drm_driver'
   include/drm/drm_drv.h:610: warning: Function parameter or member 'gem_prime_mmap' not described in 'drm_driver'
   drivers/gpu/drm/drm_prime.c:342: warning: Function parameter or member 'attach' not described in 'drm_gem_unmap_dma_buf'
   drivers/gpu/drm/drm_prime.c:342: warning: Function parameter or member 'sgt' not described in 'drm_gem_unmap_dma_buf'
   drivers/gpu/drm/drm_prime.c:342: warning: Function parameter or member 'dir' not described in 'drm_gem_unmap_dma_buf'
   drivers/gpu/drm/drm_prime.c:438: warning: Function parameter or member 'dma_buf' not described in 'drm_gem_dmabuf_kmap_atomic'
   drivers/gpu/drm/drm_prime.c:438: warning: Function parameter or member 'page_num' not described in 'drm_gem_dmabuf_kmap_atomic'
   drivers/gpu/drm/drm_prime.c:450: warning: Function parameter or member 'dma_buf' not described in 'drm_gem_dmabuf_kunmap_atomic'
   drivers/gpu/drm/drm_prime.c:450: warning: Function parameter or member 'page_num' not described in 'drm_gem_dmabuf_kunmap_atomic'
   drivers/gpu/drm/drm_prime.c:450: warning: Function parameter or member 'addr' not described in 'drm_gem_dmabuf_kunmap_atomic'
   drivers/gpu/drm/drm_prime.c:461: warning: Function parameter or member 'dma_buf' not described in 'drm_gem_dmabuf_kmap'
   drivers/gpu/drm/drm_prime.c:461: warning: Function parameter or member 'page_num' not described in 'drm_gem_dmabuf_kmap'
   drivers/gpu/drm/drm_prime.c:473: warning: Function parameter or member 'dma_buf' not described in 'drm_gem_dmabuf_kunmap'
   drivers/gpu/drm/drm_prime.c:473: warning: Function parameter or member 'page_num' not described in 'drm_gem_dmabuf_kunmap'
   drivers/gpu/drm/drm_prime.c:473: warning: Function parameter or member 'addr' not described in 'drm_gem_dmabuf_kunmap'
   include/media/v4l2-dev.h:42: warning: Enum value 'VFL_TYPE_MAX' not described in enum 'vfl_devnode_type'
   include/linux/skbuff.h:850: warning: Function parameter or member 'dev_scratch' not described in 'sk_buff'
   include/linux/skbuff.h:850: warning: Function parameter or member 'ip_defrag_offset' not described in 'sk_buff'
   include/linux/skbuff.h:850: warning: Function parameter or member 'skb_mstamp' not described in 'sk_buff'
   include/linux/skbuff.h:850: warning: Function parameter or member '__cloned_offset' not described in 'sk_buff'
   include/linux/skbuff.h:850: warning: Function parameter or member 'head_frag' not described in 'sk_buff'
   include/linux/skbuff.h:850: warning: Function parameter or member '__unused' not described in 'sk_buff'
   include/linux/skbuff.h:850: warning: Function parameter or member '__pkt_type_offset' not described in 'sk_buff'
   include/linux/skbuff.h:850: warning: Function parameter or member 'pfmemalloc' not described in 'sk_buff'
   include/linux/skbuff.h:850: warning: Function parameter or member 'encapsulation' not described in 'sk_buff'
   include/linux/skbuff.h:850: warning: Function parameter or member 'encap_hdr_csum' not described in 'sk_buff'
   include/linux/skbuff.h:850: warning: Function parameter or member 'csum_valid' not described in 'sk_buff'
   include/linux/skbuff.h:850: warning: Function parameter or member 'csum_complete_sw' not described in 'sk_buff'
   include/linux/skbuff.h:850: warning: Function parameter or member 'csum_level' not described in 'sk_buff'
   include/linux/skbuff.h:850: warning: Function parameter or member 'inner_protocol_type' not described in 'sk_buff'
   include/linux/skbuff.h:850: warning: Function parameter or member 'remcsum_offload' not described in 'sk_buff'
   include/linux/skbuff.h:850: warning: Function parameter or member 'offload_fwd_mark' not described in 'sk_buff'
   include/linux/skbuff.h:850: warning: Function parameter or member 'offload_mr_fwd_mark' not described in 'sk_buff'
   include/linux/skbuff.h:850: warning: Function parameter or member 'sender_cpu' not described in 'sk_buff'
   include/linux/skbuff.h:850: warning: Function parameter or member 'reserved_tailroom' not described in 'sk_buff'
   include/linux/skbuff.h:850: warning: Function parameter or member 'inner_ipproto' not described in 'sk_buff'
   include/net/sock.h:234: warning: Function parameter or member 'skc_addrpair' not described in 'sock_common'
   include/net/sock.h:234: warning: Function parameter or member 'skc_portpair' not described in 'sock_common'
   include/net/sock.h:234: warning: Function parameter or member 'skc_ipv6only' not described in 'sock_common'
   include/net/sock.h:234: warning: Function parameter or member 'skc_net_refcnt' not described in 'sock_common'
   include/net/sock.h:234: warning: Function parameter or member 'skc_v6_daddr' not described in 'sock_common'
   include/net/sock.h:234: warning: Function parameter or member 'skc_v6_rcv_saddr' not described in 'sock_common'
   include/net/sock.h:234: warning: Function parameter or member 'skc_cookie' not described in 'sock_common'
   include/net/sock.h:234: warning: Function parameter or member 'skc_listener' not described in 'sock_common'
   include/net/sock.h:234: warning: Function parameter or member 'skc_tw_dr' not described in 'sock_common'
   include/net/sock.h:234: warning: Function parameter or member 'skc_rcv_wnd' not described in 'sock_common'
   include/net/sock.h:234: warning: Function parameter or member 'skc_tw_rcv_nxt' not described in 'sock_common'
   include/net/sock.h:488: warning: Function parameter or member 'sk_backlog.rmem_alloc' not described in 'sock'
   include/net/sock.h:488: warning: Function parameter or member 'sk_backlog.len' not described in 'sock'
   include/net/sock.h:488: warning: Function parameter or member 'sk_backlog.head' not described in 'sock'
   include/net/sock.h:488: warning: Function parameter or member 'sk_backlog.tail' not described in 'sock'
   include/net/sock.h:488: warning: Function parameter or member 'sk_wq_raw' not described in 'sock'
   include/net/sock.h:488: warning: Function parameter or member 'tcp_rtx_queue' not described in 'sock'
   include/net/sock.h:488: warning: Function parameter or member 'sk_route_forced_caps' not described in 'sock'
   include/linux/netdevice.h:1955: warning: Function parameter or member 'adj_list.upper' not described in 'net_device'
   include/linux/netdevice.h:1955: warning: Function parameter or member 'adj_list.lower' not described in 'net_device'
   include/linux/netdevice.h:1955: warning: Function parameter or member 'gso_partial_features' not described in 'net_device'
   include/linux/netdevice.h:1955: warning: Function parameter or member 'switchdev_ops' not described in 'net_device'
   include/linux/netdevice.h:1955: warning: Function parameter or member 'l3mdev_ops' not described in 'net_device'
   include/linux/netdevice.h:1955: warning: Function parameter or member 'xfrmdev_ops' not described in 'net_device'
   include/linux/netdevice.h:1955: warning: Function parameter or member 'name_assign_type' not described in 'net_device'
   include/linux/netdevice.h:1955: warning: Function parameter or member 'ieee802154_ptr' not described in 'net_device'

vim +330 include/linux/counter.h

624995ae William Breathitt Gray 2018-05-16 @330  

:::::: The code at line 330 was first introduced by commit
:::::: 624995aed3646d19eb4ce4cd7f527fe95a165a92 counter: Introduce the Generic Counter interface

:::::: TO: William Breathitt Gray <vilhelm.gray@gmail.com>
:::::: CC: 0day robot <lkp@intel.com>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 6365 bytes --]

Re: [PATCH v6 1/9] counter: Introduce the Generic Counter interface

[Jonathan Cameron]

On Wed, 16 May 2018 13:50:43 -0400
William Breathitt Gray <vilhelm.gray@gmail.com> wrote:

> This patch introduces the Generic Counter interface for supporting
> counter devices.
> 
> In the context of the Generic Counter interface, a counter is defined as
> a device that reports one or more "counts" based on the state changes of
> one or more "signals" as evaluated by a defined "count function."
> 
> Driver callbacks should be provided to communicate with the device: to
> read and write various Signals and Counts, and to set and get the
> "action mode" and "count function" for various Synapses and Counts
> respectively.
> 
> To support a counter device, a driver must first allocate the available
> Counter Signals via counter_signal structures. These Signals should
> be stored as an array and set to the signals array member of an
> allocated counter_device structure before the Counter is registered to
> the system.
> 
> Counter Counts may be allocated via counter_count structures, and
> respective Counter Signal associations (Synapses) made via
> counter_synapse structures. Associated counter_synapse structures are
> stored as an array and set to the the synapses array member of the
> respective counter_count structure. These counter_count structures are
> set to the counts array member of an allocated counter_device structure
> before the Counter is registered to the system.
> 
> A counter device is registered to the system by passing the respective
> initialized counter_device structure to the counter_register function;
> similarly, the counter_unregister function unregisters the respective
> Counter. The devm_counter_register and devm_counter_unregister functions
> serve as device memory-managed versions of the counter_register and
> counter_unregister functions respectively.
> 
> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>

A few minor comments inline.  I do somewhat wonder if we can cut
back on the huge amount of 'similar' code in here, but there tend to
be just enough small differences to make that really tricky...

Nothing major enough in here that I really plan on reading it again
(though you never know if you change lots ;)

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> ---
>  MAINTAINERS                       |    7 +
>  drivers/Kconfig                   |    2 +
>  drivers/Makefile                  |    1 +
>  drivers/counter/Kconfig           |   18 +
>  drivers/counter/Makefile          |    8 +
>  drivers/counter/generic-counter.c | 1541 +++++++++++++++++++++++++++++
>  include/linux/counter.h           |  554 +++++++++++
>  7 files changed, 2131 insertions(+)
>  create mode 100644 drivers/counter/Kconfig
>  create mode 100644 drivers/counter/Makefile
>  create mode 100644 drivers/counter/generic-counter.c
>  create mode 100644 include/linux/counter.h
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 4b65225d443a..2a016d73ab72 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -3669,6 +3669,13 @@ W:	http://www.fi.muni.cz/~kas/cosa/
>  S:	Maintained
>  F:	drivers/net/wan/cosa*
>  
> +COUNTER SUBSYSTEM
> +M:	William Breathitt Gray <vilhelm.gray@gmail.com>
> +L:	linux-iio@vger.kernel.org
> +S:	Maintained
> +F:	drivers/counter/
> +F:	include/linux/counter.h
> +
>  CPMAC ETHERNET DRIVER
>  M:	Florian Fainelli <f.fainelli@gmail.com>
>  L:	netdev@vger.kernel.org
> diff --git a/drivers/Kconfig b/drivers/Kconfig
> index 95b9ccc08165..70b3cc88dc0b 100644
> --- a/drivers/Kconfig
> +++ b/drivers/Kconfig
> @@ -165,6 +165,8 @@ source "drivers/memory/Kconfig"
>  
>  source "drivers/iio/Kconfig"
>  
> +source "drivers/counter/Kconfig"
> +
Same comment as below.

>  source "drivers/ntb/Kconfig"
>  
>  source "drivers/vme/Kconfig"
> diff --git a/drivers/Makefile b/drivers/Makefile
> index 24cd47014657..5914c78688c3 100644
> --- a/drivers/Makefile
> +++ b/drivers/Makefile
> @@ -165,6 +165,7 @@ obj-$(CONFIG_PM_DEVFREQ)	+= devfreq/
>  obj-$(CONFIG_EXTCON)		+= extcon/
>  obj-$(CONFIG_MEMORY)		+= memory/
>  obj-$(CONFIG_IIO)		+= iio/
> +obj-$(CONFIG_COUNTER)		+= counter/

I can see your logic in putting this here, but I think the convention
is to go at the end rather than grouping.

>  obj-$(CONFIG_VME_BUS)		+= vme/
>  obj-$(CONFIG_IPACK_BUS)		+= ipack/
>  obj-$(CONFIG_NTB)		+= ntb/
> diff --git a/drivers/counter/Kconfig b/drivers/counter/Kconfig
> new file mode 100644
> index 000000000000..65fa92abd5a4
> --- /dev/null
> +++ b/drivers/counter/Kconfig
> @@ -0,0 +1,18 @@
> +#
> +# Counter devices
> +#
> +# When adding new entries keep the list in alphabetical order
> +
> +menuconfig COUNTER
> +	tristate "Counter support"
> +	help
> +	  Provides Generic Counter interface support for counter devices.
> +
> +	  Counter devices are prevalent within a diverse spectrum of industries.
> +	  The ubiquitous presence of these devices necessitates a common
> +	  interface and standard of interaction and exposure. This driver API
> +	  attempts to resolve the issue of duplicate code found among existing
> +	  counter device drivers by providing a generic counter interface for
> +	  consumption. The Generic Counter interface enables drivers to support
> +	  and expose a common set of components and functionality present in
> +	  counter devices.
> diff --git a/drivers/counter/Makefile b/drivers/counter/Makefile
> new file mode 100644
> index 000000000000..ad1ba7109cdc
> --- /dev/null
> +++ b/drivers/counter/Makefile
> @@ -0,0 +1,8 @@
> +#
> +# Makefile for Counter devices
> +#
> +
> +# When adding new entries keep the list in alphabetical order
> +
> +obj-$(CONFIG_COUNTER) += counter.o
> +counter-y := generic-counter.o
> diff --git a/drivers/counter/generic-counter.c b/drivers/counter/generic-counter.c
> new file mode 100644
> index 000000000000..0d83b862453f
> --- /dev/null
> +++ b/drivers/counter/generic-counter.c
> @@ -0,0 +1,1541 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Generic Counter interface
> + * Copyright (C) 2017 William Breathitt Gray
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License, version 2, as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful, but
> + * WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * General Public License for more details.

As below, SPDX and license seems silly.  Unless you are feeling paranoid
just drop the license text.

> + */
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/export.h>
> +#include <linux/fs.h>
> +#include <linux/gfp.h>
> +#include <linux/idr.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/list.h>
> +#include <linux/module.h>
> +#include <linux/printk.h>
> +#include <linux/slab.h>
> +#include <linux/string.h>
> +#include <linux/sysfs.h>
> +#include <linux/types.h>
> +
> +#include <linux/counter.h>
> +
> +const char *const count_direction_str[2] = {
> +	[COUNT_DIRECTION_FORWARD] = "forward",
> +	[COUNT_DIRECTION_BACKWARD] = "backward"
> +};
> +EXPORT_SYMBOL(count_direction_str);
> +
> +const char *const count_mode_str[4] = {
> +	[COUNT_MODE_NORMAL] = "normal",
> +	[COUNT_MODE_RANGE_LIMIT] = "range limit",
> +	[COUNT_MODE_NON_RECYCLE] = "non-recycle",
> +	[COUNT_MODE_MODULO_N] = "modulo-n"
> +};
> +EXPORT_SYMBOL(count_mode_str);
> +
> +ssize_t counter_signal_enum_read(struct counter_device *counter,
> +				 struct counter_signal *signal, void *priv,
> +				 char *buf)
> +{
> +	const struct counter_signal_enum_ext *const e = priv;
> +	int err;
> +	size_t index;
> +
> +	if (!e->get)
> +		return -EINVAL;
> +
> +	err = e->get(counter, signal, &index);
> +	if (err)
> +		return err;
> +
> +	if (index >= e->num_items)
> +		return -EINVAL;
> +
> +	return scnprintf(buf, PAGE_SIZE, "%s\n", e->items[index]);
> +}
> +EXPORT_SYMBOL(counter_signal_enum_read);
> +
> +ssize_t counter_signal_enum_write(struct counter_device *counter,
> +				  struct counter_signal *signal, void *priv,
> +				  const char *buf, size_t len)
> +{
> +	const struct counter_signal_enum_ext *const e = priv;
> +	ssize_t index;
> +	int err;
> +
> +	if (!e->set)
> +		return -EINVAL;
> +
> +	index = __sysfs_match_string(e->items, e->num_items, buf);
> +	if (index < 0)
> +		return index;
> +
> +	err = e->set(counter, signal, index);
> +	if (err)
> +		return err;
> +
> +	return len;
> +}
> +EXPORT_SYMBOL(counter_signal_enum_write);
> +
> +ssize_t counter_signal_enum_available_read(struct counter_device *counter,
> +					   struct counter_signal *signal,
> +					   void *priv, char *buf)
> +{
> +	const struct counter_signal_enum_ext *const e = priv;
> +	size_t i;
> +	size_t len = 0;
> +
> +	if (!e->num_items)
> +		return 0;
> +
> +	for (i = 0; i < e->num_items; i++)
> +		len += scnprintf(buf + len, PAGE_SIZE - len, "%s\n",
> +			e->items[i]);
> +
> +	return len;
> +}
> +EXPORT_SYMBOL(counter_signal_enum_available_read);
> +
> +ssize_t counter_count_enum_read(struct counter_device *counter,
> +				struct counter_count *count, void *priv,
> +				char *buf)
> +{
> +	const struct counter_count_enum_ext *const e = priv;
> +	int err;
> +	size_t index;
> +
> +	if (!e->get)
> +		return -EINVAL;
> +
> +	err = e->get(counter, count, &index);
> +	if (err)
> +		return err;
> +
> +	if (index >= e->num_items)
> +		return -EINVAL;
> +
> +	return scnprintf(buf, PAGE_SIZE, "%s\n", e->items[index]);
> +}
> +EXPORT_SYMBOL(counter_count_enum_read);
> +
> +ssize_t counter_count_enum_write(struct counter_device *counter,
> +				 struct counter_count *count, void *priv,
> +				 const char *buf, size_t len)
> +{
> +	const struct counter_count_enum_ext *const e = priv;
> +	ssize_t index;
> +	int err;
> +
> +	if (!e->set)
> +		return -EINVAL;
> +
> +	index = __sysfs_match_string(e->items, e->num_items, buf);
> +	if (index < 0)
> +		return index;
> +
> +	err = e->set(counter, count, index);
> +	if (err)
> +		return err;
> +
> +	return len;
> +}
> +EXPORT_SYMBOL(counter_count_enum_write);
> +
> +ssize_t counter_count_enum_available_read(struct counter_device *counter,
> +					  struct counter_count *count,
> +					  void *priv, char *buf)
> +{
> +	const struct counter_count_enum_ext *const e = priv;
> +	size_t i;
> +	size_t len = 0;
> +
> +	if (!e->num_items)
> +		return 0;
> +
> +	for (i = 0; i < e->num_items; i++)
> +		len += scnprintf(buf + len, PAGE_SIZE - len, "%s\n",
> +			e->items[i]);
> +
> +	return len;
> +}
> +EXPORT_SYMBOL(counter_count_enum_available_read);
> +
> +ssize_t counter_device_enum_read(struct counter_device *counter, void *priv,
> +				 char *buf)
> +{
> +	const struct counter_device_enum_ext *const e = priv;
> +	int err;
> +	size_t index;
> +
> +	if (!e->get)
> +		return -EINVAL;
> +
> +	err = e->get(counter, &index);
> +	if (err)
> +		return err;
> +
> +	if (index >= e->num_items)
> +		return -EINVAL;
> +
> +	return scnprintf(buf, PAGE_SIZE, "%s\n", e->items[index]);
> +}
> +EXPORT_SYMBOL(counter_device_enum_read);
> +
> +ssize_t counter_device_enum_write(struct counter_device *counter, void *priv,
> +				  const char *buf, size_t len)
> +{
> +	const struct counter_device_enum_ext *const e = priv;
> +	ssize_t index;
> +	int err;
> +
> +	if (!e->set)
> +		return -EINVAL;
> +
> +	index = __sysfs_match_string(e->items, e->num_items, buf);
> +	if (index < 0)
> +		return index;
> +
> +	err = e->set(counter, index);
> +	if (err)
> +		return err;
> +
> +	return len;
> +}
> +EXPORT_SYMBOL(counter_device_enum_write);
> +
> +ssize_t counter_device_enum_available_read(struct counter_device *counter,
> +					   void *priv, char *buf)
> +{
> +	const struct counter_device_enum_ext *const e = priv;
> +	size_t i;
> +	size_t len = 0;
> +
> +	if (!e->num_items)
> +		return 0;
> +
> +	for (i = 0; i < e->num_items; i++)
> +		len += scnprintf(buf + len, PAGE_SIZE - len, "%s\n",
> +			e->items[i]);
> +
> +	return len;
> +}
> +EXPORT_SYMBOL(counter_device_enum_available_read);
> +
> +static const char *const signal_level_str[] = {
> +	[SIGNAL_LEVEL_LOW] = "low",
> +	[SIGNAL_LEVEL_HIGH] = "high"
> +};
> +
> +/**
> + * set_signal_read_value - set signal_read_value data
> + * @val:	signal_read_value structure to set
> + * @type:	property Signal data represents
> + * @data:	Signal data
> + *
> + * This function sets an opaque signal_read_value structure with the provided
> + * Signal data.
> + */
> +void set_signal_read_value(struct signal_read_value *const val,
> +			   const enum signal_value_type type, void *const data)
> +{
> +	if (type == SIGNAL_LEVEL)
> +		val->len = scnprintf(val->buf, PAGE_SIZE, "%s\n",
> +			signal_level_str[*(enum signal_level *)data]);
> +	else
> +		val->len = 0;
> +}
> +EXPORT_SYMBOL(set_signal_read_value);
> +
> +/**
> + * set_count_read_value - set count_read_value data
> + * @val:	count_read_value structure to set
> + * @type:	property Count data represents
> + * @data:	Count data
> + *
> + * This function sets an opaque count_read_value structure with the provided
> + * Count data.
> + */
> +void set_count_read_value(struct count_read_value *const val,
> +			  const enum count_value_type type, void *const data)
> +{
> +	switch (type) {
> +	case COUNT_POSITION_UNSIGNED:
> +		val->len = scnprintf(val->buf, PAGE_SIZE, "%lu\n",
> +				     *(unsigned long *)data);
> +		break;
> +	case COUNT_POSITION_SIGNED:
> +		val->len = scnprintf(val->buf, PAGE_SIZE, "%ld\n",
> +				     *(long *)data);
> +		break;
> +	default:
> +		val->len = 0;
> +	}
> +}
> +EXPORT_SYMBOL(set_count_read_value);
> +
> +/**
> + * get_count_write_value - get count_write_value data
> + * @data:	Count data
> + * @type:	property Count data represents
> + * @val:	count_write_value structure containing data
> + *
> + * This function extracts Count data from the provided opaque count_write_value
> + * structure and stores it at the address provided by @data.
> + *
> + * RETURNS:
> + * 0 on success, negative error number on failure.
> + */
> +int get_count_write_value(void *const data, const enum count_value_type type,
> +			  const struct count_write_value *const val)
> +{
> +	int err;
> +
> +	switch (type) {
> +	case COUNT_POSITION_UNSIGNED:
> +		err = kstrtoul(val->buf, 0, data);
> +		if (err)
> +			return err;
> +		break;
> +	case COUNT_POSITION_SIGNED:
> +		err = kstrtol(val->buf, 0, data);
> +		if (err)
> +			return err;
> +		break;
> +	}
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(get_count_write_value);
> +
> +struct counter_device_attr {
> +	struct device_attribute		dev_attr;
> +	struct list_head		l;
> +	void				*component;
> +};
> +
> +static int counter_attribute_create(
> +	struct counter_device_attr_group *const group,
> +	const char *const prefix,
> +	const char *const name,
> +	ssize_t (*show)(struct device *dev, struct device_attribute *attr,
> +			char *buf),
> +	ssize_t (*store)(struct device *dev, struct device_attribute *attr,
> +			 const char *buf, size_t len),
> +	void *const component)
> +{
> +	struct counter_device_attr *counter_attr;
> +	struct device_attribute *dev_attr;
> +	int err;
> +	struct list_head *const attr_list = &group->attr_list;
> +
> +	/* Allocate a Counter device attribute */
> +	counter_attr = kzalloc(sizeof(*counter_attr), GFP_KERNEL);
> +	if (!counter_attr)
> +		return -ENOMEM;
> +	dev_attr = &counter_attr->dev_attr;
> +
> +	sysfs_attr_init(&dev_attr->attr);
> +
> +	/* Configure device attribute */
> +	dev_attr->attr.name = kasprintf(GFP_KERNEL, "%s%s", prefix, name);
> +	if (!dev_attr->attr.name) {
> +		err = -ENOMEM;
> +		goto err_free_counter_attr;
> +	}
> +	if (show) {
> +		dev_attr->attr.mode |= 0444;
> +		dev_attr->show = show;
> +	}
> +	if (store) {
> +		dev_attr->attr.mode |= 0200;
> +		dev_attr->store = store;
> +	}
> +
> +	/* Store associated Counter component with attribute */
> +	counter_attr->component = component;
> +
> +	/* Keep track of the attribute for later cleanup */
> +	list_add(&counter_attr->l, attr_list);
> +	group->num_attr++;
> +
> +	return 0;
> +
> +err_free_counter_attr:
> +	kfree(counter_attr);
> +	return err;
> +}
> +
> +#define to_counter_attr(_dev_attr) \
> +	container_of(_dev_attr, struct counter_device_attr, dev_attr)
> +
> +struct signal_comp_t {
> +	struct counter_signal	*signal;
> +};
> +
> +static ssize_t counter_signal_show(struct device *dev,
> +				   struct device_attribute *attr, char *buf)
> +{
> +	struct counter_device *const counter = dev_get_drvdata(dev);
> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
> +	const struct signal_comp_t *const component = devattr->component;
> +	struct counter_signal *const signal = component->signal;
> +	int err;
> +	struct signal_read_value val = { .buf = buf };
> +
> +	err = counter->ops->signal_read(counter, signal, &val);
> +	if (err)
> +		return err;
> +
> +	return val.len;
> +}
> +
> +struct name_comp_t {
> +	const char	*name;
> +};
> +
> +static ssize_t counter_device_attr_name_show(struct device *dev,
> +					     struct device_attribute *attr,
> +					     char *buf)
> +{
> +	const struct name_comp_t *const comp = to_counter_attr(attr)->component;
> +
> +	return scnprintf(buf, PAGE_SIZE, "%s\n", comp->name);
> +}
> +
> +static int counter_name_attribute_create(
> +	struct counter_device_attr_group *const group,
> +	const char *const name)
> +{
> +	struct name_comp_t *name_comp;
> +	int err;
> +
> +	/* Skip if no name */
> +	if (!name)
> +		return 0;
> +
> +	/* Allocate name attribute component */
> +	name_comp = kmalloc(sizeof(*name_comp), GFP_KERNEL);
> +	if (!name_comp)
> +		return -ENOMEM;
> +	name_comp->name = name;
> +
> +	/* Allocate Signal name attribute */
> +	err = counter_attribute_create(group, "", "name",
> +				       counter_device_attr_name_show, NULL,
> +				       name_comp);
> +	if (err)
> +		goto err_free_name_comp;
> +
> +	return 0;
> +
> +err_free_name_comp:
> +	kfree(name_comp);
> +	return err;
> +}
> +
> +struct signal_ext_comp_t {
> +	struct counter_signal		*signal;
> +	const struct counter_signal_ext	*ext;
> +};
> +
> +static ssize_t counter_signal_ext_show(struct device *dev,
> +				       struct device_attribute *attr, char *buf)
> +{
> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
> +	const struct signal_ext_comp_t *const comp = devattr->component;
> +	const struct counter_signal_ext *const ext = comp->ext;
> +
> +	return ext->read(dev_get_drvdata(dev), comp->signal, ext->priv, buf);
> +}
> +
> +static ssize_t counter_signal_ext_store(struct device *dev,
> +					struct device_attribute *attr,
> +					const char *buf, size_t len)
> +{
> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
> +	const struct signal_ext_comp_t *const comp = devattr->component;
> +	const struct counter_signal_ext *const ext = comp->ext;
> +
> +	return ext->write(dev_get_drvdata(dev), comp->signal, ext->priv, buf,
> +		len);
> +}
> +
> +static void free_counter_device_attr_list(struct list_head *attr_list)
> +{
> +	struct counter_device_attr *p, *n;
> +
> +	list_for_each_entry_safe(p, n, attr_list, l) {
> +		kfree(p->dev_attr.attr.name);
> +		kfree(p->component);
> +		list_del(&p->l);
> +		kfree(p);
> +	}
> +}
> +
> +static int counter_signal_ext_register(
> +	struct counter_device_attr_group *const group,
> +	struct counter_signal *const signal)
> +{
> +	const size_t num_ext = signal->num_ext;
> +	size_t i;
> +	const struct counter_signal_ext *ext;
> +	struct signal_ext_comp_t *signal_ext_comp;
> +	int err;
> +
> +	/* Create an attribute for each extension */
> +	for (i = 0 ; i < num_ext; i++) {
> +		ext = signal->ext + i;
> +
> +		/* Allocate signal_ext attribute component */
> +		signal_ext_comp = kmalloc(sizeof(*signal_ext_comp), GFP_KERNEL);
> +		if (!signal_ext_comp) {
> +			err = -ENOMEM;
> +			goto err_free_attr_list;
> +		}
> +		signal_ext_comp->signal = signal;
> +		signal_ext_comp->ext = ext;
> +
> +		/* Allocate a Counter device attribute */
> +		err = counter_attribute_create(group, "", ext->name,
> +			(ext->read) ? counter_signal_ext_show : NULL,
> +			(ext->write) ? counter_signal_ext_store : NULL,
> +			signal_ext_comp);
> +		if (err) {
> +			kfree(signal_ext_comp);
> +			goto err_free_attr_list;
> +		}
> +	}
> +
> +	return 0;
> +
> +err_free_attr_list:
> +	free_counter_device_attr_list(&group->attr_list);
> +	return err;
> +}
> +
> +static int counter_signal_attributes_create(
> +	struct counter_device_attr_group *const group,
> +	const struct counter_device *const counter,
> +	struct counter_signal *const signal)
> +{
> +	struct signal_comp_t *signal_comp;
> +	int err;
> +
> +	/* Allocate Signal attribute component */
> +	signal_comp = kmalloc(sizeof(*signal_comp), GFP_KERNEL);
> +	if (!signal_comp)
> +		return -ENOMEM;
> +	signal_comp->signal = signal;
> +
> +	/* Create main Signal attribute */
> +	err = counter_attribute_create(group, "", "signal",
> +		(counter->ops->signal_read) ? counter_signal_show : NULL, NULL,
> +		signal_comp);
> +	if (err) {
> +		kfree(signal_comp);
> +		return err;
> +	}
> +
> +	/* Create Signal name attribute */
> +	err = counter_name_attribute_create(group, signal->name);
> +	if (err)
> +		goto err_free_attr_list;
> +
> +	/* Register Signal extension attributes */
> +	err = counter_signal_ext_register(group, signal);
> +	if (err)
> +		goto err_free_attr_list;
> +
> +	return 0;
> +
> +err_free_attr_list:
> +	free_counter_device_attr_list(&group->attr_list);
> +	return err;
> +}
> +
> +static int counter_signals_register(
> +	struct counter_device_attr_group *const groups_list,
> +	const struct counter_device *const counter)
> +{
> +	const size_t num_signals = counter->num_signals;
> +	size_t i;
> +	struct counter_signal *signal;
> +	const char *name;
> +	int err;
> +
> +	/* Register each Signal */
> +	for (i = 0; i < num_signals; i++) {
> +		signal = counter->signals + i;
> +
> +		/* Generate Signal attribute directory name */
> +		name = kasprintf(GFP_KERNEL, "signal%d", signal->id);
> +		if (!name) {
> +			err = -ENOMEM;
> +			goto err_free_attr_groups;
> +		}
> +		groups_list[i].attr_group.name = name;
> +
> +		/* Create all attributes associated with Signal */
> +		err = counter_signal_attributes_create(groups_list + i, counter,
> +						       signal);
> +		if (err)
> +			goto err_free_attr_groups;
> +	}
> +
> +	return 0;
> +
> +err_free_attr_groups:
> +	do {
> +		kfree(groups_list[i].attr_group.name);
> +		free_counter_device_attr_list(&groups_list[i].attr_list);
> +	} while (i--);
> +	return err;
> +}
> +
> +static const char *const synapse_action_str[] = {
> +	[SYNAPSE_ACTION_NONE] = "none",
> +	[SYNAPSE_ACTION_RISING_EDGE] = "rising edge",
> +	[SYNAPSE_ACTION_FALLING_EDGE] = "falling edge",
> +	[SYNAPSE_ACTION_BOTH_EDGES] = "both edges"
> +};
> +
> +struct action_comp_t {
> +	struct counter_synapse	*synapse;
> +	struct counter_count	*count;
> +};
> +
> +static ssize_t counter_action_show(struct device *dev,
> +				   struct device_attribute *attr, char *buf)
> +{
> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
> +	int err;
> +	struct counter_device *const counter = dev_get_drvdata(dev);
> +	const struct action_comp_t *const component = devattr->component;
> +	struct counter_count *const count = component->count;
> +	struct counter_synapse *const synapse = component->synapse;
> +	size_t action_index;
> +	enum synapse_action action;
> +
> +	err = counter->ops->action_get(counter, count, synapse, &action_index);
> +	if (err)
> +		return err;
> +
> +	synapse->action = action_index;
> +
> +	action = synapse->actions_list[action_index];
> +	return scnprintf(buf, PAGE_SIZE, "%s\n", synapse_action_str[action]);
> +}
> +
> +static ssize_t counter_action_store(struct device *dev,
> +				    struct device_attribute *attr,
> +				    const char *buf, size_t len)
> +{
> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
> +	const struct action_comp_t *const component = devattr->component;
> +	struct counter_synapse *const synapse = component->synapse;
> +	size_t action_index;
> +	const size_t num_actions = synapse->num_actions;
> +	enum synapse_action action;
> +	int err;
> +	struct counter_device *const counter = dev_get_drvdata(dev);
> +	struct counter_count *const count = component->count;
> +
> +	/* Find requested action mode */
> +	for (action_index = 0; action_index < num_actions; action_index++) {
> +		action = synapse->actions_list[action_index];
> +		if (sysfs_streq(buf, synapse_action_str[action]))
> +			break;
> +	}
> +	/* If requested action mode not found */
> +	if (action_index >= num_actions)
> +		return -EINVAL;
> +
> +	err = counter->ops->action_set(counter, count, synapse, action_index);
> +	if (err)
> +		return err;
> +
> +	synapse->action = action_index;
> +
> +	return len;
> +}
> +
> +struct action_avail_comp_t {
> +	const enum synapse_action	*actions_list;
> +	size_t				num_actions;
> +};
> +
> +static ssize_t counter_synapse_action_available_show(struct device *dev,
> +	struct device_attribute *attr, char *buf)
> +{
> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
> +	const struct action_avail_comp_t *const component = devattr->component;
> +	const enum synapse_action *const actions_list = component->actions_list;

I'm not sure this local variable helps much either...

> +	const size_t num_actions = component->num_actions;

Local variable adds nothing as far as I can see..  Just use it inline.


> +	size_t i;
> +	enum synapse_action action;
> +	ssize_t len = 0;
> +
> +	for (i = 0; i < num_actions; i++) {
> +		action = actions_list[i];
> +		len += scnprintf(buf + len, PAGE_SIZE - len, "%s\n",
> +			synapse_action_str[action]);
> +	}
> +
> +	return len;
> +}
> +
> +static int counter_synapses_register(
> +	struct counter_device_attr_group *const group,
> +	const struct counter_device *const counter,
> +	struct counter_count *const count, const char *const count_attr_name)
> +{
> +	const size_t num_synapses = count->num_synapses;

Local variable doesn't add anything. Only used once.

> +	size_t i;
> +	struct counter_synapse *synapse;
> +	const char *prefix;
> +	struct action_comp_t *action_comp;
> +	int err;
> +	struct action_avail_comp_t *avail_comp;
> +
> +	/* Register each Synapse */
> +	for (i = 0; i < num_synapses; i++) {
> +		synapse = count->synapses + i;
> +
> +		/* Generate attribute prefix */
> +		prefix = kasprintf(GFP_KERNEL, "signal%d_",
> +				   synapse->signal->id);
> +		if (!prefix) {
> +			err = -ENOMEM;
> +			goto err_free_attr_list;
> +		}
> +
> +		/* Allocate action attribute component */
> +		action_comp = kmalloc(sizeof(*action_comp), GFP_KERNEL);
> +		if (!action_comp) {
> +			err = -ENOMEM;
> +			goto err_free_prefix;
> +		}
> +		action_comp->synapse = synapse;
> +		action_comp->count = count;
> +
> +		/* Create action attribute */
> +		err = counter_attribute_create(group, prefix, "action",
> +			(counter->ops->action_get) ? counter_action_show : NULL,
> +			(counter->ops->action_set) ? counter_action_store : NULL,
> +			action_comp);
> +		if (err) {
> +			kfree(action_comp);
> +			goto err_free_prefix;
> +		}
> +
> +		/* Allocate action available attribute component */
> +		avail_comp = kmalloc(sizeof(*avail_comp), GFP_KERNEL);
> +		if (!avail_comp) {
> +			err = -ENOMEM;
> +			goto err_free_prefix;
> +		}
> +		avail_comp->actions_list = synapse->actions_list;
> +		avail_comp->num_actions = synapse->num_actions;
> +
> +		/* Create action_available attribute */
> +		err = counter_attribute_create(group, prefix,
> +			"action_available",
> +			counter_synapse_action_available_show, NULL,
> +			avail_comp);
> +		if (err) {
> +			kfree(avail_comp);
> +			goto err_free_prefix;
> +		}
> +
> +		kfree(prefix);
> +	}
> +
> +	return 0;
> +
> +err_free_prefix:
> +	kfree(prefix);
> +err_free_attr_list:
> +	free_counter_device_attr_list(&group->attr_list);
> +	return err;
> +}
> +
> +struct count_comp_t {
> +	struct counter_count	*count;
> +};
> +
> +static ssize_t counter_count_show(struct device *dev,
> +				  struct device_attribute *attr,
> +				  char *buf)
> +{
> +	struct counter_device *const counter = dev_get_drvdata(dev);
> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
> +	const struct count_comp_t *const component = devattr->component;
> +	struct counter_count *const count = component->count;
> +	int err;
> +	struct count_read_value val = { .buf = buf };
> +
> +	err = counter->ops->count_read(counter, count, &val);
> +	if (err)
> +		return err;
> +
> +	return val.len;
> +}
> +
> +static ssize_t counter_count_store(struct device *dev,
> +				   struct device_attribute *attr,
> +				   const char *buf, size_t len)
> +{
> +	struct counter_device *const counter = dev_get_drvdata(dev);
> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
> +	const struct count_comp_t *const component = devattr->component;
> +	struct counter_count *const count = component->count;
> +	int err;
> +	struct count_write_value val = { .buf = buf };
> +
> +	err = counter->ops->count_write(counter, count, &val);
> +	if (err)
> +		return err;
> +
> +	return len;
> +}
> +
> +static const char *const count_function_str[] = {
> +	[COUNT_FUNCTION_INCREASE] = "increase",
> +	[COUNT_FUNCTION_DECREASE] = "decrease",
> +	[COUNT_FUNCTION_PULSE_DIRECTION] = "pulse-direction",
> +	[COUNT_FUNCTION_QUADRATURE_X1_A] = "quadrature x1 a",
> +	[COUNT_FUNCTION_QUADRATURE_X1_B] = "quadrature x1 b",
> +	[COUNT_FUNCTION_QUADRATURE_X2_A] = "quadrature x2 a",
> +	[COUNT_FUNCTION_QUADRATURE_X2_B] = "quadrature x2 b",
> +	[COUNT_FUNCTION_QUADRATURE_X2_RISING] = "quadrature x2 rising",
> +	[COUNT_FUNCTION_QUADRATURE_X2_FALLING] = "quadrature x2 falling",
> +	[COUNT_FUNCTION_QUADRATURE_X4] = "quadrature x4"
> +};
> +
> +static ssize_t counter_function_show(struct device *dev,
> +				     struct device_attribute *attr, char *buf)
> +{
> +	int err;
> +	struct counter_device *const counter = dev_get_drvdata(dev);
> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
> +	const struct count_comp_t *const component = devattr->component;
> +	struct counter_count *const count = component->count;
> +	size_t func_index;
> +	enum count_function function;
> +
> +	err = counter->ops->function_get(counter, count, &func_index);
> +	if (err)
> +		return err;
> +
> +	count->function = func_index;
> +
> +	function = count->functions_list[func_index];
> +	return scnprintf(buf, PAGE_SIZE, "%s\n", count_function_str[function]);
> +}
> +
> +static ssize_t counter_function_store(struct device *dev,
> +				      struct device_attribute *attr,
> +				      const char *buf, size_t len)
> +{
> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
> +	const struct count_comp_t *const component = devattr->component;
> +	struct counter_count *const count = component->count;
> +	const size_t num_functions = count->num_functions;
> +	size_t func_index;
> +	enum count_function function;
> +	int err;
> +	struct counter_device *const counter = dev_get_drvdata(dev);
> +
> +	/* Find requested Count function mode */
> +	for (func_index = 0; func_index < num_functions; func_index++) {
> +		function = count->functions_list[func_index];
> +		if (sysfs_streq(buf, count_function_str[function]))
> +			break;
> +	}
> +	/* Return error if requested Count function mode not found */
> +	if (func_index >= num_functions)
> +		return -EINVAL;
> +
> +	err = counter->ops->function_set(counter, count, func_index);
> +	if (err)
> +		return err;
> +
> +	count->function = func_index;
> +
> +	return len;
> +}
> +
> +struct count_ext_comp_t {
> +	struct counter_count		*count;
> +	const struct counter_count_ext	*ext;
> +};
> +
> +static ssize_t counter_count_ext_show(struct device *dev,
> +				      struct device_attribute *attr, char *buf)
> +{
> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
> +	const struct count_ext_comp_t *const comp = devattr->component;
> +	const struct counter_count_ext *const ext = comp->ext;
> +
> +	return ext->read(dev_get_drvdata(dev), comp->count, ext->priv, buf);
> +}
> +
> +static ssize_t counter_count_ext_store(struct device *dev,
> +				       struct device_attribute *attr,
> +				       const char *buf, size_t len)
> +{
> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
> +	const struct count_ext_comp_t *const comp = devattr->component;
> +	const struct counter_count_ext *const ext = comp->ext;
> +
> +	return ext->write(dev_get_drvdata(dev), comp->count, ext->priv, buf,
> +		len);
> +}
> +
> +static int counter_count_ext_register(
> +	struct counter_device_attr_group *const group,
> +	struct counter_count *const count)
> +{
> +	const size_t num_ext = count->num_ext;

Used in one place, just put it inline?

> +	size_t i;
> +	const struct counter_count_ext *ext;
> +	struct count_ext_comp_t *count_ext_comp;
> +	int err;
> +
> +	/* Create an attribute for each extension */
> +	for (i = 0 ; i < num_ext; i++) {
> +		ext = count->ext + i;
> +
> +		/* Allocate count_ext attribute component */
> +		count_ext_comp = kmalloc(sizeof(*count_ext_comp), GFP_KERNEL);
> +		if (!count_ext_comp) {
> +			err = -ENOMEM;
> +			goto err_free_attr_list;
> +		}
> +		count_ext_comp->count = count;
> +		count_ext_comp->ext = ext;
> +
> +		/* Allocate count_ext attribute */
> +		err = counter_attribute_create(group, "", ext->name,
> +			(ext->read) ? counter_count_ext_show : NULL,
> +			(ext->write) ? counter_count_ext_store : NULL,
> +			count_ext_comp);
> +		if (err) {
> +			kfree(count_ext_comp);
> +			goto err_free_attr_list;
> +		}
> +	}
> +
> +	return 0;
> +
> +err_free_attr_list:
> +	free_counter_device_attr_list(&group->attr_list);
> +	return err;
> +}
> +
> +struct func_avail_comp_t {
> +	const enum count_function	*functions_list;
> +	size_t				num_functions;
> +};
> +
> +static ssize_t counter_count_function_available_show(struct device *dev,
> +	struct device_attribute *attr, char *buf)
> +{
> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
> +	const struct func_avail_comp_t *const component = devattr->component;
> +	const enum count_function *const func_list = component->functions_list;
> +	const size_t num_functions = component->num_functions;
> +	size_t i;
> +	enum count_function function;
> +	ssize_t len = 0;
> +
> +	for (i = 0; i < num_functions; i++) {
> +		function = func_list[i];
> +		len += scnprintf(buf + len, PAGE_SIZE - len, "%s\n",
> +			count_function_str[function]);
> +	}
> +
> +	return len;
> +}
> +
> +static int counter_count_attributes_create(
> +	struct counter_device_attr_group *const group,
> +	const struct counter_device *const counter,
> +	struct counter_count *const count)
> +{
> +	struct count_comp_t *count_comp;
> +	int err;
> +	struct count_comp_t *func_comp;
> +	struct func_avail_comp_t *avail_comp;
> +
> +	/* Allocate count attribute component */
> +	count_comp = kmalloc(sizeof(*count_comp), GFP_KERNEL);
> +	if (!count_comp)
> +		return -ENOMEM;
> +	count_comp->count = count;
> +
> +	/* Create main Count attribute */
> +	err = counter_attribute_create(group, "", "count",
> +		(counter->ops->count_read) ? counter_count_show : NULL,
> +		(counter->ops->count_write) ? counter_count_store : NULL,
> +		count_comp);
> +	if (err) {
> +		kfree(count_comp);
> +		return err;
> +	}
> +
> +	/* Allocate function attribute component */
> +	func_comp = kmalloc(sizeof(*func_comp), GFP_KERNEL);
> +	if (!func_comp) {
> +		err = -ENOMEM;
> +		goto err_free_attr_list;
> +	}
> +	func_comp->count = count;
> +
> +	/* Create Count function attribute */
> +	err = counter_attribute_create(group, "", "function",
> +		(counter->ops->function_get) ? counter_function_show : NULL,
> +		(counter->ops->function_set) ? counter_function_store : NULL,
> +		func_comp);
> +	if (err) {
> +		kfree(func_comp);
> +		goto err_free_attr_list;
> +	}
> +
> +	/* Allocate function available attribute component */
> +	avail_comp = kmalloc(sizeof(*avail_comp), GFP_KERNEL);
> +	if (!avail_comp) {
> +		err = -ENOMEM;
> +		goto err_free_attr_list;
> +	}
> +	avail_comp->functions_list = count->functions_list;
> +	avail_comp->num_functions = count->num_functions;
> +
> +	/* Create Count function_available attribute */
> +	err = counter_attribute_create(group, "", "function_available",
> +				       counter_count_function_available_show,
> +				       NULL, avail_comp);
> +	if (err) {
> +		kfree(avail_comp);
> +		goto err_free_attr_list;
> +	}
> +
> +	/* Create Count name attribute */
> +	err = counter_name_attribute_create(group, count->name);
> +	if (err)
> +		goto err_free_attr_list;
> +
> +	/* Register Count extension attributes */
> +	err = counter_count_ext_register(group, count);
> +	if (err)
> +		goto err_free_attr_list;
> +
> +	return 0;
> +
> +err_free_attr_list:
> +	free_counter_device_attr_list(&group->attr_list);
> +	return err;
> +}
> +
> +static int counter_counts_register(
> +	struct counter_device_attr_group *const groups_list,
> +	const struct counter_device *const counter)
> +{
> +	const size_t num_counts = counter->num_counts;

I think this is only used on one place.  Not sure having
a local variable is worthwhile.

> +	size_t i;
> +	struct counter_count *count;
> +	const char *name;
> +	int err;
> +
> +	/* Register each Count */
> +	for (i = 0; i < num_counts; i++) {
> +		count = counter->counts + i;
> +
> +		/* Generate Count attribute directory name */
> +		name = kasprintf(GFP_KERNEL, "count%d", count->id);
> +		if (!name) {
> +			err = -ENOMEM;
> +			goto err_free_attr_groups;
> +		}
> +		groups_list[i].attr_group.name = name;
> +
> +		/* Register the Synapses associated with each Count */
> +		err = counter_synapses_register(groups_list + i, counter, count,
> +						name);
> +		if (err)
> +			goto err_free_attr_groups;
> +
> +		/* Create all attributes associated with Count */
> +		err = counter_count_attributes_create(groups_list + i, counter,
> +						      count);
> +		if (err)
> +			goto err_free_attr_groups;
> +	}
> +
> +	return 0;
> +
> +err_free_attr_groups:
> +	do {
> +		kfree(groups_list[i].attr_group.name);
> +		free_counter_device_attr_list(&groups_list[i].attr_list);
> +	} while (i--);
> +	return err;
> +}
> +
> +struct size_comp_t {
> +	size_t size;
> +};
> +
> +static ssize_t counter_device_attr_size_show(struct device *dev,
> +					     struct device_attribute *attr,
> +					     char *buf)
> +{
> +	const struct size_comp_t *const comp = to_counter_attr(attr)->component;
> +
> +	return scnprintf(buf, PAGE_SIZE, "%zu\n", comp->size);
> +}
> +
> +static int counter_size_attribute_create(
> +	struct counter_device_attr_group *const group,
> +	const size_t size, const char *const name)
> +{
> +	struct size_comp_t *size_comp;
> +	int err;
> +
> +	/* Allocate size attribute component */
> +	size_comp = kmalloc(sizeof(*size_comp), GFP_KERNEL);
> +	if (!size_comp)
> +		return -ENOMEM;
> +	size_comp->size = size;
> +
> +	err = counter_attribute_create(group, "", name,
> +				       counter_device_attr_size_show, NULL,
> +				       size_comp);
> +	if (err)
> +		goto err_free_size_comp;
> +
> +	return 0;
> +
> +err_free_size_comp:
> +	kfree(size_comp);
> +	return err;
> +}
> +
> +struct ext_comp_t {
> +	const struct counter_device_ext	*ext;
> +};
> +
> +static ssize_t counter_device_ext_show(struct device *dev,
> +				       struct device_attribute *attr, char *buf)
> +{
> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
> +	const struct ext_comp_t *const component = devattr->component;
> +	const struct counter_device_ext *const ext = component->ext;
> +
> +	return ext->read(dev_get_drvdata(dev), ext->priv, buf);
> +}
> +
> +static ssize_t counter_device_ext_store(struct device *dev,
> +					struct device_attribute *attr,
> +					const char *buf, size_t len)
> +{
> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
> +	const struct ext_comp_t *const component = devattr->component;
> +	const struct counter_device_ext *const ext = component->ext;
> +
> +	return ext->write(dev_get_drvdata(dev), ext->priv, buf, len);
> +}
> +
> +static int counter_device_ext_register(
> +	struct counter_device_attr_group *const group,
> +	struct counter_device *const counter)
> +{
> +	const size_t num_ext = counter->num_ext;

num_ext only used in one place so if anything the local variable
is hurting readability.

> +	struct ext_comp_t *ext_comp;
> +	size_t i;
> +	const struct counter_device_ext *ext;
> +	int err;
> +
> +	/* Create an attribute for each extension */
> +	for (i = 0 ; i < num_ext; i++) {
> +		ext = counter->ext + i;

This local variable isn't gaining us much that I can see. Just
use the value directly.

> +
> +		/* Allocate extension attribute component */
> +		ext_comp = kmalloc(sizeof(*ext_comp), GFP_KERNEL);
> +		if (!ext_comp) {
> +			err = -ENOMEM;
> +			goto err_free_attr_list;
> +		}
> +
> +		ext_comp->ext = ext;
> +
> +		/* Allocate extension attribute */
> +		err = counter_attribute_create(group, "", ext->name,
> +			(ext->read) ? counter_device_ext_show : NULL,
> +			(ext->write) ? counter_device_ext_store : NULL,
> +			ext_comp);
> +		if (err) {
> +			kfree(ext_comp);
> +			goto err_free_attr_list;
> +		}
> +	}
> +
> +	return 0;
> +
> +err_free_attr_list:
> +	free_counter_device_attr_list(&group->attr_list);
> +	return err;
> +}
> +
> +static int counter_global_attr_register(
> +	struct counter_device_attr_group *const group,
> +	struct counter_device *const counter)
> +{
> +	int err;
> +
> +	/* Create name attribute */
> +	err = counter_name_attribute_create(group, counter->name);
> +	if (err)
> +		return err;
> +
> +	/* Create num_counts attribute */
> +	err = counter_size_attribute_create(group, counter->num_counts,
> +					    "num_counts");
> +	if (err)
> +		goto err_free_attr_list;
> +
> +	/* Create num_signals attribute */
> +	err = counter_size_attribute_create(group, counter->num_signals,
> +					    "num_signals");
> +	if (err)
> +		goto err_free_attr_list;
> +
> +	/* Register Counter device extension attributes */
> +	err = counter_device_ext_register(group, counter);
> +	if (err)
> +		goto err_free_attr_list;
> +
> +	return 0;
> +
> +err_free_attr_list:
> +	free_counter_device_attr_list(&group->attr_list);
> +	return err;
> +}
> +
> +static void free_counter_device_groups_list(
> +	struct counter_device_attr_group *const groups_list,
> +	const size_t num_groups)
> +{
> +	struct counter_device_attr_group *group;
> +	size_t i;
> +
> +	for (i = 0; i < num_groups; i++) {
> +		group = groups_list + i;
> +

I'd like to see a comment somewhere here on the fact this cleans up both
the registered per counter stuff and the global attributes (that took
a bit of chasing to check it did...)

> +		kfree(group->attr_group.name);
> +		kfree(group->attr_group.attrs);
> +		free_counter_device_attr_list(&group->attr_list);
> +	}
> +
> +	kfree(groups_list);
> +}
> +
> +static int prepare_counter_device_groups_list(
> +	struct counter_device *const counter)
> +{
> +	const size_t total_num_groups =
> +		counter->num_signals + counter->num_counts + 1;
> +	struct counter_device_attr_group *groups_list;
> +	size_t i;
> +	int err;
> +	size_t num_groups = 0;
> +
> +	/* Allocate space for attribute groups (signals. counts, and ext) */
> +	groups_list = kcalloc(total_num_groups, sizeof(*groups_list),
> +			      GFP_KERNEL);
> +	if (!groups_list)
> +		return -ENOMEM;
> +
> +	/* Initialize attribute lists */
> +	for (i = 0; i < total_num_groups; i++)
> +		INIT_LIST_HEAD(&groups_list[i].attr_list);
> +
> +	/* Register Signals */
> +	err = counter_signals_register(groups_list, counter);
> +	if (err)
> +		goto err_free_groups_list;
> +	num_groups += counter->num_signals;
> +
> +	/* Register Counts and respective Synapses */
> +	err = counter_counts_register(groups_list + num_groups, counter);
> +	if (err)
> +		goto err_free_groups_list;
> +	num_groups += counter->num_counts;
> +
> +	/* Register Counter global attributes */
> +	err = counter_global_attr_register(groups_list + num_groups, counter);
> +	if (err)
> +		goto err_free_groups_list;
> +	num_groups++;
> +
> +	/* Store groups_list in device_state */
> +	counter->device_state->groups_list = groups_list;
> +	counter->device_state->num_groups = num_groups;
> +
> +	return 0;
> +
> +err_free_groups_list:
> +	free_counter_device_groups_list(groups_list, num_groups);

Consistent naming would be good.

counter_device_groups_list_free.

I would tidy this up throughout.  I know from experience that
you'll probably end up doing so eventually and it is easier whilst
there isn't too much code.

> +	return err;
> +}
> +
> +static int prepare_counter_device_groups(
> +	struct counter_device_state *const device_state)
> +{
> +	size_t i;
> +	struct counter_device_attr_group *group;
> +	int err;
> +	size_t j;

Tidy this up a little,
size_t i, j;

> +	struct counter_device_attr *p;
> +
> +	/* Allocate attribute groups for association with device */
> +	device_state->groups = kcalloc(device_state->num_groups + 1,
> +				       sizeof(*device_state->groups),
> +				       GFP_KERNEL);
> +	if (!device_state->groups)
> +		return -ENOMEM;
> +
> +	/* Prepare each group of attributes for association */
> +	for (i = 0; i < device_state->num_groups; i++) {
> +		group = device_state->groups_list + i;
> +
> +		/* Allocate space for attribute pointers in attribute group */
> +		group->attr_group.attrs = kcalloc(group->num_attr + 1,
> +			sizeof(*group->attr_group.attrs), GFP_KERNEL);
> +		if (!group->attr_group.attrs) {
> +			err = -ENOMEM;
> +			goto err_free_groups;
> +		}
> +
> +		/* Add attribute pointers to attribute group */
> +		j = 0;
> +		list_for_each_entry(p, &group->attr_list, l)
> +			group->attr_group.attrs[j++] = &p->dev_attr.attr;
> +
> +		/* Group attributes in attribute group */
> +		device_state->groups[i] = &group->attr_group;
> +	}
> +	/* Associate attributes with device */
> +	device_state->dev.groups = device_state->groups;
> +
> +	return 0;
> +
> +err_free_groups:

I'm not convinced this is cleaning up properly.  What about
the kcalloc of group->attr_group.attrs for previous loops?

> +	kfree(device_state->groups);
> +	return err;
> +}
> +
> +/* Provides a unique ID for each counter device */
> +static DEFINE_IDA(counter_ida);
> +
> +static void counter_device_release(struct device *dev)
> +{
> +	struct counter_device *const counter = dev_get_drvdata(dev);
> +	struct counter_device_state *const device_state = counter->device_state;
> +
> +	kfree(device_state->groups);
> +	free_counter_device_groups_list(device_state->groups_list,
> +					device_state->num_groups);
> +	ida_simple_remove(&counter_ida, device_state->id);
> +	kfree(device_state);
> +}
> +
> +static struct device_type counter_device_type = {
> +	.name = "counter_device",
> +	.release = counter_device_release
> +};
> +
> +static struct bus_type counter_bus_type = {
> +	.name = "counter"
> +};
> +
> +/**
> + * counter_register - register Counter to the system
> + * @counter:	pointer to Counter to register
> + *
> + * This function registers a Counter to the system. A sysfs "counter" directory
> + * will be created and populated with sysfs attributes correlating with the
> + * Counter Signals, Synapses, and Counts respectively.
> + */
> +int counter_register(struct counter_device *const counter)
> +{
> +	struct counter_device_state *device_state;
> +	int err;
> +
> +	/* Allocate internal state container for Counter device */
> +	device_state = kzalloc(sizeof(*device_state), GFP_KERNEL);
> +	if (!device_state)
> +		return -ENOMEM;
> +	counter->device_state = device_state;
> +
> +	/* Acquire unique ID */
> +	device_state->id = ida_simple_get(&counter_ida, 0, 0, GFP_KERNEL);
> +	if (device_state->id < 0) {
> +		err = device_state->id;
> +		goto err_free_device_state;
> +	}
> +
> +	/* Configure device structure for Counter */
> +	device_state->dev.type = &counter_device_type;
> +	device_state->dev.bus = &counter_bus_type;
> +	if (counter->parent) {
> +		device_state->dev.parent = counter->parent;
> +		device_state->dev.of_node = counter->parent->of_node;
> +	}
> +	dev_set_name(&device_state->dev, "counter%d", device_state->id);
> +	device_initialize(&device_state->dev);
> +	dev_set_drvdata(&device_state->dev, counter);
> +
> +	/* Prepare device attributes */
> +	err = prepare_counter_device_groups_list(counter);
> +	if (err)
> +		goto err_free_id;
> +
> +	/* Organize device attributes to groups and match to device */
> +	err = prepare_counter_device_groups(device_state);
> +	if (err)
> +		goto err_free_groups_list;
> +
> +	/* Add device to system */
> +	err = device_add(&device_state->dev);
> +	if (err)
> +		goto err_free_groups;
> +
> +	return 0;
> +
> +err_free_groups:
> +	kfree(device_state->groups);
> +err_free_groups_list:
> +	free_counter_device_groups_list(device_state->groups_list,
> +					device_state->num_groups);
> +err_free_id:
> +	ida_simple_remove(&counter_ida, device_state->id);
> +err_free_device_state:
> +	kfree(device_state);
> +	return err;
> +}
> +EXPORT_SYMBOL(counter_register);
> +
> +/**
> + * counter_unregister - unregister Counter from the system
> + * @counter:	pointer to Counter to unregister
> + *
> + * The Counter is unregistered from the system; all allocated memory is freed.
> + */
> +void counter_unregister(struct counter_device *const counter)
> +{
> +	if (counter)
> +		device_del(&counter->device_state->dev);
> +}
> +EXPORT_SYMBOL(counter_unregister);
> +
> +static void devm_counter_unreg(struct device *dev, void *res)
> +{
> +	counter_unregister(*(struct counter_device **)res);
> +}
> +
> +/**
> + * devm_counter_register - Resource-managed counter_register
> + * @dev:	device to allocate counter_device for
> + * @counter:	pointer to Counter to register
> + *
> + * Managed counter_register. The Counter registered with this function is
> + * automatically unregistered on driver detach. This function calls
> + * counter_register internally. Refer to that function for more information.
> + *
> + * If an Counter registered with this function needs to be unregistered
> + * separately, devm_counter_unregister must be used.
> + *
> + * RETURNS:
> + * 0 on success, negative error number on failure.
> + */
> +int devm_counter_register(struct device *dev,
> +			  struct counter_device *const counter)
> +{
> +	struct counter_device **ptr;
> +	int ret;
> +
> +	ptr = devres_alloc(devm_counter_unreg, sizeof(*ptr), GFP_KERNEL);
> +	if (!ptr)
> +		return -ENOMEM;
> +
> +	ret = counter_register(counter);
> +	if (!ret) {
> +		*ptr = counter;
> +		devres_add(dev, ptr);
> +	} else {
> +		devres_free(ptr);
> +	}
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(devm_counter_register);
> +
> +static int devm_counter_match(struct device *dev, void *res, void *data)
> +{
> +	struct counter_device **r = res;
> +
> +	if (!r || !*r) {
> +		WARN_ON(!r || !*r);
> +		return 0;
> +	}
> +
> +	return *r == data;
> +}
> +
> +/**
> + * devm_counter_unregister - Resource-managed counter_unregister
> + * @dev:	device this counter_device belongs to
> + * @counter:	pointer to Counter associated with the device
> + *
> + * Unregister Counter registered with devm_counter_register.
> + */
> +void devm_counter_unregister(struct device *dev,
> +			     struct counter_device *const counter)
> +{
> +	int rc;
> +
> +	rc = devres_release(dev, devm_counter_unreg, devm_counter_match,
> +			    counter);
> +	WARN_ON(rc);
> +}
> +EXPORT_SYMBOL(devm_counter_unregister);
> +
> +static int __init counter_init(void)
> +{
> +	return bus_register(&counter_bus_type);
> +}
> +
> +static void __exit counter_exit(void)
> +{
> +	bus_unregister(&counter_bus_type);
> +}
> +
> +subsys_initcall(counter_init);
> +module_exit(counter_exit);
> +
> +MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
> +MODULE_DESCRIPTION("Generic Counter interface");
> +MODULE_LICENSE("GPL v2");
> diff --git a/include/linux/counter.h b/include/linux/counter.h
> new file mode 100644
> index 000000000000..a0b0349d098a
> --- /dev/null
> +++ b/include/linux/counter.h
> @@ -0,0 +1,554 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Counter interface
> + * Copyright (C) 2017 William Breathitt Gray
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License, version 2, as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful, but
> + * WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * General Public License for more details.

It's a bit controversial, but most people consider SPDX headers equivalent
of the license statement.  As such you normally don't have both and just
go for the SPDK header.

I thought we were also standardising on 
// SPDX-...


> + */
> +#ifndef _COUNTER_H_
> +#define _COUNTER_H_
> +
> +#include <linux/device.h>
> +#include <linux/types.h>
> +
> +enum count_direction {
> +	COUNT_DIRECTION_FORWARD = 0,
> +	COUNT_DIRECTION_BACKWARD
> +};
> +extern const char *const count_direction_str[2];
> +
> +enum count_mode {
> +	COUNT_MODE_NORMAL = 0,
> +	COUNT_MODE_RANGE_LIMIT,
> +	COUNT_MODE_NON_RECYCLE,
> +	COUNT_MODE_MODULO_N
> +};
> +extern const char *const count_mode_str[4];
> +
> +struct counter_device;
> +struct counter_signal;
> +
> +/**
> + * struct counter_signal_ext - Counter Signal extensions
> + * @name:	attribute name
> + * @read:	read callback for this attribute; may be NULL
> + * @write:	write callback for this attribute; may be NULL
> + * @priv:	data private to the driver
> + */
> +struct counter_signal_ext {
> +	const char	*name;
> +	ssize_t		(*read)(struct counter_device *counter,
> +				struct counter_signal *signal, void *priv,
> +				char *buf);
> +	ssize_t		(*write)(struct counter_device *counter,
> +				 struct counter_signal *signal, void *priv,
> +				 const char *buf, size_t len);
> +	void		*priv;
> +};
> +
> +/**
> + * struct counter_signal - Counter Signal node
> + * @id:		unique ID used to identify signal
> + * @name:	device-specific Signal name; ideally, this should match the name
> + *		as it appears in the datasheet documentation
> + * @ext:	optional array of Counter Signal extensions
> + * @num_ext:	number of Counter Signal extensions specified in @ext
> + * @priv:	optional private data supplied by driver
> + */
> +struct counter_signal {
> +	int		id;
> +	const char	*name;
> +
> +	const struct counter_signal_ext	*ext;
> +	size_t				num_ext;
> +
> +	void	*priv;
> +};
> +
> +/**
> + * struct counter_signal_enum_ext - Signal enum extension attribute
> + * @items:	Array of strings
> + * @num_items:	Number of items specified in @items
> + * @set:	Set callback function; may be NULL
> + * @get:	Get callback function; may be NULL
> + *
> + * The counter_signal_enum_ext structure can be used to implement enum style
> + * Signal extension attributes. Enum style attributes are those which have a set
> + * of strings that map to unsigned integer values. The Generic Counter Signal
> + * enum extension helper code takes care of mapping between value and string, as
> + * well as generating a "_available" file which contains a list of all available
> + * items. The get callback is used to query the currently active item; the index
> + * of the item within the respective items array is returned via the 'item'
> + * parameter. The set callback is called when the attribute is updated; the
> + * 'item' parameter contains the index of the newly activated item within the
> + * respective items array.
> + */
> +struct counter_signal_enum_ext {
> +	const char * const	*items;
> +	size_t			num_items;
> +	int			(*get)(struct counter_device *counter,
> +				       struct counter_signal *signal,
> +				       size_t *item);
> +	int			(*set)(struct counter_device *counter,
> +				       struct counter_signal *signal,
> +				       size_t item);
> +};
> +
> +ssize_t counter_signal_enum_read(struct counter_device *counter,
> +				 struct counter_signal *signal, void *priv,
> +				 char *buf);
> +ssize_t counter_signal_enum_write(struct counter_device *counter,
> +				  struct counter_signal *signal, void *priv,
> +				  const char *buf, size_t len);
> +
> +/**
> + * COUNTER_SIGNAL_ENUM() - Initialize Signal enum extension
> + * @_name:	Attribute name
> + * @_e:		Pointer to a counter_count_enum structure
> + *
> + * This should usually be used together with COUNTER_SIGNAL_ENUM_AVAILABLE()
> + */
> +#define COUNTER_SIGNAL_ENUM(_name, _e) \
> +{ \
> +	.name = (_name), \
> +	.read = counter_signal_enum_read, \
> +	.write = counter_signal_enum_write, \
> +	.priv = (_e) \
> +}
> +
> +ssize_t counter_signal_enum_available_read(struct counter_device *counter,
> +					   struct counter_signal *signal,
> +					   void *priv, char *buf);
> +
> +/**
> + * COUNTER_SIGNAL_ENUM_AVAILABLE() - Initialize Signal enum available extension
> + * @_name:	Attribute name ("_available" will be appended to the name)
> + * @_e:		Pointer to a counter_signal_enum structure
> + *
> + * Creates a read only attribute that lists all the available enum items in a
> + * newline separated list. This should usually be used together with
> + * COUNTER_SIGNAL_ENUM()
> + */
> +#define COUNTER_SIGNAL_ENUM_AVAILABLE(_name, _e) \
> +{ \
> +	.name = (_name "_available"), \
> +	.read = counter_signal_enum_available_read, \
> +	.priv = (_e) \
> +}
> +
> +enum synapse_action {
> +	SYNAPSE_ACTION_NONE = 0,
> +	SYNAPSE_ACTION_RISING_EDGE,
> +	SYNAPSE_ACTION_FALLING_EDGE,
> +	SYNAPSE_ACTION_BOTH_EDGES
> +};
> +
> +/**
> + * struct counter_synapse - Counter Synapse node
> + * @action:		index of current action mode
> + * @actions_list:	array of available action modes
> + * @num_actions:	number of action modes specified in @actions_list
> + * @signal:		pointer to associated signal
> + */
> +struct counter_synapse {
> +	size_t					action;
> +	const enum synapse_action		*actions_list;
> +	size_t					num_actions;
> +
> +	struct counter_signal			*signal;
> +};
> +
> +struct counter_count;
> +
> +/**
> + * struct counter_count_ext - Counter Count extension
> + * @name:	attribute name
> + * @read:	read callback for this attribute; may be NULL
> + * @write:	write callback for this attribute; may be NULL
> + * @priv:	data private to the driver
> + */
> +struct counter_count_ext {
> +	const char	*name;
> +	ssize_t		(*read)(struct counter_device *counter,
> +				struct counter_count *count, void *priv,
> +				char *buf);
> +	ssize_t		(*write)(struct counter_device *counter,
> +				 struct counter_count *count, void *priv,
> +				 const char *buf, size_t len);
> +	void		*priv;
> +};
> +
> +enum count_function {
> +	COUNT_FUNCTION_INCREASE = 0,
> +	COUNT_FUNCTION_DECREASE,
> +	COUNT_FUNCTION_PULSE_DIRECTION,
> +	COUNT_FUNCTION_QUADRATURE_X1_A,
> +	COUNT_FUNCTION_QUADRATURE_X1_B,
> +	COUNT_FUNCTION_QUADRATURE_X2_A,
> +	COUNT_FUNCTION_QUADRATURE_X2_B,
> +	COUNT_FUNCTION_QUADRATURE_X2_RISING,
> +	COUNT_FUNCTION_QUADRATURE_X2_FALLING,
> +	COUNT_FUNCTION_QUADRATURE_X4
> +};
> +
> +/**
> + * struct counter_count - Counter Count node
> + * @id:			unique ID used to identify Count
> + * @name:		device-specific Count name; ideally, this should match
> + *			the name as it appears in the datasheet documentation
> + * @function:		index of current function mode
> + * @functions_list:	array available function modes
> + * @num_functions:	number of function modes specified in @functions_list
> + * @synapses:		array of synapses for initialization
> + * @num_synapses:	number of synapses specified in @synapses
> + * @ext:		optional array of Counter Count extensions
> + * @num_ext:		number of Counter Count extensions specified in @ext
> + * @priv:		optional private data supplied by driver
> + */
> +struct counter_count {
> +	int			id;
> +	const char		*name;
> +
> +	size_t					function;
> +	const enum count_function		*functions_list;
> +	size_t					num_functions;

There is a very good illustration here of the issues with using
tabs to pretty print structure elements.  I would drop them entirely as
personally I'm not sure they help readability and you will forever be having
more noise in patches because of the need to change the number of tabs
due to name changes etc.

> +
> +	struct counter_synapse	*synapses;
> +	size_t			num_synapses;
> +
> +	const struct counter_count_ext	*ext;
> +	size_t				num_ext;
> +
> +	void	*priv;
> +};
> +
> +/**
> + * struct counter_count_enum_ext - Count enum extension attribute
> + * @items:	Array of strings
> + * @num_items:	Number of items specified in @items
> + * @set:	Set callback function; may be NULL
> + * @get:	Get callback function; may be NULL
> + *
> + * The counter_count_enum_ext structure can be used to implement enum style
> + * Count extension attributes. Enum style attributes are those which have a set
> + * of strings that map to unsigned integer values. The Generic Counter Count
> + * enum extension helper code takes care of mapping between value and string, as
> + * well as generating a "_available" file which contains a list of all available
> + * items. The get callback is used to query the currently active item; the index
> + * of the item within the respective items array is returned via the 'item'
> + * parameter. The set callback is called when the attribute is updated; the
> + * 'item' parameter contains the index of the newly activated item within the
> + * respective items array.
> + */
> +struct counter_count_enum_ext {
> +	const char * const	*items;
> +	size_t			num_items;
> +	int			(*get)(struct counter_device *counter,
> +				       struct counter_count *count,
> +				       size_t *item);
> +	int			(*set)(struct counter_device *counter,
> +				       struct counter_count *count,
> +				       size_t item);
> +};
> +
> +ssize_t counter_count_enum_read(struct counter_device *counter,
> +				struct counter_count *count, void *priv,
> +				char *buf);
> +ssize_t counter_count_enum_write(struct counter_device *counter,
> +				 struct counter_count *count, void *priv,
> +				 const char *buf, size_t len);
> +
> +/**
> + * COUNTER_COUNT_ENUM() - Initialize Count enum extension
> + * @_name:	Attribute name
> + * @_e:		Pointer to a counter_count_enum structure
> + *
> + * This should usually be used together with COUNTER_COUNT_ENUM_AVAILABLE()
> + */
> +#define COUNTER_COUNT_ENUM(_name, _e) \
> +{ \
> +	.name = (_name), \
> +	.read = counter_count_enum_read, \
> +	.write = counter_count_enum_write, \
> +	.priv = (_e) \
> +}
> +
> +ssize_t counter_count_enum_available_read(struct counter_device *counter,
> +					  struct counter_count *count,
> +					  void *priv, char *buf);
> +
> +/**
> + * COUNTER_COUNT_ENUM_AVAILABLE() - Initialize Count enum available extension
> + * @_name:	Attribute name ("_available" will be appended to the name)
> + * @_e:		Pointer to a counter_count_enum structure
> + *
> + * Creates a read only attribute that lists all the available enum items in a
> + * newline separated list. This should usually be used together with
> + * COUNTER_COUNT_ENUM()
> + */
> +#define COUNTER_COUNT_ENUM_AVAILABLE(_name, _e) \
> +{ \
> +	.name = (_name "_available"), \
> +	.read = counter_count_enum_available_read, \
> +	.priv = (_e) \
> +}
> +
> +/**
> + * struct counter_device_attr_group - internal container for attribute group
> + * @attr_group:	Counter sysfs attributes group
> + * @attr_list:	list to keep track of created Counter sysfs attributes
> + * @num_attr:	number of Counter sysfs attributes
> + */
> +struct counter_device_attr_group {
> +	struct attribute_group	attr_group;
> +	struct list_head	attr_list;
> +	size_t			num_attr;
> +};
> +
> +/**
> + * struct counter_device_state - internal state container for a Counter device
> + * @id:		unique ID used to identify the Counter
> + * @dev:	internal device structure
> + * @groups_list	attribute groups list (groups for Signals, Counts, and ext)

Run kernel-doc script over these files.  You are missing some :s and it would
have told you that.

> + * @num_groups	number of attribute groups containers
> + * @groups:	Counter sysfs attribute groups (used to populate @dev.groups)
> + */
> +struct counter_device_state {
> +	int					id;
> +	struct device				dev;
> +	struct counter_device_attr_group	*groups_list;
> +	size_t					num_groups;
> +	const struct attribute_group		**groups;
> +};
> +
> +/**
> + * struct signal_read_value - Opaque Signal read value
> + * @buf:	string representation of Signal read value
> + * @len:	length of string in @buf
> + */
> +struct signal_read_value {
> +	char	*buf;
> +	size_t	len;
> +};
> +
> +/**
> + * struct count_read_value - Opaque Count read value
> + * @buf:	string representation of Count read value
> + * @len:	length of string in @buf
> + */
> +struct count_read_value {
> +	char	*buf;
> +	size_t	len;
> +};
> +
> +/**
> + * struct count_write_value - Opaque Count write value
> + * @buf:	string representation of Count write value
> + */
> +struct count_write_value {
> +	const char	*buf;
> +};
> +
> +/**
> + * struct counter_ops - Callbacks from driver
> + * @signal_read:	optional read callback for Signal attribute. The read
> + *			value of the respective Signal should be passed back via
> + *			the val parameter. val points to an opaque type which
> + *			should be set only via the set_signal_read_value
> + *			function.

This last part had me a little confused.  I would make it clear that this
set_signal_read_value function should be called to set the value within this
signal_read callback rather than elsewhere...  

> + * @count_read:		optional read callback for Count attribute. The read
> + *			value of the respective Count should be passed back via
> + *			the val parameter. val points to an opaque type which
> + *			should be set only via the set_count_read_value
> + *			function.
> + * @count_write:	optional write callback for Count attribute. The write
> + *			value for the respective Count is passed in via the val
> + *			parameter. val points to an opaque type which should be
> + *			access only via the get_count_write_value function.
> + * @function_get:	function to get the current count function mode. Returns
> + *			0 on success and negative error code on error. The index
> + *			of the respective Count's returned function mode should
> + *			be passed back via the function parameter.
> + * @function_set:	function to set the count function mode. function is the
> + *			index of the requested function mode from the respective
> + *			Count's functions_list array.
> + * @action_get:		function to get the current action mode. Returns 0 on
> + *			success and negative error code on error. The index of
> + *			the respective Signal's returned action mode should be
> + *			passed back via the action parameter.
> + * @action_set:		function to set the action mode. action is the index of
> + *			the requested action mode from the respective Synapse's
> + *			actions_list array.
> + */
> +struct counter_ops {
> +	int	(*signal_read)(struct counter_device *counter,
> +			       struct counter_signal *signal,
> +			       struct signal_read_value *val);
> +	int	(*count_read)(struct counter_device *counter,
> +			      struct counter_count *count,
> +			      struct count_read_value *val);
> +	int	(*count_write)(struct counter_device *counter,
> +			       struct counter_count *count,
> +			       struct count_write_value *val);
> +	int	(*function_get)(struct counter_device *counter,
> +				struct counter_count *count, size_t *function);
> +	int	(*function_set)(struct counter_device *counter,
> +				struct counter_count *count, size_t function);
> +	int	(*action_get)(struct counter_device *counter,
> +			      struct counter_count *count,
> +			      struct counter_synapse *synapse, size_t *action);
> +	int	(*action_set)(struct counter_device *counter,
> +			      struct counter_count *count,
> +			      struct counter_synapse *synapse, size_t action);
> +};
> +
> +/**
> + * struct counter_device_ext - Counter device extension
> + * @name:	attribute name
> + * @read:	read callback for this attribute; may be NULL
> + * @write:	write callback for this attribute; may be NULL
> + * @priv:	data private to the driver
> + */
> +struct counter_device_ext {
> +	const char	*name;
> +	ssize_t		(*read)(struct counter_device *counter, void *priv,
> +				char *buf);
> +	ssize_t		(*write)(struct counter_device *counter, void *priv,
> +				 const char *buf, size_t len);
> +	void		*priv;
> +};
> +
> +/**
> + * struct counter_device_enum_ext - Counter enum extension attribute
> + * @items:	Array of strings
> + * @num_items:	Number of items specified in @items
> + * @set:	Set callback function; may be NULL
> + * @get:	Get callback function; may be NULL
> + *
> + * The counter_device_enum_ext structure can be used to implement enum style
> + * Counter extension attributes. Enum style attributes are those which have a
> + * set of strings that map to unsigned integer values. The Generic Counter enum
> + * extension helper code takes care of mapping between value and string, as well
> + * as generating a "_available" file which contains a list of all available
> + * items. The get callback is used to query the currently active item; the index
> + * of the item within the respective items array is returned via the 'item'
> + * parameter. The set callback is called when the attribute is updated; the
> + * 'item' parameter contains the index of the newly activated item within the
> + * respective items array.
> + */
> +struct counter_device_enum_ext {
> +	const char * const	*items;
> +	size_t			num_items;
> +	int			(*get)(struct counter_device *counter,
> +				       size_t *item);
> +	int			(*set)(struct counter_device *counter,
> +				       size_t item);
> +};
> +
> +ssize_t counter_device_enum_read(struct counter_device *counter, void *priv,
> +				 char *buf);
> +ssize_t counter_device_enum_write(struct counter_device *counter, void *priv,
> +				  const char *buf, size_t len);
> +
> +/**
> + * COUNTER_DEVICE_ENUM() - Initialize Counter enum extension
> + * @_name:	Attribute name
> + * @_e:		Pointer to a counter_device_enum structure
> + *
> + * This should usually be used together with COUNTER_DEVICE_ENUM_AVAILABLE()
> + */
> +#define COUNTER_DEVICE_ENUM(_name, _e) \
> +{ \
> +	.name = (_name), \
> +	.read = counter_device_enum_read, \
> +	.write = counter_device_enum_write, \
> +	.priv = (_e) \
> +}
> +
> +ssize_t counter_device_enum_available_read(struct counter_device *counter,
> +					   void *priv, char *buf);
> +
> +/**
> + * COUNTER_DEVICE_ENUM_AVAILABLE() - Initialize Counter enum available extension
> + * @_name:	Attribute name ("_available" will be appended to the name)
> + * @_e:		Pointer to a counter_device_enum structure
> + *
> + * Creates a read only attribute that lists all the available enum items in a
> + * newline separated list. This should usually be used together with
> + * COUNTER_DEVICE_ENUM()
> + */
> +#define COUNTER_DEVICE_ENUM_AVAILABLE(_name, _e) \
> +{ \
> +	.name = (_name "_available"), \
> +	.read = counter_device_enum_available_read, \
> +	.priv = (_e) \
> +}
> +
> +/**
> + * struct counter_device - Counter data structure
> + * @name:		name of the device as it appears in the datasheet
> + * @parent:		optional parent device providing the counters
> + * @device_state:	internal device state container
> + * @ops:		callbacks from driver
> + * @signals:		array of Signals
> + * @num_signals:	number of Signals specified in @signals
> + * @counts:		array of Counts
> + * @num_counts:		number of Counts specified in @counts
> + * @ext:		optional array of Counter device extensions
> + * @num_ext:		number of Counter device extensions specified in @ext
> + * @priv:		optional private data supplied by driver
> + */
> +struct counter_device {
> +	const char			*name;
> +	struct device			*parent;
> +	struct counter_device_state	*device_state;
> +
> +	const struct counter_ops	*ops;
> +
> +	struct counter_signal	*signals;
> +	size_t			num_signals;
> +	struct counter_count	*counts;
> +	size_t			num_counts;
> +
> +	const struct counter_device_ext	*ext;
> +	size_t				num_ext;
> +
> +	void	*priv;
> +};
> +
> +enum signal_level {
> +	SIGNAL_LEVEL_LOW = 0,
> +	SIGNAL_LEVEL_HIGH
> +};
> +
> +enum signal_value_type {
> +	SIGNAL_LEVEL = 0
> +};
> +
> +enum count_value_type {
> +	COUNT_POSITION_UNSIGNED = 0,
> +	COUNT_POSITION_SIGNED
> +};
> +
> +void set_signal_read_value(struct signal_read_value *const val,
> +			   const enum signal_value_type type, void *const data);
> +void set_count_read_value(struct count_read_value *const val,
> +			  const enum count_value_type type, void *const data);
> +int get_count_write_value(void *const data, const enum count_value_type type,
> +			  const struct count_write_value *const val);

I wonder if naming wise, we would be better sticking to the
noun_verb naming format.

signal_read_value_set
count_read_value_set
count_write_value_get

for example?

> +
> +int counter_register(struct counter_device *const counter);
> +void counter_unregister(struct counter_device *const counter);
> +int devm_counter_register(struct device *dev,
> +			  struct counter_device *const counter);
> +void devm_counter_unregister(struct device *dev,
> +			     struct counter_device *const counter);
> +
> +#endif /* _COUNTER_H_ */

Re: [PATCH v6 2/9] counter: Documentation: Add Generic Counter sysfs documentation

[Jonathan Cameron]

On Wed, 16 May 2018 13:50:55 -0400
William Breathitt Gray <vilhelm.gray@gmail.com> wrote:

> This patch adds standard documentation for the userspace sysfs
> attributes of the Generic Counter interface.
> 
> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>

Some really minor stuff inline.  No functional changes.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
>  Documentation/ABI/testing/sysfs-bus-counter | 241 ++++++++++++++++++++
>  MAINTAINERS                                 |   1 +
>  2 files changed, 242 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-bus-counter
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-counter b/Documentation/ABI/testing/sysfs-bus-counter
> new file mode 100644
> index 000000000000..e4a45d231b4f
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-bus-counter
> @@ -0,0 +1,241 @@
> +What:		/sys/bus/counter/devices/counterX/countY/count
> +KernelVersion:	4.18
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Count data of Count Y represented as a string.
> +
> +What:		/sys/bus/counter/devices/counterX/countY/ceiling
> +KernelVersion:	4.18
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Count value ceiling for Count Y. This is the upper limit for the
> +		respective counter.
> +
> +What:		/sys/bus/counter/devices/counterX/countY/floor
> +KernelVersion:	4.18
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Count value floor for Count Y. This is the lower limit for the
> +		respective counter.
> +
> +What:		/sys/bus/counter/devices/counterX/countY/count_mode
> +KernelVersion:	4.18
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Count mode for channel Y. The ceiling and floor values for
> +		Count Y are used by the count mode where required. The following
> +		count modes are available:
> +
> +		Normal:
> +			Counting is continuous in either direction.
> +
> +		Range Limit:
> +			An upper or lower limit is set, mimicking limit switches
> +			in the mechanical counterpart. The upper limit is set to
> +			the Count Y ceiling value, while the lower limit is set
> +			to the Count Y floor value. The counter freezes at
> +			count = ceiling when counting up, and at count = floor
> +			when counting down. At either of these limits, the
> +			counting is resumed only when the count direction is
> +			reversed.
> +
> +		Non-Recycle:
> +			The counter is disabled whenever a counter overflow or
> +			underflow takes place. The counter is re-enabled when a
> +			new count value is loaded to the counter via a preset
> +			operation or direct write.
> +
> +		Modulo-N:
> +			A count value boundary is set between the Count Y floor
> +			value and the Count Y ceiling value. The counter is
> +			reset to the Cunt Y floor value at count = ceiling when
> +			counting up, while the counter is set to the Count Y
> +			ceiling value at count = floor when counting down; the
> +			counter does not freeze at the boundary points, but
> +			counts continuously throughout.
> +
> +What:		/sys/bus/counter/devices/counterX/countY/count_mode_available
> +What:		/sys/bus/counter/devices/counterX/countY/error_noise_available
> +What:		/sys/bus/counter/devices/counterX/countY/function_available
> +What:		/sys/bus/counter/devices/counterX/countY/signalZ_action_available
> +KernelVersion:	4.18
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Discrete set of available values for the respective Count Y
> +		configuration are listed in this file. Values are delineated by
> +		newline characters.
> +
> +What:		/sys/bus/counter/devices/counterX/countY/direction
> +KernelVersion:	4.18
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Read-only attribute that indicates the count direction of Count
> +		Y. Two count directions are available: forward and backward.
> +
> +		Some counter devices are able to determine the direction of
> +		their counting. For example, quadrature encoding counters can
> +		determine the direction of movement by evaluating the leading
> +		phase of the respective A and B quadrature encoding signals.
> +		This attribute exposes such count directions.
> +
> +What:		/sys/bus/counter/devices/counterX/countY/enable
> +KernelVersion:	4.18
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Whether channel Y counter is enabled. Valid attribute values are
> +		boolean.
> +
> +		This attribute is intended to serve as a pause/unpause mechanism
> +		for Count Y. Suppose a counter device is used to count the total
> +		movement of a conveyor belt: this attribute allows an operator
> +		to temporarily pause the counter, service the conveyor belt,
> +		and then finally unpause the counter to continue where it had
> +		left off.
> +
> +What:		/sys/bus/counter/devices/counterX/countY/error_noise
> +KernelVersion:	4.18
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Read-only attribute that indicates whether excessive noise is
> +		present at the channel Y counter inputs.
> +
> +What:		/sys/bus/counter/devices/counterX/countY/function
> +KernelVersion:	4.18
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Count function mode of Count Y; count function evaluation is
> +		triggered by conditions specified by the Count Y signalZ_action
> +		attributes. The following count functions are available:
> +
> +		Increase:
> +			Accumulated count is incremented.
> +
> +		Decrease:
> +			Accumulated count is decremented.
> +
> +		Pulse-Direction:
> +			Rising edges on quadrature pair signal A updates the
> +			respective count. The input level of quadrature pair
> +			signal B determines direction.
> +
> +		Quadrature x1 A:
> +			If direction is forward, rising edges on quadrature pair
> +			signal A updates the respective count; if the direction
> +			is backward, falling edges on quadrature pair signal A
> +			updates the respective count. Quadrature encoding
> +			determines the direction.
> +
> +		Quadrature x1 B:
> +			If direction is forward, rising edges on quadrature pair
> +			signal B updates the respective count; if the direction
> +			is backward, falling edges on quadrature pair signal B
> +			updates the respective count. Quadrature encoding
> +			determines the direction.
> +
> +		Quadrature x2 A:
> +			Any state transition on quadrature pair signal A updates
> +			the respective count. Quadrature encoding determines the
> +			direction.
> +
> +		Quadrature x2 B:
> +			Any state transition on quadrature pair signal B updates
> +			the respective count. Quadrature encoding determines the
> +			direction.
> +
> +		Quadrature x2 Rising:
> +			Rising edges on either quadrature pair signals updates
> +			the respective count. Quadrature encoding determines the
> +			direction.
> +
> +		Quadrature x2 Falling:
> +			Falling edges on either quadrature pair signals updates
> +			the respective count. Quadrature encoding determines the
> +			direction.
> +
> +		Quadrature x4:
> +			Any state transition on either quadrature pair signals
> +			updates	the respective count. Quadrature encoding
> +			determines the direction.
> +
> +What:		/sys/bus/counter/devices/counterX/countY/name
> +KernelVersion:	4.18
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Read-only attribute that indicates the device-specific name of
> +		Count Y. If possible, this should match the name of the
> +		respective channel as it appears in the device datasheet
> +		documentation text.
> +
> +What:		/sys/bus/counter/devices/counterX/countY/preset
> +KernelVersion:	4.18
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		If the counter device supports preset registers, the preset
> +		count for channel Y is provided by this attribute.

I would add a small block of text here saying what a "preset" typically is.
It is a term heavily used in encoders etc, but perhaps not some other types
of counter.

> +
> +What:		/sys/bus/counter/devices/counterX/countY/preset_enable
> +KernelVersion:	4.18
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Whether channel Y counter preset operation is enabled. Valid
> +		attribute values are boolean.
> +
> +What:		/sys/bus/counter/devices/counterX/countY/signalZ_action
> +KernelVersion:	4.18
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Action mode of Count Y for Signal Z. This attribute indicates
> +		the condition of Signal Z that triggers the count function
> +		evaluation for Count Y. The following action modes are
> +		available:
> +
> +		None:
> +			Signal does not trigger the count function. In
> +			Pulse-Direction count function mode, this Signal is
> +			evaluated as Direction.
> +
> +		Rising Edge:
> +			Low state transitions to high state.
> +
> +		Falling Edge:
> +			High state transitions to low state.
> +
> +		Both Edges:
> +			Any state transition.
> +
> +What:		/sys/bus/counter/devices/counterX/name
> +KernelVersion:	4.18
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Read-only attribute that indicates the device-specific name of
> +		the Counter. This should match the name of the device as it
> +		appears in its respective datasheet documentation text.

As below, I'm not sure if "documentation text" makes it clearer or less clear..

> +
> +What:		/sys/bus/counter/devices/counterX/num_counts
> +KernelVersion:	4.18
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Read-only attribute that indicates the total number of Counts
> +		belonging to the Counter.
> +
> +What:		/sys/bus/counter/devices/counterX/num_signals
> +KernelVersion:	4.18
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Read-only attribute that indicates the total number of Signals
> +		belonging to the Counter.
> +
> +What:		/sys/bus/counter/devices/counterX/signalY/signal
> +KernelVersion:	4.18
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Signal data of Signal Y represented as a string.
> +
> +What:		/sys/bus/counter/devices/counterX/signalY/name
> +KernelVersion:	4.18
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Read-only attribute that indicates the device-specific name of
> +		Signal Y. If possible, this should match the name of the
> +		respective signal as it appears in the device datasheet
> +		documentation text.

Not sure "documentation text" adds any clarity over the simply "device datasheet"

> diff --git a/MAINTAINERS b/MAINTAINERS
> index 2a016d73ab72..1413e3eb49e5 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -3673,6 +3673,7 @@ COUNTER SUBSYSTEM
>  M:	William Breathitt Gray <vilhelm.gray@gmail.com>
>  L:	linux-iio@vger.kernel.org
>  S:	Maintained
> +F:	Documentation/ABI/testing/sysfs-bus-counter*
>  F:	drivers/counter/
>  F:	include/linux/counter.h
>  

Re: [PATCH v6 3/9] docs: Add Generic Counter interface documentation

[Jonathan Cameron]

On Wed, 16 May 2018 13:51:06 -0400
William Breathitt Gray <vilhelm.gray@gmail.com> wrote:

> This patch adds high-level documentation about the Generic Counter
> interface.
> 
> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>

Various comments inline.  I've been doing a lot long reviews recently
(outside of the kernel world) and keep discovering the old rule that
everytime you read a document you'll find something else to
improve :(

Jonathan
> ---
>  Documentation/driver-api/generic-counter.rst | 336 +++++++++++++++++++
>  Documentation/driver-api/index.rst           |   1 +
>  MAINTAINERS                                  |   1 +
>  3 files changed, 338 insertions(+)
>  create mode 100644 Documentation/driver-api/generic-counter.rst
> 
> diff --git a/Documentation/driver-api/generic-counter.rst b/Documentation/driver-api/generic-counter.rst
> new file mode 100644
> index 000000000000..5c6b9c008c06
> --- /dev/null
> +++ b/Documentation/driver-api/generic-counter.rst
> @@ -0,0 +1,336 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +=========================
> +Generic Counter Interface
> +=========================
> +
> +Introduction
> +============
> +
> +Counter devices are prevalent within a diverse spectrum of industries.
> +The ubiquitous presence of these devices necessitates a common interface
> +and standard of interaction and exposure. This driver API attempts to
> +resolve the issue of duplicate code found among existing counter device
> +drivers by introducing a generic counter interface for consumption. The
> +Generic Counter interface enables drivers to support and expose a common
> +set of components and functionality present in counter devices.
> +
> +Theory
> +======
> +
> +Counter devices can vary greatly in design, but regardless of whether
> +some devices are quadrature encoder counters or tally counters, all
> +counter devices consist of a core set of components. This core set of
> +components, shared by all counter devices, is what forms the essence of
> +the Generic Counter interface.
> +
> +There are three core components to a counter:

Enumerate them here.  If people are reading this as a paged document (pdf etc)
then the list of 3 as titles of next few sections may not be clear.

* Count

* Signal

* Synapse 

> +
> +COUNT
> +-----
> +A Count represents the count data for a set of Signals. The Generic
> +Counter interface provides the following available count data types:
> +
> +* COUNT_POSITION_UNSIGNED:
> +  Unsigned integer value representing position.
> +
> +* COUNT_POSITION_SIGNED:
> +  Signed integer value representing position.

Just a thought: As the '0' position is effectively arbitrary is there any
actual difference between signed and unsigned? If we defined all counters
to be unsigned and just offset any signed ones so the range still fitted
would we end up with a simpler interface - there would be no real loss
of meaning that I can see..  I suppose it might not be what people expect
though when they see their counters start at a large positive value...




> +
> +A Count has a count function mode which represents the update behavior
> +for the count data. The Generic Counter interface provides the following
> +available count function modes:
> +
> +* Increase:
> +  Accumulated count is incremented.
> +
> +* Decrease:
> +  Accumulated count is decremented.
> +
> +* Pulse-Direction:
> +  Rising edges on quadrature pair signal A updates the respective count.
> +  The input level of quadrature pair signal B determines direction.
> +
Perhaps group the quadrature modes for the point of view of this document?
Might be slightly easier to read?  

* Quadrature Modes

  - x1 A: etc.

> +* Quadrature x1 A:
> +  If direction is forward, rising edges on quadrature pair signal A
> +  updates the respective count; if the direction is backward, falling
> +  edges on quadrature pair signal A updates the respective count.
> +  Quadrature encoding determines the direction.
> +
> +* Quadrature x1 B:
> +  If direction is forward, rising edges on quadrature pair signal B
> +  updates the respective count; if the direction is backward, falling
> +  edges on quadrature pair signal B updates the respective count.
> +  Quadrature encoding determines the direction.
> +
> +* Quadrature x2 A:
> +  Any state transition on quadrature pair signal A updates the
> +  respective count. Quadrature encoding determines the direction.
> +
> +* Quadrature x2 B:
> +  Any state transition on quadrature pair signal B updates the
> +  respective count. Quadrature encoding determines the direction.
> +
> +* Quadrature x2 Rising:
> +  Rising edges on either quadrature pair signals updates the respective
> +  count. Quadrature encoding determines the direction.

This one I've never met.  Really? There are devices who do this form
of crazy? It gives really uneven counting and I'm failing to see when
it would ever make sense...  References for these odd corner cases
would be good.


__|---|____|-----|____
____|----|____|-----|____

001122222223334444444


> +
> +* Quadrature x2 Falling:
> +  Falling edges on either quadrature pair signals updates the respective
> +  count. Quadrature encoding determines the direction.
> +
> +* Quadrature x4:
> +  Any state transition on either quadrature pair signals updates the
> +  respective count. Quadrature encoding determines the direction.
> +
> +A Count has a set of one or more associated Signals.
> +
> +SIGNAL
> +------
> +A Signal represents a counter input data; this is the input data that is
> +analyzed by the counter to determine the count data; e.g. a quadrature
> +signal output line of a rotary encoder. Not all counter devices provide
> +user access to the Signal data.
> +
> +The Generic Counter interface provides the following available signal
> +data types for when the Signal data is available for user access:
> +
> +* SIGNAL_LEVEL_LOW:
> +  Signal line is in a low state.
> +
> +* SIGNAL_LEVEL_HIGH:
> +  Signal line is in a high state.
> +
> +A Signal may be associated with one or more Counts.
> +
> +SYNAPSE
> +-------
> +A Synapse represents the association of a Signal with a respective
> +Count. Signal data affects respective Count data, and the Synapse
> +represents this relationship.
> +
> +The Synapse action mode specifies the Signal data condition which
> +triggers the respective Count's count function evaluation to update the
> +count data. The Generic Counter interface provides the following
> +available action modes:
> +
> +* None:
> +  Signal does not trigger the count function. In Pulse-Direction count
> +  function mode, this Signal is evaluated as Direction.
> +
> +* Rising Edge:
> +  Low state transitions to high state.
> +
> +* Falling Edge:
> +  High state transitions to low state.
> +
> +* Both Edges:
> +  Any state transition.
> +
> +A counter is defined as a set of input signals associated with count
> +data that are generated by the evaluation of the state of the associated
> +input signals as defined by the respective count functions. Within the
> +context of the Generic Counter interface, a counter consists of Counts
> +each associated with a set of Signals, whose respective Synapse
> +instances represent the count function update conditions for the
> +associated Counts.
> +
> +Paradigm
> +========
> +
> +The most basic counter device may be expressed as a single Count
> +associated with a single Signal via a single Synapse. Take for example
> +a counter device which simply accumulates a count of rising edges on a
> +source input line::
> +
> +                Count                Synapse        Signal
> +                -----                -------        ------
> +        +---------------------+
> +        | Data: Count         |    Rising Edge     ________
> +        | Function: Increase  |  <-------------   / Source \
> +        |                     |                  ____________
> +        +---------------------+
> +
> +In this example, the Signal is a source input line with a pulsing
> +voltage, while the Count is a persistent count value which is repeatedly
> +incremented. The Signal is associated with the respective Count via a
> +Synapse. The increase function is triggered by the Signal data condition
> +specified by the Synapse -- in this case a rising edge condition on the
> +voltage input line. In summary, the counter device existence and
> +behavior is aptly represented by respective Count, Signal, and Synapse
> +components: a rising edge condition triggers an increase function on an
> +accumulating count datum.
> +
> +A counter device is not limited to a single Signal; in fact, in theory
> +many Signals may be associated with even a single Count. For example, a
> +quadrature encoder counter device can keep track of position based on
> +the states of two input lines::
> +
> +                   Count                 Synapse     Signal
> +                   -----                 -------     ------
> +        +-------------------------+
> +        | Data: Position          |    Both Edges     ___
> +        | Function: Quadrature x4 |  <------------   / A \
> +        |                         |                 _______
> +        |                         |
> +        |                         |    Both Edges     ___
> +        |                         |  <------------   / B \
> +        |                         |                 _______
> +        +-------------------------+
> +
> +In this example, two Signals (quadrature encoder lines A and B) are
> +associated with a single Count: a rising or falling edge on either A or
> +B triggers the "Quadrature x4" function which determines the direction
> +of movement and updates the respective position data. The "Quadrature
> +x4" function is likely implemented in the hardware of the quadrature
> +encoder counter device; the Count, Signals, and Synapses simply
> +represent this hardware behavior and functionality.
> +
> +Signals associated with the same Count can have differing Synapse action
> +mode conditions. For example, a quadrature encoder counter device
> +operating in a non-quadrature Pulse-Direction mode could have one input
> +line dedicated for movement and a second input line dedicated for
> +direction::
> +
> +                   Count                   Synapse      Signal
> +                   -----                   -------      ------
> +        +---------------------------+
> +        | Data: Position            |    Rising Edge     ___
> +        | Function: Pulse-Direction |  <-------------   / A \ (Movement)
> +        |                           |                  _______
> +        |                           |
> +        |                           |       None         ___
> +        |                           |  <-------------   / B \ (Direction)
> +        |                           |                  _______
> +        +---------------------------+
> +
> +Only Signal A triggers the "Pulse-Direction" update function, but the
> +instantaneous state of Signal B is still required in order to know the
> +direction so that the position data may be properly updated. Ultimately,
> +both Signals are associated with the same Count via two respective
> +Synapses, but only one Synapse has an active action mode condition which
> +triggers the respective count function while the other is left with a
> +"None" condition action mode to indicate its respective Signal's
> +availability for state evaluation despite its non-triggering mode.
> +
> +Keep in mind that the Signal, Synapse, and Count are abstract
> +representations which do not need to be closely married to their
> +respective physical sources. This allows the user of a counter to
> +divorce themselves from the nuances of physical components (such as
> +whether an input line is differential or single-ended) and instead focus
> +on the core idea of what the data and process represent (e.g. position
> +as interpreted from quadrature encoding data).
> +
> +Userspace Interface
> +===================
> +
> +Several sysfs attributes are generated by the Generic Counter interface,
> +and reside under the /sys/bus/counter/devices/counterX directory, where
> +counterX refers to the respective counter device. Please see
> +Documentation/ABI/testing/sys-bus-counter-generic-sysfs for detailed
> +information on each Generic Counter interface sysfs attribute.
> +
> +Through these sysfs attributes, programs and scripts may interact with
> +the Generic Counter paradigm Counts, Signals, and Synapses of respective
> +counter devices.
> +
> +Driver API
> +==========
> +
> +Driver authors may utilize the Generic Counter interface in their code
> +by including the include/linux/iio/counter.h header file. This header

Didn't this move?

> +file provides several core data structures, function prototypes, and
> +macros for defining a counter device.
> +
> +.. kernel-doc:: include/linux/counter.h
> +   :internal:
> +
> +.. kernel-doc:: drivers/counter/generic-counter.c
> +   :export:
> +
> +Implementation
> +==============
> +
> +To support a counter device, a driver must first allocate the available
> +Counter Signals via counter_signal structures. These Signals should
> +be stored as an array and set to the signals array member of an
> +allocated counter_device structure before the Counter is registered to
> +the system.
> +
> +Counter Counts may be allocated via counter_count structures, and
> +respective Counter Signal associations (Synapses) made via
> +counter_synapse structures. Associated counter_synapse structures are
> +stored as an array and set to the the synapses array member of the
> +respective counter_count structure. These counter_count structures are
> +set to the counts array member of an allocated counter_device structure
> +before the Counter is registered to the system.
> +
> +Driver callbacks should be provided to the counter_device structure via
> +a constant counter_ops structure in order to communicate with the
> +device: to read and write various Signals and Counts, and to set and get
> +the "action mode" and "function mode" for various Synapses and Counts
> +respectively.
> +
> +A defined counter_device structure may be registered to the system by
> +passing it to the counter_register function, and unregistered by passing
> +it to the counter_unregister function. Similarly, the
> +devm_counter_register and devm_counter_unregister functions may be used
> +if device memory-managed registration is desired.
> +
> +Extension sysfs attributes can be created for auxiliary functionality
> +and data by passing in defined counter_device_ext, counter_count_ext,
> +and counter_signal_ext structures. In these cases, the
> +counter_device_ext structure is used for global configuration of the
> +respective Counter device, while the counter_count_ext and
> +counter_signal_ext structures allow for auxiliary exposure and
> +configuration of a specific Count or Signal respectively.
> +
> +Architecture
> +============
> +
> +When the Generic Counter interface counter module is loaded, the
> +counter_init function is called which registers a bus_type named
> +"counter" to the system. Subsequently, when the module is unloaded, the
> +counter_exit function is called which unregisters the bus_type named
> +"counter" from the system.
> +
> +Counter devices are registered to the system via the counter_register
> +function, and later removed via the counter_unregister function. The
> +counter_register function establishes a unique ID for the Counter
> +device and creates a respective sysfs directory, where X is the
> +mentioned unique ID:
> +
> +    /sys/bus/counter/devices/counterX
> +
> +Sysfs attributes are created within the counterX directory to expose
> +functionality, configurations, and data relating to the Counts, Signals,
> +and Synapses of the Counter device, as well as options and information
> +for the Counter device itself.
> +
> +Each Signal has a directory created to house its relevant sysfs
> +attributes, where Y is the unique ID of the respective Signal:
> +
> +    /sys/bus/counter/devices/counterX/signalY
> +
> +Similarly, each Count has a directory created to house its relevant
> +sysfs attributes, where Y is the unique ID of the respective Count:
> +
> +    /sys/bus/counter/devices/counterX/countY
> +
> +For a more detailed breakdown of the available Generic Counter interface
> +sysfs attributes, please refer to the
> +Documentation/ABI/testing/sys-bus-counter file.
> +
> +The Signals and Counts associated with the Counter device are registered
> +to the system as well by the counter_register function. The
> +signal_read/signal_write driver callbacks are associated with their
> +respective Signal attributes, while the count_read/count_write and
> +function_get/function_set driver callbacks are associated with their
> +respective Count attributes; similarly, the same is true for the
> +action_get/action_set driver callbacks and their respective Synapse
> +attributes. If a driver callback is left undefined, then the respective
> +read/write permission is left disabled for the relevant attributes.
> +
> +Similarly, extension sysfs attributes are created for the defined
> +counter_device_ext, counter_count_ext, and counter_signal_ext
> +structures that are passed in.
> diff --git a/Documentation/driver-api/index.rst b/Documentation/driver-api/index.rst
> index 6d8352c0f354..5fd747c4f2ce 100644
> --- a/Documentation/driver-api/index.rst
> +++ b/Documentation/driver-api/index.rst
> @@ -25,6 +25,7 @@ available subsections can be seen below.
>     frame-buffer
>     regulator
>     iio/index
> +   generic-counter
>     input
>     usb/index
>     pci
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 1413e3eb49e5..7a01aa63fb33 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -3674,6 +3674,7 @@ M:	William Breathitt Gray <vilhelm.gray@gmail.com>
>  L:	linux-iio@vger.kernel.org
>  S:	Maintained
>  F:	Documentation/ABI/testing/sysfs-bus-counter*
> +F:	Documentation/driver-api/generic-counter.rst
>  F:	drivers/counter/
>  F:	include/linux/counter.h
>  

Re: [PATCH v6 4/9] counter: 104-quad-8: Add Generic Counter interface support

[Jonathan Cameron]

On Wed, 16 May 2018 13:51:25 -0400
William Breathitt Gray <vilhelm.gray@gmail.com> wrote:

> This patch adds support for the Generic Counter interface to the
> 104-QUAD-8 driver. The existing 104-QUAD-8 device interface should not
> be affected by this patch; all changes are intended as supplemental
> additions as perceived by the user.
> 
> Generic Counter Counts are created for the eight quadrature channel
> counts, as well as their respective quadrature A and B Signals (which
> are associated via respective Synapse structures) and respective index
> Signals.
> 
> The new Generic Counter interface sysfs attributes are intended to
> expose the same functionality and data available via the existing
> 104-QUAD-8 IIO device interface; the Generic Counter interface serves
> to provide the respective functionality and data in a standard way
> expected of counter devices.
> 
> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>

A few general comments that applied just as well to the original driver
as they do to the modified version.

I wonder if this would be easier to review as two patches.
Move the driver then add the counter interfaces?

Right now people kind of have to review the old IIO driver and
all the new stuff which is a big job..

Jonathan
> ---
>  MAINTAINERS                      |    4 +-
>  drivers/counter/104-quad-8.c     | 1335 ++++++++++++++++++++++++++++++
>  drivers/counter/Kconfig          |   21 +
>  drivers/counter/Makefile         |    2 +
>  drivers/iio/counter/104-quad-8.c |  596 -------------
>  drivers/iio/counter/Kconfig      |   17 -
>  drivers/iio/counter/Makefile     |    1 -
>  7 files changed, 1360 insertions(+), 616 deletions(-)
>  create mode 100644 drivers/counter/104-quad-8.c
>  delete mode 100644 drivers/iio/counter/104-quad-8.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 7a01aa63fb33..f11bf7885aeb 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -266,12 +266,12 @@ L:	linux-gpio@vger.kernel.org
>  S:	Maintained
>  F:	drivers/gpio/gpio-104-idio-16.c
>  
> -ACCES 104-QUAD-8 IIO DRIVER
> +ACCES 104-QUAD-8 DRIVER
>  M:	William Breathitt Gray <vilhelm.gray@gmail.com>
>  L:	linux-iio@vger.kernel.org
>  S:	Maintained
>  F:	Documentation/ABI/testing/sysfs-bus-iio-counter-104-quad-8
> -F:	drivers/iio/counter/104-quad-8.c
> +F:	drivers/counter/104-quad-8.c
>  
>  ACCES PCI-IDIO-16 GPIO DRIVER
>  M:	William Breathitt Gray <vilhelm.gray@gmail.com>
> diff --git a/drivers/counter/104-quad-8.c b/drivers/counter/104-quad-8.c
> new file mode 100644
> index 000000000000..7c72fb72d660
> --- /dev/null
> +++ b/drivers/counter/104-quad-8.c
> @@ -0,0 +1,1335 @@
> +// SPDX-License-Identifier: GPL-2.0-only

If you are happy with SPDX drop the GPL text below to keep things
short.

> +/*
> + * IIO driver for the ACCES 104-QUAD-8
> + * Copyright (C) 2016 William Breathitt Gray
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License, version 2, as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful, but
> + * WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * General Public License for more details.
> + *
> + * This driver supports the ACCES 104-QUAD-8 and ACCES 104-QUAD-4.
> + */
> +#include <linux/bitops.h>
...
> +static int quad8_probe(struct device *dev, unsigned int id)
> +{
> +	struct iio_dev *indio_dev;
> +	struct quad8_iio *quad8iio;
> +	int i, j;
> +	unsigned int base_offset;
> +	int err;
> +
> +	if (!devm_request_region(dev, base[id], QUAD8_EXTENT, dev_name(dev))) {
> +		dev_err(dev, "Unable to lock port addresses (0x%X-0x%X)\n",
> +			base[id], base[id] + QUAD8_EXTENT);
> +		return -EBUSY;
> +	}
> +
> +	/* Allocate IIO device; this also allocates driver data structure */
> +	indio_dev = devm_iio_device_alloc(dev, sizeof(*quad8iio));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	/* Initialize IIO device */
> +	indio_dev->info = &quad8_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->num_channels = ARRAY_SIZE(quad8_channels);
> +	indio_dev->channels = quad8_channels;
> +	indio_dev->name = dev_name(dev);
> +	indio_dev->dev.parent = dev;
> +
> +	/* Initialize Counter device and driver data */
> +	quad8iio = iio_priv(indio_dev);
> +	quad8iio->counter.name = dev_name(dev);
> +	quad8iio->counter.parent = dev;
> +	quad8iio->counter.ops = &quad8_ops;
> +	quad8iio->counter.counts = quad8_counts;
> +	quad8iio->counter.num_counts = ARRAY_SIZE(quad8_counts);
> +	quad8iio->counter.signals = quad8_signals;
> +	quad8iio->counter.num_signals = ARRAY_SIZE(quad8_signals);
> +	quad8iio->counter.priv = quad8iio;
> +	quad8iio->base = base[id];
> +
> +	/* Reset all counters and disable interrupt function */
> +	outb(0x01, base[id] + 0x11);
> +	/* Set initial configuration for all counters */
> +	for (i = 0; i < QUAD8_NUM_COUNTERS; i++) {
> +		base_offset = base[id] + 2 * i;
> +		/* Reset Byte Pointer */
> +		outb(0x01, base_offset + 1);

I'm going to be fussy.  There are lots of values
in here that look like register bits and you could exchange much of
this documentation for a some good defines...

Taking base_offset + 1 bits 5 and 6 look to select the actual register
and the rest of them do the control.

Anyhow, not critical but the readability of this code could be improved
somewhat.

> +		/* Reset Preset Register */
> +		for (j = 0; j < 3; j++)
> +			outb(0x00, base_offset);
> +		/* Reset Borrow, Carry, Compare, and Sign flags */
> +		outb(0x04, base_offset + 1);
> +		/* Reset Error flag */
> +		outb(0x06, base_offset + 1);
> +		/* Binary encoding; Normal count; non-quadrature mode */
> +		outb(0x20, base_offset + 1);
> +		/* Disable A and B inputs; preset on index; FLG1 as Carry */
> +		outb(0x40, base_offset + 1);
> +		/* Disable index function; negative index polarity */
> +		outb(0x60, base_offset + 1);
> +	}
> +	/* Enable all counters */
> +	outb(0x00, base[id] + 0x11);
> +
> +	/* Register IIO device */
> +	err = devm_iio_device_register(dev, indio_dev);
> +	if (err)
> +		return err;
> +
> +	/* Register Counter device */
> +	return devm_counter_register(dev, &quad8iio->counter);
> +}
> +
> +static struct isa_driver quad8_driver = {
> +	.probe = quad8_probe,
> +	.driver = {
> +		.name = "104-quad-8"
> +	}
> +};
> +
> +module_isa_driver(quad8_driver, num_quad8);
> +
> +MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
> +MODULE_DESCRIPTION("ACCES 104-QUAD-8 IIO driver");
> +MODULE_LICENSE("GPL v2");
> diff --git a/drivers/counter/Kconfig b/drivers/counter/Kconfig
> index 65fa92abd5a4..73f03372484f 100644
> --- a/drivers/counter/Kconfig
> +++ b/drivers/counter/Kconfig
> @@ -16,3 +16,24 @@ menuconfig COUNTER
>  	  consumption. The Generic Counter interface enables drivers to support
>  	  and expose a common set of components and functionality present in
>  	  counter devices.
> +
> +if COUNTER
> +
> +config 104_QUAD_8
> +	tristate "ACCES 104-QUAD-8 driver"
> +	depends on PC104 && X86 && IIO
> +	select ISA_BUS_API
> +	help
> +	  Say yes here to build support for the ACCES 104-QUAD-8 quadrature
> +	  encoder counter/interface device family (104-QUAD-8, 104-QUAD-4).
> +
> +	  Performing a write to a counter's IIO_CHAN_INFO_RAW sets the counter and
> +	  also clears the counter's respective error flag. Although the counters
> +	  have a 25-bit range, only the lower 24 bits may be set, either directly
> +	  or via a counter's preset attribute. Interrupts are not supported by
> +	  this driver.

This text probably wants to be updated to reflect the new counter subsystem support..

> +
> +	  The base port addresses for the devices may be configured via the base
> +	  array module parameter.
> +
> +endif # COUNTER
> diff --git a/drivers/counter/Makefile b/drivers/counter/Makefile
> index ad1ba7109cdc..23a4f6263e45 100644
> --- a/drivers/counter/Makefile
> +++ b/drivers/counter/Makefile
> @@ -6,3 +6,5 @@
>  
>  obj-$(CONFIG_COUNTER) += counter.o
>  counter-y := generic-counter.o
> +
> +obj-$(CONFIG_104_QUAD_8)	+= 104-quad-8.o
> diff --git a/drivers/iio/counter/104-quad-8.c b/drivers/iio/counter/104-quad-8.c
...

Re: [PATCH v6 6/9] dt-bindings: counter: Document stm32 quadrature encoder

[Jonathan Cameron]

On Fri, 18 May 2018 11:28:15 -0500
Rob Herring <robh@kernel.org> wrote:

> On Thu, May 17, 2018 at 08:59:40PM +0200, Benjamin Gaignard wrote:
> > 2018-05-17 18:23 GMT+02:00 Rob Herring <robh+dt@kernel.org>:  
> > > On Wed, May 16, 2018 at 12:51 PM, William Breathitt Gray
> > > <vilhelm.gray@gmail.com> wrote:  
> > >> From: Benjamin Gaignard <benjamin.gaignard@st.com>  
> > >
> > > v6? Where's v1-v5?
> > >  
> > >> Add bindings for STM32 Timer quadrature encoder.
> > >> It is a sub-node of STM32 Timer which implement the
> > >> counter part of the hardware.
> > >>
> > >> Cc: Rob Herring <robh+dt@kernel.org>
> > >> Cc: Mark Rutland <mark.rutland@arm.com>
> > >> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
> > >> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
> > >> ---
> > >>  .../bindings/counter/stm32-timer-cnt.txt      | 26 +++++++++++++++++++
> > >>  .../devicetree/bindings/mfd/stm32-timers.txt  |  7 +++++
> > >>  2 files changed, 33 insertions(+)
> > >>  create mode 100644 Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt
> > >>
> > >> diff --git a/Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt b/Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt
> > >> new file mode 100644
> > >> index 000000000000..377728128bef
> > >> --- /dev/null
> > >> +++ b/Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt
> > >> @@ -0,0 +1,26 @@
> > >> +STMicroelectronics STM32 Timer quadrature encoder
> > >> +
> > >> +STM32 Timer provides quadrature encoder counter mode to detect  
> > >
> > > 'mode' does not sound like a sub-block of the timers block.  
> > 
> > quadrature encoding is one of the counting modes of this hardware
> > block which is enable to count on other signals/triggers  
> 
> You don't need a child node and compatible to set a mode.

A pile of extra hardware becomes relevant and you only want
to be in this state if you have appropriate external device
wired up.  In this case there is admittedly not a lot here
but some devices will look a bit more like a touchscreen controller.

They are often build on top of an ADC module, but have a load
of touch screen only signals and electrical elements that
warrant being represented as a separate node in the DT.


> 
> > >> +angular position and direction of rotary elements,
> > >> +from IN1 and IN2 input signals.
> > >> +
> > >> +Must be a sub-node of an STM32 Timer device tree node.
> > >> +See ../mfd/stm32-timers.txt for details about the parent node.
> > >> +
> > >> +Required properties:
> > >> +- compatible:          Must be "st,stm32-timer-counter".
> > >> +- pinctrl-names:       Set to "default".
> > >> +- pinctrl-0:           List of phandles pointing to pin configuration nodes,
> > >> +                       to set IN1/IN2 pins in mode of operation for Low-Power
> > >> +                       Timer input on external pin.
> > >> +
> > >> +Example:
> > >> +       timers@40010000  {
> > >> +               compatible = "st,stm32-timers";
> > >> +               ...
> > >> +               counter {
> > >> +                       compatible = "st,stm32-timer-counter";  
> > >
> > > Is there only 1? How is the counter addressed?  
> > 
> > Yes there is only one counter per hardware block.
> > Counter is addressed like the two others sub-nodes and the details
> > about parent mode are describe in stm32-timers.txt
> > Should I add them here too ? so example will be like that:  
> 
> No, you should drop the child node and add pinctrl to the parent.
> 
> Any other functions this block has that you plan on adding? Please make 
> bindings as complete as possible, not what you currently have drivers 
> for.
> 
> > timers@40010000  {
> >   #address-cells = <1>;
> >   #size-cells = <0>;
> >   compatible = "st,stm32-timers";
> >   reg = <0x40010000 0x400>;
> >   clocks = <&rcc 0 160>;
> >   clock-names = "int";
> >   counter {
> >     compatible = "st,stm32-timer-counter";
> >     pinctrl-names = "default";
> >     pinctrl-0 = <&tim1_in_pins>;
> >     };
> >  };
> > 
> > Benjamin  
> > >
> > > _______________________________________________
> > > linux-arm-kernel mailing list
> > > linux-arm-kernel@lists.infradead.org
> > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel  

Re: [PATCH v6 9/9] iio: counter: Remove IIO counter subdirectory

[Jonathan Cameron]

On Wed, 16 May 2018 13:52:39 -0400
William Breathitt Gray <vilhelm.gray@gmail.com> wrote:

> This patch removes the IIO counter subdirectory which is now superceded
> by the Counter subsystem. Deprecation warnings are added to the
> documentation of the relevant IIO counter sysfs attributes.
> 
> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>

Please drop the directory when it becomes empty rather than in a later
patch.  IIRC there are some issues with empty Makefiles that will
make building inbetween tricky.

For the deprecated markings.

Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
>  Documentation/ABI/testing/sysfs-bus-iio          |  8 ++++++++
>  .../ABI/testing/sysfs-bus-iio-counter-104-quad-8 | 16 ++++++++++++++++
>  drivers/iio/Kconfig                              |  1 -
>  drivers/iio/Makefile                             |  1 -
>  drivers/iio/counter/Kconfig                      |  8 --------
>  drivers/iio/counter/Makefile                     |  5 -----
>  6 files changed, 24 insertions(+), 15 deletions(-)
>  delete mode 100644 drivers/iio/counter/Kconfig
>  delete mode 100644 drivers/iio/counter/Makefile
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
> index 731146c3b138..6115d97b075e 100644
> --- a/Documentation/ABI/testing/sysfs-bus-iio
> +++ b/Documentation/ABI/testing/sysfs-bus-iio
> @@ -1637,6 +1637,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_raw
>  KernelVersion:	4.10
>  Contact:	linux-iio@vger.kernel.org
>  Description:
> +		This interface is deprecated; please use the Counter subsystem.
> +
>  		Raw counter device counts from channel Y. For quadrature
>  		counters, multiplication by an available [Y]_scale results in
>  		the counts of a single quadrature signal phase from channel Y.
> @@ -1645,6 +1647,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_indexY_raw
>  KernelVersion:	4.10
>  Contact:	linux-iio@vger.kernel.org
>  Description:
> +		This interface is deprecated; please use the Counter subsystem.
> +
>  		Raw counter device index value from channel Y. This attribute
>  		provides an absolute positional reference (e.g. a pulse once per
>  		revolution) which may be used to home positional systems as
> @@ -1654,6 +1658,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_count_count_direction_available
>  KernelVersion:	4.12
>  Contact:	linux-iio@vger.kernel.org
>  Description:
> +		This interface is deprecated; please use the Counter subsystem.
> +
>  		A list of possible counting directions which are:
>  		- "up"	: counter device is increasing.
>  		- "down": counter device is decreasing.
> @@ -1662,4 +1668,6 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_count_direction
>  KernelVersion:	4.12
>  Contact:	linux-iio@vger.kernel.org
>  Description:
> +		This interface is deprecated; please use the Counter subsystem.
> +
>  		Raw counter device counters direction for channel Y.
> diff --git a/Documentation/ABI/testing/sysfs-bus-iio-counter-104-quad-8 b/Documentation/ABI/testing/sysfs-bus-iio-counter-104-quad-8
> index 7fac2c268d9a..bac3d0d48b7b 100644
> --- a/Documentation/ABI/testing/sysfs-bus-iio-counter-104-quad-8
> +++ b/Documentation/ABI/testing/sysfs-bus-iio-counter-104-quad-8
> @@ -6,6 +6,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_index_synchronous_mode_available
>  KernelVersion:	4.10
>  Contact:	linux-iio@vger.kernel.org
>  Description:
> +		This interface is deprecated; please use the Counter subsystem.
> +
>  		Discrete set of available values for the respective counter
>  		configuration are listed in this file.
>  
> @@ -13,6 +15,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_count_mode
>  KernelVersion:	4.10
>  Contact:	linux-iio@vger.kernel.org
>  Description:
> +		This interface is deprecated; please use the Counter subsystem.
> +
>  		Count mode for channel Y. Four count modes are available:
>  		normal, range limit, non-recycle, and modulo-n. The preset value
>  		for channel Y is used by the count mode where required.
> @@ -47,6 +51,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_noise_error
>  KernelVersion:	4.10
>  Contact:	linux-iio@vger.kernel.org
>  Description:
> +		This interface is deprecated; please use the Counter subsystem.
> +
>  		Read-only attribute that indicates whether excessive noise is
>  		present at the channel Y count inputs in quadrature clock mode;
>  		irrelevant in non-quadrature clock mode.
> @@ -55,6 +61,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_preset
>  KernelVersion:	4.10
>  Contact:	linux-iio@vger.kernel.org
>  Description:
> +		This interface is deprecated; please use the Counter subsystem.
> +
>  		If the counter device supports preset registers, the preset
>  		count for channel Y is provided by this attribute.
>  
> @@ -62,6 +70,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_quadrature_mode
>  KernelVersion:	4.10
>  Contact:	linux-iio@vger.kernel.org
>  Description:
> +		This interface is deprecated; please use the Counter subsystem.
> +
>  		Configure channel Y counter for non-quadrature or quadrature
>  		clock mode. Selecting non-quadrature clock mode will disable
>  		synchronous load mode. In quadrature clock mode, the channel Y
> @@ -83,6 +93,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_set_to_preset_on_index
>  KernelVersion:	4.10
>  Contact:	linux-iio@vger.kernel.org
>  Description:
> +		This interface is deprecated; please use the Counter subsystem.
> +
>  		Whether to set channel Y counter with channel Y preset value
>  		when channel Y index input is active, or continuously count.
>  		Valid attribute values are boolean.
> @@ -91,6 +103,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_indexY_index_polarity
>  KernelVersion:	4.10
>  Contact:	linux-iio@vger.kernel.org
>  Description:
> +		This interface is deprecated; please use the Counter subsystem.
> +
>  		Active level of channel Y index input; irrelevant in
>  		non-synchronous load mode.
>  
> @@ -98,6 +112,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_indexY_synchronous_mode
>  KernelVersion:	4.10
>  Contact:	linux-iio@vger.kernel.org
>  Description:
> +		This interface is deprecated; please use the Counter subsystem.
> +
>  		Configure channel Y counter for non-synchronous or synchronous
>  		load mode. Synchronous load mode cannot be selected in
>  		non-quadrature clock mode.
> diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
> index d69e85a8bdc3..1152efad91a1 100644
> --- a/drivers/iio/Kconfig
> +++ b/drivers/iio/Kconfig
> @@ -74,7 +74,6 @@ source "drivers/iio/afe/Kconfig"
>  source "drivers/iio/amplifiers/Kconfig"
>  source "drivers/iio/chemical/Kconfig"
>  source "drivers/iio/common/Kconfig"
> -source "drivers/iio/counter/Kconfig"
>  source "drivers/iio/dac/Kconfig"
>  source "drivers/iio/dummy/Kconfig"
>  source "drivers/iio/frequency/Kconfig"
> diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile
> index d8cba9c229c0..7bdd31f1b88f 100644
> --- a/drivers/iio/Makefile
> +++ b/drivers/iio/Makefile
> @@ -20,7 +20,6 @@ obj-y += amplifiers/
>  obj-y += buffer/
>  obj-y += chemical/
>  obj-y += common/
> -obj-y += counter/
>  obj-y += dac/
>  obj-y += dummy/
>  obj-y += gyro/
> diff --git a/drivers/iio/counter/Kconfig b/drivers/iio/counter/Kconfig
> deleted file mode 100644
> index 95a7a0df6cac..000000000000
> --- a/drivers/iio/counter/Kconfig
> +++ /dev/null
> @@ -1,8 +0,0 @@
> -#
> -# Counter devices
> -#
> -# When adding new entries keep the list in alphabetical order
> -
> -menu "Counters"
> -
> -endmenu
> diff --git a/drivers/iio/counter/Makefile b/drivers/iio/counter/Makefile
> deleted file mode 100644
> index 8fd3d954775a..000000000000
> --- a/drivers/iio/counter/Makefile
> +++ /dev/null
> @@ -1,5 +0,0 @@
> -#
> -# Makefile for IIO counter devices
> -#
> -
> -# When adding new entries keep the list in alphabetical order

Re: [PATCH v6 1/9] counter: Introduce the Generic Counter interface

[William Breathitt Gray]

On Sun, May 20, 2018 at 04:06:52PM +0100, Jonathan Cameron wrote:
>On Wed, 16 May 2018 13:50:43 -0400
>William Breathitt Gray <vilhelm.gray@gmail.com> wrote:
>
>> This patch introduces the Generic Counter interface for supporting
>> counter devices.
>> 
>> In the context of the Generic Counter interface, a counter is defined as
>> a device that reports one or more "counts" based on the state changes of
>> one or more "signals" as evaluated by a defined "count function."
>> 
>> Driver callbacks should be provided to communicate with the device: to
>> read and write various Signals and Counts, and to set and get the
>> "action mode" and "count function" for various Synapses and Counts
>> respectively.
>> 
>> To support a counter device, a driver must first allocate the available
>> Counter Signals via counter_signal structures. These Signals should
>> be stored as an array and set to the signals array member of an
>> allocated counter_device structure before the Counter is registered to
>> the system.
>> 
>> Counter Counts may be allocated via counter_count structures, and
>> respective Counter Signal associations (Synapses) made via
>> counter_synapse structures. Associated counter_synapse structures are
>> stored as an array and set to the the synapses array member of the
>> respective counter_count structure. These counter_count structures are
>> set to the counts array member of an allocated counter_device structure
>> before the Counter is registered to the system.
>> 
>> A counter device is registered to the system by passing the respective
>> initialized counter_device structure to the counter_register function;
>> similarly, the counter_unregister function unregisters the respective
>> Counter. The devm_counter_register and devm_counter_unregister functions
>> serve as device memory-managed versions of the counter_register and
>> counter_unregister functions respectively.
>> 
>> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
>
>A few minor comments inline.  I do somewhat wonder if we can cut
>back on the huge amount of 'similar' code in here, but there tend to
>be just enough small differences to make that really tricky...
>
>Nothing major enough in here that I really plan on reading it again
>(though you never know if you change lots ;)
>
>Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

These look like quick tidy-up suggestions so I expect to incorporate
them in the next revision without trouble. I'll also look around to
organize the repetitive code into functions for reuse where possible, in
order to help clean up the code and make the logic clearer. In short
though, I don't expect any major changes in the next revision, just
minor formatting and cleanup.

William Breathitt Gray

>> ---
>>  MAINTAINERS                       |    7 +
>>  drivers/Kconfig                   |    2 +
>>  drivers/Makefile                  |    1 +
>>  drivers/counter/Kconfig           |   18 +
>>  drivers/counter/Makefile          |    8 +
>>  drivers/counter/generic-counter.c | 1541 +++++++++++++++++++++++++++++
>>  include/linux/counter.h           |  554 +++++++++++
>>  7 files changed, 2131 insertions(+)
>>  create mode 100644 drivers/counter/Kconfig
>>  create mode 100644 drivers/counter/Makefile
>>  create mode 100644 drivers/counter/generic-counter.c
>>  create mode 100644 include/linux/counter.h
>> 
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index 4b65225d443a..2a016d73ab72 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -3669,6 +3669,13 @@ W:	http://www.fi.muni.cz/~kas/cosa/
>>  S:	Maintained
>>  F:	drivers/net/wan/cosa*
>>  
>> +COUNTER SUBSYSTEM
>> +M:	William Breathitt Gray <vilhelm.gray@gmail.com>
>> +L:	linux-iio@vger.kernel.org
>> +S:	Maintained
>> +F:	drivers/counter/
>> +F:	include/linux/counter.h
>> +
>>  CPMAC ETHERNET DRIVER
>>  M:	Florian Fainelli <f.fainelli@gmail.com>
>>  L:	netdev@vger.kernel.org
>> diff --git a/drivers/Kconfig b/drivers/Kconfig
>> index 95b9ccc08165..70b3cc88dc0b 100644
>> --- a/drivers/Kconfig
>> +++ b/drivers/Kconfig
>> @@ -165,6 +165,8 @@ source "drivers/memory/Kconfig"
>>  
>>  source "drivers/iio/Kconfig"
>>  
>> +source "drivers/counter/Kconfig"
>> +
>Same comment as below.
>
>>  source "drivers/ntb/Kconfig"
>>  
>>  source "drivers/vme/Kconfig"
>> diff --git a/drivers/Makefile b/drivers/Makefile
>> index 24cd47014657..5914c78688c3 100644
>> --- a/drivers/Makefile
>> +++ b/drivers/Makefile
>> @@ -165,6 +165,7 @@ obj-$(CONFIG_PM_DEVFREQ)	+= devfreq/
>>  obj-$(CONFIG_EXTCON)		+= extcon/
>>  obj-$(CONFIG_MEMORY)		+= memory/
>>  obj-$(CONFIG_IIO)		+= iio/
>> +obj-$(CONFIG_COUNTER)		+= counter/
>
>I can see your logic in putting this here, but I think the convention
>is to go at the end rather than grouping.
>
>>  obj-$(CONFIG_VME_BUS)		+= vme/
>>  obj-$(CONFIG_IPACK_BUS)		+= ipack/
>>  obj-$(CONFIG_NTB)		+= ntb/
>> diff --git a/drivers/counter/Kconfig b/drivers/counter/Kconfig
>> new file mode 100644
>> index 000000000000..65fa92abd5a4
>> --- /dev/null
>> +++ b/drivers/counter/Kconfig
>> @@ -0,0 +1,18 @@
>> +#
>> +# Counter devices
>> +#
>> +# When adding new entries keep the list in alphabetical order
>> +
>> +menuconfig COUNTER
>> +	tristate "Counter support"
>> +	help
>> +	  Provides Generic Counter interface support for counter devices.
>> +
>> +	  Counter devices are prevalent within a diverse spectrum of industries.
>> +	  The ubiquitous presence of these devices necessitates a common
>> +	  interface and standard of interaction and exposure. This driver API
>> +	  attempts to resolve the issue of duplicate code found among existing
>> +	  counter device drivers by providing a generic counter interface for
>> +	  consumption. The Generic Counter interface enables drivers to support
>> +	  and expose a common set of components and functionality present in
>> +	  counter devices.
>> diff --git a/drivers/counter/Makefile b/drivers/counter/Makefile
>> new file mode 100644
>> index 000000000000..ad1ba7109cdc
>> --- /dev/null
>> +++ b/drivers/counter/Makefile
>> @@ -0,0 +1,8 @@
>> +#
>> +# Makefile for Counter devices
>> +#
>> +
>> +# When adding new entries keep the list in alphabetical order
>> +
>> +obj-$(CONFIG_COUNTER) += counter.o
>> +counter-y := generic-counter.o
>> diff --git a/drivers/counter/generic-counter.c b/drivers/counter/generic-counter.c
>> new file mode 100644
>> index 000000000000..0d83b862453f
>> --- /dev/null
>> +++ b/drivers/counter/generic-counter.c
>> @@ -0,0 +1,1541 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * Generic Counter interface
>> + * Copyright (C) 2017 William Breathitt Gray
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License, version 2, as
>> + * published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope that it will be useful, but
>> + * WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>> + * General Public License for more details.
>
>As below, SPDX and license seems silly.  Unless you are feeling paranoid
>just drop the license text.
>
>> + */
>> +#include <linux/device.h>
>> +#include <linux/err.h>
>> +#include <linux/export.h>
>> +#include <linux/fs.h>
>> +#include <linux/gfp.h>
>> +#include <linux/idr.h>
>> +#include <linux/init.h>
>> +#include <linux/kernel.h>
>> +#include <linux/list.h>
>> +#include <linux/module.h>
>> +#include <linux/printk.h>
>> +#include <linux/slab.h>
>> +#include <linux/string.h>
>> +#include <linux/sysfs.h>
>> +#include <linux/types.h>
>> +
>> +#include <linux/counter.h>
>> +
>> +const char *const count_direction_str[2] = {
>> +	[COUNT_DIRECTION_FORWARD] = "forward",
>> +	[COUNT_DIRECTION_BACKWARD] = "backward"
>> +};
>> +EXPORT_SYMBOL(count_direction_str);
>> +
>> +const char *const count_mode_str[4] = {
>> +	[COUNT_MODE_NORMAL] = "normal",
>> +	[COUNT_MODE_RANGE_LIMIT] = "range limit",
>> +	[COUNT_MODE_NON_RECYCLE] = "non-recycle",
>> +	[COUNT_MODE_MODULO_N] = "modulo-n"
>> +};
>> +EXPORT_SYMBOL(count_mode_str);
>> +
>> +ssize_t counter_signal_enum_read(struct counter_device *counter,
>> +				 struct counter_signal *signal, void *priv,
>> +				 char *buf)
>> +{
>> +	const struct counter_signal_enum_ext *const e = priv;
>> +	int err;
>> +	size_t index;
>> +
>> +	if (!e->get)
>> +		return -EINVAL;
>> +
>> +	err = e->get(counter, signal, &index);
>> +	if (err)
>> +		return err;
>> +
>> +	if (index >= e->num_items)
>> +		return -EINVAL;
>> +
>> +	return scnprintf(buf, PAGE_SIZE, "%s\n", e->items[index]);
>> +}
>> +EXPORT_SYMBOL(counter_signal_enum_read);
>> +
>> +ssize_t counter_signal_enum_write(struct counter_device *counter,
>> +				  struct counter_signal *signal, void *priv,
>> +				  const char *buf, size_t len)
>> +{
>> +	const struct counter_signal_enum_ext *const e = priv;
>> +	ssize_t index;
>> +	int err;
>> +
>> +	if (!e->set)
>> +		return -EINVAL;
>> +
>> +	index = __sysfs_match_string(e->items, e->num_items, buf);
>> +	if (index < 0)
>> +		return index;
>> +
>> +	err = e->set(counter, signal, index);
>> +	if (err)
>> +		return err;
>> +
>> +	return len;
>> +}
>> +EXPORT_SYMBOL(counter_signal_enum_write);
>> +
>> +ssize_t counter_signal_enum_available_read(struct counter_device *counter,
>> +					   struct counter_signal *signal,
>> +					   void *priv, char *buf)
>> +{
>> +	const struct counter_signal_enum_ext *const e = priv;
>> +	size_t i;
>> +	size_t len = 0;
>> +
>> +	if (!e->num_items)
>> +		return 0;
>> +
>> +	for (i = 0; i < e->num_items; i++)
>> +		len += scnprintf(buf + len, PAGE_SIZE - len, "%s\n",
>> +			e->items[i]);
>> +
>> +	return len;
>> +}
>> +EXPORT_SYMBOL(counter_signal_enum_available_read);
>> +
>> +ssize_t counter_count_enum_read(struct counter_device *counter,
>> +				struct counter_count *count, void *priv,
>> +				char *buf)
>> +{
>> +	const struct counter_count_enum_ext *const e = priv;
>> +	int err;
>> +	size_t index;
>> +
>> +	if (!e->get)
>> +		return -EINVAL;
>> +
>> +	err = e->get(counter, count, &index);
>> +	if (err)
>> +		return err;
>> +
>> +	if (index >= e->num_items)
>> +		return -EINVAL;
>> +
>> +	return scnprintf(buf, PAGE_SIZE, "%s\n", e->items[index]);
>> +}
>> +EXPORT_SYMBOL(counter_count_enum_read);
>> +
>> +ssize_t counter_count_enum_write(struct counter_device *counter,
>> +				 struct counter_count *count, void *priv,
>> +				 const char *buf, size_t len)
>> +{
>> +	const struct counter_count_enum_ext *const e = priv;
>> +	ssize_t index;
>> +	int err;
>> +
>> +	if (!e->set)
>> +		return -EINVAL;
>> +
>> +	index = __sysfs_match_string(e->items, e->num_items, buf);
>> +	if (index < 0)
>> +		return index;
>> +
>> +	err = e->set(counter, count, index);
>> +	if (err)
>> +		return err;
>> +
>> +	return len;
>> +}
>> +EXPORT_SYMBOL(counter_count_enum_write);
>> +
>> +ssize_t counter_count_enum_available_read(struct counter_device *counter,
>> +					  struct counter_count *count,
>> +					  void *priv, char *buf)
>> +{
>> +	const struct counter_count_enum_ext *const e = priv;
>> +	size_t i;
>> +	size_t len = 0;
>> +
>> +	if (!e->num_items)
>> +		return 0;
>> +
>> +	for (i = 0; i < e->num_items; i++)
>> +		len += scnprintf(buf + len, PAGE_SIZE - len, "%s\n",
>> +			e->items[i]);
>> +
>> +	return len;
>> +}
>> +EXPORT_SYMBOL(counter_count_enum_available_read);
>> +
>> +ssize_t counter_device_enum_read(struct counter_device *counter, void *priv,
>> +				 char *buf)
>> +{
>> +	const struct counter_device_enum_ext *const e = priv;
>> +	int err;
>> +	size_t index;
>> +
>> +	if (!e->get)
>> +		return -EINVAL;
>> +
>> +	err = e->get(counter, &index);
>> +	if (err)
>> +		return err;
>> +
>> +	if (index >= e->num_items)
>> +		return -EINVAL;
>> +
>> +	return scnprintf(buf, PAGE_SIZE, "%s\n", e->items[index]);
>> +}
>> +EXPORT_SYMBOL(counter_device_enum_read);
>> +
>> +ssize_t counter_device_enum_write(struct counter_device *counter, void *priv,
>> +				  const char *buf, size_t len)
>> +{
>> +	const struct counter_device_enum_ext *const e = priv;
>> +	ssize_t index;
>> +	int err;
>> +
>> +	if (!e->set)
>> +		return -EINVAL;
>> +
>> +	index = __sysfs_match_string(e->items, e->num_items, buf);
>> +	if (index < 0)
>> +		return index;
>> +
>> +	err = e->set(counter, index);
>> +	if (err)
>> +		return err;
>> +
>> +	return len;
>> +}
>> +EXPORT_SYMBOL(counter_device_enum_write);
>> +
>> +ssize_t counter_device_enum_available_read(struct counter_device *counter,
>> +					   void *priv, char *buf)
>> +{
>> +	const struct counter_device_enum_ext *const e = priv;
>> +	size_t i;
>> +	size_t len = 0;
>> +
>> +	if (!e->num_items)
>> +		return 0;
>> +
>> +	for (i = 0; i < e->num_items; i++)
>> +		len += scnprintf(buf + len, PAGE_SIZE - len, "%s\n",
>> +			e->items[i]);
>> +
>> +	return len;
>> +}
>> +EXPORT_SYMBOL(counter_device_enum_available_read);
>> +
>> +static const char *const signal_level_str[] = {
>> +	[SIGNAL_LEVEL_LOW] = "low",
>> +	[SIGNAL_LEVEL_HIGH] = "high"
>> +};
>> +
>> +/**
>> + * set_signal_read_value - set signal_read_value data
>> + * @val:	signal_read_value structure to set
>> + * @type:	property Signal data represents
>> + * @data:	Signal data
>> + *
>> + * This function sets an opaque signal_read_value structure with the provided
>> + * Signal data.
>> + */
>> +void set_signal_read_value(struct signal_read_value *const val,
>> +			   const enum signal_value_type type, void *const data)
>> +{
>> +	if (type == SIGNAL_LEVEL)
>> +		val->len = scnprintf(val->buf, PAGE_SIZE, "%s\n",
>> +			signal_level_str[*(enum signal_level *)data]);
>> +	else
>> +		val->len = 0;
>> +}
>> +EXPORT_SYMBOL(set_signal_read_value);
>> +
>> +/**
>> + * set_count_read_value - set count_read_value data
>> + * @val:	count_read_value structure to set
>> + * @type:	property Count data represents
>> + * @data:	Count data
>> + *
>> + * This function sets an opaque count_read_value structure with the provided
>> + * Count data.
>> + */
>> +void set_count_read_value(struct count_read_value *const val,
>> +			  const enum count_value_type type, void *const data)
>> +{
>> +	switch (type) {
>> +	case COUNT_POSITION_UNSIGNED:
>> +		val->len = scnprintf(val->buf, PAGE_SIZE, "%lu\n",
>> +				     *(unsigned long *)data);
>> +		break;
>> +	case COUNT_POSITION_SIGNED:
>> +		val->len = scnprintf(val->buf, PAGE_SIZE, "%ld\n",
>> +				     *(long *)data);
>> +		break;
>> +	default:
>> +		val->len = 0;
>> +	}
>> +}
>> +EXPORT_SYMBOL(set_count_read_value);
>> +
>> +/**
>> + * get_count_write_value - get count_write_value data
>> + * @data:	Count data
>> + * @type:	property Count data represents
>> + * @val:	count_write_value structure containing data
>> + *
>> + * This function extracts Count data from the provided opaque count_write_value
>> + * structure and stores it at the address provided by @data.
>> + *
>> + * RETURNS:
>> + * 0 on success, negative error number on failure.
>> + */
>> +int get_count_write_value(void *const data, const enum count_value_type type,
>> +			  const struct count_write_value *const val)
>> +{
>> +	int err;
>> +
>> +	switch (type) {
>> +	case COUNT_POSITION_UNSIGNED:
>> +		err = kstrtoul(val->buf, 0, data);
>> +		if (err)
>> +			return err;
>> +		break;
>> +	case COUNT_POSITION_SIGNED:
>> +		err = kstrtol(val->buf, 0, data);
>> +		if (err)
>> +			return err;
>> +		break;
>> +	}
>> +
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL(get_count_write_value);
>> +
>> +struct counter_device_attr {
>> +	struct device_attribute		dev_attr;
>> +	struct list_head		l;
>> +	void				*component;
>> +};
>> +
>> +static int counter_attribute_create(
>> +	struct counter_device_attr_group *const group,
>> +	const char *const prefix,
>> +	const char *const name,
>> +	ssize_t (*show)(struct device *dev, struct device_attribute *attr,
>> +			char *buf),
>> +	ssize_t (*store)(struct device *dev, struct device_attribute *attr,
>> +			 const char *buf, size_t len),
>> +	void *const component)
>> +{
>> +	struct counter_device_attr *counter_attr;
>> +	struct device_attribute *dev_attr;
>> +	int err;
>> +	struct list_head *const attr_list = &group->attr_list;
>> +
>> +	/* Allocate a Counter device attribute */
>> +	counter_attr = kzalloc(sizeof(*counter_attr), GFP_KERNEL);
>> +	if (!counter_attr)
>> +		return -ENOMEM;
>> +	dev_attr = &counter_attr->dev_attr;
>> +
>> +	sysfs_attr_init(&dev_attr->attr);
>> +
>> +	/* Configure device attribute */
>> +	dev_attr->attr.name = kasprintf(GFP_KERNEL, "%s%s", prefix, name);
>> +	if (!dev_attr->attr.name) {
>> +		err = -ENOMEM;
>> +		goto err_free_counter_attr;
>> +	}
>> +	if (show) {
>> +		dev_attr->attr.mode |= 0444;
>> +		dev_attr->show = show;
>> +	}
>> +	if (store) {
>> +		dev_attr->attr.mode |= 0200;
>> +		dev_attr->store = store;
>> +	}
>> +
>> +	/* Store associated Counter component with attribute */
>> +	counter_attr->component = component;
>> +
>> +	/* Keep track of the attribute for later cleanup */
>> +	list_add(&counter_attr->l, attr_list);
>> +	group->num_attr++;
>> +
>> +	return 0;
>> +
>> +err_free_counter_attr:
>> +	kfree(counter_attr);
>> +	return err;
>> +}
>> +
>> +#define to_counter_attr(_dev_attr) \
>> +	container_of(_dev_attr, struct counter_device_attr, dev_attr)
>> +
>> +struct signal_comp_t {
>> +	struct counter_signal	*signal;
>> +};
>> +
>> +static ssize_t counter_signal_show(struct device *dev,
>> +				   struct device_attribute *attr, char *buf)
>> +{
>> +	struct counter_device *const counter = dev_get_drvdata(dev);
>> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
>> +	const struct signal_comp_t *const component = devattr->component;
>> +	struct counter_signal *const signal = component->signal;
>> +	int err;
>> +	struct signal_read_value val = { .buf = buf };
>> +
>> +	err = counter->ops->signal_read(counter, signal, &val);
>> +	if (err)
>> +		return err;
>> +
>> +	return val.len;
>> +}
>> +
>> +struct name_comp_t {
>> +	const char	*name;
>> +};
>> +
>> +static ssize_t counter_device_attr_name_show(struct device *dev,
>> +					     struct device_attribute *attr,
>> +					     char *buf)
>> +{
>> +	const struct name_comp_t *const comp = to_counter_attr(attr)->component;
>> +
>> +	return scnprintf(buf, PAGE_SIZE, "%s\n", comp->name);
>> +}
>> +
>> +static int counter_name_attribute_create(
>> +	struct counter_device_attr_group *const group,
>> +	const char *const name)
>> +{
>> +	struct name_comp_t *name_comp;
>> +	int err;
>> +
>> +	/* Skip if no name */
>> +	if (!name)
>> +		return 0;
>> +
>> +	/* Allocate name attribute component */
>> +	name_comp = kmalloc(sizeof(*name_comp), GFP_KERNEL);
>> +	if (!name_comp)
>> +		return -ENOMEM;
>> +	name_comp->name = name;
>> +
>> +	/* Allocate Signal name attribute */
>> +	err = counter_attribute_create(group, "", "name",
>> +				       counter_device_attr_name_show, NULL,
>> +				       name_comp);
>> +	if (err)
>> +		goto err_free_name_comp;
>> +
>> +	return 0;
>> +
>> +err_free_name_comp:
>> +	kfree(name_comp);
>> +	return err;
>> +}
>> +
>> +struct signal_ext_comp_t {
>> +	struct counter_signal		*signal;
>> +	const struct counter_signal_ext	*ext;
>> +};
>> +
>> +static ssize_t counter_signal_ext_show(struct device *dev,
>> +				       struct device_attribute *attr, char *buf)
>> +{
>> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
>> +	const struct signal_ext_comp_t *const comp = devattr->component;
>> +	const struct counter_signal_ext *const ext = comp->ext;
>> +
>> +	return ext->read(dev_get_drvdata(dev), comp->signal, ext->priv, buf);
>> +}
>> +
>> +static ssize_t counter_signal_ext_store(struct device *dev,
>> +					struct device_attribute *attr,
>> +					const char *buf, size_t len)
>> +{
>> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
>> +	const struct signal_ext_comp_t *const comp = devattr->component;
>> +	const struct counter_signal_ext *const ext = comp->ext;
>> +
>> +	return ext->write(dev_get_drvdata(dev), comp->signal, ext->priv, buf,
>> +		len);
>> +}
>> +
>> +static void free_counter_device_attr_list(struct list_head *attr_list)
>> +{
>> +	struct counter_device_attr *p, *n;
>> +
>> +	list_for_each_entry_safe(p, n, attr_list, l) {
>> +		kfree(p->dev_attr.attr.name);
>> +		kfree(p->component);
>> +		list_del(&p->l);
>> +		kfree(p);
>> +	}
>> +}
>> +
>> +static int counter_signal_ext_register(
>> +	struct counter_device_attr_group *const group,
>> +	struct counter_signal *const signal)
>> +{
>> +	const size_t num_ext = signal->num_ext;
>> +	size_t i;
>> +	const struct counter_signal_ext *ext;
>> +	struct signal_ext_comp_t *signal_ext_comp;
>> +	int err;
>> +
>> +	/* Create an attribute for each extension */
>> +	for (i = 0 ; i < num_ext; i++) {
>> +		ext = signal->ext + i;
>> +
>> +		/* Allocate signal_ext attribute component */
>> +		signal_ext_comp = kmalloc(sizeof(*signal_ext_comp), GFP_KERNEL);
>> +		if (!signal_ext_comp) {
>> +			err = -ENOMEM;
>> +			goto err_free_attr_list;
>> +		}
>> +		signal_ext_comp->signal = signal;
>> +		signal_ext_comp->ext = ext;
>> +
>> +		/* Allocate a Counter device attribute */
>> +		err = counter_attribute_create(group, "", ext->name,
>> +			(ext->read) ? counter_signal_ext_show : NULL,
>> +			(ext->write) ? counter_signal_ext_store : NULL,
>> +			signal_ext_comp);
>> +		if (err) {
>> +			kfree(signal_ext_comp);
>> +			goto err_free_attr_list;
>> +		}
>> +	}
>> +
>> +	return 0;
>> +
>> +err_free_attr_list:
>> +	free_counter_device_attr_list(&group->attr_list);
>> +	return err;
>> +}
>> +
>> +static int counter_signal_attributes_create(
>> +	struct counter_device_attr_group *const group,
>> +	const struct counter_device *const counter,
>> +	struct counter_signal *const signal)
>> +{
>> +	struct signal_comp_t *signal_comp;
>> +	int err;
>> +
>> +	/* Allocate Signal attribute component */
>> +	signal_comp = kmalloc(sizeof(*signal_comp), GFP_KERNEL);
>> +	if (!signal_comp)
>> +		return -ENOMEM;
>> +	signal_comp->signal = signal;
>> +
>> +	/* Create main Signal attribute */
>> +	err = counter_attribute_create(group, "", "signal",
>> +		(counter->ops->signal_read) ? counter_signal_show : NULL, NULL,
>> +		signal_comp);
>> +	if (err) {
>> +		kfree(signal_comp);
>> +		return err;
>> +	}
>> +
>> +	/* Create Signal name attribute */
>> +	err = counter_name_attribute_create(group, signal->name);
>> +	if (err)
>> +		goto err_free_attr_list;
>> +
>> +	/* Register Signal extension attributes */
>> +	err = counter_signal_ext_register(group, signal);
>> +	if (err)
>> +		goto err_free_attr_list;
>> +
>> +	return 0;
>> +
>> +err_free_attr_list:
>> +	free_counter_device_attr_list(&group->attr_list);
>> +	return err;
>> +}
>> +
>> +static int counter_signals_register(
>> +	struct counter_device_attr_group *const groups_list,
>> +	const struct counter_device *const counter)
>> +{
>> +	const size_t num_signals = counter->num_signals;
>> +	size_t i;
>> +	struct counter_signal *signal;
>> +	const char *name;
>> +	int err;
>> +
>> +	/* Register each Signal */
>> +	for (i = 0; i < num_signals; i++) {
>> +		signal = counter->signals + i;
>> +
>> +		/* Generate Signal attribute directory name */
>> +		name = kasprintf(GFP_KERNEL, "signal%d", signal->id);
>> +		if (!name) {
>> +			err = -ENOMEM;
>> +			goto err_free_attr_groups;
>> +		}
>> +		groups_list[i].attr_group.name = name;
>> +
>> +		/* Create all attributes associated with Signal */
>> +		err = counter_signal_attributes_create(groups_list + i, counter,
>> +						       signal);
>> +		if (err)
>> +			goto err_free_attr_groups;
>> +	}
>> +
>> +	return 0;
>> +
>> +err_free_attr_groups:
>> +	do {
>> +		kfree(groups_list[i].attr_group.name);
>> +		free_counter_device_attr_list(&groups_list[i].attr_list);
>> +	} while (i--);
>> +	return err;
>> +}
>> +
>> +static const char *const synapse_action_str[] = {
>> +	[SYNAPSE_ACTION_NONE] = "none",
>> +	[SYNAPSE_ACTION_RISING_EDGE] = "rising edge",
>> +	[SYNAPSE_ACTION_FALLING_EDGE] = "falling edge",
>> +	[SYNAPSE_ACTION_BOTH_EDGES] = "both edges"
>> +};
>> +
>> +struct action_comp_t {
>> +	struct counter_synapse	*synapse;
>> +	struct counter_count	*count;
>> +};
>> +
>> +static ssize_t counter_action_show(struct device *dev,
>> +				   struct device_attribute *attr, char *buf)
>> +{
>> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
>> +	int err;
>> +	struct counter_device *const counter = dev_get_drvdata(dev);
>> +	const struct action_comp_t *const component = devattr->component;
>> +	struct counter_count *const count = component->count;
>> +	struct counter_synapse *const synapse = component->synapse;
>> +	size_t action_index;
>> +	enum synapse_action action;
>> +
>> +	err = counter->ops->action_get(counter, count, synapse, &action_index);
>> +	if (err)
>> +		return err;
>> +
>> +	synapse->action = action_index;
>> +
>> +	action = synapse->actions_list[action_index];
>> +	return scnprintf(buf, PAGE_SIZE, "%s\n", synapse_action_str[action]);
>> +}
>> +
>> +static ssize_t counter_action_store(struct device *dev,
>> +				    struct device_attribute *attr,
>> +				    const char *buf, size_t len)
>> +{
>> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
>> +	const struct action_comp_t *const component = devattr->component;
>> +	struct counter_synapse *const synapse = component->synapse;
>> +	size_t action_index;
>> +	const size_t num_actions = synapse->num_actions;
>> +	enum synapse_action action;
>> +	int err;
>> +	struct counter_device *const counter = dev_get_drvdata(dev);
>> +	struct counter_count *const count = component->count;
>> +
>> +	/* Find requested action mode */
>> +	for (action_index = 0; action_index < num_actions; action_index++) {
>> +		action = synapse->actions_list[action_index];
>> +		if (sysfs_streq(buf, synapse_action_str[action]))
>> +			break;
>> +	}
>> +	/* If requested action mode not found */
>> +	if (action_index >= num_actions)
>> +		return -EINVAL;
>> +
>> +	err = counter->ops->action_set(counter, count, synapse, action_index);
>> +	if (err)
>> +		return err;
>> +
>> +	synapse->action = action_index;
>> +
>> +	return len;
>> +}
>> +
>> +struct action_avail_comp_t {
>> +	const enum synapse_action	*actions_list;
>> +	size_t				num_actions;
>> +};
>> +
>> +static ssize_t counter_synapse_action_available_show(struct device *dev,
>> +	struct device_attribute *attr, char *buf)
>> +{
>> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
>> +	const struct action_avail_comp_t *const component = devattr->component;
>> +	const enum synapse_action *const actions_list = component->actions_list;
>
>I'm not sure this local variable helps much either...
>
>> +	const size_t num_actions = component->num_actions;
>
>Local variable adds nothing as far as I can see..  Just use it inline.
>
>
>> +	size_t i;
>> +	enum synapse_action action;
>> +	ssize_t len = 0;
>> +
>> +	for (i = 0; i < num_actions; i++) {
>> +		action = actions_list[i];
>> +		len += scnprintf(buf + len, PAGE_SIZE - len, "%s\n",
>> +			synapse_action_str[action]);
>> +	}
>> +
>> +	return len;
>> +}
>> +
>> +static int counter_synapses_register(
>> +	struct counter_device_attr_group *const group,
>> +	const struct counter_device *const counter,
>> +	struct counter_count *const count, const char *const count_attr_name)
>> +{
>> +	const size_t num_synapses = count->num_synapses;
>
>Local variable doesn't add anything. Only used once.
>
>> +	size_t i;
>> +	struct counter_synapse *synapse;
>> +	const char *prefix;
>> +	struct action_comp_t *action_comp;
>> +	int err;
>> +	struct action_avail_comp_t *avail_comp;
>> +
>> +	/* Register each Synapse */
>> +	for (i = 0; i < num_synapses; i++) {
>> +		synapse = count->synapses + i;
>> +
>> +		/* Generate attribute prefix */
>> +		prefix = kasprintf(GFP_KERNEL, "signal%d_",
>> +				   synapse->signal->id);
>> +		if (!prefix) {
>> +			err = -ENOMEM;
>> +			goto err_free_attr_list;
>> +		}
>> +
>> +		/* Allocate action attribute component */
>> +		action_comp = kmalloc(sizeof(*action_comp), GFP_KERNEL);
>> +		if (!action_comp) {
>> +			err = -ENOMEM;
>> +			goto err_free_prefix;
>> +		}
>> +		action_comp->synapse = synapse;
>> +		action_comp->count = count;
>> +
>> +		/* Create action attribute */
>> +		err = counter_attribute_create(group, prefix, "action",
>> +			(counter->ops->action_get) ? counter_action_show : NULL,
>> +			(counter->ops->action_set) ? counter_action_store : NULL,
>> +			action_comp);
>> +		if (err) {
>> +			kfree(action_comp);
>> +			goto err_free_prefix;
>> +		}
>> +
>> +		/* Allocate action available attribute component */
>> +		avail_comp = kmalloc(sizeof(*avail_comp), GFP_KERNEL);
>> +		if (!avail_comp) {
>> +			err = -ENOMEM;
>> +			goto err_free_prefix;
>> +		}
>> +		avail_comp->actions_list = synapse->actions_list;
>> +		avail_comp->num_actions = synapse->num_actions;
>> +
>> +		/* Create action_available attribute */
>> +		err = counter_attribute_create(group, prefix,
>> +			"action_available",
>> +			counter_synapse_action_available_show, NULL,
>> +			avail_comp);
>> +		if (err) {
>> +			kfree(avail_comp);
>> +			goto err_free_prefix;
>> +		}
>> +
>> +		kfree(prefix);
>> +	}
>> +
>> +	return 0;
>> +
>> +err_free_prefix:
>> +	kfree(prefix);
>> +err_free_attr_list:
>> +	free_counter_device_attr_list(&group->attr_list);
>> +	return err;
>> +}
>> +
>> +struct count_comp_t {
>> +	struct counter_count	*count;
>> +};
>> +
>> +static ssize_t counter_count_show(struct device *dev,
>> +				  struct device_attribute *attr,
>> +				  char *buf)
>> +{
>> +	struct counter_device *const counter = dev_get_drvdata(dev);
>> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
>> +	const struct count_comp_t *const component = devattr->component;
>> +	struct counter_count *const count = component->count;
>> +	int err;
>> +	struct count_read_value val = { .buf = buf };
>> +
>> +	err = counter->ops->count_read(counter, count, &val);
>> +	if (err)
>> +		return err;
>> +
>> +	return val.len;
>> +}
>> +
>> +static ssize_t counter_count_store(struct device *dev,
>> +				   struct device_attribute *attr,
>> +				   const char *buf, size_t len)
>> +{
>> +	struct counter_device *const counter = dev_get_drvdata(dev);
>> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
>> +	const struct count_comp_t *const component = devattr->component;
>> +	struct counter_count *const count = component->count;
>> +	int err;
>> +	struct count_write_value val = { .buf = buf };
>> +
>> +	err = counter->ops->count_write(counter, count, &val);
>> +	if (err)
>> +		return err;
>> +
>> +	return len;
>> +}
>> +
>> +static const char *const count_function_str[] = {
>> +	[COUNT_FUNCTION_INCREASE] = "increase",
>> +	[COUNT_FUNCTION_DECREASE] = "decrease",
>> +	[COUNT_FUNCTION_PULSE_DIRECTION] = "pulse-direction",
>> +	[COUNT_FUNCTION_QUADRATURE_X1_A] = "quadrature x1 a",
>> +	[COUNT_FUNCTION_QUADRATURE_X1_B] = "quadrature x1 b",
>> +	[COUNT_FUNCTION_QUADRATURE_X2_A] = "quadrature x2 a",
>> +	[COUNT_FUNCTION_QUADRATURE_X2_B] = "quadrature x2 b",
>> +	[COUNT_FUNCTION_QUADRATURE_X2_RISING] = "quadrature x2 rising",
>> +	[COUNT_FUNCTION_QUADRATURE_X2_FALLING] = "quadrature x2 falling",
>> +	[COUNT_FUNCTION_QUADRATURE_X4] = "quadrature x4"
>> +};
>> +
>> +static ssize_t counter_function_show(struct device *dev,
>> +				     struct device_attribute *attr, char *buf)
>> +{
>> +	int err;
>> +	struct counter_device *const counter = dev_get_drvdata(dev);
>> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
>> +	const struct count_comp_t *const component = devattr->component;
>> +	struct counter_count *const count = component->count;
>> +	size_t func_index;
>> +	enum count_function function;
>> +
>> +	err = counter->ops->function_get(counter, count, &func_index);
>> +	if (err)
>> +		return err;
>> +
>> +	count->function = func_index;
>> +
>> +	function = count->functions_list[func_index];
>> +	return scnprintf(buf, PAGE_SIZE, "%s\n", count_function_str[function]);
>> +}
>> +
>> +static ssize_t counter_function_store(struct device *dev,
>> +				      struct device_attribute *attr,
>> +				      const char *buf, size_t len)
>> +{
>> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
>> +	const struct count_comp_t *const component = devattr->component;
>> +	struct counter_count *const count = component->count;
>> +	const size_t num_functions = count->num_functions;
>> +	size_t func_index;
>> +	enum count_function function;
>> +	int err;
>> +	struct counter_device *const counter = dev_get_drvdata(dev);
>> +
>> +	/* Find requested Count function mode */
>> +	for (func_index = 0; func_index < num_functions; func_index++) {
>> +		function = count->functions_list[func_index];
>> +		if (sysfs_streq(buf, count_function_str[function]))
>> +			break;
>> +	}
>> +	/* Return error if requested Count function mode not found */
>> +	if (func_index >= num_functions)
>> +		return -EINVAL;
>> +
>> +	err = counter->ops->function_set(counter, count, func_index);
>> +	if (err)
>> +		return err;
>> +
>> +	count->function = func_index;
>> +
>> +	return len;
>> +}
>> +
>> +struct count_ext_comp_t {
>> +	struct counter_count		*count;
>> +	const struct counter_count_ext	*ext;
>> +};
>> +
>> +static ssize_t counter_count_ext_show(struct device *dev,
>> +				      struct device_attribute *attr, char *buf)
>> +{
>> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
>> +	const struct count_ext_comp_t *const comp = devattr->component;
>> +	const struct counter_count_ext *const ext = comp->ext;
>> +
>> +	return ext->read(dev_get_drvdata(dev), comp->count, ext->priv, buf);
>> +}
>> +
>> +static ssize_t counter_count_ext_store(struct device *dev,
>> +				       struct device_attribute *attr,
>> +				       const char *buf, size_t len)
>> +{
>> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
>> +	const struct count_ext_comp_t *const comp = devattr->component;
>> +	const struct counter_count_ext *const ext = comp->ext;
>> +
>> +	return ext->write(dev_get_drvdata(dev), comp->count, ext->priv, buf,
>> +		len);
>> +}
>> +
>> +static int counter_count_ext_register(
>> +	struct counter_device_attr_group *const group,
>> +	struct counter_count *const count)
>> +{
>> +	const size_t num_ext = count->num_ext;
>
>Used in one place, just put it inline?
>
>> +	size_t i;
>> +	const struct counter_count_ext *ext;
>> +	struct count_ext_comp_t *count_ext_comp;
>> +	int err;
>> +
>> +	/* Create an attribute for each extension */
>> +	for (i = 0 ; i < num_ext; i++) {
>> +		ext = count->ext + i;
>> +
>> +		/* Allocate count_ext attribute component */
>> +		count_ext_comp = kmalloc(sizeof(*count_ext_comp), GFP_KERNEL);
>> +		if (!count_ext_comp) {
>> +			err = -ENOMEM;
>> +			goto err_free_attr_list;
>> +		}
>> +		count_ext_comp->count = count;
>> +		count_ext_comp->ext = ext;
>> +
>> +		/* Allocate count_ext attribute */
>> +		err = counter_attribute_create(group, "", ext->name,
>> +			(ext->read) ? counter_count_ext_show : NULL,
>> +			(ext->write) ? counter_count_ext_store : NULL,
>> +			count_ext_comp);
>> +		if (err) {
>> +			kfree(count_ext_comp);
>> +			goto err_free_attr_list;
>> +		}
>> +	}
>> +
>> +	return 0;
>> +
>> +err_free_attr_list:
>> +	free_counter_device_attr_list(&group->attr_list);
>> +	return err;
>> +}
>> +
>> +struct func_avail_comp_t {
>> +	const enum count_function	*functions_list;
>> +	size_t				num_functions;
>> +};
>> +
>> +static ssize_t counter_count_function_available_show(struct device *dev,
>> +	struct device_attribute *attr, char *buf)
>> +{
>> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
>> +	const struct func_avail_comp_t *const component = devattr->component;
>> +	const enum count_function *const func_list = component->functions_list;
>> +	const size_t num_functions = component->num_functions;
>> +	size_t i;
>> +	enum count_function function;
>> +	ssize_t len = 0;
>> +
>> +	for (i = 0; i < num_functions; i++) {
>> +		function = func_list[i];
>> +		len += scnprintf(buf + len, PAGE_SIZE - len, "%s\n",
>> +			count_function_str[function]);
>> +	}
>> +
>> +	return len;
>> +}
>> +
>> +static int counter_count_attributes_create(
>> +	struct counter_device_attr_group *const group,
>> +	const struct counter_device *const counter,
>> +	struct counter_count *const count)
>> +{
>> +	struct count_comp_t *count_comp;
>> +	int err;
>> +	struct count_comp_t *func_comp;
>> +	struct func_avail_comp_t *avail_comp;
>> +
>> +	/* Allocate count attribute component */
>> +	count_comp = kmalloc(sizeof(*count_comp), GFP_KERNEL);
>> +	if (!count_comp)
>> +		return -ENOMEM;
>> +	count_comp->count = count;
>> +
>> +	/* Create main Count attribute */
>> +	err = counter_attribute_create(group, "", "count",
>> +		(counter->ops->count_read) ? counter_count_show : NULL,
>> +		(counter->ops->count_write) ? counter_count_store : NULL,
>> +		count_comp);
>> +	if (err) {
>> +		kfree(count_comp);
>> +		return err;
>> +	}
>> +
>> +	/* Allocate function attribute component */
>> +	func_comp = kmalloc(sizeof(*func_comp), GFP_KERNEL);
>> +	if (!func_comp) {
>> +		err = -ENOMEM;
>> +		goto err_free_attr_list;
>> +	}
>> +	func_comp->count = count;
>> +
>> +	/* Create Count function attribute */
>> +	err = counter_attribute_create(group, "", "function",
>> +		(counter->ops->function_get) ? counter_function_show : NULL,
>> +		(counter->ops->function_set) ? counter_function_store : NULL,
>> +		func_comp);
>> +	if (err) {
>> +		kfree(func_comp);
>> +		goto err_free_attr_list;
>> +	}
>> +
>> +	/* Allocate function available attribute component */
>> +	avail_comp = kmalloc(sizeof(*avail_comp), GFP_KERNEL);
>> +	if (!avail_comp) {
>> +		err = -ENOMEM;
>> +		goto err_free_attr_list;
>> +	}
>> +	avail_comp->functions_list = count->functions_list;
>> +	avail_comp->num_functions = count->num_functions;
>> +
>> +	/* Create Count function_available attribute */
>> +	err = counter_attribute_create(group, "", "function_available",
>> +				       counter_count_function_available_show,
>> +				       NULL, avail_comp);
>> +	if (err) {
>> +		kfree(avail_comp);
>> +		goto err_free_attr_list;
>> +	}
>> +
>> +	/* Create Count name attribute */
>> +	err = counter_name_attribute_create(group, count->name);
>> +	if (err)
>> +		goto err_free_attr_list;
>> +
>> +	/* Register Count extension attributes */
>> +	err = counter_count_ext_register(group, count);
>> +	if (err)
>> +		goto err_free_attr_list;
>> +
>> +	return 0;
>> +
>> +err_free_attr_list:
>> +	free_counter_device_attr_list(&group->attr_list);
>> +	return err;
>> +}
>> +
>> +static int counter_counts_register(
>> +	struct counter_device_attr_group *const groups_list,
>> +	const struct counter_device *const counter)
>> +{
>> +	const size_t num_counts = counter->num_counts;
>
>I think this is only used on one place.  Not sure having
>a local variable is worthwhile.
>
>> +	size_t i;
>> +	struct counter_count *count;
>> +	const char *name;
>> +	int err;
>> +
>> +	/* Register each Count */
>> +	for (i = 0; i < num_counts; i++) {
>> +		count = counter->counts + i;
>> +
>> +		/* Generate Count attribute directory name */
>> +		name = kasprintf(GFP_KERNEL, "count%d", count->id);
>> +		if (!name) {
>> +			err = -ENOMEM;
>> +			goto err_free_attr_groups;
>> +		}
>> +		groups_list[i].attr_group.name = name;
>> +
>> +		/* Register the Synapses associated with each Count */
>> +		err = counter_synapses_register(groups_list + i, counter, count,
>> +						name);
>> +		if (err)
>> +			goto err_free_attr_groups;
>> +
>> +		/* Create all attributes associated with Count */
>> +		err = counter_count_attributes_create(groups_list + i, counter,
>> +						      count);
>> +		if (err)
>> +			goto err_free_attr_groups;
>> +	}
>> +
>> +	return 0;
>> +
>> +err_free_attr_groups:
>> +	do {
>> +		kfree(groups_list[i].attr_group.name);
>> +		free_counter_device_attr_list(&groups_list[i].attr_list);
>> +	} while (i--);
>> +	return err;
>> +}
>> +
>> +struct size_comp_t {
>> +	size_t size;
>> +};
>> +
>> +static ssize_t counter_device_attr_size_show(struct device *dev,
>> +					     struct device_attribute *attr,
>> +					     char *buf)
>> +{
>> +	const struct size_comp_t *const comp = to_counter_attr(attr)->component;
>> +
>> +	return scnprintf(buf, PAGE_SIZE, "%zu\n", comp->size);
>> +}
>> +
>> +static int counter_size_attribute_create(
>> +	struct counter_device_attr_group *const group,
>> +	const size_t size, const char *const name)
>> +{
>> +	struct size_comp_t *size_comp;
>> +	int err;
>> +
>> +	/* Allocate size attribute component */
>> +	size_comp = kmalloc(sizeof(*size_comp), GFP_KERNEL);
>> +	if (!size_comp)
>> +		return -ENOMEM;
>> +	size_comp->size = size;
>> +
>> +	err = counter_attribute_create(group, "", name,
>> +				       counter_device_attr_size_show, NULL,
>> +				       size_comp);
>> +	if (err)
>> +		goto err_free_size_comp;
>> +
>> +	return 0;
>> +
>> +err_free_size_comp:
>> +	kfree(size_comp);
>> +	return err;
>> +}
>> +
>> +struct ext_comp_t {
>> +	const struct counter_device_ext	*ext;
>> +};
>> +
>> +static ssize_t counter_device_ext_show(struct device *dev,
>> +				       struct device_attribute *attr, char *buf)
>> +{
>> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
>> +	const struct ext_comp_t *const component = devattr->component;
>> +	const struct counter_device_ext *const ext = component->ext;
>> +
>> +	return ext->read(dev_get_drvdata(dev), ext->priv, buf);
>> +}
>> +
>> +static ssize_t counter_device_ext_store(struct device *dev,
>> +					struct device_attribute *attr,
>> +					const char *buf, size_t len)
>> +{
>> +	const struct counter_device_attr *const devattr = to_counter_attr(attr);
>> +	const struct ext_comp_t *const component = devattr->component;
>> +	const struct counter_device_ext *const ext = component->ext;
>> +
>> +	return ext->write(dev_get_drvdata(dev), ext->priv, buf, len);
>> +}
>> +
>> +static int counter_device_ext_register(
>> +	struct counter_device_attr_group *const group,
>> +	struct counter_device *const counter)
>> +{
>> +	const size_t num_ext = counter->num_ext;
>
>num_ext only used in one place so if anything the local variable
>is hurting readability.
>
>> +	struct ext_comp_t *ext_comp;
>> +	size_t i;
>> +	const struct counter_device_ext *ext;
>> +	int err;
>> +
>> +	/* Create an attribute for each extension */
>> +	for (i = 0 ; i < num_ext; i++) {
>> +		ext = counter->ext + i;
>
>This local variable isn't gaining us much that I can see. Just
>use the value directly.
>
>> +
>> +		/* Allocate extension attribute component */
>> +		ext_comp = kmalloc(sizeof(*ext_comp), GFP_KERNEL);
>> +		if (!ext_comp) {
>> +			err = -ENOMEM;
>> +			goto err_free_attr_list;
>> +		}
>> +
>> +		ext_comp->ext = ext;
>> +
>> +		/* Allocate extension attribute */
>> +		err = counter_attribute_create(group, "", ext->name,
>> +			(ext->read) ? counter_device_ext_show : NULL,
>> +			(ext->write) ? counter_device_ext_store : NULL,
>> +			ext_comp);
>> +		if (err) {
>> +			kfree(ext_comp);
>> +			goto err_free_attr_list;
>> +		}
>> +	}
>> +
>> +	return 0;
>> +
>> +err_free_attr_list:
>> +	free_counter_device_attr_list(&group->attr_list);
>> +	return err;
>> +}
>> +
>> +static int counter_global_attr_register(
>> +	struct counter_device_attr_group *const group,
>> +	struct counter_device *const counter)
>> +{
>> +	int err;
>> +
>> +	/* Create name attribute */
>> +	err = counter_name_attribute_create(group, counter->name);
>> +	if (err)
>> +		return err;
>> +
>> +	/* Create num_counts attribute */
>> +	err = counter_size_attribute_create(group, counter->num_counts,
>> +					    "num_counts");
>> +	if (err)
>> +		goto err_free_attr_list;
>> +
>> +	/* Create num_signals attribute */
>> +	err = counter_size_attribute_create(group, counter->num_signals,
>> +					    "num_signals");
>> +	if (err)
>> +		goto err_free_attr_list;
>> +
>> +	/* Register Counter device extension attributes */
>> +	err = counter_device_ext_register(group, counter);
>> +	if (err)
>> +		goto err_free_attr_list;
>> +
>> +	return 0;
>> +
>> +err_free_attr_list:
>> +	free_counter_device_attr_list(&group->attr_list);
>> +	return err;
>> +}
>> +
>> +static void free_counter_device_groups_list(
>> +	struct counter_device_attr_group *const groups_list,
>> +	const size_t num_groups)
>> +{
>> +	struct counter_device_attr_group *group;
>> +	size_t i;
>> +
>> +	for (i = 0; i < num_groups; i++) {
>> +		group = groups_list + i;
>> +
>
>I'd like to see a comment somewhere here on the fact this cleans up both
>the registered per counter stuff and the global attributes (that took
>a bit of chasing to check it did...)
>
>> +		kfree(group->attr_group.name);
>> +		kfree(group->attr_group.attrs);
>> +		free_counter_device_attr_list(&group->attr_list);
>> +	}
>> +
>> +	kfree(groups_list);
>> +}
>> +
>> +static int prepare_counter_device_groups_list(
>> +	struct counter_device *const counter)
>> +{
>> +	const size_t total_num_groups =
>> +		counter->num_signals + counter->num_counts + 1;
>> +	struct counter_device_attr_group *groups_list;
>> +	size_t i;
>> +	int err;
>> +	size_t num_groups = 0;
>> +
>> +	/* Allocate space for attribute groups (signals. counts, and ext) */
>> +	groups_list = kcalloc(total_num_groups, sizeof(*groups_list),
>> +			      GFP_KERNEL);
>> +	if (!groups_list)
>> +		return -ENOMEM;
>> +
>> +	/* Initialize attribute lists */
>> +	for (i = 0; i < total_num_groups; i++)
>> +		INIT_LIST_HEAD(&groups_list[i].attr_list);
>> +
>> +	/* Register Signals */
>> +	err = counter_signals_register(groups_list, counter);
>> +	if (err)
>> +		goto err_free_groups_list;
>> +	num_groups += counter->num_signals;
>> +
>> +	/* Register Counts and respective Synapses */
>> +	err = counter_counts_register(groups_list + num_groups, counter);
>> +	if (err)
>> +		goto err_free_groups_list;
>> +	num_groups += counter->num_counts;
>> +
>> +	/* Register Counter global attributes */
>> +	err = counter_global_attr_register(groups_list + num_groups, counter);
>> +	if (err)
>> +		goto err_free_groups_list;
>> +	num_groups++;
>> +
>> +	/* Store groups_list in device_state */
>> +	counter->device_state->groups_list = groups_list;
>> +	counter->device_state->num_groups = num_groups;
>> +
>> +	return 0;
>> +
>> +err_free_groups_list:
>> +	free_counter_device_groups_list(groups_list, num_groups);
>
>Consistent naming would be good.
>
>counter_device_groups_list_free.
>
>I would tidy this up throughout.  I know from experience that
>you'll probably end up doing so eventually and it is easier whilst
>there isn't too much code.
>
>> +	return err;
>> +}
>> +
>> +static int prepare_counter_device_groups(
>> +	struct counter_device_state *const device_state)
>> +{
>> +	size_t i;
>> +	struct counter_device_attr_group *group;
>> +	int err;
>> +	size_t j;
>
>Tidy this up a little,
>size_t i, j;
>
>> +	struct counter_device_attr *p;
>> +
>> +	/* Allocate attribute groups for association with device */
>> +	device_state->groups = kcalloc(device_state->num_groups + 1,
>> +				       sizeof(*device_state->groups),
>> +				       GFP_KERNEL);
>> +	if (!device_state->groups)
>> +		return -ENOMEM;
>> +
>> +	/* Prepare each group of attributes for association */
>> +	for (i = 0; i < device_state->num_groups; i++) {
>> +		group = device_state->groups_list + i;
>> +
>> +		/* Allocate space for attribute pointers in attribute group */
>> +		group->attr_group.attrs = kcalloc(group->num_attr + 1,
>> +			sizeof(*group->attr_group.attrs), GFP_KERNEL);
>> +		if (!group->attr_group.attrs) {
>> +			err = -ENOMEM;
>> +			goto err_free_groups;
>> +		}
>> +
>> +		/* Add attribute pointers to attribute group */
>> +		j = 0;
>> +		list_for_each_entry(p, &group->attr_list, l)
>> +			group->attr_group.attrs[j++] = &p->dev_attr.attr;
>> +
>> +		/* Group attributes in attribute group */
>> +		device_state->groups[i] = &group->attr_group;
>> +	}
>> +	/* Associate attributes with device */
>> +	device_state->dev.groups = device_state->groups;
>> +
>> +	return 0;
>> +
>> +err_free_groups:
>
>I'm not convinced this is cleaning up properly.  What about
>the kcalloc of group->attr_group.attrs for previous loops?
>
>> +	kfree(device_state->groups);
>> +	return err;
>> +}
>> +
>> +/* Provides a unique ID for each counter device */
>> +static DEFINE_IDA(counter_ida);
>> +
>> +static void counter_device_release(struct device *dev)
>> +{
>> +	struct counter_device *const counter = dev_get_drvdata(dev);
>> +	struct counter_device_state *const device_state = counter->device_state;
>> +
>> +	kfree(device_state->groups);
>> +	free_counter_device_groups_list(device_state->groups_list,
>> +					device_state->num_groups);
>> +	ida_simple_remove(&counter_ida, device_state->id);
>> +	kfree(device_state);
>> +}
>> +
>> +static struct device_type counter_device_type = {
>> +	.name = "counter_device",
>> +	.release = counter_device_release
>> +};
>> +
>> +static struct bus_type counter_bus_type = {
>> +	.name = "counter"
>> +};
>> +
>> +/**
>> + * counter_register - register Counter to the system
>> + * @counter:	pointer to Counter to register
>> + *
>> + * This function registers a Counter to the system. A sysfs "counter" directory
>> + * will be created and populated with sysfs attributes correlating with the
>> + * Counter Signals, Synapses, and Counts respectively.
>> + */
>> +int counter_register(struct counter_device *const counter)
>> +{
>> +	struct counter_device_state *device_state;
>> +	int err;
>> +
>> +	/* Allocate internal state container for Counter device */
>> +	device_state = kzalloc(sizeof(*device_state), GFP_KERNEL);
>> +	if (!device_state)
>> +		return -ENOMEM;
>> +	counter->device_state = device_state;
>> +
>> +	/* Acquire unique ID */
>> +	device_state->id = ida_simple_get(&counter_ida, 0, 0, GFP_KERNEL);
>> +	if (device_state->id < 0) {
>> +		err = device_state->id;
>> +		goto err_free_device_state;
>> +	}
>> +
>> +	/* Configure device structure for Counter */
>> +	device_state->dev.type = &counter_device_type;
>> +	device_state->dev.bus = &counter_bus_type;
>> +	if (counter->parent) {
>> +		device_state->dev.parent = counter->parent;
>> +		device_state->dev.of_node = counter->parent->of_node;
>> +	}
>> +	dev_set_name(&device_state->dev, "counter%d", device_state->id);
>> +	device_initialize(&device_state->dev);
>> +	dev_set_drvdata(&device_state->dev, counter);
>> +
>> +	/* Prepare device attributes */
>> +	err = prepare_counter_device_groups_list(counter);
>> +	if (err)
>> +		goto err_free_id;
>> +
>> +	/* Organize device attributes to groups and match to device */
>> +	err = prepare_counter_device_groups(device_state);
>> +	if (err)
>> +		goto err_free_groups_list;
>> +
>> +	/* Add device to system */
>> +	err = device_add(&device_state->dev);
>> +	if (err)
>> +		goto err_free_groups;
>> +
>> +	return 0;
>> +
>> +err_free_groups:
>> +	kfree(device_state->groups);
>> +err_free_groups_list:
>> +	free_counter_device_groups_list(device_state->groups_list,
>> +					device_state->num_groups);
>> +err_free_id:
>> +	ida_simple_remove(&counter_ida, device_state->id);
>> +err_free_device_state:
>> +	kfree(device_state);
>> +	return err;
>> +}
>> +EXPORT_SYMBOL(counter_register);
>> +
>> +/**
>> + * counter_unregister - unregister Counter from the system
>> + * @counter:	pointer to Counter to unregister
>> + *
>> + * The Counter is unregistered from the system; all allocated memory is freed.
>> + */
>> +void counter_unregister(struct counter_device *const counter)
>> +{
>> +	if (counter)
>> +		device_del(&counter->device_state->dev);
>> +}
>> +EXPORT_SYMBOL(counter_unregister);
>> +
>> +static void devm_counter_unreg(struct device *dev, void *res)
>> +{
>> +	counter_unregister(*(struct counter_device **)res);
>> +}
>> +
>> +/**
>> + * devm_counter_register - Resource-managed counter_register
>> + * @dev:	device to allocate counter_device for
>> + * @counter:	pointer to Counter to register
>> + *
>> + * Managed counter_register. The Counter registered with this function is
>> + * automatically unregistered on driver detach. This function calls
>> + * counter_register internally. Refer to that function for more information.
>> + *
>> + * If an Counter registered with this function needs to be unregistered
>> + * separately, devm_counter_unregister must be used.
>> + *
>> + * RETURNS:
>> + * 0 on success, negative error number on failure.
>> + */
>> +int devm_counter_register(struct device *dev,
>> +			  struct counter_device *const counter)
>> +{
>> +	struct counter_device **ptr;
>> +	int ret;
>> +
>> +	ptr = devres_alloc(devm_counter_unreg, sizeof(*ptr), GFP_KERNEL);
>> +	if (!ptr)
>> +		return -ENOMEM;
>> +
>> +	ret = counter_register(counter);
>> +	if (!ret) {
>> +		*ptr = counter;
>> +		devres_add(dev, ptr);
>> +	} else {
>> +		devres_free(ptr);
>> +	}
>> +
>> +	return ret;
>> +}
>> +EXPORT_SYMBOL(devm_counter_register);
>> +
>> +static int devm_counter_match(struct device *dev, void *res, void *data)
>> +{
>> +	struct counter_device **r = res;
>> +
>> +	if (!r || !*r) {
>> +		WARN_ON(!r || !*r);
>> +		return 0;
>> +	}
>> +
>> +	return *r == data;
>> +}
>> +
>> +/**
>> + * devm_counter_unregister - Resource-managed counter_unregister
>> + * @dev:	device this counter_device belongs to
>> + * @counter:	pointer to Counter associated with the device
>> + *
>> + * Unregister Counter registered with devm_counter_register.
>> + */
>> +void devm_counter_unregister(struct device *dev,
>> +			     struct counter_device *const counter)
>> +{
>> +	int rc;
>> +
>> +	rc = devres_release(dev, devm_counter_unreg, devm_counter_match,
>> +			    counter);
>> +	WARN_ON(rc);
>> +}
>> +EXPORT_SYMBOL(devm_counter_unregister);
>> +
>> +static int __init counter_init(void)
>> +{
>> +	return bus_register(&counter_bus_type);
>> +}
>> +
>> +static void __exit counter_exit(void)
>> +{
>> +	bus_unregister(&counter_bus_type);
>> +}
>> +
>> +subsys_initcall(counter_init);
>> +module_exit(counter_exit);
>> +
>> +MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
>> +MODULE_DESCRIPTION("Generic Counter interface");
>> +MODULE_LICENSE("GPL v2");
>> diff --git a/include/linux/counter.h b/include/linux/counter.h
>> new file mode 100644
>> index 000000000000..a0b0349d098a
>> --- /dev/null
>> +++ b/include/linux/counter.h
>> @@ -0,0 +1,554 @@
>> +/* SPDX-License-Identifier: GPL-2.0-only */
>> +/*
>> + * Counter interface
>> + * Copyright (C) 2017 William Breathitt Gray
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License, version 2, as
>> + * published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope that it will be useful, but
>> + * WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>> + * General Public License for more details.
>
>It's a bit controversial, but most people consider SPDX headers equivalent
>of the license statement.  As such you normally don't have both and just
>go for the SPDK header.
>
>I thought we were also standardising on 
>// SPDX-...
>
>
>> + */
>> +#ifndef _COUNTER_H_
>> +#define _COUNTER_H_
>> +
>> +#include <linux/device.h>
>> +#include <linux/types.h>
>> +
>> +enum count_direction {
>> +	COUNT_DIRECTION_FORWARD = 0,
>> +	COUNT_DIRECTION_BACKWARD
>> +};
>> +extern const char *const count_direction_str[2];
>> +
>> +enum count_mode {
>> +	COUNT_MODE_NORMAL = 0,
>> +	COUNT_MODE_RANGE_LIMIT,
>> +	COUNT_MODE_NON_RECYCLE,
>> +	COUNT_MODE_MODULO_N
>> +};
>> +extern const char *const count_mode_str[4];
>> +
>> +struct counter_device;
>> +struct counter_signal;
>> +
>> +/**
>> + * struct counter_signal_ext - Counter Signal extensions
>> + * @name:	attribute name
>> + * @read:	read callback for this attribute; may be NULL
>> + * @write:	write callback for this attribute; may be NULL
>> + * @priv:	data private to the driver
>> + */
>> +struct counter_signal_ext {
>> +	const char	*name;
>> +	ssize_t		(*read)(struct counter_device *counter,
>> +				struct counter_signal *signal, void *priv,
>> +				char *buf);
>> +	ssize_t		(*write)(struct counter_device *counter,
>> +				 struct counter_signal *signal, void *priv,
>> +				 const char *buf, size_t len);
>> +	void		*priv;
>> +};
>> +
>> +/**
>> + * struct counter_signal - Counter Signal node
>> + * @id:		unique ID used to identify signal
>> + * @name:	device-specific Signal name; ideally, this should match the name
>> + *		as it appears in the datasheet documentation
>> + * @ext:	optional array of Counter Signal extensions
>> + * @num_ext:	number of Counter Signal extensions specified in @ext
>> + * @priv:	optional private data supplied by driver
>> + */
>> +struct counter_signal {
>> +	int		id;
>> +	const char	*name;
>> +
>> +	const struct counter_signal_ext	*ext;
>> +	size_t				num_ext;
>> +
>> +	void	*priv;
>> +};
>> +
>> +/**
>> + * struct counter_signal_enum_ext - Signal enum extension attribute
>> + * @items:	Array of strings
>> + * @num_items:	Number of items specified in @items
>> + * @set:	Set callback function; may be NULL
>> + * @get:	Get callback function; may be NULL
>> + *
>> + * The counter_signal_enum_ext structure can be used to implement enum style
>> + * Signal extension attributes. Enum style attributes are those which have a set
>> + * of strings that map to unsigned integer values. The Generic Counter Signal
>> + * enum extension helper code takes care of mapping between value and string, as
>> + * well as generating a "_available" file which contains a list of all available
>> + * items. The get callback is used to query the currently active item; the index
>> + * of the item within the respective items array is returned via the 'item'
>> + * parameter. The set callback is called when the attribute is updated; the
>> + * 'item' parameter contains the index of the newly activated item within the
>> + * respective items array.
>> + */
>> +struct counter_signal_enum_ext {
>> +	const char * const	*items;
>> +	size_t			num_items;
>> +	int			(*get)(struct counter_device *counter,
>> +				       struct counter_signal *signal,
>> +				       size_t *item);
>> +	int			(*set)(struct counter_device *counter,
>> +				       struct counter_signal *signal,
>> +				       size_t item);
>> +};
>> +
>> +ssize_t counter_signal_enum_read(struct counter_device *counter,
>> +				 struct counter_signal *signal, void *priv,
>> +				 char *buf);
>> +ssize_t counter_signal_enum_write(struct counter_device *counter,
>> +				  struct counter_signal *signal, void *priv,
>> +				  const char *buf, size_t len);
>> +
>> +/**
>> + * COUNTER_SIGNAL_ENUM() - Initialize Signal enum extension
>> + * @_name:	Attribute name
>> + * @_e:		Pointer to a counter_count_enum structure
>> + *
>> + * This should usually be used together with COUNTER_SIGNAL_ENUM_AVAILABLE()
>> + */
>> +#define COUNTER_SIGNAL_ENUM(_name, _e) \
>> +{ \
>> +	.name = (_name), \
>> +	.read = counter_signal_enum_read, \
>> +	.write = counter_signal_enum_write, \
>> +	.priv = (_e) \
>> +}
>> +
>> +ssize_t counter_signal_enum_available_read(struct counter_device *counter,
>> +					   struct counter_signal *signal,
>> +					   void *priv, char *buf);
>> +
>> +/**
>> + * COUNTER_SIGNAL_ENUM_AVAILABLE() - Initialize Signal enum available extension
>> + * @_name:	Attribute name ("_available" will be appended to the name)
>> + * @_e:		Pointer to a counter_signal_enum structure
>> + *
>> + * Creates a read only attribute that lists all the available enum items in a
>> + * newline separated list. This should usually be used together with
>> + * COUNTER_SIGNAL_ENUM()
>> + */
>> +#define COUNTER_SIGNAL_ENUM_AVAILABLE(_name, _e) \
>> +{ \
>> +	.name = (_name "_available"), \
>> +	.read = counter_signal_enum_available_read, \
>> +	.priv = (_e) \
>> +}
>> +
>> +enum synapse_action {
>> +	SYNAPSE_ACTION_NONE = 0,
>> +	SYNAPSE_ACTION_RISING_EDGE,
>> +	SYNAPSE_ACTION_FALLING_EDGE,
>> +	SYNAPSE_ACTION_BOTH_EDGES
>> +};
>> +
>> +/**
>> + * struct counter_synapse - Counter Synapse node
>> + * @action:		index of current action mode
>> + * @actions_list:	array of available action modes
>> + * @num_actions:	number of action modes specified in @actions_list
>> + * @signal:		pointer to associated signal
>> + */
>> +struct counter_synapse {
>> +	size_t					action;
>> +	const enum synapse_action		*actions_list;
>> +	size_t					num_actions;
>> +
>> +	struct counter_signal			*signal;
>> +};
>> +
>> +struct counter_count;
>> +
>> +/**
>> + * struct counter_count_ext - Counter Count extension
>> + * @name:	attribute name
>> + * @read:	read callback for this attribute; may be NULL
>> + * @write:	write callback for this attribute; may be NULL
>> + * @priv:	data private to the driver
>> + */
>> +struct counter_count_ext {
>> +	const char	*name;
>> +	ssize_t		(*read)(struct counter_device *counter,
>> +				struct counter_count *count, void *priv,
>> +				char *buf);
>> +	ssize_t		(*write)(struct counter_device *counter,
>> +				 struct counter_count *count, void *priv,
>> +				 const char *buf, size_t len);
>> +	void		*priv;
>> +};
>> +
>> +enum count_function {
>> +	COUNT_FUNCTION_INCREASE = 0,
>> +	COUNT_FUNCTION_DECREASE,
>> +	COUNT_FUNCTION_PULSE_DIRECTION,
>> +	COUNT_FUNCTION_QUADRATURE_X1_A,
>> +	COUNT_FUNCTION_QUADRATURE_X1_B,
>> +	COUNT_FUNCTION_QUADRATURE_X2_A,
>> +	COUNT_FUNCTION_QUADRATURE_X2_B,
>> +	COUNT_FUNCTION_QUADRATURE_X2_RISING,
>> +	COUNT_FUNCTION_QUADRATURE_X2_FALLING,
>> +	COUNT_FUNCTION_QUADRATURE_X4
>> +};
>> +
>> +/**
>> + * struct counter_count - Counter Count node
>> + * @id:			unique ID used to identify Count
>> + * @name:		device-specific Count name; ideally, this should match
>> + *			the name as it appears in the datasheet documentation
>> + * @function:		index of current function mode
>> + * @functions_list:	array available function modes
>> + * @num_functions:	number of function modes specified in @functions_list
>> + * @synapses:		array of synapses for initialization
>> + * @num_synapses:	number of synapses specified in @synapses
>> + * @ext:		optional array of Counter Count extensions
>> + * @num_ext:		number of Counter Count extensions specified in @ext
>> + * @priv:		optional private data supplied by driver
>> + */
>> +struct counter_count {
>> +	int			id;
>> +	const char		*name;
>> +
>> +	size_t					function;
>> +	const enum count_function		*functions_list;
>> +	size_t					num_functions;
>
>There is a very good illustration here of the issues with using
>tabs to pretty print structure elements.  I would drop them entirely as
>personally I'm not sure they help readability and you will forever be having
>more noise in patches because of the need to change the number of tabs
>due to name changes etc.
>
>> +
>> +	struct counter_synapse	*synapses;
>> +	size_t			num_synapses;
>> +
>> +	const struct counter_count_ext	*ext;
>> +	size_t				num_ext;
>> +
>> +	void	*priv;
>> +};
>> +
>> +/**
>> + * struct counter_count_enum_ext - Count enum extension attribute
>> + * @items:	Array of strings
>> + * @num_items:	Number of items specified in @items
>> + * @set:	Set callback function; may be NULL
>> + * @get:	Get callback function; may be NULL
>> + *
>> + * The counter_count_enum_ext structure can be used to implement enum style
>> + * Count extension attributes. Enum style attributes are those which have a set
>> + * of strings that map to unsigned integer values. The Generic Counter Count
>> + * enum extension helper code takes care of mapping between value and string, as
>> + * well as generating a "_available" file which contains a list of all available
>> + * items. The get callback is used to query the currently active item; the index
>> + * of the item within the respective items array is returned via the 'item'
>> + * parameter. The set callback is called when the attribute is updated; the
>> + * 'item' parameter contains the index of the newly activated item within the
>> + * respective items array.
>> + */
>> +struct counter_count_enum_ext {
>> +	const char * const	*items;
>> +	size_t			num_items;
>> +	int			(*get)(struct counter_device *counter,
>> +				       struct counter_count *count,
>> +				       size_t *item);
>> +	int			(*set)(struct counter_device *counter,
>> +				       struct counter_count *count,
>> +				       size_t item);
>> +};
>> +
>> +ssize_t counter_count_enum_read(struct counter_device *counter,
>> +				struct counter_count *count, void *priv,
>> +				char *buf);
>> +ssize_t counter_count_enum_write(struct counter_device *counter,
>> +				 struct counter_count *count, void *priv,
>> +				 const char *buf, size_t len);
>> +
>> +/**
>> + * COUNTER_COUNT_ENUM() - Initialize Count enum extension
>> + * @_name:	Attribute name
>> + * @_e:		Pointer to a counter_count_enum structure
>> + *
>> + * This should usually be used together with COUNTER_COUNT_ENUM_AVAILABLE()
>> + */
>> +#define COUNTER_COUNT_ENUM(_name, _e) \
>> +{ \
>> +	.name = (_name), \
>> +	.read = counter_count_enum_read, \
>> +	.write = counter_count_enum_write, \
>> +	.priv = (_e) \
>> +}
>> +
>> +ssize_t counter_count_enum_available_read(struct counter_device *counter,
>> +					  struct counter_count *count,
>> +					  void *priv, char *buf);
>> +
>> +/**
>> + * COUNTER_COUNT_ENUM_AVAILABLE() - Initialize Count enum available extension
>> + * @_name:	Attribute name ("_available" will be appended to the name)
>> + * @_e:		Pointer to a counter_count_enum structure
>> + *
>> + * Creates a read only attribute that lists all the available enum items in a
>> + * newline separated list. This should usually be used together with
>> + * COUNTER_COUNT_ENUM()
>> + */
>> +#define COUNTER_COUNT_ENUM_AVAILABLE(_name, _e) \
>> +{ \
>> +	.name = (_name "_available"), \
>> +	.read = counter_count_enum_available_read, \
>> +	.priv = (_e) \
>> +}
>> +
>> +/**
>> + * struct counter_device_attr_group - internal container for attribute group
>> + * @attr_group:	Counter sysfs attributes group
>> + * @attr_list:	list to keep track of created Counter sysfs attributes
>> + * @num_attr:	number of Counter sysfs attributes
>> + */
>> +struct counter_device_attr_group {
>> +	struct attribute_group	attr_group;
>> +	struct list_head	attr_list;
>> +	size_t			num_attr;
>> +};
>> +
>> +/**
>> + * struct counter_device_state - internal state container for a Counter device
>> + * @id:		unique ID used to identify the Counter
>> + * @dev:	internal device structure
>> + * @groups_list	attribute groups list (groups for Signals, Counts, and ext)
>
>Run kernel-doc script over these files.  You are missing some :s and it would
>have told you that.
>
>> + * @num_groups	number of attribute groups containers
>> + * @groups:	Counter sysfs attribute groups (used to populate @dev.groups)
>> + */
>> +struct counter_device_state {
>> +	int					id;
>> +	struct device				dev;
>> +	struct counter_device_attr_group	*groups_list;
>> +	size_t					num_groups;
>> +	const struct attribute_group		**groups;
>> +};
>> +
>> +/**
>> + * struct signal_read_value - Opaque Signal read value
>> + * @buf:	string representation of Signal read value
>> + * @len:	length of string in @buf
>> + */
>> +struct signal_read_value {
>> +	char	*buf;
>> +	size_t	len;
>> +};
>> +
>> +/**
>> + * struct count_read_value - Opaque Count read value
>> + * @buf:	string representation of Count read value
>> + * @len:	length of string in @buf
>> + */
>> +struct count_read_value {
>> +	char	*buf;
>> +	size_t	len;
>> +};
>> +
>> +/**
>> + * struct count_write_value - Opaque Count write value
>> + * @buf:	string representation of Count write value
>> + */
>> +struct count_write_value {
>> +	const char	*buf;
>> +};
>> +
>> +/**
>> + * struct counter_ops - Callbacks from driver
>> + * @signal_read:	optional read callback for Signal attribute. The read
>> + *			value of the respective Signal should be passed back via
>> + *			the val parameter. val points to an opaque type which
>> + *			should be set only via the set_signal_read_value
>> + *			function.
>
>This last part had me a little confused.  I would make it clear that this
>set_signal_read_value function should be called to set the value within this
>signal_read callback rather than elsewhere...  
>
>> + * @count_read:		optional read callback for Count attribute. The read
>> + *			value of the respective Count should be passed back via
>> + *			the val parameter. val points to an opaque type which
>> + *			should be set only via the set_count_read_value
>> + *			function.
>> + * @count_write:	optional write callback for Count attribute. The write
>> + *			value for the respective Count is passed in via the val
>> + *			parameter. val points to an opaque type which should be
>> + *			access only via the get_count_write_value function.
>> + * @function_get:	function to get the current count function mode. Returns
>> + *			0 on success and negative error code on error. The index
>> + *			of the respective Count's returned function mode should
>> + *			be passed back via the function parameter.
>> + * @function_set:	function to set the count function mode. function is the
>> + *			index of the requested function mode from the respective
>> + *			Count's functions_list array.
>> + * @action_get:		function to get the current action mode. Returns 0 on
>> + *			success and negative error code on error. The index of
>> + *			the respective Signal's returned action mode should be
>> + *			passed back via the action parameter.
>> + * @action_set:		function to set the action mode. action is the index of
>> + *			the requested action mode from the respective Synapse's
>> + *			actions_list array.
>> + */
>> +struct counter_ops {
>> +	int	(*signal_read)(struct counter_device *counter,
>> +			       struct counter_signal *signal,
>> +			       struct signal_read_value *val);
>> +	int	(*count_read)(struct counter_device *counter,
>> +			      struct counter_count *count,
>> +			      struct count_read_value *val);
>> +	int	(*count_write)(struct counter_device *counter,
>> +			       struct counter_count *count,
>> +			       struct count_write_value *val);
>> +	int	(*function_get)(struct counter_device *counter,
>> +				struct counter_count *count, size_t *function);
>> +	int	(*function_set)(struct counter_device *counter,
>> +				struct counter_count *count, size_t function);
>> +	int	(*action_get)(struct counter_device *counter,
>> +			      struct counter_count *count,
>> +			      struct counter_synapse *synapse, size_t *action);
>> +	int	(*action_set)(struct counter_device *counter,
>> +			      struct counter_count *count,
>> +			      struct counter_synapse *synapse, size_t action);
>> +};
>> +
>> +/**
>> + * struct counter_device_ext - Counter device extension
>> + * @name:	attribute name
>> + * @read:	read callback for this attribute; may be NULL
>> + * @write:	write callback for this attribute; may be NULL
>> + * @priv:	data private to the driver
>> + */
>> +struct counter_device_ext {
>> +	const char	*name;
>> +	ssize_t		(*read)(struct counter_device *counter, void *priv,
>> +				char *buf);
>> +	ssize_t		(*write)(struct counter_device *counter, void *priv,
>> +				 const char *buf, size_t len);
>> +	void		*priv;
>> +};
>> +
>> +/**
>> + * struct counter_device_enum_ext - Counter enum extension attribute
>> + * @items:	Array of strings
>> + * @num_items:	Number of items specified in @items
>> + * @set:	Set callback function; may be NULL
>> + * @get:	Get callback function; may be NULL
>> + *
>> + * The counter_device_enum_ext structure can be used to implement enum style
>> + * Counter extension attributes. Enum style attributes are those which have a
>> + * set of strings that map to unsigned integer values. The Generic Counter enum
>> + * extension helper code takes care of mapping between value and string, as well
>> + * as generating a "_available" file which contains a list of all available
>> + * items. The get callback is used to query the currently active item; the index
>> + * of the item within the respective items array is returned via the 'item'
>> + * parameter. The set callback is called when the attribute is updated; the
>> + * 'item' parameter contains the index of the newly activated item within the
>> + * respective items array.
>> + */
>> +struct counter_device_enum_ext {
>> +	const char * const	*items;
>> +	size_t			num_items;
>> +	int			(*get)(struct counter_device *counter,
>> +				       size_t *item);
>> +	int			(*set)(struct counter_device *counter,
>> +				       size_t item);
>> +};
>> +
>> +ssize_t counter_device_enum_read(struct counter_device *counter, void *priv,
>> +				 char *buf);
>> +ssize_t counter_device_enum_write(struct counter_device *counter, void *priv,
>> +				  const char *buf, size_t len);
>> +
>> +/**
>> + * COUNTER_DEVICE_ENUM() - Initialize Counter enum extension
>> + * @_name:	Attribute name
>> + * @_e:		Pointer to a counter_device_enum structure
>> + *
>> + * This should usually be used together with COUNTER_DEVICE_ENUM_AVAILABLE()
>> + */
>> +#define COUNTER_DEVICE_ENUM(_name, _e) \
>> +{ \
>> +	.name = (_name), \
>> +	.read = counter_device_enum_read, \
>> +	.write = counter_device_enum_write, \
>> +	.priv = (_e) \
>> +}
>> +
>> +ssize_t counter_device_enum_available_read(struct counter_device *counter,
>> +					   void *priv, char *buf);
>> +
>> +/**
>> + * COUNTER_DEVICE_ENUM_AVAILABLE() - Initialize Counter enum available extension
>> + * @_name:	Attribute name ("_available" will be appended to the name)
>> + * @_e:		Pointer to a counter_device_enum structure
>> + *
>> + * Creates a read only attribute that lists all the available enum items in a
>> + * newline separated list. This should usually be used together with
>> + * COUNTER_DEVICE_ENUM()
>> + */
>> +#define COUNTER_DEVICE_ENUM_AVAILABLE(_name, _e) \
>> +{ \
>> +	.name = (_name "_available"), \
>> +	.read = counter_device_enum_available_read, \
>> +	.priv = (_e) \
>> +}
>> +
>> +/**
>> + * struct counter_device - Counter data structure
>> + * @name:		name of the device as it appears in the datasheet
>> + * @parent:		optional parent device providing the counters
>> + * @device_state:	internal device state container
>> + * @ops:		callbacks from driver
>> + * @signals:		array of Signals
>> + * @num_signals:	number of Signals specified in @signals
>> + * @counts:		array of Counts
>> + * @num_counts:		number of Counts specified in @counts
>> + * @ext:		optional array of Counter device extensions
>> + * @num_ext:		number of Counter device extensions specified in @ext
>> + * @priv:		optional private data supplied by driver
>> + */
>> +struct counter_device {
>> +	const char			*name;
>> +	struct device			*parent;
>> +	struct counter_device_state	*device_state;
>> +
>> +	const struct counter_ops	*ops;
>> +
>> +	struct counter_signal	*signals;
>> +	size_t			num_signals;
>> +	struct counter_count	*counts;
>> +	size_t			num_counts;
>> +
>> +	const struct counter_device_ext	*ext;
>> +	size_t				num_ext;
>> +
>> +	void	*priv;
>> +};
>> +
>> +enum signal_level {
>> +	SIGNAL_LEVEL_LOW = 0,
>> +	SIGNAL_LEVEL_HIGH
>> +};
>> +
>> +enum signal_value_type {
>> +	SIGNAL_LEVEL = 0
>> +};
>> +
>> +enum count_value_type {
>> +	COUNT_POSITION_UNSIGNED = 0,
>> +	COUNT_POSITION_SIGNED
>> +};
>> +
>> +void set_signal_read_value(struct signal_read_value *const val,
>> +			   const enum signal_value_type type, void *const data);
>> +void set_count_read_value(struct count_read_value *const val,
>> +			  const enum count_value_type type, void *const data);
>> +int get_count_write_value(void *const data, const enum count_value_type type,
>> +			  const struct count_write_value *const val);
>
>I wonder if naming wise, we would be better sticking to the
>noun_verb naming format.
>
>signal_read_value_set
>count_read_value_set
>count_write_value_get
>
>for example?
>
>> +
>> +int counter_register(struct counter_device *const counter);
>> +void counter_unregister(struct counter_device *const counter);
>> +int devm_counter_register(struct device *dev,
>> +			  struct counter_device *const counter);
>> +void devm_counter_unregister(struct device *dev,
>> +			     struct counter_device *const counter);
>> +
>> +#endif /* _COUNTER_H_ */
>

Re: [PATCH v6 3/9] docs: Add Generic Counter interface documentation

[William Breathitt Gray]

On Sun, May 20, 2018 at 04:31:09PM +0100, Jonathan Cameron wrote:
>On Wed, 16 May 2018 13:51:06 -0400
>William Breathitt Gray <vilhelm.gray@gmail.com> wrote:
>
>> This patch adds high-level documentation about the Generic Counter
>> interface.
>> 
>> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
>
>Various comments inline.  I've been doing a lot long reviews recently
>(outside of the kernel world) and keep discovering the old rule that
>everytime you read a document you'll find something else to
>improve :(
>
>Jonathan

But it is good too to have multiple eyes on this -- I have found as an
author my brain tends to skip over minor errors while rereading
passages, so having persons reading it for both the first and subsequent
times helps catch those mistakes I may have overlooked in my mind. :)

>> ---
>>  Documentation/driver-api/generic-counter.rst | 336 +++++++++++++++++++
>>  Documentation/driver-api/index.rst           |   1 +
>>  MAINTAINERS                                  |   1 +
>>  3 files changed, 338 insertions(+)
>>  create mode 100644 Documentation/driver-api/generic-counter.rst
>> 
>> diff --git a/Documentation/driver-api/generic-counter.rst b/Documentation/driver-api/generic-counter.rst
>> new file mode 100644
>> index 000000000000..5c6b9c008c06
>> --- /dev/null
>> +++ b/Documentation/driver-api/generic-counter.rst
>> @@ -0,0 +1,336 @@
>> +.. SPDX-License-Identifier: GPL-2.0
>> +
>> +=========================
>> +Generic Counter Interface
>> +=========================
>> +
>> +Introduction
>> +============
>> +
>> +Counter devices are prevalent within a diverse spectrum of industries.
>> +The ubiquitous presence of these devices necessitates a common interface
>> +and standard of interaction and exposure. This driver API attempts to
>> +resolve the issue of duplicate code found among existing counter device
>> +drivers by introducing a generic counter interface for consumption. The
>> +Generic Counter interface enables drivers to support and expose a common
>> +set of components and functionality present in counter devices.
>> +
>> +Theory
>> +======
>> +
>> +Counter devices can vary greatly in design, but regardless of whether
>> +some devices are quadrature encoder counters or tally counters, all
>> +counter devices consist of a core set of components. This core set of
>> +components, shared by all counter devices, is what forms the essence of
>> +the Generic Counter interface.
>> +
>> +There are three core components to a counter:
>
>Enumerate them here.  If people are reading this as a paged document (pdf etc)
>then the list of 3 as titles of next few sections may not be clear.
>
>* Count
>
>* Signal
>
>* Synapse 
>
>> +
>> +COUNT
>> +-----
>> +A Count represents the count data for a set of Signals. The Generic
>> +Counter interface provides the following available count data types:
>> +
>> +* COUNT_POSITION_UNSIGNED:
>> +  Unsigned integer value representing position.
>> +
>> +* COUNT_POSITION_SIGNED:
>> +  Signed integer value representing position.
>
>Just a thought: As the '0' position is effectively arbitrary is there any
>actual difference between signed and unsigned? If we defined all counters
>to be unsigned and just offset any signed ones so the range still fitted
>would we end up with a simpler interface - there would be no real loss
>of meaning that I can see..  I suppose it might not be what people expect
>though when they see their counters start at a large positive value...

This is something I've been on the fence about for a while. I would
actually prefer the interface to have simply a COUNT_POSITION data type
to represent position and leave it as unsigned; distinguishing between
signed and unsigned position seems ultimately arbitrary given that it's
mathematically just an offset as you have pointed out.

If we were to go down this route, then we'd have a count value that may
always be represented using an unsigned data type, with an offset value
that may always be represented using a signed data type -- the
relationship being such: position = count + offset. Is that correct?

My reason for giving the option for either signed or unsigned position
was to help minimize the work userspace would have to do in order to get
the value in which they're actually interested. I suppose it was a
question of how abstract I want to make the interface -- although,
making it simpler for userspace put more of a burden on the kernel side.

However, the "offset" value route may actually be more robust in the end
because userspace would have to know whether they want a signed or
unsigned position regardless in order to parse, so with count and offet
defined we know they will always be unsigned and signed respectively.

>
>
>
>
>> +
>> +A Count has a count function mode which represents the update behavior
>> +for the count data. The Generic Counter interface provides the following
>> +available count function modes:
>> +
>> +* Increase:
>> +  Accumulated count is incremented.
>> +
>> +* Decrease:
>> +  Accumulated count is decremented.
>> +
>> +* Pulse-Direction:
>> +  Rising edges on quadrature pair signal A updates the respective count.
>> +  The input level of quadrature pair signal B determines direction.
>> +
>Perhaps group the quadrature modes for the point of view of this document?
>Might be slightly easier to read?  
>
>* Quadrature Modes
>
>  - x1 A: etc.
>
>> +* Quadrature x1 A:
>> +  If direction is forward, rising edges on quadrature pair signal A
>> +  updates the respective count; if the direction is backward, falling
>> +  edges on quadrature pair signal A updates the respective count.
>> +  Quadrature encoding determines the direction.
>> +
>> +* Quadrature x1 B:
>> +  If direction is forward, rising edges on quadrature pair signal B
>> +  updates the respective count; if the direction is backward, falling
>> +  edges on quadrature pair signal B updates the respective count.
>> +  Quadrature encoding determines the direction.
>> +
>> +* Quadrature x2 A:
>> +  Any state transition on quadrature pair signal A updates the
>> +  respective count. Quadrature encoding determines the direction.
>> +
>> +* Quadrature x2 B:
>> +  Any state transition on quadrature pair signal B updates the
>> +  respective count. Quadrature encoding determines the direction.
>> +
>> +* Quadrature x2 Rising:
>> +  Rising edges on either quadrature pair signals updates the respective
>> +  count. Quadrature encoding determines the direction.
>
>This one I've never met.  Really? There are devices who do this form
>of crazy? It gives really uneven counting and I'm failing to see when
>it would ever make sense...  References for these odd corner cases
>would be good.
>
>
>__|---|____|-----|____
>____|----|____|-----|____
>
>001122222223334444444

That's the same reaction I had when I discovered this -- in fact the
STM32 LP Timer is the first time I've come across such a quadrature
mode. I'm not sure of the use case for this mode, because positioning
wouldn't be precise as you've pointed out. Perhaps Fabrice or Benjamin
can probe the ST guys responsible for this design choice to figure out
the rationale.

I'm leaving in these modes for now, as they do exist in the STM32 LP
Timer, but it does make me curious what the intentions for them were
(perhaps use cases outside of traditional quadrature encoder
positioning).

>
>
>> +
>> +* Quadrature x2 Falling:
>> +  Falling edges on either quadrature pair signals updates the respective
>> +  count. Quadrature encoding determines the direction.
>> +
>> +* Quadrature x4:
>> +  Any state transition on either quadrature pair signals updates the
>> +  respective count. Quadrature encoding determines the direction.
>> +
>> +A Count has a set of one or more associated Signals.
>> +
>> +SIGNAL
>> +------
>> +A Signal represents a counter input data; this is the input data that is
>> +analyzed by the counter to determine the count data; e.g. a quadrature
>> +signal output line of a rotary encoder. Not all counter devices provide
>> +user access to the Signal data.
>> +
>> +The Generic Counter interface provides the following available signal
>> +data types for when the Signal data is available for user access:
>> +
>> +* SIGNAL_LEVEL_LOW:
>> +  Signal line is in a low state.
>> +
>> +* SIGNAL_LEVEL_HIGH:
>> +  Signal line is in a high state.
>> +
>> +A Signal may be associated with one or more Counts.
>> +
>> +SYNAPSE
>> +-------
>> +A Synapse represents the association of a Signal with a respective
>> +Count. Signal data affects respective Count data, and the Synapse
>> +represents this relationship.
>> +
>> +The Synapse action mode specifies the Signal data condition which
>> +triggers the respective Count's count function evaluation to update the
>> +count data. The Generic Counter interface provides the following
>> +available action modes:
>> +
>> +* None:
>> +  Signal does not trigger the count function. In Pulse-Direction count
>> +  function mode, this Signal is evaluated as Direction.
>> +
>> +* Rising Edge:
>> +  Low state transitions to high state.
>> +
>> +* Falling Edge:
>> +  High state transitions to low state.
>> +
>> +* Both Edges:
>> +  Any state transition.
>> +
>> +A counter is defined as a set of input signals associated with count
>> +data that are generated by the evaluation of the state of the associated
>> +input signals as defined by the respective count functions. Within the
>> +context of the Generic Counter interface, a counter consists of Counts
>> +each associated with a set of Signals, whose respective Synapse
>> +instances represent the count function update conditions for the
>> +associated Counts.
>> +
>> +Paradigm
>> +========
>> +
>> +The most basic counter device may be expressed as a single Count
>> +associated with a single Signal via a single Synapse. Take for example
>> +a counter device which simply accumulates a count of rising edges on a
>> +source input line::
>> +
>> +                Count                Synapse        Signal
>> +                -----                -------        ------
>> +        +---------------------+
>> +        | Data: Count         |    Rising Edge     ________
>> +        | Function: Increase  |  <-------------   / Source \
>> +        |                     |                  ____________
>> +        +---------------------+
>> +
>> +In this example, the Signal is a source input line with a pulsing
>> +voltage, while the Count is a persistent count value which is repeatedly
>> +incremented. The Signal is associated with the respective Count via a
>> +Synapse. The increase function is triggered by the Signal data condition
>> +specified by the Synapse -- in this case a rising edge condition on the
>> +voltage input line. In summary, the counter device existence and
>> +behavior is aptly represented by respective Count, Signal, and Synapse
>> +components: a rising edge condition triggers an increase function on an
>> +accumulating count datum.
>> +
>> +A counter device is not limited to a single Signal; in fact, in theory
>> +many Signals may be associated with even a single Count. For example, a
>> +quadrature encoder counter device can keep track of position based on
>> +the states of two input lines::
>> +
>> +                   Count                 Synapse     Signal
>> +                   -----                 -------     ------
>> +        +-------------------------+
>> +        | Data: Position          |    Both Edges     ___
>> +        | Function: Quadrature x4 |  <------------   / A \
>> +        |                         |                 _______
>> +        |                         |
>> +        |                         |    Both Edges     ___
>> +        |                         |  <------------   / B \
>> +        |                         |                 _______
>> +        +-------------------------+
>> +
>> +In this example, two Signals (quadrature encoder lines A and B) are
>> +associated with a single Count: a rising or falling edge on either A or
>> +B triggers the "Quadrature x4" function which determines the direction
>> +of movement and updates the respective position data. The "Quadrature
>> +x4" function is likely implemented in the hardware of the quadrature
>> +encoder counter device; the Count, Signals, and Synapses simply
>> +represent this hardware behavior and functionality.
>> +
>> +Signals associated with the same Count can have differing Synapse action
>> +mode conditions. For example, a quadrature encoder counter device
>> +operating in a non-quadrature Pulse-Direction mode could have one input
>> +line dedicated for movement and a second input line dedicated for
>> +direction::
>> +
>> +                   Count                   Synapse      Signal
>> +                   -----                   -------      ------
>> +        +---------------------------+
>> +        | Data: Position            |    Rising Edge     ___
>> +        | Function: Pulse-Direction |  <-------------   / A \ (Movement)
>> +        |                           |                  _______
>> +        |                           |
>> +        |                           |       None         ___
>> +        |                           |  <-------------   / B \ (Direction)
>> +        |                           |                  _______
>> +        +---------------------------+
>> +
>> +Only Signal A triggers the "Pulse-Direction" update function, but the
>> +instantaneous state of Signal B is still required in order to know the
>> +direction so that the position data may be properly updated. Ultimately,
>> +both Signals are associated with the same Count via two respective
>> +Synapses, but only one Synapse has an active action mode condition which
>> +triggers the respective count function while the other is left with a
>> +"None" condition action mode to indicate its respective Signal's
>> +availability for state evaluation despite its non-triggering mode.
>> +
>> +Keep in mind that the Signal, Synapse, and Count are abstract
>> +representations which do not need to be closely married to their
>> +respective physical sources. This allows the user of a counter to
>> +divorce themselves from the nuances of physical components (such as
>> +whether an input line is differential or single-ended) and instead focus
>> +on the core idea of what the data and process represent (e.g. position
>> +as interpreted from quadrature encoding data).
>> +
>> +Userspace Interface
>> +===================
>> +
>> +Several sysfs attributes are generated by the Generic Counter interface,
>> +and reside under the /sys/bus/counter/devices/counterX directory, where
>> +counterX refers to the respective counter device. Please see
>> +Documentation/ABI/testing/sys-bus-counter-generic-sysfs for detailed
>> +information on each Generic Counter interface sysfs attribute.
>> +
>> +Through these sysfs attributes, programs and scripts may interact with
>> +the Generic Counter paradigm Counts, Signals, and Synapses of respective
>> +counter devices.
>> +
>> +Driver API
>> +==========
>> +
>> +Driver authors may utilize the Generic Counter interface in their code
>> +by including the include/linux/iio/counter.h header file. This header
>
>Didn't this move?

Yes you are correct, looks like an oversight I made. I'll cleanup this
and the rest with the next revision then.

William Breathitt Gray

>
>> +file provides several core data structures, function prototypes, and
>> +macros for defining a counter device.
>> +
>> +.. kernel-doc:: include/linux/counter.h
>> +   :internal:
>> +
>> +.. kernel-doc:: drivers/counter/generic-counter.c
>> +   :export:
>> +
>> +Implementation
>> +==============
>> +
>> +To support a counter device, a driver must first allocate the available
>> +Counter Signals via counter_signal structures. These Signals should
>> +be stored as an array and set to the signals array member of an
>> +allocated counter_device structure before the Counter is registered to
>> +the system.
>> +
>> +Counter Counts may be allocated via counter_count structures, and
>> +respective Counter Signal associations (Synapses) made via
>> +counter_synapse structures. Associated counter_synapse structures are
>> +stored as an array and set to the the synapses array member of the
>> +respective counter_count structure. These counter_count structures are
>> +set to the counts array member of an allocated counter_device structure
>> +before the Counter is registered to the system.
>> +
>> +Driver callbacks should be provided to the counter_device structure via
>> +a constant counter_ops structure in order to communicate with the
>> +device: to read and write various Signals and Counts, and to set and get
>> +the "action mode" and "function mode" for various Synapses and Counts
>> +respectively.
>> +
>> +A defined counter_device structure may be registered to the system by
>> +passing it to the counter_register function, and unregistered by passing
>> +it to the counter_unregister function. Similarly, the
>> +devm_counter_register and devm_counter_unregister functions may be used
>> +if device memory-managed registration is desired.
>> +
>> +Extension sysfs attributes can be created for auxiliary functionality
>> +and data by passing in defined counter_device_ext, counter_count_ext,
>> +and counter_signal_ext structures. In these cases, the
>> +counter_device_ext structure is used for global configuration of the
>> +respective Counter device, while the counter_count_ext and
>> +counter_signal_ext structures allow for auxiliary exposure and
>> +configuration of a specific Count or Signal respectively.
>> +
>> +Architecture
>> +============
>> +
>> +When the Generic Counter interface counter module is loaded, the
>> +counter_init function is called which registers a bus_type named
>> +"counter" to the system. Subsequently, when the module is unloaded, the
>> +counter_exit function is called which unregisters the bus_type named
>> +"counter" from the system.
>> +
>> +Counter devices are registered to the system via the counter_register
>> +function, and later removed via the counter_unregister function. The
>> +counter_register function establishes a unique ID for the Counter
>> +device and creates a respective sysfs directory, where X is the
>> +mentioned unique ID:
>> +
>> +    /sys/bus/counter/devices/counterX
>> +
>> +Sysfs attributes are created within the counterX directory to expose
>> +functionality, configurations, and data relating to the Counts, Signals,
>> +and Synapses of the Counter device, as well as options and information
>> +for the Counter device itself.
>> +
>> +Each Signal has a directory created to house its relevant sysfs
>> +attributes, where Y is the unique ID of the respective Signal:
>> +
>> +    /sys/bus/counter/devices/counterX/signalY
>> +
>> +Similarly, each Count has a directory created to house its relevant
>> +sysfs attributes, where Y is the unique ID of the respective Count:
>> +
>> +    /sys/bus/counter/devices/counterX/countY
>> +
>> +For a more detailed breakdown of the available Generic Counter interface
>> +sysfs attributes, please refer to the
>> +Documentation/ABI/testing/sys-bus-counter file.
>> +
>> +The Signals and Counts associated with the Counter device are registered
>> +to the system as well by the counter_register function. The
>> +signal_read/signal_write driver callbacks are associated with their
>> +respective Signal attributes, while the count_read/count_write and
>> +function_get/function_set driver callbacks are associated with their
>> +respective Count attributes; similarly, the same is true for the
>> +action_get/action_set driver callbacks and their respective Synapse
>> +attributes. If a driver callback is left undefined, then the respective
>> +read/write permission is left disabled for the relevant attributes.
>> +
>> +Similarly, extension sysfs attributes are created for the defined
>> +counter_device_ext, counter_count_ext, and counter_signal_ext
>> +structures that are passed in.
>> diff --git a/Documentation/driver-api/index.rst b/Documentation/driver-api/index.rst
>> index 6d8352c0f354..5fd747c4f2ce 100644
>> --- a/Documentation/driver-api/index.rst
>> +++ b/Documentation/driver-api/index.rst
>> @@ -25,6 +25,7 @@ available subsections can be seen below.
>>     frame-buffer
>>     regulator
>>     iio/index
>> +   generic-counter
>>     input
>>     usb/index
>>     pci
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index 1413e3eb49e5..7a01aa63fb33 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -3674,6 +3674,7 @@ M:	William Breathitt Gray <vilhelm.gray@gmail.com>
>>  L:	linux-iio@vger.kernel.org
>>  S:	Maintained
>>  F:	Documentation/ABI/testing/sysfs-bus-counter*
>> +F:	Documentation/driver-api/generic-counter.rst
>>  F:	drivers/counter/
>>  F:	include/linux/counter.h
>>  
>

Re: [PATCH v6 4/9] counter: 104-quad-8: Add Generic Counter interface support

[William Breathitt Gray]

On Sun, May 20, 2018 at 04:42:53PM +0100, Jonathan Cameron wrote:
>On Wed, 16 May 2018 13:51:25 -0400
>William Breathitt Gray <vilhelm.gray@gmail.com> wrote:
>
>> This patch adds support for the Generic Counter interface to the
>> 104-QUAD-8 driver. The existing 104-QUAD-8 device interface should not
>> be affected by this patch; all changes are intended as supplemental
>> additions as perceived by the user.
>> 
>> Generic Counter Counts are created for the eight quadrature channel
>> counts, as well as their respective quadrature A and B Signals (which
>> are associated via respective Synapse structures) and respective index
>> Signals.
>> 
>> The new Generic Counter interface sysfs attributes are intended to
>> expose the same functionality and data available via the existing
>> 104-QUAD-8 IIO device interface; the Generic Counter interface serves
>> to provide the respective functionality and data in a standard way
>> expected of counter devices.
>> 
>> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
>
>A few general comments that applied just as well to the original driver
>as they do to the modified version.
>
>I wonder if this would be easier to review as two patches.
>Move the driver then add the counter interfaces?
>
>Right now people kind of have to review the old IIO driver and
>all the new stuff which is a big job..
>
>Jonathan

This looks like more simple cleanup, so I expect to incorporate your
suggestions without problem here as well. I'll also try to make the code
easier to read by writing some defines for the magic numbers throughout.

William Breathitt Gray

>> ---
>>  MAINTAINERS                      |    4 +-
>>  drivers/counter/104-quad-8.c     | 1335 ++++++++++++++++++++++++++++++
>>  drivers/counter/Kconfig          |   21 +
>>  drivers/counter/Makefile         |    2 +
>>  drivers/iio/counter/104-quad-8.c |  596 -------------
>>  drivers/iio/counter/Kconfig      |   17 -
>>  drivers/iio/counter/Makefile     |    1 -
>>  7 files changed, 1360 insertions(+), 616 deletions(-)
>>  create mode 100644 drivers/counter/104-quad-8.c
>>  delete mode 100644 drivers/iio/counter/104-quad-8.c
>> 
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index 7a01aa63fb33..f11bf7885aeb 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -266,12 +266,12 @@ L:	linux-gpio@vger.kernel.org
>>  S:	Maintained
>>  F:	drivers/gpio/gpio-104-idio-16.c
>>  
>> -ACCES 104-QUAD-8 IIO DRIVER
>> +ACCES 104-QUAD-8 DRIVER
>>  M:	William Breathitt Gray <vilhelm.gray@gmail.com>
>>  L:	linux-iio@vger.kernel.org
>>  S:	Maintained
>>  F:	Documentation/ABI/testing/sysfs-bus-iio-counter-104-quad-8
>> -F:	drivers/iio/counter/104-quad-8.c
>> +F:	drivers/counter/104-quad-8.c
>>  
>>  ACCES PCI-IDIO-16 GPIO DRIVER
>>  M:	William Breathitt Gray <vilhelm.gray@gmail.com>
>> diff --git a/drivers/counter/104-quad-8.c b/drivers/counter/104-quad-8.c
>> new file mode 100644
>> index 000000000000..7c72fb72d660
>> --- /dev/null
>> +++ b/drivers/counter/104-quad-8.c
>> @@ -0,0 +1,1335 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>
>If you are happy with SPDX drop the GPL text below to keep things
>short.
>
>> +/*
>> + * IIO driver for the ACCES 104-QUAD-8
>> + * Copyright (C) 2016 William Breathitt Gray
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License, version 2, as
>> + * published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope that it will be useful, but
>> + * WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>> + * General Public License for more details.
>> + *
>> + * This driver supports the ACCES 104-QUAD-8 and ACCES 104-QUAD-4.
>> + */
>> +#include <linux/bitops.h>
>...
>> +static int quad8_probe(struct device *dev, unsigned int id)
>> +{
>> +	struct iio_dev *indio_dev;
>> +	struct quad8_iio *quad8iio;
>> +	int i, j;
>> +	unsigned int base_offset;
>> +	int err;
>> +
>> +	if (!devm_request_region(dev, base[id], QUAD8_EXTENT, dev_name(dev))) {
>> +		dev_err(dev, "Unable to lock port addresses (0x%X-0x%X)\n",
>> +			base[id], base[id] + QUAD8_EXTENT);
>> +		return -EBUSY;
>> +	}
>> +
>> +	/* Allocate IIO device; this also allocates driver data structure */
>> +	indio_dev = devm_iio_device_alloc(dev, sizeof(*quad8iio));
>> +	if (!indio_dev)
>> +		return -ENOMEM;
>> +
>> +	/* Initialize IIO device */
>> +	indio_dev->info = &quad8_info;
>> +	indio_dev->modes = INDIO_DIRECT_MODE;
>> +	indio_dev->num_channels = ARRAY_SIZE(quad8_channels);
>> +	indio_dev->channels = quad8_channels;
>> +	indio_dev->name = dev_name(dev);
>> +	indio_dev->dev.parent = dev;
>> +
>> +	/* Initialize Counter device and driver data */
>> +	quad8iio = iio_priv(indio_dev);
>> +	quad8iio->counter.name = dev_name(dev);
>> +	quad8iio->counter.parent = dev;
>> +	quad8iio->counter.ops = &quad8_ops;
>> +	quad8iio->counter.counts = quad8_counts;
>> +	quad8iio->counter.num_counts = ARRAY_SIZE(quad8_counts);
>> +	quad8iio->counter.signals = quad8_signals;
>> +	quad8iio->counter.num_signals = ARRAY_SIZE(quad8_signals);
>> +	quad8iio->counter.priv = quad8iio;
>> +	quad8iio->base = base[id];
>> +
>> +	/* Reset all counters and disable interrupt function */
>> +	outb(0x01, base[id] + 0x11);
>> +	/* Set initial configuration for all counters */
>> +	for (i = 0; i < QUAD8_NUM_COUNTERS; i++) {
>> +		base_offset = base[id] + 2 * i;
>> +		/* Reset Byte Pointer */
>> +		outb(0x01, base_offset + 1);
>
>I'm going to be fussy.  There are lots of values
>in here that look like register bits and you could exchange much of
>this documentation for a some good defines...
>
>Taking base_offset + 1 bits 5 and 6 look to select the actual register
>and the rest of them do the control.
>
>Anyhow, not critical but the readability of this code could be improved
>somewhat.
>
>> +		/* Reset Preset Register */
>> +		for (j = 0; j < 3; j++)
>> +			outb(0x00, base_offset);
>> +		/* Reset Borrow, Carry, Compare, and Sign flags */
>> +		outb(0x04, base_offset + 1);
>> +		/* Reset Error flag */
>> +		outb(0x06, base_offset + 1);
>> +		/* Binary encoding; Normal count; non-quadrature mode */
>> +		outb(0x20, base_offset + 1);
>> +		/* Disable A and B inputs; preset on index; FLG1 as Carry */
>> +		outb(0x40, base_offset + 1);
>> +		/* Disable index function; negative index polarity */
>> +		outb(0x60, base_offset + 1);
>> +	}
>> +	/* Enable all counters */
>> +	outb(0x00, base[id] + 0x11);
>> +
>> +	/* Register IIO device */
>> +	err = devm_iio_device_register(dev, indio_dev);
>> +	if (err)
>> +		return err;
>> +
>> +	/* Register Counter device */
>> +	return devm_counter_register(dev, &quad8iio->counter);
>> +}
>> +
>> +static struct isa_driver quad8_driver = {
>> +	.probe = quad8_probe,
>> +	.driver = {
>> +		.name = "104-quad-8"
>> +	}
>> +};
>> +
>> +module_isa_driver(quad8_driver, num_quad8);
>> +
>> +MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
>> +MODULE_DESCRIPTION("ACCES 104-QUAD-8 IIO driver");
>> +MODULE_LICENSE("GPL v2");
>> diff --git a/drivers/counter/Kconfig b/drivers/counter/Kconfig
>> index 65fa92abd5a4..73f03372484f 100644
>> --- a/drivers/counter/Kconfig
>> +++ b/drivers/counter/Kconfig
>> @@ -16,3 +16,24 @@ menuconfig COUNTER
>>  	  consumption. The Generic Counter interface enables drivers to support
>>  	  and expose a common set of components and functionality present in
>>  	  counter devices.
>> +
>> +if COUNTER
>> +
>> +config 104_QUAD_8
>> +	tristate "ACCES 104-QUAD-8 driver"
>> +	depends on PC104 && X86 && IIO
>> +	select ISA_BUS_API
>> +	help
>> +	  Say yes here to build support for the ACCES 104-QUAD-8 quadrature
>> +	  encoder counter/interface device family (104-QUAD-8, 104-QUAD-4).
>> +
>> +	  Performing a write to a counter's IIO_CHAN_INFO_RAW sets the counter and
>> +	  also clears the counter's respective error flag. Although the counters
>> +	  have a 25-bit range, only the lower 24 bits may be set, either directly
>> +	  or via a counter's preset attribute. Interrupts are not supported by
>> +	  this driver.
>
>This text probably wants to be updated to reflect the new counter subsystem support..
>
>> +
>> +	  The base port addresses for the devices may be configured via the base
>> +	  array module parameter.
>> +
>> +endif # COUNTER
>> diff --git a/drivers/counter/Makefile b/drivers/counter/Makefile
>> index ad1ba7109cdc..23a4f6263e45 100644
>> --- a/drivers/counter/Makefile
>> +++ b/drivers/counter/Makefile
>> @@ -6,3 +6,5 @@
>>  
>>  obj-$(CONFIG_COUNTER) += counter.o
>>  counter-y := generic-counter.o
>> +
>> +obj-$(CONFIG_104_QUAD_8)	+= 104-quad-8.o
>> diff --git a/drivers/iio/counter/104-quad-8.c b/drivers/iio/counter/104-quad-8.c
>...

Re: [PATCH v6 9/9] iio: counter: Remove IIO counter subdirectory

[William Breathitt Gray]

On Sun, May 20, 2018 at 04:53:02PM +0100, Jonathan Cameron wrote:
>On Wed, 16 May 2018 13:52:39 -0400
>William Breathitt Gray <vilhelm.gray@gmail.com> wrote:
>
>> This patch removes the IIO counter subdirectory which is now superceded
>> by the Counter subsystem. Deprecation warnings are added to the
>> documentation of the relevant IIO counter sysfs attributes.
>> 
>> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
>
>Please drop the directory when it becomes empty rather than in a later
>patch.  IIRC there are some issues with empty Makefiles that will
>make building inbetween tricky.
>
>For the deprecated markings.
>
>Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

I'll have the directory removal occur with the removal of the last
module then when the directory becomes empty.

Regarding the deprecation markings, should I select a specific kernel
version to date the removal of these attributes, or leave the future
date open as this patch is now?

William Breathitt Gray

>
>> ---
>>  Documentation/ABI/testing/sysfs-bus-iio          |  8 ++++++++
>>  .../ABI/testing/sysfs-bus-iio-counter-104-quad-8 | 16 ++++++++++++++++
>>  drivers/iio/Kconfig                              |  1 -
>>  drivers/iio/Makefile                             |  1 -
>>  drivers/iio/counter/Kconfig                      |  8 --------
>>  drivers/iio/counter/Makefile                     |  5 -----
>>  6 files changed, 24 insertions(+), 15 deletions(-)
>>  delete mode 100644 drivers/iio/counter/Kconfig
>>  delete mode 100644 drivers/iio/counter/Makefile
>> 
>> diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
>> index 731146c3b138..6115d97b075e 100644
>> --- a/Documentation/ABI/testing/sysfs-bus-iio
>> +++ b/Documentation/ABI/testing/sysfs-bus-iio
>> @@ -1637,6 +1637,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_raw
>>  KernelVersion:	4.10
>>  Contact:	linux-iio@vger.kernel.org
>>  Description:
>> +		This interface is deprecated; please use the Counter subsystem.
>> +
>>  		Raw counter device counts from channel Y. For quadrature
>>  		counters, multiplication by an available [Y]_scale results in
>>  		the counts of a single quadrature signal phase from channel Y.
>> @@ -1645,6 +1647,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_indexY_raw
>>  KernelVersion:	4.10
>>  Contact:	linux-iio@vger.kernel.org
>>  Description:
>> +		This interface is deprecated; please use the Counter subsystem.
>> +
>>  		Raw counter device index value from channel Y. This attribute
>>  		provides an absolute positional reference (e.g. a pulse once per
>>  		revolution) which may be used to home positional systems as
>> @@ -1654,6 +1658,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_count_count_direction_available
>>  KernelVersion:	4.12
>>  Contact:	linux-iio@vger.kernel.org
>>  Description:
>> +		This interface is deprecated; please use the Counter subsystem.
>> +
>>  		A list of possible counting directions which are:
>>  		- "up"	: counter device is increasing.
>>  		- "down": counter device is decreasing.
>> @@ -1662,4 +1668,6 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_count_direction
>>  KernelVersion:	4.12
>>  Contact:	linux-iio@vger.kernel.org
>>  Description:
>> +		This interface is deprecated; please use the Counter subsystem.
>> +
>>  		Raw counter device counters direction for channel Y.
>> diff --git a/Documentation/ABI/testing/sysfs-bus-iio-counter-104-quad-8 b/Documentation/ABI/testing/sysfs-bus-iio-counter-104-quad-8
>> index 7fac2c268d9a..bac3d0d48b7b 100644
>> --- a/Documentation/ABI/testing/sysfs-bus-iio-counter-104-quad-8
>> +++ b/Documentation/ABI/testing/sysfs-bus-iio-counter-104-quad-8
>> @@ -6,6 +6,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_index_synchronous_mode_available
>>  KernelVersion:	4.10
>>  Contact:	linux-iio@vger.kernel.org
>>  Description:
>> +		This interface is deprecated; please use the Counter subsystem.
>> +
>>  		Discrete set of available values for the respective counter
>>  		configuration are listed in this file.
>>  
>> @@ -13,6 +15,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_count_mode
>>  KernelVersion:	4.10
>>  Contact:	linux-iio@vger.kernel.org
>>  Description:
>> +		This interface is deprecated; please use the Counter subsystem.
>> +
>>  		Count mode for channel Y. Four count modes are available:
>>  		normal, range limit, non-recycle, and modulo-n. The preset value
>>  		for channel Y is used by the count mode where required.
>> @@ -47,6 +51,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_noise_error
>>  KernelVersion:	4.10
>>  Contact:	linux-iio@vger.kernel.org
>>  Description:
>> +		This interface is deprecated; please use the Counter subsystem.
>> +
>>  		Read-only attribute that indicates whether excessive noise is
>>  		present at the channel Y count inputs in quadrature clock mode;
>>  		irrelevant in non-quadrature clock mode.
>> @@ -55,6 +61,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_preset
>>  KernelVersion:	4.10
>>  Contact:	linux-iio@vger.kernel.org
>>  Description:
>> +		This interface is deprecated; please use the Counter subsystem.
>> +
>>  		If the counter device supports preset registers, the preset
>>  		count for channel Y is provided by this attribute.
>>  
>> @@ -62,6 +70,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_quadrature_mode
>>  KernelVersion:	4.10
>>  Contact:	linux-iio@vger.kernel.org
>>  Description:
>> +		This interface is deprecated; please use the Counter subsystem.
>> +
>>  		Configure channel Y counter for non-quadrature or quadrature
>>  		clock mode. Selecting non-quadrature clock mode will disable
>>  		synchronous load mode. In quadrature clock mode, the channel Y
>> @@ -83,6 +93,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_set_to_preset_on_index
>>  KernelVersion:	4.10
>>  Contact:	linux-iio@vger.kernel.org
>>  Description:
>> +		This interface is deprecated; please use the Counter subsystem.
>> +
>>  		Whether to set channel Y counter with channel Y preset value
>>  		when channel Y index input is active, or continuously count.
>>  		Valid attribute values are boolean.
>> @@ -91,6 +103,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_indexY_index_polarity
>>  KernelVersion:	4.10
>>  Contact:	linux-iio@vger.kernel.org
>>  Description:
>> +		This interface is deprecated; please use the Counter subsystem.
>> +
>>  		Active level of channel Y index input; irrelevant in
>>  		non-synchronous load mode.
>>  
>> @@ -98,6 +112,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_indexY_synchronous_mode
>>  KernelVersion:	4.10
>>  Contact:	linux-iio@vger.kernel.org
>>  Description:
>> +		This interface is deprecated; please use the Counter subsystem.
>> +
>>  		Configure channel Y counter for non-synchronous or synchronous
>>  		load mode. Synchronous load mode cannot be selected in
>>  		non-quadrature clock mode.
>> diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
>> index d69e85a8bdc3..1152efad91a1 100644
>> --- a/drivers/iio/Kconfig
>> +++ b/drivers/iio/Kconfig
>> @@ -74,7 +74,6 @@ source "drivers/iio/afe/Kconfig"
>>  source "drivers/iio/amplifiers/Kconfig"
>>  source "drivers/iio/chemical/Kconfig"
>>  source "drivers/iio/common/Kconfig"
>> -source "drivers/iio/counter/Kconfig"
>>  source "drivers/iio/dac/Kconfig"
>>  source "drivers/iio/dummy/Kconfig"
>>  source "drivers/iio/frequency/Kconfig"
>> diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile
>> index d8cba9c229c0..7bdd31f1b88f 100644
>> --- a/drivers/iio/Makefile
>> +++ b/drivers/iio/Makefile
>> @@ -20,7 +20,6 @@ obj-y += amplifiers/
>>  obj-y += buffer/
>>  obj-y += chemical/
>>  obj-y += common/
>> -obj-y += counter/
>>  obj-y += dac/
>>  obj-y += dummy/
>>  obj-y += gyro/
>> diff --git a/drivers/iio/counter/Kconfig b/drivers/iio/counter/Kconfig
>> deleted file mode 100644
>> index 95a7a0df6cac..000000000000
>> --- a/drivers/iio/counter/Kconfig
>> +++ /dev/null
>> @@ -1,8 +0,0 @@
>> -#
>> -# Counter devices
>> -#
>> -# When adding new entries keep the list in alphabetical order
>> -
>> -menu "Counters"
>> -
>> -endmenu
>> diff --git a/drivers/iio/counter/Makefile b/drivers/iio/counter/Makefile
>> deleted file mode 100644
>> index 8fd3d954775a..000000000000
>> --- a/drivers/iio/counter/Makefile
>> +++ /dev/null
>> @@ -1,5 +0,0 @@
>> -#
>> -# Makefile for IIO counter devices
>> -#
>> -
>> -# When adding new entries keep the list in alphabetical order
>

Re: [PATCH v6 9/9] iio: counter: Remove IIO counter subdirectory

[Jonathan Cameron]

On Mon, 21 May 2018 09:58:28 -0400
William Breathitt Gray <vilhelm.gray@gmail.com> wrote:

> On Sun, May 20, 2018 at 04:53:02PM +0100, Jonathan Cameron wrote:
> >On Wed, 16 May 2018 13:52:39 -0400
> >William Breathitt Gray <vilhelm.gray@gmail.com> wrote:
> >  
> >> This patch removes the IIO counter subdirectory which is now superceded
> >> by the Counter subsystem. Deprecation warnings are added to the
> >> documentation of the relevant IIO counter sysfs attributes.
> >> 
> >> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>  
> >
> >Please drop the directory when it becomes empty rather than in a later
> >patch.  IIRC there are some issues with empty Makefiles that will
> >make building inbetween tricky.
> >
> >For the deprecated markings.
> >
> >Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>  
> 
> I'll have the directory removal occur with the removal of the last
> module then when the directory becomes empty.
> 
> Regarding the deprecation markings, should I select a specific kernel
> version to date the removal of these attributes, or leave the future
> date open as this patch is now?

Leave it open.  The ultimate test is whether it is actually enough of a burden
to make us want to clean up the deprecated interface.

This burden may be that it is a pain to implement something new, or to test
or to maintain the code (or something I haven't thought of).

If it's not it may stay there for ever.

Jonathan
> 
> William Breathitt Gray
> 
> >  
> >> ---
> >>  Documentation/ABI/testing/sysfs-bus-iio          |  8 ++++++++
> >>  .../ABI/testing/sysfs-bus-iio-counter-104-quad-8 | 16 ++++++++++++++++
> >>  drivers/iio/Kconfig                              |  1 -
> >>  drivers/iio/Makefile                             |  1 -
> >>  drivers/iio/counter/Kconfig                      |  8 --------
> >>  drivers/iio/counter/Makefile                     |  5 -----
> >>  6 files changed, 24 insertions(+), 15 deletions(-)
> >>  delete mode 100644 drivers/iio/counter/Kconfig
> >>  delete mode 100644 drivers/iio/counter/Makefile
> >> 
> >> diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
> >> index 731146c3b138..6115d97b075e 100644
> >> --- a/Documentation/ABI/testing/sysfs-bus-iio
> >> +++ b/Documentation/ABI/testing/sysfs-bus-iio
> >> @@ -1637,6 +1637,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_raw
> >>  KernelVersion:	4.10
> >>  Contact:	linux-iio@vger.kernel.org
> >>  Description:
> >> +		This interface is deprecated; please use the Counter subsystem.
> >> +
> >>  		Raw counter device counts from channel Y. For quadrature
> >>  		counters, multiplication by an available [Y]_scale results in
> >>  		the counts of a single quadrature signal phase from channel Y.
> >> @@ -1645,6 +1647,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_indexY_raw
> >>  KernelVersion:	4.10
> >>  Contact:	linux-iio@vger.kernel.org
> >>  Description:
> >> +		This interface is deprecated; please use the Counter subsystem.
> >> +
> >>  		Raw counter device index value from channel Y. This attribute
> >>  		provides an absolute positional reference (e.g. a pulse once per
> >>  		revolution) which may be used to home positional systems as
> >> @@ -1654,6 +1658,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_count_count_direction_available
> >>  KernelVersion:	4.12
> >>  Contact:	linux-iio@vger.kernel.org
> >>  Description:
> >> +		This interface is deprecated; please use the Counter subsystem.
> >> +
> >>  		A list of possible counting directions which are:
> >>  		- "up"	: counter device is increasing.
> >>  		- "down": counter device is decreasing.
> >> @@ -1662,4 +1668,6 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_count_direction
> >>  KernelVersion:	4.12
> >>  Contact:	linux-iio@vger.kernel.org
> >>  Description:
> >> +		This interface is deprecated; please use the Counter subsystem.
> >> +
> >>  		Raw counter device counters direction for channel Y.
> >> diff --git a/Documentation/ABI/testing/sysfs-bus-iio-counter-104-quad-8 b/Documentation/ABI/testing/sysfs-bus-iio-counter-104-quad-8
> >> index 7fac2c268d9a..bac3d0d48b7b 100644
> >> --- a/Documentation/ABI/testing/sysfs-bus-iio-counter-104-quad-8
> >> +++ b/Documentation/ABI/testing/sysfs-bus-iio-counter-104-quad-8
> >> @@ -6,6 +6,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_index_synchronous_mode_available
> >>  KernelVersion:	4.10
> >>  Contact:	linux-iio@vger.kernel.org
> >>  Description:
> >> +		This interface is deprecated; please use the Counter subsystem.
> >> +
> >>  		Discrete set of available values for the respective counter
> >>  		configuration are listed in this file.
> >>  
> >> @@ -13,6 +15,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_count_mode
> >>  KernelVersion:	4.10
> >>  Contact:	linux-iio@vger.kernel.org
> >>  Description:
> >> +		This interface is deprecated; please use the Counter subsystem.
> >> +
> >>  		Count mode for channel Y. Four count modes are available:
> >>  		normal, range limit, non-recycle, and modulo-n. The preset value
> >>  		for channel Y is used by the count mode where required.
> >> @@ -47,6 +51,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_noise_error
> >>  KernelVersion:	4.10
> >>  Contact:	linux-iio@vger.kernel.org
> >>  Description:
> >> +		This interface is deprecated; please use the Counter subsystem.
> >> +
> >>  		Read-only attribute that indicates whether excessive noise is
> >>  		present at the channel Y count inputs in quadrature clock mode;
> >>  		irrelevant in non-quadrature clock mode.
> >> @@ -55,6 +61,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_preset
> >>  KernelVersion:	4.10
> >>  Contact:	linux-iio@vger.kernel.org
> >>  Description:
> >> +		This interface is deprecated; please use the Counter subsystem.
> >> +
> >>  		If the counter device supports preset registers, the preset
> >>  		count for channel Y is provided by this attribute.
> >>  
> >> @@ -62,6 +70,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_quadrature_mode
> >>  KernelVersion:	4.10
> >>  Contact:	linux-iio@vger.kernel.org
> >>  Description:
> >> +		This interface is deprecated; please use the Counter subsystem.
> >> +
> >>  		Configure channel Y counter for non-quadrature or quadrature
> >>  		clock mode. Selecting non-quadrature clock mode will disable
> >>  		synchronous load mode. In quadrature clock mode, the channel Y
> >> @@ -83,6 +93,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_countY_set_to_preset_on_index
> >>  KernelVersion:	4.10
> >>  Contact:	linux-iio@vger.kernel.org
> >>  Description:
> >> +		This interface is deprecated; please use the Counter subsystem.
> >> +
> >>  		Whether to set channel Y counter with channel Y preset value
> >>  		when channel Y index input is active, or continuously count.
> >>  		Valid attribute values are boolean.
> >> @@ -91,6 +103,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_indexY_index_polarity
> >>  KernelVersion:	4.10
> >>  Contact:	linux-iio@vger.kernel.org
> >>  Description:
> >> +		This interface is deprecated; please use the Counter subsystem.
> >> +
> >>  		Active level of channel Y index input; irrelevant in
> >>  		non-synchronous load mode.
> >>  
> >> @@ -98,6 +112,8 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_indexY_synchronous_mode
> >>  KernelVersion:	4.10
> >>  Contact:	linux-iio@vger.kernel.org
> >>  Description:
> >> +		This interface is deprecated; please use the Counter subsystem.
> >> +
> >>  		Configure channel Y counter for non-synchronous or synchronous
> >>  		load mode. Synchronous load mode cannot be selected in
> >>  		non-quadrature clock mode.
> >> diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
> >> index d69e85a8bdc3..1152efad91a1 100644
> >> --- a/drivers/iio/Kconfig
> >> +++ b/drivers/iio/Kconfig
> >> @@ -74,7 +74,6 @@ source "drivers/iio/afe/Kconfig"
> >>  source "drivers/iio/amplifiers/Kconfig"
> >>  source "drivers/iio/chemical/Kconfig"
> >>  source "drivers/iio/common/Kconfig"
> >> -source "drivers/iio/counter/Kconfig"
> >>  source "drivers/iio/dac/Kconfig"
> >>  source "drivers/iio/dummy/Kconfig"
> >>  source "drivers/iio/frequency/Kconfig"
> >> diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile
> >> index d8cba9c229c0..7bdd31f1b88f 100644
> >> --- a/drivers/iio/Makefile
> >> +++ b/drivers/iio/Makefile
> >> @@ -20,7 +20,6 @@ obj-y += amplifiers/
> >>  obj-y += buffer/
> >>  obj-y += chemical/
> >>  obj-y += common/
> >> -obj-y += counter/
> >>  obj-y += dac/
> >>  obj-y += dummy/
> >>  obj-y += gyro/
> >> diff --git a/drivers/iio/counter/Kconfig b/drivers/iio/counter/Kconfig
> >> deleted file mode 100644
> >> index 95a7a0df6cac..000000000000
> >> --- a/drivers/iio/counter/Kconfig
> >> +++ /dev/null
> >> @@ -1,8 +0,0 @@
> >> -#
> >> -# Counter devices
> >> -#
> >> -# When adding new entries keep the list in alphabetical order
> >> -
> >> -menu "Counters"
> >> -
> >> -endmenu
> >> diff --git a/drivers/iio/counter/Makefile b/drivers/iio/counter/Makefile
> >> deleted file mode 100644
> >> index 8fd3d954775a..000000000000
> >> --- a/drivers/iio/counter/Makefile
> >> +++ /dev/null
> >> @@ -1,5 +0,0 @@
> >> -#
> >> -# Makefile for IIO counter devices
> >> -#
> >> -
> >> -# When adding new entries keep the list in alphabetical order  
> >  
> --
> To unsubscribe from this list: send the line "unsubscribe linux-iio" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH v6 3/9] docs: Add Generic Counter interface documentation

[Jonathan Cameron]

...
> >> +
> >> +COUNT
> >> +-----
> >> +A Count represents the count data for a set of Signals. The Generic
> >> +Counter interface provides the following available count data types:
> >> +
> >> +* COUNT_POSITION_UNSIGNED:
> >> +  Unsigned integer value representing position.
> >> +
> >> +* COUNT_POSITION_SIGNED:
> >> +  Signed integer value representing position.  
> >
> >Just a thought: As the '0' position is effectively arbitrary is there any
> >actual difference between signed and unsigned? If we defined all counters
> >to be unsigned and just offset any signed ones so the range still fitted
> >would we end up with a simpler interface - there would be no real loss
> >of meaning that I can see..  I suppose it might not be what people expect
> >though when they see their counters start at a large positive value...  
> 
> This is something I've been on the fence about for a while. I would
> actually prefer the interface to have simply a COUNT_POSITION data type
> to represent position and leave it as unsigned; distinguishing between
> signed and unsigned position seems ultimately arbitrary given that it's
> mathematically just an offset as you have pointed out.
> 
> If we were to go down this route, then we'd have a count value that may
> always be represented using an unsigned data type, with an offset value
> that may always be represented using a signed data type -- the
> relationship being such: position = count + offset. Is that correct?

Given the positions are all arbitrary (such as limits etc) there is no
real need to have 0 as in anyway special.  So you could just apply an
offset to everything then don't make them visible to userspace at all.

> 
> My reason for giving the option for either signed or unsigned position
> was to help minimize the work userspace would have to do in order to get
> the value in which they're actually interested. I suppose it was a
> question of how abstract I want to make the interface -- although,
> making it simpler for userspace put more of a burden on the kernel side.
> 
> However, the "offset" value route may actually be more robust in the end
> because userspace would have to know whether they want a signed or
> unsigned position regardless in order to parse, so with count and offet
> defined we know they will always be unsigned and signed respectively.

Hmm. It's not obvious to me which is the best option.

> 
> >
> >
> >
> >  
> >> +
> >> +A Count has a count function mode which represents the update behavior
> >> +for the count data. The Generic Counter interface provides the following
> >> +available count function modes:
> >> +
> >> +* Increase:
> >> +  Accumulated count is incremented.
> >> +
> >> +* Decrease:
> >> +  Accumulated count is decremented.
> >> +
> >> +* Pulse-Direction:
> >> +  Rising edges on quadrature pair signal A updates the respective count.
> >> +  The input level of quadrature pair signal B determines direction.
> >> +  
> >Perhaps group the quadrature modes for the point of view of this document?
> >Might be slightly easier to read?  
> >
> >* Quadrature Modes
> >
> >  - x1 A: etc.
> >  
> >> +* Quadrature x1 A:
> >> +  If direction is forward, rising edges on quadrature pair signal A
> >> +  updates the respective count; if the direction is backward, falling
> >> +  edges on quadrature pair signal A updates the respective count.
> >> +  Quadrature encoding determines the direction.
> >> +
> >> +* Quadrature x1 B:
> >> +  If direction is forward, rising edges on quadrature pair signal B
> >> +  updates the respective count; if the direction is backward, falling
> >> +  edges on quadrature pair signal B updates the respective count.
> >> +  Quadrature encoding determines the direction.
> >> +
> >> +* Quadrature x2 A:
> >> +  Any state transition on quadrature pair signal A updates the
> >> +  respective count. Quadrature encoding determines the direction.
> >> +
> >> +* Quadrature x2 B:
> >> +  Any state transition on quadrature pair signal B updates the
> >> +  respective count. Quadrature encoding determines the direction.
> >> +
> >> +* Quadrature x2 Rising:
> >> +  Rising edges on either quadrature pair signals updates the respective
> >> +  count. Quadrature encoding determines the direction.  
> >
> >This one I've never met.  Really? There are devices who do this form
> >of crazy? It gives really uneven counting and I'm failing to see when
> >it would ever make sense...  References for these odd corner cases
> >would be good.
> >
> >
> >__|---|____|-----|____
> >____|----|____|-----|____
> >
> >001122222223334444444  
> 
> That's the same reaction I had when I discovered this -- in fact the
> STM32 LP Timer is the first time I've come across such a quadrature
> mode. I'm not sure of the use case for this mode, because positioning
> wouldn't be precise as you've pointed out. Perhaps Fabrice or Benjamin
> can probe the ST guys responsible for this design choice to figure out
> the rationale.

Hmm.  My inclination would be to not support it unless someone can up
with a meaningful use.  We are adding ABI (be it not much) for a case
that to us makes no sense.

Looks rather like the sort of thing that is a side effect of the
implementation rather than deliberate.

> 
> I'm leaving in these modes for now, as they do exist in the STM32 LP
> Timer, but it does make me curious what the intentions for them were
> (perhaps use cases outside of traditional quadrature encoder
> positioning).
> 

Sure if there is a usecase then fair enough.

Jonathan

Re: [PATCH v6 3/9] docs: Add Generic Counter interface documentation

[Fabrice Gasnier]

On 05/22/2018 07:08 PM, Jonathan Cameron wrote:
>>>> +* Quadrature x2 Rising:
>>>> +  Rising edges on either quadrature pair signals updates the respective
>>>> +  count. Quadrature encoding determines the direction.  
>>> This one I've never met.  Really? There are devices who do this form
>>> of crazy? It gives really uneven counting and I'm failing to see when
>>> it would ever make sense...  References for these odd corner cases
>>> would be good.
>>>
>>>
>>> __|---|____|-----|____
>>> ____|----|____|-----|____
>>>
>>> 001122222223334444444  
>> That's the same reaction I had when I discovered this -- in fact the
>> STM32 LP Timer is the first time I've come across such a quadrature
>> mode. I'm not sure of the use case for this mode, because positioning
>> wouldn't be precise as you've pointed out. Perhaps Fabrice or Benjamin
>> can probe the ST guys responsible for this design choice to figure out
>> the rationale.
> Hmm.  My inclination would be to not support it unless someone can up
> with a meaningful use.  We are adding ABI (be it not much) for a case
> that to us makes no sense.

Hi Jonathan, William,

Sorry for the late reply. To follow your advise, we can probably drop
this for now. I think simple counter, or quadrature x4 will be mostly
used for now. As you pointed out, there's not much ABI for x2
rising/falling cases. It will not be a big deal to add it later if needed.

I can help to update (remove & test) this in LP-Timer counter driver if
you wish.

Please let me know,

Thanks,
Fabrice

> 
> Looks rather like the sort of thing that is a side effect of the
> implementation rather than deliberate.
> 
>> I'm leaving in these modes for now, as they do exist in the STM32 LP
>> Timer, but it does make me curious what the intentions for them were
>> (perhaps use cases outside of traditional quadrature encoder
>> positioning).
>>
> Sure if there is a usecase then fair enough.
> 
> Jonathan
> 
> 

Re: [PATCH v6 3/9] docs: Add Generic Counter interface documentation

[William Breathitt Gray]

On Fri, May 25, 2018 at 11:26:11AM +0200, Fabrice Gasnier wrote:
>On 05/22/2018 07:08 PM, Jonathan Cameron wrote:
>>>>> +* Quadrature x2 Rising:
>>>>> +  Rising edges on either quadrature pair signals updates the respective
>>>>> +  count. Quadrature encoding determines the direction.  
>>>> This one I've never met.  Really? There are devices who do this form
>>>> of crazy? It gives really uneven counting and I'm failing to see when
>>>> it would ever make sense...  References for these odd corner cases
>>>> would be good.
>>>>
>>>>
>>>> __|---|____|-----|____
>>>> ____|----|____|-----|____
>>>>
>>>> 001122222223334444444  
>>> That's the same reaction I had when I discovered this -- in fact the
>>> STM32 LP Timer is the first time I've come across such a quadrature
>>> mode. I'm not sure of the use case for this mode, because positioning
>>> wouldn't be precise as you've pointed out. Perhaps Fabrice or Benjamin
>>> can probe the ST guys responsible for this design choice to figure out
>>> the rationale.
>> Hmm.  My inclination would be to not support it unless someone can up
>> with a meaningful use.  We are adding ABI (be it not much) for a case
>> that to us makes no sense.
>
>Hi Jonathan, William,
>
>Sorry for the late reply. To follow your advise, we can probably drop
>this for now. I think simple counter, or quadrature x4 will be mostly
>used for now. As you pointed out, there's not much ABI for x2
>rising/falling cases. It will not be a big deal to add it later if needed.
>
>I can help to update (remove & test) this in LP-Timer counter driver if
>you wish.
>
>Please let me know,
>
>Thanks,
>Fabrice

All right, let's postpone the COUNT_FUNCTION_QUADRATURE_X2_RISING and
COUNT_FUNCTION_QUADRATURE_X2_FALLING modes for now. Fabrice, send me
over an update patch removing these modes from the LP-Timer counter
driver and I'll squash it in with the next patchset revision.

I'll keep the rest of the quadrature modes the same as they are used in
the other counter drivers as well (with the remaining "Quadrature x1 B"
staying to complete the pattern) and I've seen real world use cases for
each:

    * COUNT_FUNCTION_QUADRATURE_X1_A
    * COUNT_FUNCTION_QUADRATURE_X1_B
    * COUNT_FUNCTION_QUADRATURE_X2_A
    * COUNT_FUNCTION_QUADRATURE_X2_B

Adding support in the future for "Quadrature x2 Rising" and "Quadrature
x2 Falling" will be trivial, so really the main requirement in order to
bring these modes back is to provide reasonable use cases for them. My
suspicion is that there was some rationale for these Quadrature x2 modes
in the STM32 LP-Timer -- afterall, why else would the engineers go
through the trouble of designing and implementing it -- but until that
use case is clear, it's best to wait on changing the Generic Counter ABI
lest we end up with an interface that is never used in the real world.

William Breathitt Gray

>
>> 
>> Looks rather like the sort of thing that is a side effect of the
>> implementation rather than deliberate.
>> 
>>> I'm leaving in these modes for now, as they do exist in the STM32 LP
>>> Timer, but it does make me curious what the intentions for them were
>>> (perhaps use cases outside of traditional quadrature encoder
>>> positioning).
>>>
>> Sure if there is a usecase then fair enough.
>> 
>> Jonathan
>> 
>> 

Re: [PATCH v6 6/9] dt-bindings: counter: Document stm32 quadrature encoder

[Benjamin Gaignard]

2018-05-18 18:28 GMT+02:00 Rob Herring <robh@kernel.org>:
> On Thu, May 17, 2018 at 08:59:40PM +0200, Benjamin Gaignard wrote:
>> 2018-05-17 18:23 GMT+02:00 Rob Herring <robh+dt@kernel.org>:
>> > On Wed, May 16, 2018 at 12:51 PM, William Breathitt Gray
>> > <vilhelm.gray@gmail.com> wrote:
>> >> From: Benjamin Gaignard <benjamin.gaignard@st.com>
>> >
>> > v6? Where's v1-v5?
>> >
>> >> Add bindings for STM32 Timer quadrature encoder.
>> >> It is a sub-node of STM32 Timer which implement the
>> >> counter part of the hardware.
>> >>
>> >> Cc: Rob Herring <robh+dt@kernel.org>
>> >> Cc: Mark Rutland <mark.rutland@arm.com>
>> >> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
>> >> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
>> >> ---
>> >>  .../bindings/counter/stm32-timer-cnt.txt      | 26 +++++++++++++++++++
>> >>  .../devicetree/bindings/mfd/stm32-timers.txt  |  7 +++++
>> >>  2 files changed, 33 insertions(+)
>> >>  create mode 100644 Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt
>> >>
>> >> diff --git a/Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt b/Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt
>> >> new file mode 100644
>> >> index 000000000000..377728128bef
>> >> --- /dev/null
>> >> +++ b/Documentation/devicetree/bindings/counter/stm32-timer-cnt.txt
>> >> @@ -0,0 +1,26 @@
>> >> +STMicroelectronics STM32 Timer quadrature encoder
>> >> +
>> >> +STM32 Timer provides quadrature encoder counter mode to detect
>> >
>> > 'mode' does not sound like a sub-block of the timers block.
>>
>> quadrature encoding is one of the counting modes of this hardware
>> block which is enable to count on other signals/triggers
>
> You don't need a child node and compatible to set a mode.

"mode" isn't the good word here because quadratic encoder enable a
sub-block of this hardware.
Timer internal counter input could be internal or external clocks,
some IIO triggers
or the output of the quadratic encoder sub-block.
It is a child like pwm or IIO trigger.

>
>> >> +angular position and direction of rotary elements,
>> >> +from IN1 and IN2 input signals.
>> >> +
>> >> +Must be a sub-node of an STM32 Timer device tree node.
>> >> +See ../mfd/stm32-timers.txt for details about the parent node.
>> >> +
>> >> +Required properties:
>> >> +- compatible:          Must be "st,stm32-timer-counter".
>> >> +- pinctrl-names:       Set to "default".
>> >> +- pinctrl-0:           List of phandles pointing to pin configuration nodes,
>> >> +                       to set IN1/IN2 pins in mode of operation for Low-Power
>> >> +                       Timer input on external pin.
>> >> +
>> >> +Example:
>> >> +       timers@40010000  {
>> >> +               compatible = "st,stm32-timers";
>> >> +               ...
>> >> +               counter {
>> >> +                       compatible = "st,stm32-timer-counter";
>> >
>> > Is there only 1? How is the counter addressed?
>>
>> Yes there is only one counter per hardware block.
>> Counter is addressed like the two others sub-nodes and the details
>> about parent mode are describe in stm32-timers.txt
>> Should I add them here too ? so example will be like that:
>
> No, you should drop the child node and add pinctrl to the parent.
>
> Any other functions this block has that you plan on adding? Please make
> bindings as complete as possible, not what you currently have drivers
> for.

Counter framework didn't exist when I pushed timer node but thanks to
William's effort
it will allow us to use this kindf of hardware

Benjamin

>
>> timers@40010000  {
>>   #address-cells = <1>;
>>   #size-cells = <0>;
>>   compatible = "st,stm32-timers";
>>   reg = <0x40010000 0x400>;
>>   clocks = <&rcc 0 160>;
>>   clock-names = "int";
>>   counter {
>>     compatible = "st,stm32-timer-counter";
>>     pinctrl-names = "default";
>>     pinctrl-0 = <&tim1_in_pins>;
>>     };
>>  };
>>
>> Benjamin
>> >
>> > _______________________________________________
>> > linux-arm-kernel mailing list
>> > linux-arm-kernel@lists.infradead.org
>> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel



-- 
Benjamin Gaignard

Graphic Study Group

Linaro.org │ Open source software for ARM SoCs

Follow Linaro: Facebook | Twitter | Blog