[PATCH v5 03/11] nvmem: Add a simple NVMEM framework for nvmem providers

[Srinivas Kandagatla <srinivas.kandagatla@linaro.org>]

This patch adds just providers part of the framework just to enable easy
review.

Up until now, NVMEM drivers like eeprom were stored in drivers/misc,
where they all had to duplicate pretty much the same code to register
a sysfs file, allow in-kernel users to access the content of the devices
they were driving, etc.

This was also a problem as far as other in-kernel users were involved, since
the solutions used were pretty much different from on driver to another,
there was a rather big abstraction leak.

This introduction of this framework aims at solving this. It also
introduces DT representation for consumer devices to go get the data
they require (MAC Addresses, SoC/Revision ID, part numbers, and so on)
from the nvmems.

Having regmap interface to this framework would give much better
abstraction for nvmems on different buses.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
[Maxime Ripard: intial version of eeprom framework]
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
---
 drivers/Kconfig                |   2 +
 drivers/Makefile               |   1 +
 drivers/nvmem/Kconfig          |  10 ++
 drivers/nvmem/Makefile         |   6 +
 drivers/nvmem/core.c           | 398 +++++++++++++++++++++++++++++++++++++++++
 include/linux/nvmem-provider.h |  53 ++++++
 6 files changed, 470 insertions(+)
 create mode 100644 drivers/nvmem/Kconfig
 create mode 100644 drivers/nvmem/Makefile
 create mode 100644 drivers/nvmem/core.c
 create mode 100644 include/linux/nvmem-provider.h

diff --git a/drivers/Kconfig b/drivers/Kconfig
index c0cc96b..69d7305 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -182,4 +182,6 @@ source "drivers/thunderbolt/Kconfig"
 
 source "drivers/android/Kconfig"
 
+source "drivers/nvmem/Kconfig"
+
 endmenu
diff --git a/drivers/Makefile b/drivers/Makefile
index 46d2554..f86b897 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -165,3 +165,4 @@ obj-$(CONFIG_RAS)		+= ras/
 obj-$(CONFIG_THUNDERBOLT)	+= thunderbolt/
 obj-$(CONFIG_CORESIGHT)		+= hwtracing/coresight/
 obj-$(CONFIG_ANDROID)		+= android/
+obj-$(CONFIG_NVMEM)		+= nvmem/
diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
new file mode 100644
index 0000000..f157b6d
--- /dev/null
+++ b/drivers/nvmem/Kconfig
@@ -0,0 +1,10 @@
+menuconfig NVMEM
+	tristate "NVMEM Support"
+	select REGMAP
+	help
+	  Support for NVMEM devices.
+
+	  This framework is designed to provide a generic interface to NVMEM
+	  from both the Linux Kernel and the userspace.
+
+	  If unsure, say no.
diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
new file mode 100644
index 0000000..6df2c69
--- /dev/null
+++ b/drivers/nvmem/Makefile
@@ -0,0 +1,6 @@
+#
+# Makefile for nvmem drivers.
+#
+
+obj-$(CONFIG_NVMEM)		+= nvmem_core.o
+nvmem_core-y			:= core.o
diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
new file mode 100644
index 0000000..6c2f0b1
--- /dev/null
+++ b/drivers/nvmem/core.c
@@ -0,0 +1,398 @@
+/*
+ * nvmem framework core.
+ *
+ * Copyright (C) 2015 Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
+ * Copyright (C) 2013 Maxime Ripard <maxime.ripard@free-electrons.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only 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/nvmem-provider.h>
+#include <linux/export.h>
+#include <linux/fs.h>
+#include <linux/idr.h>
+#include <linux/init.h>
+#include <linux/regmap.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+
+struct nvmem_device {
+	const char		*name;
+	struct regmap		*regmap;
+	struct module		*owner;
+	struct device		dev;
+	int			stride;
+	int			word_size;
+	int			ncells;
+	int			id;
+	int			users;
+	size_t			size;
+	bool			read_only;
+};
+
+struct nvmem_cell {
+	const char *name;
+	int			offset;
+	int			bytes;
+	int			bit_offset;
+	int			nbits;
+	struct nvmem_device	*nvmem;
+	struct list_head	node;
+};
+
+static DEFINE_MUTEX(nvmem_mutex);
+static DEFINE_IDA(nvmem_ida);
+
+static LIST_HEAD(nvmem_cells);
+static DEFINE_MUTEX(nvmem_cells_mutex);
+
+#define to_nvmem_device(d) container_of(d, struct nvmem_device, dev)
+
+static ssize_t bin_attr_nvmem_read(struct file *filp, struct kobject *kobj,
+				    struct bin_attribute *attr,
+				    char *buf, loff_t pos, size_t count)
+{
+	struct device *dev = container_of(kobj, struct device, kobj);
+	struct nvmem_device *nvmem = to_nvmem_device(dev);
+	int rc;
+
+	/* Stop the user from reading */
+	if (pos > nvmem->size)
+		return 0;
+
+	if (pos + count > nvmem->size)
+		count = nvmem->size - pos;
+
+	count = count/nvmem->word_size * nvmem->word_size;
+
+	rc = regmap_raw_read(nvmem->regmap, pos, buf, count);
+
+	if (IS_ERR_VALUE(rc))
+		return rc;
+
+	return count;
+}
+
+static ssize_t bin_attr_nvmem_write(struct file *filp, struct kobject *kobj,
+				     struct bin_attribute *attr,
+				     char *buf, loff_t pos, size_t count)
+{
+	struct device *dev = container_of(kobj, struct device, kobj);
+	struct nvmem_device *nvmem = to_nvmem_device(dev);
+	int rc;
+
+	/* Stop the user from writing */
+	if (pos > nvmem->size)
+		return 0;
+
+	if (pos + count > nvmem->size)
+		count = nvmem->size - pos;
+
+	count = count/nvmem->word_size * nvmem->word_size;
+
+	rc = regmap_raw_write(nvmem->regmap, pos, buf, count);
+
+	if (IS_ERR_VALUE(rc))
+		return rc;
+
+	return count;
+}
+
+/* default read/write permissions */
+static struct bin_attribute bin_attr_nvmem = {
+	.attr	= {
+		.name	= "nvmem",
+		.mode	= S_IWUSR | S_IRUGO,
+	},
+	.read	= bin_attr_nvmem_read,
+	.write	= bin_attr_nvmem_write,
+};
+
+static struct bin_attribute *nvmem_bin_attributes[] = {
+	&bin_attr_nvmem,
+	NULL,
+};
+
+static const struct attribute_group nvmem_bin_group = {
+	.bin_attrs	= nvmem_bin_attributes,
+};
+
+static const struct attribute_group *nvmem_dev_groups[] = {
+	&nvmem_bin_group,
+	NULL,
+};
+
+/* read only permission */
+static struct bin_attribute bin_attr_ro_nvmem = {
+	.attr	= {
+		.name	= "nvmem",
+		.mode	= S_IRUGO,
+	},
+	.read	= bin_attr_nvmem_read,
+};
+
+static struct bin_attribute *nvmem_bin_ro_attributes[] = {
+	&bin_attr_ro_nvmem,
+	NULL,
+};
+static const struct attribute_group nvmem_bin_ro_group = {
+	.bin_attrs	= nvmem_bin_ro_attributes,
+};
+
+static void nvmem_release(struct device *dev)
+{
+	struct nvmem_device *nvmem = to_nvmem_device(dev);
+
+	ida_simple_remove(&nvmem_ida, nvmem->id);
+	kfree(nvmem);
+}
+
+static struct class nvmem_class = {
+	.name		= "nvmem",
+	.dev_groups	= nvmem_dev_groups,
+	.dev_release	= nvmem_release,
+};
+
+static int of_nvmem_match(struct device *dev, const void *nvmem_np)
+{
+	return dev->of_node == nvmem_np;
+}
+
+static struct nvmem_device *of_nvmem_find(struct device_node *nvmem_np)
+{
+	struct device *d;
+
+	if (!nvmem_np)
+		return NULL;
+
+	d = class_find_device(&nvmem_class, NULL, nvmem_np, of_nvmem_match);
+
+	return d ? to_nvmem_device(d) : NULL;
+}
+
+static struct nvmem_cell *nvmem_find_cell(const char *cell_id)
+{
+	struct nvmem_cell *p;
+
+	list_for_each_entry(p, &nvmem_cells, node) {
+		if (p && !strcmp(p->name, cell_id))
+			return p;
+	}
+
+	return NULL;
+}
+
+static void nvmem_cell_drop(struct nvmem_cell *cell)
+{
+	mutex_lock(&nvmem_cells_mutex);
+	list_del(&cell->node);
+	mutex_unlock(&nvmem_cells_mutex);
+	kfree(cell);
+}
+
+static void nvmem_device_remove_all_cells(struct nvmem_device *nvmem)
+{
+	struct nvmem_cell *cell = NULL;
+	struct list_head *p, *n;
+
+	list_for_each_safe(p, n, &nvmem_cells) {
+		cell = list_entry(p, struct nvmem_cell, node);
+		if (cell->nvmem == nvmem)
+			nvmem_cell_drop(cell);
+	}
+}
+
+static void nvmem_cell_add(struct nvmem_cell *cell)
+{
+	mutex_lock(&nvmem_cells_mutex);
+	list_add_tail(&cell->node, &nvmem_cells);
+	mutex_unlock(&nvmem_cells_mutex);
+}
+
+static int nvmem_cell_info_to_nvmem_cell(struct nvmem_device *nvmem,
+				   struct nvmem_cell_info *info,
+				   struct nvmem_cell *cell)
+{
+	cell->nvmem = nvmem;
+	cell->offset = info->offset;
+	cell->bytes = info->bytes;
+	cell->name = info->name;
+
+	cell->bit_offset = info->bit_offset;
+	cell->nbits = info->nbits;
+
+	if (cell->nbits)
+		cell->bytes = DIV_ROUND_UP(cell->nbits + cell->bit_offset,
+					   BITS_PER_BYTE);
+
+	if (!IS_ALIGNED(cell->offset, nvmem->stride)) {
+		dev_err(&nvmem->dev,
+			"cell %s unaligned to nvmem stride %d\n",
+			cell->name, nvmem->stride);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int nvmem_add_cells(struct nvmem_device *nvmem,
+			   struct nvmem_config *cfg)
+{
+	struct nvmem_cell **cells;
+	struct nvmem_cell_info *info = cfg->cells;
+	int i, rval;
+
+	cells = kzalloc(sizeof(*cells) * cfg->ncells, GFP_KERNEL);
+	if (!cells)
+		return -ENOMEM;
+
+	for (i = 0; i < cfg->ncells; i++) {
+		cells[i] = kzalloc(sizeof(struct nvmem_cell), GFP_KERNEL);
+		if (!cells[i]) {
+			rval = -ENOMEM;
+			goto err;
+		}
+
+		rval = nvmem_cell_info_to_nvmem_cell(nvmem, &info[i], cells[i]);
+		if (IS_ERR_VALUE(rval)) {
+			kfree(cells[i]);
+			goto err;
+		}
+
+		nvmem_cell_add(cells[i]);
+	}
+
+	nvmem->ncells = cfg->ncells;
+	/* remove tmp array */
+	kfree(cells);
+
+	return 0;
+err:
+	while (--i)
+		nvmem_cell_drop(cells[i]);
+
+	return rval;
+}
+
+/**
+ * nvmem_register(): Register a nvmem device for given nvmem.
+ * Also creates an binary entry in /sys/class/nvmem/dev-name/nvmem
+ *
+ * @nvmem: nvmem device that needs to be created
+ *
+ * The return value will be an ERR_PTR() on error or a valid pointer
+ * to nvmem_device.
+ */
+
+struct nvmem_device *nvmem_register(struct nvmem_config *config)
+{
+	struct nvmem_device *nvmem;
+	struct regmap *rm;
+	int rval;
+
+	if (!config->dev)
+		return ERR_PTR(-EINVAL);
+
+	rm = dev_get_regmap(config->dev, NULL);
+	if (!rm) {
+		dev_err(config->dev, "Regmap not found\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	nvmem = kzalloc(sizeof(*nvmem), GFP_KERNEL);
+	if (!nvmem)
+		return ERR_PTR(-ENOMEM);
+
+	nvmem->id = ida_simple_get(&nvmem_ida, 0, 0, GFP_KERNEL);
+	if (nvmem->id < 0) {
+		kfree(nvmem);
+		return ERR_PTR(nvmem->id);
+	}
+
+	nvmem->regmap = rm;
+	nvmem->owner = config->owner;
+	nvmem->stride = regmap_get_reg_stride(rm);
+	nvmem->word_size = regmap_get_val_bytes(rm);
+	nvmem->size = regmap_get_max_register(rm) + nvmem->stride;
+	nvmem->dev.class = &nvmem_class;
+	nvmem->dev.parent = config->dev;
+	nvmem->dev.of_node = config->dev->of_node;
+	dev_set_name(&nvmem->dev, "%s%d",
+		     config->name ? : "nvmem", config->id);
+
+	nvmem->read_only = of_property_read_bool(nvmem->dev.of_node,
+						 "read-only");
+
+	device_initialize(&nvmem->dev);
+
+	dev_dbg(&nvmem->dev, "Registering nvmem device %s\n",
+		dev_name(&nvmem->dev));
+
+	rval = device_add(&nvmem->dev);
+	if (rval) {
+		ida_simple_remove(&nvmem_ida, nvmem->id);
+		kfree(nvmem);
+		return ERR_PTR(rval);
+	}
+
+	/* update sysfs attributes */
+	if (nvmem->read_only)
+		sysfs_update_group(&nvmem->dev.kobj, &nvmem_bin_ro_group);
+
+	if (config->cells)
+		nvmem_add_cells(nvmem, config);
+
+	return nvmem;
+}
+EXPORT_SYMBOL_GPL(nvmem_register);
+
+/**
+ * nvmem_unregister(): Unregister previously registered nvmem device
+ *
+ * @nvmem: Pointer to previously registered nvmem device.
+ *
+ * The return value will be an non zero on error or a zero on success.
+ */
+int nvmem_unregister(struct nvmem_device *nvmem)
+{
+	mutex_lock(&nvmem_mutex);
+	if (nvmem->users) {
+		mutex_unlock(&nvmem_mutex);
+		return -EBUSY;
+	}
+	mutex_unlock(&nvmem_mutex);
+
+	nvmem_device_remove_all_cells(nvmem);
+	device_del(&nvmem->dev);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(nvmem_unregister);
+
+static int nvmem_init(void)
+{
+	return class_register(&nvmem_class);
+}
+
+static void nvmem_exit(void)
+{
+	class_unregister(&nvmem_class);
+}
+
+subsys_initcall(nvmem_init);
+module_exit(nvmem_exit);
+
+MODULE_AUTHOR("Srinivas Kandagatla <srinivas.kandagatla@linaro.org");
+MODULE_AUTHOR("Maxime Ripard <maxime.ripard@free-electrons.com");
+MODULE_DESCRIPTION("nvmem Driver Core");
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/nvmem-provider.h b/include/linux/nvmem-provider.h
new file mode 100644
index 0000000..4908b37
--- /dev/null
+++ b/include/linux/nvmem-provider.h
@@ -0,0 +1,53 @@
+/*
+ * nvmem framework provider.
+ *
+ * Copyright (C) 2015 Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
+ * Copyright (C) 2013 Maxime Ripard <maxime.ripard@free-electrons.com>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2.  This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#ifndef _LINUX_NVMEM_PROVIDER_H
+#define _LINUX_NVMEM_PROVIDER_H
+
+struct nvmem_device;
+
+struct nvmem_cell_info {
+	const char		*name;
+	int			offset;
+	int			bytes;
+	int			bit_offset;
+	int			nbits;
+};
+
+struct nvmem_config {
+	struct device		*dev;
+	const char		*name;
+	int			id;
+	struct module		*owner;
+	struct nvmem_cell_info	*cells;
+	int			ncells;
+};
+
+#if IS_ENABLED(CONFIG_NVMEM)
+
+struct nvmem_device *nvmem_register(struct nvmem_config *cfg);
+int nvmem_unregister(struct nvmem_device *nvmem);
+
+#else
+
+static inline struct nvmem_device *nvmem_register(struct nvmem_config *cfg)
+{
+	return ERR_PTR(-ENOSYS);
+}
+
+static inline int nvmem_unregister(struct nvmem_device *nvmem)
+{
+	return -ENOSYS;
+}
+
+#endif /* CONFIG_NVMEM */
+
+#endif  /* ifndef _LINUX_NVMEM_PROVIDER_H */
-- 
1.9.1