[RFC PATCH 0/7] mux controller astraction and iio/i2c muxes

[RFC PATCH 0/7] mux controller astraction and iio/i2c muxes

[Peter Rosin]

Hi!

This is work in progress, I'm asking for early feedback.

I have a piece of hardware that is using the same 3 GPIO pins
to control four 8-way muxes. Three of them control ADC lines
to an ADS1015 chip with an iio driver, and the last one
controls the SDA line of an i2c bus. We have some deployed
code to handle this, but you do not want to see it or ever
hear about it. I'm not sure why I even mention it. Anyway,
the situation has nagged me to no end for quite some time.

So, after first getting more intimate with the i2c muxing code
and later discovering the drivers/iio/inkern.c file and
writing a couple of drivers making use of it, I came up with
what I think is an acceptable solution; add a generic mux
controller driver that is shared between all instances, and
combine that with an iio mux driver and a new generic i2c mux
driver. The new i2c mux I called "simple" since it is only
hooking the i2c muxing and the new mux controller (much like
the alsa simple card driver does for ASoC).

My initial (private) version didn't add "mux" as a new bus,
but I couldn't get decent type-checking and nice devicetree
integration with that. It does however feel a bit rich to
add a new bus for something as small as mux controllers?

One thing that I would like to do, but don't see a solution
for, is to move the mux control code that is present in
various drivers in drivers/i2c/muxes to this new minimalistic
muxing subsystem, thus converting all present i2c muxes (but
perhaps not gates and arbitrators) to be i2c-mux-simple muxes.

I'm using an rwsem to lock a mux, but that isn't really a
perfect fit. Is there a better locking primitive that I don't
know about that fits better? I had a mutex at one point, but
that didn't allow any concurrent accesses at all. At least
the rwsem allows concurrent access as long as all users
agree on the mux state, but I suspect that the rwsem will
degrade to the mutex situation pretty quickly if there is
any contention.

Also, the "mux" name feels a bit ambitious, there are many muxes
in the world, and this tiny bit of code is probably not good
enough to be a nice fit for all...

This is all very fresh code and only lightly tested, but it
feels very promising! Now, go ahead and rip this to pieces...

Cheers,
Peter

Peter Rosin (7):
  dt-bindings: document devicetree bindings for mux-gpio
  misc: minimal mux subsystem and gpio-based mux controller
  iio: inkern: api for manipulating ext_info of iio channels
  dt-bindings: iio: iio-mux: document iio-mux bindings
  iio: multiplexer: new iio category and iio-mux driver
  dt-bindings: i2c: i2c-mux-simple: document i2c-mux-simple bindings
  i2c: i2c-mux-simple: new driver

 .../devicetree/bindings/i2c/i2c-mux-simple.txt     |  91 ++++++
 .../bindings/iio/multiplexer/iio-mux.txt           |  59 ++++
 .../devicetree/bindings/misc/mux-gpio.txt          |  76 +++++
 drivers/i2c/muxes/Kconfig                          |  12 +
 drivers/i2c/muxes/Makefile                         |   1 +
 drivers/i2c/muxes/i2c-mux-simple.c                 | 172 +++++++++++
 drivers/iio/Kconfig                                |   1 +
 drivers/iio/Makefile                               |   1 +
 drivers/iio/inkern.c                               |  40 +++
 drivers/iio/multiplexer/Kconfig                    |  17 ++
 drivers/iio/multiplexer/Makefile                   |   6 +
 drivers/iio/multiplexer/iio-mux.c                  | 313 +++++++++++++++++++++
 drivers/misc/Kconfig                               |   6 +
 drivers/misc/Makefile                              |   2 +
 drivers/misc/mux-core.c                            | 285 +++++++++++++++++++
 drivers/misc/mux-gpio.c                            | 105 +++++++
 include/linux/iio/consumer.h                       |   5 +
 include/linux/mux.h                                |  54 ++++
 18 files changed, 1246 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/i2c/i2c-mux-simple.txt
 create mode 100644 Documentation/devicetree/bindings/iio/multiplexer/iio-mux.txt
 create mode 100644 Documentation/devicetree/bindings/misc/mux-gpio.txt
 create mode 100644 drivers/i2c/muxes/i2c-mux-simple.c
 create mode 100644 drivers/iio/multiplexer/Kconfig
 create mode 100644 drivers/iio/multiplexer/Makefile
 create mode 100644 drivers/iio/multiplexer/iio-mux.c
 create mode 100644 drivers/misc/mux-core.c
 create mode 100644 drivers/misc/mux-gpio.c
 create mode 100644 include/linux/mux.h

-- 
2.1.4

[RFC PATCH 0/7] mux controller astraction and iio/i2c muxes

[Peter Rosin]

Hi!

This is work in progress, I'm asking for early feedback.

I have a piece of hardware that is using the same 3 GPIO pins
to control four 8-way muxes. Three of them control ADC lines
to an ADS1015 chip with an iio driver, and the last one
controls the SDA line of an i2c bus. We have some deployed
code to handle this, but you do not want to see it or ever
hear about it. I'm not sure why I even mention it. Anyway,
the situation has nagged me to no end for quite some time.

So, after first getting more intimate with the i2c muxing code
and later discovering the drivers/iio/inkern.c file and
writing a couple of drivers making use of it, I came up with
what I think is an acceptable solution; add a generic mux
controller driver that is shared between all instances, and
combine that with an iio mux driver and a new generic i2c mux
driver. The new i2c mux I called "simple" since it is only
hooking the i2c muxing and the new mux controller (much like
the alsa simple card driver does for ASoC).

My initial (private) version didn't add "mux" as a new bus,
but I couldn't get decent type-checking and nice devicetree
integration with that. It does however feel a bit rich to
add a new bus for something as small as mux controllers?

One thing that I would like to do, but don't see a solution
for, is to move the mux control code that is present in
various drivers in drivers/i2c/muxes to this new minimalistic
muxing subsystem, thus converting all present i2c muxes (but
perhaps not gates and arbitrators) to be i2c-mux-simple muxes.

I'm using an rwsem to lock a mux, but that isn't really a
perfect fit. Is there a better locking primitive that I don't
know about that fits better? I had a mutex at one point, but
that didn't allow any concurrent accesses at all. At least
the rwsem allows concurrent access as long as all users
agree on the mux state, but I suspect that the rwsem will
degrade to the mutex situation pretty quickly if there is
any contention.

Also, the "mux" name feels a bit ambitious, there are many muxes
in the world, and this tiny bit of code is probably not good
enough to be a nice fit for all...

This is all very fresh code and only lightly tested, but it
feels very promising! Now, go ahead and rip this to pieces...

Cheers,
Peter

Peter Rosin (7):
  dt-bindings: document devicetree bindings for mux-gpio
  misc: minimal mux subsystem and gpio-based mux controller
  iio: inkern: api for manipulating ext_info of iio channels
  dt-bindings: iio: iio-mux: document iio-mux bindings
  iio: multiplexer: new iio category and iio-mux driver
  dt-bindings: i2c: i2c-mux-simple: document i2c-mux-simple bindings
  i2c: i2c-mux-simple: new driver

 .../devicetree/bindings/i2c/i2c-mux-simple.txt     |  91 ++++++
 .../bindings/iio/multiplexer/iio-mux.txt           |  59 ++++
 .../devicetree/bindings/misc/mux-gpio.txt          |  76 +++++
 drivers/i2c/muxes/Kconfig                          |  12 +
 drivers/i2c/muxes/Makefile                         |   1 +
 drivers/i2c/muxes/i2c-mux-simple.c                 | 172 +++++++++++
 drivers/iio/Kconfig                                |   1 +
 drivers/iio/Makefile                               |   1 +
 drivers/iio/inkern.c                               |  40 +++
 drivers/iio/multiplexer/Kconfig                    |  17 ++
 drivers/iio/multiplexer/Makefile                   |   6 +
 drivers/iio/multiplexer/iio-mux.c                  | 313 +++++++++++++++++++++
 drivers/misc/Kconfig                               |   6 +
 drivers/misc/Makefile                              |   2 +
 drivers/misc/mux-core.c                            | 285 +++++++++++++++++++
 drivers/misc/mux-gpio.c                            | 105 +++++++
 include/linux/iio/consumer.h                       |   5 +
 include/linux/mux.h                                |  54 ++++
 18 files changed, 1246 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/i2c/i2c-mux-simple.txt
 create mode 100644 Documentation/devicetree/bindings/iio/multiplexer/iio-mux.txt
 create mode 100644 Documentation/devicetree/bindings/misc/mux-gpio.txt
 create mode 100644 drivers/i2c/muxes/i2c-mux-simple.c
 create mode 100644 drivers/iio/multiplexer/Kconfig
 create mode 100644 drivers/iio/multiplexer/Makefile
 create mode 100644 drivers/iio/multiplexer/iio-mux.c
 create mode 100644 drivers/misc/mux-core.c
 create mode 100644 drivers/misc/mux-gpio.c
 create mode 100644 include/linux/mux.h

-- 
2.1.4

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[RFC PATCH 1/7] dt-bindings: document devicetree bindings for mux-gpio

[Peter Rosin]

---
 .../devicetree/bindings/misc/mux-gpio.txt          | 76 ++++++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/misc/mux-gpio.txt

diff --git a/Documentation/devicetree/bindings/misc/mux-gpio.txt b/Documentation/devicetree/bindings/misc/mux-gpio.txt
new file mode 100644
index 000000000000..8c1745ecd4ff
--- /dev/null
+++ b/Documentation/devicetree/bindings/misc/mux-gpio.txt
@@ -0,0 +1,76 @@
+GPIO-based multiplexer controller bindings
+
+Define what GPIO pins are used to control a multiplexer. Or several
+multiplexers, if the same pins control more than one multiplexer.
+
+Required properties:
+- compatible : "mux-gpio"
+- mux-gpios : list of gpios used to control the multiplexer, least
+	      significant bit first.
+
+Example:
+	control_mux: control-adc-mux {
+		compatible = "mux-gpio";
+
+		mux-gpios = <&pioA 0 GPIO_ACTIVE_HIGH>,
+			    <&pioA 1 GPIO_ACTIVE_HIGH>;
+	};
+
+	adc-mux {
+		compatible = "iio-mux";
+		io-channels = <&adc 0>;
+		io-channel-names = "parent";
+
+		control-muxes = <&control_mux>;
+		control-mux-names = "mux";
+
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		sync-1@0 {
+			reg = <0>;
+		};
+
+		in@1 {
+			reg = <1>;
+		};
+
+		out@2 {
+			reg = <2>;
+		};
+
+		sync-2@3 {
+			reg = <3>;
+		};
+	};
+
+	i2c-mux {
+		compatible = "i2c-mux-simple,mux-locked";
+		i2c-parent = <&i2c1>;
+
+		control-muxes = <&control_mux>;
+		control-mux-names = "mux";
+
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		i2c@0 {
+			reg = <0>;
+			#address-cells = <1>;
+			#size-cells = <0>;
+
+			ssd1307: oled@3c {
+				/* ... */
+			};
+		};
+
+		i2c@3 {
+			reg = <3>;
+			#address-cells = <1>;
+			#size-cells = <0>;
+
+			pca9555: pca9555@20 {
+				/* ... */
+			};
+		};
+	};
-- 
2.1.4

[RFC PATCH 1/7] dt-bindings: document devicetree bindings for mux-gpio

[Peter Rosin]

---
 .../devicetree/bindings/misc/mux-gpio.txt          | 76 ++++++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/misc/mux-gpio.txt

diff --git a/Documentation/devicetree/bindings/misc/mux-gpio.txt b/Documentation/devicetree/bindings/misc/mux-gpio.txt
new file mode 100644
index 000000000000..8c1745ecd4ff
--- /dev/null
+++ b/Documentation/devicetree/bindings/misc/mux-gpio.txt
@@ -0,0 +1,76 @@
+GPIO-based multiplexer controller bindings
+
+Define what GPIO pins are used to control a multiplexer. Or several
+multiplexers, if the same pins control more than one multiplexer.
+
+Required properties:
+- compatible : "mux-gpio"
+- mux-gpios : list of gpios used to control the multiplexer, least
+	      significant bit first.
+
+Example:
+	control_mux: control-adc-mux {
+		compatible = "mux-gpio";
+
+		mux-gpios = <&pioA 0 GPIO_ACTIVE_HIGH>,
+			    <&pioA 1 GPIO_ACTIVE_HIGH>;
+	};
+
+	adc-mux {
+		compatible = "iio-mux";
+		io-channels = <&adc 0>;
+		io-channel-names = "parent";
+
+		control-muxes = <&control_mux>;
+		control-mux-names = "mux";
+
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		sync-1@0 {
+			reg = <0>;
+		};
+
+		in@1 {
+			reg = <1>;
+		};
+
+		out@2 {
+			reg = <2>;
+		};
+
+		sync-2@3 {
+			reg = <3>;
+		};
+	};
+
+	i2c-mux {
+		compatible = "i2c-mux-simple,mux-locked";
+		i2c-parent = <&i2c1>;
+
+		control-muxes = <&control_mux>;
+		control-mux-names = "mux";
+
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		i2c@0 {
+			reg = <0>;
+			#address-cells = <1>;
+			#size-cells = <0>;
+
+			ssd1307: oled@3c {
+				/* ... */
+			};
+		};
+
+		i2c@3 {
+			reg = <3>;
+			#address-cells = <1>;
+			#size-cells = <0>;
+
+			pca9555: pca9555@20 {
+				/* ... */
+			};
+		};
+	};
-- 
2.1.4

[RFC PATCH 2/7] misc: minimal mux subsystem and gpio-based mux controller

[Peter Rosin]

When both the iio subsystem and the i2c subsystem wants to update
the same mux, there needs to be some coordination. Invent a new
minimal "mux" subsystem that handles this.

Add a single backend driver for this new subsystem that can
control gpio based multiplexers.
---
 drivers/misc/Kconfig    |   6 +
 drivers/misc/Makefile   |   2 +
 drivers/misc/mux-core.c | 285 ++++++++++++++++++++++++++++++++++++++++++++++++
 drivers/misc/mux-gpio.c | 105 ++++++++++++++++++
 include/linux/mux.h     |  54 +++++++++
 5 files changed, 452 insertions(+)
 create mode 100644 drivers/misc/mux-core.c
 create mode 100644 drivers/misc/mux-gpio.c
 create mode 100644 include/linux/mux.h

diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 64971baf11fa..9e119bb78d82 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -766,6 +766,12 @@ config PANEL_BOOT_MESSAGE
 	  An empty message will only clear the display at driver init time. Any other
 	  printf()-formatted message is valid with newline and escape codes.
 
+config MUX_GPIO
+	tristate "GPIO-controlled MUX controller"
+	depends on OF
+	help
+	  GPIO-controlled MUX controller
+
 source "drivers/misc/c2port/Kconfig"
 source "drivers/misc/eeprom/Kconfig"
 source "drivers/misc/cb710/Kconfig"
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index 31983366090a..92b547bcbac1 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -53,6 +53,8 @@ obj-$(CONFIG_ECHO)		+= echo/
 obj-$(CONFIG_VEXPRESS_SYSCFG)	+= vexpress-syscfg.o
 obj-$(CONFIG_CXL_BASE)		+= cxl/
 obj-$(CONFIG_PANEL)             += panel.o
+obj-$(CONFIG_MUX_GPIO)          += mux-core.o
+obj-$(CONFIG_MUX_GPIO)          += mux-gpio.o
 
 lkdtm-$(CONFIG_LKDTM)		+= lkdtm_core.o
 lkdtm-$(CONFIG_LKDTM)		+= lkdtm_bugs.o
diff --git a/drivers/misc/mux-core.c b/drivers/misc/mux-core.c
new file mode 100644
index 000000000000..d7c7b667d1a4
--- /dev/null
+++ b/drivers/misc/mux-core.c
@@ -0,0 +1,285 @@
+/*
+ * Multiplexer subsystem
+ *
+ * Copyright (C) 2016 Axentia Technologies AB
+ *
+ * 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.
+ */
+
+#define pr_fmt(fmt) "mux-core: " fmt
+
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/idr.h>
+#include <linux/module.h>
+#include <linux/mux.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+
+static struct bus_type mux_bus_type = {
+	.name = "mux",
+};
+
+static int __init mux_init(void)
+{
+	return bus_register(&mux_bus_type);
+}
+
+static void __exit mux_exit(void)
+{
+	bus_unregister(&mux_bus_type);
+}
+
+static DEFINE_IDA(mux_ida);
+
+static void mux_control_release(struct device *dev)
+{
+	struct mux_control *mux = to_mux_control(dev);
+
+	ida_simple_remove(&mux_ida, mux->id);
+	kfree(mux);
+}
+
+static struct device_type mux_control_type = {
+	.name = "mux-control",
+	.release = mux_control_release,
+};
+
+/*
+ * Allocate a mux-control, plus an extra memory area for private use
+ * by the caller.
+ */
+struct mux_control *mux_control_alloc(size_t sizeof_priv)
+{
+	struct mux_control *mux;
+
+	mux = kzalloc(sizeof(*mux) + sizeof_priv, GFP_KERNEL);
+	if (!mux)
+		return NULL;
+
+	mux->dev.bus = &mux_bus_type;
+	mux->dev.type = &mux_control_type;
+	device_initialize(&mux->dev);
+	dev_set_drvdata(&mux->dev, mux);
+
+	init_rwsem(&mux->lock);
+	mux->priv = mux + 1;
+
+	mux->id = ida_simple_get(&mux_ida, 0, 0, GFP_KERNEL);
+	if (mux->id < 0) {
+		pr_err("mux-controlX failed to get device id\n");
+		kfree(mux);
+		return NULL;
+	}
+	dev_set_name(&mux->dev, "mux:control%d", mux->id);
+
+	return mux;
+}
+EXPORT_SYMBOL_GPL(mux_control_alloc);
+
+/*
+ * Register the mux-control, thus readying it for use.
+ */
+int mux_control_register(struct mux_control *mux)
+{
+	/* If the calling driver did not initialize of_node, do it here */
+	if (!mux->dev.of_node && mux->dev.parent)
+		mux->dev.of_node = mux->dev.parent->of_node;
+
+	return device_add(&mux->dev);
+}
+EXPORT_SYMBOL_GPL(mux_control_register);
+
+/*
+ * Take the mux-control off-line.
+ */
+void mux_control_unregister(struct mux_control *mux)
+{
+	device_del(&mux->dev);
+}
+EXPORT_SYMBOL_GPL(mux_control_unregister);
+
+/*
+ * Put away the mux-control for good.
+ */
+void mux_control_put(struct mux_control *mux)
+{
+	if (!mux)
+		return;
+	put_device(&mux->dev);
+}
+EXPORT_SYMBOL_GPL(mux_control_free);
+
+/*
+ * Select the given multiplexer channel. Call mux_control_deselect()
+ * when the operation is complete on the multiplexer channel, and the
+ * multiplexer is free for others to use.
+ */
+int mux_control_select(struct mux_control *mux, int reg)
+{
+	int ret;
+
+	if (down_read_trylock(&mux->lock)) {
+		if (mux->cache == reg)
+			return 0;
+
+		/* Sigh, the mux needs updating... */
+		up_read(&mux->lock);
+	}
+
+	/* ...or it's just contended. */
+	down_write(&mux->lock);
+
+	if (mux->cache == reg) {
+		/*
+		 * Hmmm, someone else changed the mux to my liking.
+		 * That makes me wonder how long I waited for nothing...
+		 */
+		downgrade_write(&mux->lock);
+		return 0;
+	}
+
+	ret = mux->ops->set(mux, reg);
+	if (ret < 0) {
+		up_write(&mux->lock);
+		return ret;
+	}
+
+	mux->cache = reg;
+	downgrade_write(&mux->lock);
+
+	return 1;
+}
+EXPORT_SYMBOL_GPL(mux_control_select);
+
+/*
+ * Deselect the previously selected multiplexer channel.
+ */
+int mux_control_deselect(struct mux_control *mux)
+{
+	if (mux->do_idle && mux->cache != mux->idle_state) {
+		mux->ops->set(mux, mux->idle_state);
+		mux->cache = mux->idle_state;
+	}
+
+	up_read(&mux->lock);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(mux_control_deselect);
+
+static int of_dev_node_match(struct device *dev, void *data)
+{
+	return dev->of_node == data;
+}
+
+static struct mux_control *of_find_mux_by_node(struct device_node *np)
+{
+	struct device *dev;
+
+	dev = bus_find_device(&mux_bus_type, NULL, np, of_dev_node_match);
+
+	return dev ? to_mux_control(dev) : NULL;
+}
+
+static struct mux_control *of_mux_control_get(struct device_node *np, int index)
+{
+	struct device_node *mux_np;
+	struct mux_control *mux;
+
+	mux_np = of_parse_phandle(np, "control-muxes", index);
+	if (!mux_np)
+		return NULL;
+
+	mux = of_find_mux_by_node(mux_np);
+	of_node_put(mux_np);
+
+	return mux;
+}
+
+/*
+ * Get a named mux.
+ */
+struct mux_control *mux_control_get(struct device *dev, const char *mux_name)
+{
+	struct device_node *np = dev->of_node;
+	struct mux_control *mux;
+	int index;
+
+	index = of_property_match_string(np, "control-mux-names", mux_name);
+	if (index < 0) {
+		dev_err(dev, "failed to get control-mux %s:%s(%i)\n",
+			np->full_name, mux_name ?: "", index);
+		return ERR_PTR(index);
+	}
+
+	mux = of_mux_control_get(np, index);
+	if (!mux)
+		return ERR_PTR(-EPROBE_DEFER);
+
+	return mux;
+}
+EXPORT_SYMBOL_GPL(mux_control_get);
+
+static void devm_mux_control_free(struct device *dev, void *res)
+{
+	struct mux_control *mux = *(struct mux_control **)res;
+
+	mux_control_put(mux);
+}
+
+/*
+ * Get a named mux, with resource management.
+ */
+struct mux_control *devm_mux_control_get(struct device *dev,
+					 const char *mux_name)
+{
+	struct mux_control **ptr, *mux;
+
+	ptr = devres_alloc(devm_mux_control_free, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return ERR_PTR(-ENOMEM);
+
+	mux = mux_control_get(dev, mux_name);
+	if (IS_ERR(mux)) {
+		devres_free(ptr);
+		return mux;
+	}
+
+	*ptr = mux;
+	devres_add(dev, ptr);
+
+	return mux;
+}
+EXPORT_SYMBOL_GPL(devm_mux_control_get);
+
+static int devm_mux_control_match(struct device *dev, void *res, void *data)
+{
+	struct mux_control **r = res;
+
+	if (!r || !*r) {
+		WARN_ON(!r || !*r);
+		return 0;
+	}
+
+	return *r == data;
+}
+
+/*
+ * Resource-managed version mux_control_put.
+ */
+void devm_mux_control_put(struct device *dev, struct mux_control *mux)
+{
+	WARN_ON(devres_release(dev, devm_mux_control_free,
+			       devm_mux_control_match, mux));
+}
+EXPORT_SYMBOL_GPL(devm_mux_control_put);
+
+subsys_initcall(mux_init);
+module_exit(mux_exit);
+
+MODULE_AUTHOR("Peter Rosin <peda@axentia.se");
+MODULE_DESCRIPTION("MUX subsystem");
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/misc/mux-gpio.c b/drivers/misc/mux-gpio.c
new file mode 100644
index 000000000000..5fa59a0c49cf
--- /dev/null
+++ b/drivers/misc/mux-gpio.c
@@ -0,0 +1,105 @@
+/*
+ * GPIO-controlled multiplexer driver
+ *
+ * Copyright (C) 2016 Axentia Technologies AB
+ *
+ * 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.
+ */
+
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/module.h>
+#include <linux/mux.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+
+struct mux_gpio {
+	struct gpio_descs *gpios;
+};
+
+static int mux_gpio_set(struct mux_control *mux, int val)
+{
+	struct mux_gpio *mux_gpio = mux->priv;
+	int i;
+
+	for (i = 0; i < mux_gpio->gpios->ndescs; i++)
+		gpiod_set_value_cansleep(mux_gpio->gpios->desc[i],
+					 val & (1 << i));
+
+	return 0;
+}
+
+static const struct mux_control_ops mux_gpio_ops = {
+	.set = mux_gpio_set,
+};
+
+static const struct of_device_id mux_gpio_dt_ids[] = {
+	{ .compatible = "mux-gpio", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, mux_gpio_dt_ids);
+
+static int mux_gpio_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *np = pdev->dev.of_node;
+	struct mux_control *mux;
+	struct mux_gpio *mux_gpio;
+	int ret;
+
+	if (!np)
+		return -ENODEV;
+
+	mux = mux_control_alloc(sizeof(*mux_gpio));
+	if (!mux)
+		return -ENOMEM;
+	mux_gpio = mux->priv;
+	mux->dev.parent = dev;
+	mux->ops = &mux_gpio_ops;
+
+	platform_set_drvdata(pdev, mux);
+
+	mux_gpio->gpios = devm_gpiod_get_array(dev, "mux", GPIOD_OUT_LOW);
+	if (IS_ERR(mux_gpio->gpios)) {
+		if (PTR_ERR(mux_gpio->gpios) != -EPROBE_DEFER)
+			dev_err(dev, "failed to get gpios\n");
+		mux_control_put(mux);
+		return PTR_ERR(mux_gpio->gpios);
+	}
+
+	ret = mux_control_register(mux);
+	if (ret < 0) {
+		dev_err(dev, "failed to register mux_control\n");
+		mux_control_put(mux);
+		return ret;
+	}
+
+	return ret;
+}
+
+static int mux_gpio_remove(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct mux_control *mux = to_mux_control(dev);
+
+	mux_control_unregister(mux);
+	mux_control_put(mux);
+	return 0;
+}
+
+static struct platform_driver mux_gpio_driver = {
+	.driver = {
+		.name = "mux-gpio",
+		.of_match_table	= of_match_ptr(mux_gpio_dt_ids),
+	},
+	.probe = mux_gpio_probe,
+	.remove = mux_gpio_remove,
+};
+module_platform_driver(mux_gpio_driver);
+
+MODULE_AUTHOR("Peter Rosin <peda@axentia.se");
+MODULE_DESCRIPTION("GPIO-controlled multiplexer driver");
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/mux.h b/include/linux/mux.h
new file mode 100644
index 000000000000..6513ffe749bb
--- /dev/null
+++ b/include/linux/mux.h
@@ -0,0 +1,54 @@
+/*
+ * mux.h - definitions for the multiplexer interface
+ *
+ * Copyright (C) 2016 Axentia Technologies AB
+ *
+ * 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.
+ */
+
+#ifndef _LINUX_MUX_H
+#define _LINUX_MUX_H
+
+#include <linux/device.h>
+#include <linux/rwsem.h>
+
+struct mux_control;
+
+struct mux_control_ops {
+	int (*set)(struct mux_control *mux, int reg);
+};
+
+struct mux_control {
+	struct rw_semaphore lock; /* protects the state of the mux */
+
+	struct device dev;
+	int id;
+
+	int cache;
+	bool do_idle;
+	int idle_state;
+
+	const struct mux_control_ops *ops;
+
+	void *priv;
+};
+
+#define to_mux_control(x) container_of((x), struct mux_control, dev)
+
+struct mux_control *mux_control_alloc(size_t sizeof_priv);
+int mux_control_register(struct mux_control *mux);
+void mux_control_unregister(struct mux_control *mux);
+void mux_control_put(struct mux_control *mux);
+
+int mux_control_select(struct mux_control *mux, int reg);
+int mux_control_deselect(struct mux_control *mux);
+
+struct mux_control *mux_control_get(struct device *dev,
+				    const char *mux_name);
+struct mux_control *devm_mux_control_get(struct device *dev,
+					 const char *mux_name);
+void devm_mux_control_put(struct device *dev, struct mux_control *mux);
+
+#endif /* _LINUX_MUX_H */
-- 
2.1.4

[RFC PATCH 2/7] misc: minimal mux subsystem and gpio-based mux controller

[Peter Rosin]

When both the iio subsystem and the i2c subsystem wants to update
the same mux, there needs to be some coordination. Invent a new
minimal "mux" subsystem that handles this.

Add a single backend driver for this new subsystem that can
control gpio based multiplexers.
---
 drivers/misc/Kconfig    |   6 +
 drivers/misc/Makefile   |   2 +
 drivers/misc/mux-core.c | 285 ++++++++++++++++++++++++++++++++++++++++++++++++
 drivers/misc/mux-gpio.c | 105 ++++++++++++++++++
 include/linux/mux.h     |  54 +++++++++
 5 files changed, 452 insertions(+)
 create mode 100644 drivers/misc/mux-core.c
 create mode 100644 drivers/misc/mux-gpio.c
 create mode 100644 include/linux/mux.h

diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 64971baf11fa..9e119bb78d82 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -766,6 +766,12 @@ config PANEL_BOOT_MESSAGE
 	  An empty message will only clear the display at driver init time. Any other
 	  printf()-formatted message is valid with newline and escape codes.
 
+config MUX_GPIO
+	tristate "GPIO-controlled MUX controller"
+	depends on OF
+	help
+	  GPIO-controlled MUX controller
+
 source "drivers/misc/c2port/Kconfig"
 source "drivers/misc/eeprom/Kconfig"
 source "drivers/misc/cb710/Kconfig"
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index 31983366090a..92b547bcbac1 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -53,6 +53,8 @@ obj-$(CONFIG_ECHO)		+= echo/
 obj-$(CONFIG_VEXPRESS_SYSCFG)	+= vexpress-syscfg.o
 obj-$(CONFIG_CXL_BASE)		+= cxl/
 obj-$(CONFIG_PANEL)             += panel.o
+obj-$(CONFIG_MUX_GPIO)          += mux-core.o
+obj-$(CONFIG_MUX_GPIO)          += mux-gpio.o
 
 lkdtm-$(CONFIG_LKDTM)		+= lkdtm_core.o
 lkdtm-$(CONFIG_LKDTM)		+= lkdtm_bugs.o
diff --git a/drivers/misc/mux-core.c b/drivers/misc/mux-core.c
new file mode 100644
index 000000000000..d7c7b667d1a4
--- /dev/null
+++ b/drivers/misc/mux-core.c
@@ -0,0 +1,285 @@
+/*
+ * Multiplexer subsystem
+ *
+ * Copyright (C) 2016 Axentia Technologies AB
+ *
+ * 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.
+ */
+
+#define pr_fmt(fmt) "mux-core: " fmt
+
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/idr.h>
+#include <linux/module.h>
+#include <linux/mux.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+
+static struct bus_type mux_bus_type = {
+	.name = "mux",
+};
+
+static int __init mux_init(void)
+{
+	return bus_register(&mux_bus_type);
+}
+
+static void __exit mux_exit(void)
+{
+	bus_unregister(&mux_bus_type);
+}
+
+static DEFINE_IDA(mux_ida);
+
+static void mux_control_release(struct device *dev)
+{
+	struct mux_control *mux = to_mux_control(dev);
+
+	ida_simple_remove(&mux_ida, mux->id);
+	kfree(mux);
+}
+
+static struct device_type mux_control_type = {
+	.name = "mux-control",
+	.release = mux_control_release,
+};
+
+/*
+ * Allocate a mux-control, plus an extra memory area for private use
+ * by the caller.
+ */
+struct mux_control *mux_control_alloc(size_t sizeof_priv)
+{
+	struct mux_control *mux;
+
+	mux = kzalloc(sizeof(*mux) + sizeof_priv, GFP_KERNEL);
+	if (!mux)
+		return NULL;
+
+	mux->dev.bus = &mux_bus_type;
+	mux->dev.type = &mux_control_type;
+	device_initialize(&mux->dev);
+	dev_set_drvdata(&mux->dev, mux);
+
+	init_rwsem(&mux->lock);
+	mux->priv = mux + 1;
+
+	mux->id = ida_simple_get(&mux_ida, 0, 0, GFP_KERNEL);
+	if (mux->id < 0) {
+		pr_err("mux-controlX failed to get device id\n");
+		kfree(mux);
+		return NULL;
+	}
+	dev_set_name(&mux->dev, "mux:control%d", mux->id);
+
+	return mux;
+}
+EXPORT_SYMBOL_GPL(mux_control_alloc);
+
+/*
+ * Register the mux-control, thus readying it for use.
+ */
+int mux_control_register(struct mux_control *mux)
+{
+	/* If the calling driver did not initialize of_node, do it here */
+	if (!mux->dev.of_node && mux->dev.parent)
+		mux->dev.of_node = mux->dev.parent->of_node;
+
+	return device_add(&mux->dev);
+}
+EXPORT_SYMBOL_GPL(mux_control_register);
+
+/*
+ * Take the mux-control off-line.
+ */
+void mux_control_unregister(struct mux_control *mux)
+{
+	device_del(&mux->dev);
+}
+EXPORT_SYMBOL_GPL(mux_control_unregister);
+
+/*
+ * Put away the mux-control for good.
+ */
+void mux_control_put(struct mux_control *mux)
+{
+	if (!mux)
+		return;
+	put_device(&mux->dev);
+}
+EXPORT_SYMBOL_GPL(mux_control_free);
+
+/*
+ * Select the given multiplexer channel. Call mux_control_deselect()
+ * when the operation is complete on the multiplexer channel, and the
+ * multiplexer is free for others to use.
+ */
+int mux_control_select(struct mux_control *mux, int reg)
+{
+	int ret;
+
+	if (down_read_trylock(&mux->lock)) {
+		if (mux->cache == reg)
+			return 0;
+
+		/* Sigh, the mux needs updating... */
+		up_read(&mux->lock);
+	}
+
+	/* ...or it's just contended. */
+	down_write(&mux->lock);
+
+	if (mux->cache == reg) {
+		/*
+		 * Hmmm, someone else changed the mux to my liking.
+		 * That makes me wonder how long I waited for nothing...
+		 */
+		downgrade_write(&mux->lock);
+		return 0;
+	}
+
+	ret = mux->ops->set(mux, reg);
+	if (ret < 0) {
+		up_write(&mux->lock);
+		return ret;
+	}
+
+	mux->cache = reg;
+	downgrade_write(&mux->lock);
+
+	return 1;
+}
+EXPORT_SYMBOL_GPL(mux_control_select);
+
+/*
+ * Deselect the previously selected multiplexer channel.
+ */
+int mux_control_deselect(struct mux_control *mux)
+{
+	if (mux->do_idle && mux->cache != mux->idle_state) {
+		mux->ops->set(mux, mux->idle_state);
+		mux->cache = mux->idle_state;
+	}
+
+	up_read(&mux->lock);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(mux_control_deselect);
+
+static int of_dev_node_match(struct device *dev, void *data)
+{
+	return dev->of_node == data;
+}
+
+static struct mux_control *of_find_mux_by_node(struct device_node *np)
+{
+	struct device *dev;
+
+	dev = bus_find_device(&mux_bus_type, NULL, np, of_dev_node_match);
+
+	return dev ? to_mux_control(dev) : NULL;
+}
+
+static struct mux_control *of_mux_control_get(struct device_node *np, int index)
+{
+	struct device_node *mux_np;
+	struct mux_control *mux;
+
+	mux_np = of_parse_phandle(np, "control-muxes", index);
+	if (!mux_np)
+		return NULL;
+
+	mux = of_find_mux_by_node(mux_np);
+	of_node_put(mux_np);
+
+	return mux;
+}
+
+/*
+ * Get a named mux.
+ */
+struct mux_control *mux_control_get(struct device *dev, const char *mux_name)
+{
+	struct device_node *np = dev->of_node;
+	struct mux_control *mux;
+	int index;
+
+	index = of_property_match_string(np, "control-mux-names", mux_name);
+	if (index < 0) {
+		dev_err(dev, "failed to get control-mux %s:%s(%i)\n",
+			np->full_name, mux_name ?: "", index);
+		return ERR_PTR(index);
+	}
+
+	mux = of_mux_control_get(np, index);
+	if (!mux)
+		return ERR_PTR(-EPROBE_DEFER);
+
+	return mux;
+}
+EXPORT_SYMBOL_GPL(mux_control_get);
+
+static void devm_mux_control_free(struct device *dev, void *res)
+{
+	struct mux_control *mux = *(struct mux_control **)res;
+
+	mux_control_put(mux);
+}
+
+/*
+ * Get a named mux, with resource management.
+ */
+struct mux_control *devm_mux_control_get(struct device *dev,
+					 const char *mux_name)
+{
+	struct mux_control **ptr, *mux;
+
+	ptr = devres_alloc(devm_mux_control_free, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return ERR_PTR(-ENOMEM);
+
+	mux = mux_control_get(dev, mux_name);
+	if (IS_ERR(mux)) {
+		devres_free(ptr);
+		return mux;
+	}
+
+	*ptr = mux;
+	devres_add(dev, ptr);
+
+	return mux;
+}
+EXPORT_SYMBOL_GPL(devm_mux_control_get);
+
+static int devm_mux_control_match(struct device *dev, void *res, void *data)
+{
+	struct mux_control **r = res;
+
+	if (!r || !*r) {
+		WARN_ON(!r || !*r);
+		return 0;
+	}
+
+	return *r == data;
+}
+
+/*
+ * Resource-managed version mux_control_put.
+ */
+void devm_mux_control_put(struct device *dev, struct mux_control *mux)
+{
+	WARN_ON(devres_release(dev, devm_mux_control_free,
+			       devm_mux_control_match, mux));
+}
+EXPORT_SYMBOL_GPL(devm_mux_control_put);
+
+subsys_initcall(mux_init);
+module_exit(mux_exit);
+
+MODULE_AUTHOR("Peter Rosin <peda-koto5C5qi+TLoDKTGw+V6w@public.gmane.org");
+MODULE_DESCRIPTION("MUX subsystem");
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/misc/mux-gpio.c b/drivers/misc/mux-gpio.c
new file mode 100644
index 000000000000..5fa59a0c49cf
--- /dev/null
+++ b/drivers/misc/mux-gpio.c
@@ -0,0 +1,105 @@
+/*
+ * GPIO-controlled multiplexer driver
+ *
+ * Copyright (C) 2016 Axentia Technologies AB
+ *
+ * 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.
+ */
+
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/module.h>
+#include <linux/mux.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+
+struct mux_gpio {
+	struct gpio_descs *gpios;
+};
+
+static int mux_gpio_set(struct mux_control *mux, int val)
+{
+	struct mux_gpio *mux_gpio = mux->priv;
+	int i;
+
+	for (i = 0; i < mux_gpio->gpios->ndescs; i++)
+		gpiod_set_value_cansleep(mux_gpio->gpios->desc[i],
+					 val & (1 << i));
+
+	return 0;
+}
+
+static const struct mux_control_ops mux_gpio_ops = {
+	.set = mux_gpio_set,
+};
+
+static const struct of_device_id mux_gpio_dt_ids[] = {
+	{ .compatible = "mux-gpio", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, mux_gpio_dt_ids);
+
+static int mux_gpio_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *np = pdev->dev.of_node;
+	struct mux_control *mux;
+	struct mux_gpio *mux_gpio;
+	int ret;
+
+	if (!np)
+		return -ENODEV;
+
+	mux = mux_control_alloc(sizeof(*mux_gpio));
+	if (!mux)
+		return -ENOMEM;
+	mux_gpio = mux->priv;
+	mux->dev.parent = dev;
+	mux->ops = &mux_gpio_ops;
+
+	platform_set_drvdata(pdev, mux);
+
+	mux_gpio->gpios = devm_gpiod_get_array(dev, "mux", GPIOD_OUT_LOW);
+	if (IS_ERR(mux_gpio->gpios)) {
+		if (PTR_ERR(mux_gpio->gpios) != -EPROBE_DEFER)
+			dev_err(dev, "failed to get gpios\n");
+		mux_control_put(mux);
+		return PTR_ERR(mux_gpio->gpios);
+	}
+
+	ret = mux_control_register(mux);
+	if (ret < 0) {
+		dev_err(dev, "failed to register mux_control\n");
+		mux_control_put(mux);
+		return ret;
+	}
+
+	return ret;
+}
+
+static int mux_gpio_remove(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct mux_control *mux = to_mux_control(dev);
+
+	mux_control_unregister(mux);
+	mux_control_put(mux);
+	return 0;
+}
+
+static struct platform_driver mux_gpio_driver = {
+	.driver = {
+		.name = "mux-gpio",
+		.of_match_table	= of_match_ptr(mux_gpio_dt_ids),
+	},
+	.probe = mux_gpio_probe,
+	.remove = mux_gpio_remove,
+};
+module_platform_driver(mux_gpio_driver);
+
+MODULE_AUTHOR("Peter Rosin <peda-koto5C5qi+TLoDKTGw+V6w@public.gmane.org");
+MODULE_DESCRIPTION("GPIO-controlled multiplexer driver");
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/mux.h b/include/linux/mux.h
new file mode 100644
index 000000000000..6513ffe749bb
--- /dev/null
+++ b/include/linux/mux.h
@@ -0,0 +1,54 @@
+/*
+ * mux.h - definitions for the multiplexer interface
+ *
+ * Copyright (C) 2016 Axentia Technologies AB
+ *
+ * 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.
+ */
+
+#ifndef _LINUX_MUX_H
+#define _LINUX_MUX_H
+
+#include <linux/device.h>
+#include <linux/rwsem.h>
+
+struct mux_control;
+
+struct mux_control_ops {
+	int (*set)(struct mux_control *mux, int reg);
+};
+
+struct mux_control {
+	struct rw_semaphore lock; /* protects the state of the mux */
+
+	struct device dev;
+	int id;
+
+	int cache;
+	bool do_idle;
+	int idle_state;
+
+	const struct mux_control_ops *ops;
+
+	void *priv;
+};
+
+#define to_mux_control(x) container_of((x), struct mux_control, dev)
+
+struct mux_control *mux_control_alloc(size_t sizeof_priv);
+int mux_control_register(struct mux_control *mux);
+void mux_control_unregister(struct mux_control *mux);
+void mux_control_put(struct mux_control *mux);
+
+int mux_control_select(struct mux_control *mux, int reg);
+int mux_control_deselect(struct mux_control *mux);
+
+struct mux_control *mux_control_get(struct device *dev,
+				    const char *mux_name);
+struct mux_control *devm_mux_control_get(struct device *dev,
+					 const char *mux_name);
+void devm_mux_control_put(struct device *dev, struct mux_control *mux);
+
+#endif /* _LINUX_MUX_H */
-- 
2.1.4

[RFC PATCH 3/7] iio: inkern: api for manipulating ext_info of iio channels

[Peter Rosin]

Extend the inkern api with functions for reading and writing ext_info
of iio channels.
---
 drivers/iio/inkern.c         | 40 ++++++++++++++++++++++++++++++++++++++++
 include/linux/iio/consumer.h |  5 +++++
 2 files changed, 45 insertions(+)

diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
index cfca17ba2535..5348735281ee 100644
--- a/drivers/iio/inkern.c
+++ b/drivers/iio/inkern.c
@@ -850,3 +850,43 @@ int iio_write_channel_raw(struct iio_channel *chan, int val)
 	return ret;
 }
 EXPORT_SYMBOL_GPL(iio_write_channel_raw);
+
+int iio_read_channel_ext_info(struct iio_channel *chan,
+			      const char *attr, char *buf)
+{
+	const struct iio_chan_spec_ext_info *ext_info;
+
+	if (!chan->channel->ext_info)
+		return -EINVAL;
+
+	for (ext_info = chan->channel->ext_info; ext_info->name; ++ext_info) {
+		if (strcmp(attr, ext_info->name))
+			continue;
+
+		return ext_info->read(chan->indio_dev, ext_info->private,
+				      chan->channel, buf);
+	}
+
+	return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(iio_read_channel_ext_info);
+
+int iio_write_channel_ext_info(struct iio_channel *chan,
+			       const char *attr, const char *buf, size_t len)
+{
+	const struct iio_chan_spec_ext_info *ext_info;
+
+	if (!chan->channel->ext_info)
+		return -EINVAL;
+
+	for (ext_info = chan->channel->ext_info; ext_info->name; ++ext_info) {
+		if (strcmp(attr, ext_info->name))
+			continue;
+
+		return ext_info->write(chan->indio_dev, ext_info->private,
+				       chan->channel, buf, len);
+	}
+
+	return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(iio_write_channel_ext_info);
diff --git a/include/linux/iio/consumer.h b/include/linux/iio/consumer.h
index 9a4f336d8b4a..3859981cea0a 100644
--- a/include/linux/iio/consumer.h
+++ b/include/linux/iio/consumer.h
@@ -299,4 +299,9 @@ int iio_read_channel_scale(struct iio_channel *chan, int *val,
 int iio_convert_raw_to_processed(struct iio_channel *chan, int raw,
 	int *processed, unsigned int scale);
 
+int iio_read_channel_ext_info(struct iio_channel *chan,
+			      const char *attr, char *buf);
+int iio_write_channel_ext_info(struct iio_channel *chan,
+			       const char *attr, const char *buf, size_t len);
+
 #endif
-- 
2.1.4

[RFC PATCH 3/7] iio: inkern: api for manipulating ext_info of iio channels

[Peter Rosin]

Extend the inkern api with functions for reading and writing ext_info
of iio channels.
---
 drivers/iio/inkern.c         | 40 ++++++++++++++++++++++++++++++++++++++++
 include/linux/iio/consumer.h |  5 +++++
 2 files changed, 45 insertions(+)

diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
index cfca17ba2535..5348735281ee 100644
--- a/drivers/iio/inkern.c
+++ b/drivers/iio/inkern.c
@@ -850,3 +850,43 @@ int iio_write_channel_raw(struct iio_channel *chan, int val)
 	return ret;
 }
 EXPORT_SYMBOL_GPL(iio_write_channel_raw);
+
+int iio_read_channel_ext_info(struct iio_channel *chan,
+			      const char *attr, char *buf)
+{
+	const struct iio_chan_spec_ext_info *ext_info;
+
+	if (!chan->channel->ext_info)
+		return -EINVAL;
+
+	for (ext_info = chan->channel->ext_info; ext_info->name; ++ext_info) {
+		if (strcmp(attr, ext_info->name))
+			continue;
+
+		return ext_info->read(chan->indio_dev, ext_info->private,
+				      chan->channel, buf);
+	}
+
+	return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(iio_read_channel_ext_info);
+
+int iio_write_channel_ext_info(struct iio_channel *chan,
+			       const char *attr, const char *buf, size_t len)
+{
+	const struct iio_chan_spec_ext_info *ext_info;
+
+	if (!chan->channel->ext_info)
+		return -EINVAL;
+
+	for (ext_info = chan->channel->ext_info; ext_info->name; ++ext_info) {
+		if (strcmp(attr, ext_info->name))
+			continue;
+
+		return ext_info->write(chan->indio_dev, ext_info->private,
+				       chan->channel, buf, len);
+	}
+
+	return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(iio_write_channel_ext_info);
diff --git a/include/linux/iio/consumer.h b/include/linux/iio/consumer.h
index 9a4f336d8b4a..3859981cea0a 100644
--- a/include/linux/iio/consumer.h
+++ b/include/linux/iio/consumer.h
@@ -299,4 +299,9 @@ int iio_read_channel_scale(struct iio_channel *chan, int *val,
 int iio_convert_raw_to_processed(struct iio_channel *chan, int raw,
 	int *processed, unsigned int scale);
 
+int iio_read_channel_ext_info(struct iio_channel *chan,
+			      const char *attr, char *buf);
+int iio_write_channel_ext_info(struct iio_channel *chan,
+			       const char *attr, const char *buf, size_t len);
+
 #endif
-- 
2.1.4

[RFC PATCH 4/7] dt-bindings: iio: iio-mux: document iio-mux bindings

[Peter Rosin]

---
 .../bindings/iio/multiplexer/iio-mux.txt           | 59 ++++++++++++++++++++++
 1 file changed, 59 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/multiplexer/iio-mux.txt

diff --git a/Documentation/devicetree/bindings/iio/multiplexer/iio-mux.txt b/Documentation/devicetree/bindings/iio/multiplexer/iio-mux.txt
new file mode 100644
index 000000000000..2f5c7fc35a42
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/multiplexer/iio-mux.txt
@@ -0,0 +1,59 @@
+IIO multiplexer bindings
+
+If a multiplexer is used to select when hardware signal is fed to
+e.g. an ADC channel, these bindings describe that situation.
+
+Required properties:
+- compatible : "iio-mux"
+- io-channels : Channel node of the parent channel that has multiplexed
+		input.
+- io-channel-names : Should be "parent".
+- control-muxes : Node of the multiplexer that controls the input signal.
+- control-mux-names : Should be "mux".
+- #address-cells = <1>;
+- #size-cells = <0>;
+
+Required properties for iio-mux child nodes:
+- reg : The multiplexer number.
+
+Optional properties for iio-mux child nodes:
+- iio-ext-info : Array of string pairs, the first item in each pair is the
+		 iio ext_info attribute name, and the second item in each
+		 pair is the iio ext_info value for that attribute. The
+		 mux will write these ext_info values to the corresponding
+		 ext_info attributes on every multiplexer switch.
+
+Example:
+	control_adc_mux: control-adc-mux {
+		compatible = "mux-gpio";
+
+		mux-gpios = <&pioA 0 GPIO_ACTIVE_HIGH>,
+			    <&pioA 1 GPIO_ACTIVE_HIGH>;
+	};
+
+	adc-mux {
+		compatible = "iio-mux";
+		io-channels = <&adc 0>;
+		io-channel-names = "parent";
+
+		control-muxes = <&control_adc_mux>;
+		control-mux-names = "mux";
+
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		sync@0 {
+			reg = <0>;
+			iio-ext-info = "invert", "1";
+		};
+
+		in@1 {
+			reg = <1>;
+			iio-ext-info = "invert", "1";
+		};
+
+		system-regulator@2 {
+			reg = <2>;
+			iio-ext-info = "invert", "0";
+		};
+	};
-- 
2.1.4

[RFC PATCH 4/7] dt-bindings: iio: iio-mux: document iio-mux bindings

[Peter Rosin]

---
 .../bindings/iio/multiplexer/iio-mux.txt           | 59 ++++++++++++++++++++++
 1 file changed, 59 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/multiplexer/iio-mux.txt

diff --git a/Documentation/devicetree/bindings/iio/multiplexer/iio-mux.txt b/Documentation/devicetree/bindings/iio/multiplexer/iio-mux.txt
new file mode 100644
index 000000000000..2f5c7fc35a42
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/multiplexer/iio-mux.txt
@@ -0,0 +1,59 @@
+IIO multiplexer bindings
+
+If a multiplexer is used to select when hardware signal is fed to
+e.g. an ADC channel, these bindings describe that situation.
+
+Required properties:
+- compatible : "iio-mux"
+- io-channels : Channel node of the parent channel that has multiplexed
+		input.
+- io-channel-names : Should be "parent".
+- control-muxes : Node of the multiplexer that controls the input signal.
+- control-mux-names : Should be "mux".
+- #address-cells = <1>;
+- #size-cells = <0>;
+
+Required properties for iio-mux child nodes:
+- reg : The multiplexer number.
+
+Optional properties for iio-mux child nodes:
+- iio-ext-info : Array of string pairs, the first item in each pair is the
+		 iio ext_info attribute name, and the second item in each
+		 pair is the iio ext_info value for that attribute. The
+		 mux will write these ext_info values to the corresponding
+		 ext_info attributes on every multiplexer switch.
+
+Example:
+	control_adc_mux: control-adc-mux {
+		compatible = "mux-gpio";
+
+		mux-gpios = <&pioA 0 GPIO_ACTIVE_HIGH>,
+			    <&pioA 1 GPIO_ACTIVE_HIGH>;
+	};
+
+	adc-mux {
+		compatible = "iio-mux";
+		io-channels = <&adc 0>;
+		io-channel-names = "parent";
+
+		control-muxes = <&control_adc_mux>;
+		control-mux-names = "mux";
+
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		sync@0 {
+			reg = <0>;
+			iio-ext-info = "invert", "1";
+		};
+
+		in@1 {
+			reg = <1>;
+			iio-ext-info = "invert", "1";
+		};
+
+		system-regulator@2 {
+			reg = <2>;
+			iio-ext-info = "invert", "0";
+		};
+	};
-- 
2.1.4

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[RFC PATCH 5/7] iio: multiplexer: new iio category and iio-mux driver

[Peter Rosin]

When a multiplexer changes how an iio device behaves (for example
by feeding different signals to an ADC), this driver can be used
create one virtual iio channel for each multiplexer state.

Depends on the generic multiplexer driver.
---
 drivers/iio/Kconfig               |   1 +
 drivers/iio/Makefile              |   1 +
 drivers/iio/multiplexer/Kconfig   |  17 +++
 drivers/iio/multiplexer/Makefile  |   6 +
 drivers/iio/multiplexer/iio-mux.c | 313 ++++++++++++++++++++++++++++++++++++++
 5 files changed, 338 insertions(+)
 create mode 100644 drivers/iio/multiplexer/Kconfig
 create mode 100644 drivers/iio/multiplexer/Makefile
 create mode 100644 drivers/iio/multiplexer/iio-mux.c

diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
index 6743b18194fb..dcb541d0d70e 100644
--- a/drivers/iio/Kconfig
+++ b/drivers/iio/Kconfig
@@ -82,6 +82,7 @@ source "drivers/iio/humidity/Kconfig"
 source "drivers/iio/imu/Kconfig"
 source "drivers/iio/light/Kconfig"
 source "drivers/iio/magnetometer/Kconfig"
+source "drivers/iio/multiplexer/Kconfig"
 source "drivers/iio/orientation/Kconfig"
 if IIO_TRIGGER
    source "drivers/iio/trigger/Kconfig"
diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile
index 87e4c4369e2f..f9879c29cf6f 100644
--- a/drivers/iio/Makefile
+++ b/drivers/iio/Makefile
@@ -27,6 +27,7 @@ obj-y += humidity/
 obj-y += imu/
 obj-y += light/
 obj-y += magnetometer/
+obj-y += multiplexer/
 obj-y += orientation/
 obj-y += potentiometer/
 obj-y += pressure/
diff --git a/drivers/iio/multiplexer/Kconfig b/drivers/iio/multiplexer/Kconfig
new file mode 100644
index 000000000000..31cbe4509366
--- /dev/null
+++ b/drivers/iio/multiplexer/Kconfig
@@ -0,0 +1,17 @@
+#
+# Multiplexer drivers
+#
+# When adding new entries keep the list in alphabetical order
+
+menu "Multiplexers"
+
+config IIO_MUX
+	tristate "IIO multiplexer driver"
+	depends on OF && MUX_GPIO
+	help
+	  Say yes here to build support for the IIO multiplexer.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called iio-mux.
+
+endmenu
diff --git a/drivers/iio/multiplexer/Makefile b/drivers/iio/multiplexer/Makefile
new file mode 100644
index 000000000000..68be3c4abd07
--- /dev/null
+++ b/drivers/iio/multiplexer/Makefile
@@ -0,0 +1,6 @@
+#
+# Makefile for industrial I/O multiplexer drivers
+#
+
+# When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_IIO_MUX) += iio-mux.o
diff --git a/drivers/iio/multiplexer/iio-mux.c b/drivers/iio/multiplexer/iio-mux.c
new file mode 100644
index 000000000000..6f6644fb9342
--- /dev/null
+++ b/drivers/iio/multiplexer/iio-mux.c
@@ -0,0 +1,313 @@
+/*
+ * IIO multiplexer driver
+ *
+ * Copyright (C) 2016 Axentia Technologies AB
+ *
+ * Author: Peter Rosin <peda@axentia.se>
+ *
+ * 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.
+ */
+
+#include <linux/err.h>
+#include <linux/iio/consumer.h>
+#include <linux/iio/iio.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/mux.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+
+struct mux_child {
+	u32 reg;
+
+	const char **ext_info;
+	int num_ext_info;
+};
+
+struct mux {
+	u32 cache;
+	struct mux_control *control;
+	struct iio_channel *parent;
+	struct iio_dev *indio_dev;
+	struct iio_chan_spec *c;
+	struct mux_child *child;
+};
+
+static int iio_mux_select(struct mux *mux, int idx)
+{
+	struct mux_child *child = &mux->child[idx];
+	int ret;
+	int i;
+
+	ret = mux_control_select(mux->control, child->reg);
+	if (ret < 0)
+		return ret;
+
+	if (mux->cache == child->reg)
+		return 0;
+
+	for (i = 0; i < child->num_ext_info - 1; i += 2) {
+		const char *value = child->ext_info[i + 1];
+
+		ret = iio_write_channel_ext_info(mux->parent,
+						 child->ext_info[i],
+						 value, strlen(value));
+		if (ret < 0) {
+			mux_control_deselect(mux->control);
+			return ret;
+		}
+	}
+	mux->cache = child->reg;
+
+	return 0;
+}
+
+static void iio_mux_deselect(struct mux *mux)
+{
+	mux_control_deselect(mux->control);
+}
+
+static int mux_read_raw(struct iio_dev *indio_dev,
+			struct iio_chan_spec const *chan,
+			int *val, int *val2, long mask)
+{
+	struct mux *mux = iio_priv(indio_dev);
+	int idx = chan - mux->c;
+	int ret;
+
+	ret = iio_mux_select(mux, idx);
+	if (ret < 0)
+		return ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = iio_read_channel_raw(mux->parent, val);
+		break;
+
+	case IIO_CHAN_INFO_SCALE:
+		ret = iio_read_channel_scale(mux->parent, val, val2);
+		break;
+
+	default:
+		ret = -EINVAL;
+	}
+
+	iio_mux_deselect(mux);
+
+	return ret;
+}
+
+static int mux_read_avail(struct iio_dev *indio_dev,
+			  struct iio_chan_spec const *chan,
+			  const int **vals, int *type, int *length,
+			  long mask)
+{
+	struct mux *mux = iio_priv(indio_dev);
+	int idx = chan - mux->c;
+	int ret;
+
+	ret = iio_mux_select(mux, idx);
+	if (ret < 0)
+		return ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		*type = IIO_VAL_INT;
+		ret = iio_read_avail_channel_raw(mux->parent, vals, length);
+		break;
+
+	default:
+		ret = -EINVAL;
+	}
+
+	iio_mux_deselect(mux);
+
+	return ret;
+}
+
+static int mux_write_raw(struct iio_dev *indio_dev,
+			 struct iio_chan_spec const *chan,
+			 int val, int val2, long mask)
+{
+	struct mux *mux = iio_priv(indio_dev);
+	int idx = chan - mux->c;
+	int ret;
+
+	ret = iio_mux_select(mux, idx);
+	if (ret < 0)
+		return ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = iio_write_channel_raw(mux->parent, val);
+		break;
+
+	default:
+		ret = -EINVAL;
+	}
+
+	iio_mux_deselect(mux);
+
+	return ret;
+}
+
+static const struct iio_info mux_info = {
+	.read_raw = mux_read_raw,
+	.read_avail = mux_read_avail,
+	.write_raw = mux_write_raw,
+	.driver_module = THIS_MODULE,
+};
+
+static int mux_configure_channel(struct device *dev, struct mux *mux,
+				 struct device_node *child_np, int idx)
+{
+	struct mux_child *child = &mux->child[idx];
+	struct iio_chan_spec *c = &mux->c[idx];
+	const struct iio_chan_spec *pc = mux->parent->channel;
+	int i;
+	int ret;
+
+	c->indexed = 1;
+	c->channel = idx;
+	c->output = pc->output;
+	c->datasheet_name = child_np->name;
+
+	ret = iio_get_channel_type(mux->parent, &c->type);
+	if (ret < 0) {
+		dev_err(dev, "failed to get parent channel type\n");
+		return ret;
+	}
+
+	if (iio_channel_has_info(pc, IIO_CHAN_INFO_RAW))
+		c->info_mask_separate |= BIT(IIO_CHAN_INFO_RAW);
+	if (iio_channel_has_info(pc, IIO_CHAN_INFO_SCALE))
+		c->info_mask_separate |= BIT(IIO_CHAN_INFO_SCALE);
+
+	if (iio_channel_has_available(pc, IIO_CHAN_INFO_RAW))
+		c->info_mask_separate_available |= BIT(IIO_CHAN_INFO_RAW);
+
+	ret = of_property_read_u32(child_np, "reg", &child->reg);
+	if (ret < 0) {
+		dev_err(dev, "no reg property for node '%s'\n", child_np->name);
+		return ret;
+	}
+
+	for (i = 0; i < idx; ++i) {
+		if (mux->child[i].reg == child->reg) {
+			dev_err(dev, "double use of reg %d\n", child->reg);
+			return -EINVAL;
+		}
+	}
+
+	ret = of_property_read_string_array(child_np, "iio-ext-info", NULL, 0);
+	if (ret <= 0)
+		return 0;
+
+	child->ext_info = devm_kzalloc(dev, sizeof(*child->ext_info) * ret,
+				       GFP_KERNEL);
+	if (!child->ext_info)
+		return -ENOMEM;
+
+	child->num_ext_info = ret;
+	ret = of_property_read_string_array(child_np, "iio-ext-info",
+					    child->ext_info,
+					    child->num_ext_info);
+	if (ret != child->num_ext_info)
+		return -EINVAL;
+
+	return 0;
+}
+
+static int mux_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *np = pdev->dev.of_node;
+	struct device_node *child_np;
+	struct iio_dev *indio_dev;
+	struct mux *mux;
+	int children;
+	int sizeof_priv;
+	int idx;
+	int ret;
+
+	if (!np)
+		return -ENODEV;
+
+	children = of_get_child_count(np);
+	if (children <= 0) {
+		dev_err(dev, "not even a single child\n");
+		return -EINVAL;
+	}
+
+	sizeof_priv = sizeof(*mux);
+	sizeof_priv += sizeof(*mux->child) * children;
+	sizeof_priv += sizeof(*mux->c) * children;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof_priv);
+	if (!indio_dev)
+		return -ENOMEM;
+
+	mux = iio_priv(indio_dev);
+	mux->child = (struct mux_child *)(mux + 1);
+	mux->c = (struct iio_chan_spec *)(mux->child + children);
+
+	platform_set_drvdata(pdev, indio_dev);
+
+	mux->parent = devm_iio_channel_get(dev, "parent");
+	if (IS_ERR(mux->parent)) {
+		if (PTR_ERR(mux->parent) != -EPROBE_DEFER)
+			dev_err(dev, "failed to get parent channel\n");
+		return PTR_ERR(mux->parent);
+	}
+
+	indio_dev->name = dev_name(dev);
+	indio_dev->dev.parent = dev;
+	indio_dev->info = &mux_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = mux->c;
+	indio_dev->num_channels = children;
+
+	idx = 0;
+	for_each_child_of_node(np, child_np) {
+		ret = mux_configure_channel(dev, mux, child_np, idx);
+		if (ret < 0)
+			return ret;
+		idx++;
+	}
+
+	mux->control = devm_mux_control_get(dev, "mux");
+	if (IS_ERR(mux->control)) {
+		if (PTR_ERR(mux->control) != -EPROBE_DEFER)
+			dev_err(dev, "failed to get control-mux\n");
+		return PTR_ERR(mux->control);
+	}
+
+	ret = devm_iio_device_register(dev, indio_dev);
+	if (ret) {
+		dev_err(dev, "failed to register iio device\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct of_device_id mux_match[] = {
+	{ .compatible = "iio-mux" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, mux_match);
+
+static struct platform_driver mux_driver = {
+	.probe = mux_probe,
+	.driver = {
+		.name = "iio-mux",
+		.of_match_table = mux_match,
+	},
+};
+module_platform_driver(mux_driver);
+
+MODULE_DESCRIPTION("IIO multiplexer driver");
+MODULE_AUTHOR("Peter Rosin <peda@axentia.se>");
+MODULE_LICENSE("GPL v2");
-- 
2.1.4

[RFC PATCH 5/7] iio: multiplexer: new iio category and iio-mux driver

[Peter Rosin]

When a multiplexer changes how an iio device behaves (for example
by feeding different signals to an ADC), this driver can be used
create one virtual iio channel for each multiplexer state.

Depends on the generic multiplexer driver.
---
 drivers/iio/Kconfig               |   1 +
 drivers/iio/Makefile              |   1 +
 drivers/iio/multiplexer/Kconfig   |  17 +++
 drivers/iio/multiplexer/Makefile  |   6 +
 drivers/iio/multiplexer/iio-mux.c | 313 ++++++++++++++++++++++++++++++++++++++
 5 files changed, 338 insertions(+)
 create mode 100644 drivers/iio/multiplexer/Kconfig
 create mode 100644 drivers/iio/multiplexer/Makefile
 create mode 100644 drivers/iio/multiplexer/iio-mux.c

diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
index 6743b18194fb..dcb541d0d70e 100644
--- a/drivers/iio/Kconfig
+++ b/drivers/iio/Kconfig
@@ -82,6 +82,7 @@ source "drivers/iio/humidity/Kconfig"
 source "drivers/iio/imu/Kconfig"
 source "drivers/iio/light/Kconfig"
 source "drivers/iio/magnetometer/Kconfig"
+source "drivers/iio/multiplexer/Kconfig"
 source "drivers/iio/orientation/Kconfig"
 if IIO_TRIGGER
    source "drivers/iio/trigger/Kconfig"
diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile
index 87e4c4369e2f..f9879c29cf6f 100644
--- a/drivers/iio/Makefile
+++ b/drivers/iio/Makefile
@@ -27,6 +27,7 @@ obj-y += humidity/
 obj-y += imu/
 obj-y += light/
 obj-y += magnetometer/
+obj-y += multiplexer/
 obj-y += orientation/
 obj-y += potentiometer/
 obj-y += pressure/
diff --git a/drivers/iio/multiplexer/Kconfig b/drivers/iio/multiplexer/Kconfig
new file mode 100644
index 000000000000..31cbe4509366
--- /dev/null
+++ b/drivers/iio/multiplexer/Kconfig
@@ -0,0 +1,17 @@
+#
+# Multiplexer drivers
+#
+# When adding new entries keep the list in alphabetical order
+
+menu "Multiplexers"
+
+config IIO_MUX
+	tristate "IIO multiplexer driver"
+	depends on OF && MUX_GPIO
+	help
+	  Say yes here to build support for the IIO multiplexer.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called iio-mux.
+
+endmenu
diff --git a/drivers/iio/multiplexer/Makefile b/drivers/iio/multiplexer/Makefile
new file mode 100644
index 000000000000..68be3c4abd07
--- /dev/null
+++ b/drivers/iio/multiplexer/Makefile
@@ -0,0 +1,6 @@
+#
+# Makefile for industrial I/O multiplexer drivers
+#
+
+# When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_IIO_MUX) += iio-mux.o
diff --git a/drivers/iio/multiplexer/iio-mux.c b/drivers/iio/multiplexer/iio-mux.c
new file mode 100644
index 000000000000..6f6644fb9342
--- /dev/null
+++ b/drivers/iio/multiplexer/iio-mux.c
@@ -0,0 +1,313 @@
+/*
+ * IIO multiplexer driver
+ *
+ * Copyright (C) 2016 Axentia Technologies AB
+ *
+ * Author: Peter Rosin <peda@axentia.se>
+ *
+ * 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.
+ */
+
+#include <linux/err.h>
+#include <linux/iio/consumer.h>
+#include <linux/iio/iio.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/mux.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+
+struct mux_child {
+	u32 reg;
+
+	const char **ext_info;
+	int num_ext_info;
+};
+
+struct mux {
+	u32 cache;
+	struct mux_control *control;
+	struct iio_channel *parent;
+	struct iio_dev *indio_dev;
+	struct iio_chan_spec *c;
+	struct mux_child *child;
+};
+
+static int iio_mux_select(struct mux *mux, int idx)
+{
+	struct mux_child *child = &mux->child[idx];
+	int ret;
+	int i;
+
+	ret = mux_control_select(mux->control, child->reg);
+	if (ret < 0)
+		return ret;
+
+	if (mux->cache == child->reg)
+		return 0;
+
+	for (i = 0; i < child->num_ext_info - 1; i += 2) {
+		const char *value = child->ext_info[i + 1];
+
+		ret = iio_write_channel_ext_info(mux->parent,
+						 child->ext_info[i],
+						 value, strlen(value));
+		if (ret < 0) {
+			mux_control_deselect(mux->control);
+			return ret;
+		}
+	}
+	mux->cache = child->reg;
+
+	return 0;
+}
+
+static void iio_mux_deselect(struct mux *mux)
+{
+	mux_control_deselect(mux->control);
+}
+
+static int mux_read_raw(struct iio_dev *indio_dev,
+			struct iio_chan_spec const *chan,
+			int *val, int *val2, long mask)
+{
+	struct mux *mux = iio_priv(indio_dev);
+	int idx = chan - mux->c;
+	int ret;
+
+	ret = iio_mux_select(mux, idx);
+	if (ret < 0)
+		return ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = iio_read_channel_raw(mux->parent, val);
+		break;
+
+	case IIO_CHAN_INFO_SCALE:
+		ret = iio_read_channel_scale(mux->parent, val, val2);
+		break;
+
+	default:
+		ret = -EINVAL;
+	}
+
+	iio_mux_deselect(mux);
+
+	return ret;
+}
+
+static int mux_read_avail(struct iio_dev *indio_dev,
+			  struct iio_chan_spec const *chan,
+			  const int **vals, int *type, int *length,
+			  long mask)
+{
+	struct mux *mux = iio_priv(indio_dev);
+	int idx = chan - mux->c;
+	int ret;
+
+	ret = iio_mux_select(mux, idx);
+	if (ret < 0)
+		return ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		*type = IIO_VAL_INT;
+		ret = iio_read_avail_channel_raw(mux->parent, vals, length);
+		break;
+
+	default:
+		ret = -EINVAL;
+	}
+
+	iio_mux_deselect(mux);
+
+	return ret;
+}
+
+static int mux_write_raw(struct iio_dev *indio_dev,
+			 struct iio_chan_spec const *chan,
+			 int val, int val2, long mask)
+{
+	struct mux *mux = iio_priv(indio_dev);
+	int idx = chan - mux->c;
+	int ret;
+
+	ret = iio_mux_select(mux, idx);
+	if (ret < 0)
+		return ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = iio_write_channel_raw(mux->parent, val);
+		break;
+
+	default:
+		ret = -EINVAL;
+	}
+
+	iio_mux_deselect(mux);
+
+	return ret;
+}
+
+static const struct iio_info mux_info = {
+	.read_raw = mux_read_raw,
+	.read_avail = mux_read_avail,
+	.write_raw = mux_write_raw,
+	.driver_module = THIS_MODULE,
+};
+
+static int mux_configure_channel(struct device *dev, struct mux *mux,
+				 struct device_node *child_np, int idx)
+{
+	struct mux_child *child = &mux->child[idx];
+	struct iio_chan_spec *c = &mux->c[idx];
+	const struct iio_chan_spec *pc = mux->parent->channel;
+	int i;
+	int ret;
+
+	c->indexed = 1;
+	c->channel = idx;
+	c->output = pc->output;
+	c->datasheet_name = child_np->name;
+
+	ret = iio_get_channel_type(mux->parent, &c->type);
+	if (ret < 0) {
+		dev_err(dev, "failed to get parent channel type\n");
+		return ret;
+	}
+
+	if (iio_channel_has_info(pc, IIO_CHAN_INFO_RAW))
+		c->info_mask_separate |= BIT(IIO_CHAN_INFO_RAW);
+	if (iio_channel_has_info(pc, IIO_CHAN_INFO_SCALE))
+		c->info_mask_separate |= BIT(IIO_CHAN_INFO_SCALE);
+
+	if (iio_channel_has_available(pc, IIO_CHAN_INFO_RAW))
+		c->info_mask_separate_available |= BIT(IIO_CHAN_INFO_RAW);
+
+	ret = of_property_read_u32(child_np, "reg", &child->reg);
+	if (ret < 0) {
+		dev_err(dev, "no reg property for node '%s'\n", child_np->name);
+		return ret;
+	}
+
+	for (i = 0; i < idx; ++i) {
+		if (mux->child[i].reg == child->reg) {
+			dev_err(dev, "double use of reg %d\n", child->reg);
+			return -EINVAL;
+		}
+	}
+
+	ret = of_property_read_string_array(child_np, "iio-ext-info", NULL, 0);
+	if (ret <= 0)
+		return 0;
+
+	child->ext_info = devm_kzalloc(dev, sizeof(*child->ext_info) * ret,
+				       GFP_KERNEL);
+	if (!child->ext_info)
+		return -ENOMEM;
+
+	child->num_ext_info = ret;
+	ret = of_property_read_string_array(child_np, "iio-ext-info",
+					    child->ext_info,
+					    child->num_ext_info);
+	if (ret != child->num_ext_info)
+		return -EINVAL;
+
+	return 0;
+}
+
+static int mux_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *np = pdev->dev.of_node;
+	struct device_node *child_np;
+	struct iio_dev *indio_dev;
+	struct mux *mux;
+	int children;
+	int sizeof_priv;
+	int idx;
+	int ret;
+
+	if (!np)
+		return -ENODEV;
+
+	children = of_get_child_count(np);
+	if (children <= 0) {
+		dev_err(dev, "not even a single child\n");
+		return -EINVAL;
+	}
+
+	sizeof_priv = sizeof(*mux);
+	sizeof_priv += sizeof(*mux->child) * children;
+	sizeof_priv += sizeof(*mux->c) * children;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof_priv);
+	if (!indio_dev)
+		return -ENOMEM;
+
+	mux = iio_priv(indio_dev);
+	mux->child = (struct mux_child *)(mux + 1);
+	mux->c = (struct iio_chan_spec *)(mux->child + children);
+
+	platform_set_drvdata(pdev, indio_dev);
+
+	mux->parent = devm_iio_channel_get(dev, "parent");
+	if (IS_ERR(mux->parent)) {
+		if (PTR_ERR(mux->parent) != -EPROBE_DEFER)
+			dev_err(dev, "failed to get parent channel\n");
+		return PTR_ERR(mux->parent);
+	}
+
+	indio_dev->name = dev_name(dev);
+	indio_dev->dev.parent = dev;
+	indio_dev->info = &mux_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = mux->c;
+	indio_dev->num_channels = children;
+
+	idx = 0;
+	for_each_child_of_node(np, child_np) {
+		ret = mux_configure_channel(dev, mux, child_np, idx);
+		if (ret < 0)
+			return ret;
+		idx++;
+	}
+
+	mux->control = devm_mux_control_get(dev, "mux");
+	if (IS_ERR(mux->control)) {
+		if (PTR_ERR(mux->control) != -EPROBE_DEFER)
+			dev_err(dev, "failed to get control-mux\n");
+		return PTR_ERR(mux->control);
+	}
+
+	ret = devm_iio_device_register(dev, indio_dev);
+	if (ret) {
+		dev_err(dev, "failed to register iio device\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct of_device_id mux_match[] = {
+	{ .compatible = "iio-mux" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, mux_match);
+
+static struct platform_driver mux_driver = {
+	.probe = mux_probe,
+	.driver = {
+		.name = "iio-mux",
+		.of_match_table = mux_match,
+	},
+};
+module_platform_driver(mux_driver);
+
+MODULE_DESCRIPTION("IIO multiplexer driver");
+MODULE_AUTHOR("Peter Rosin <peda@axentia.se>");
+MODULE_LICENSE("GPL v2");
-- 
2.1.4

[RFC PATCH 6/7] dt-bindings: i2c: i2c-mux-simple: document i2c-mux-simple bindings

[Peter Rosin]

---
 .../devicetree/bindings/i2c/i2c-mux-simple.txt     | 91 ++++++++++++++++++++++
 1 file changed, 91 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/i2c/i2c-mux-simple.txt

diff --git a/Documentation/devicetree/bindings/i2c/i2c-mux-simple.txt b/Documentation/devicetree/bindings/i2c/i2c-mux-simple.txt
new file mode 100644
index 000000000000..fec1ab39ad64
--- /dev/null
+++ b/Documentation/devicetree/bindings/i2c/i2c-mux-simple.txt
@@ -0,0 +1,91 @@
+Simple I2C Bus Mux
+
+This binding describes an I2C bus multiplexer that uses GPIOs to
+route the I2C signals.
+
+                                  .-----.  .-----.
+                                  | dev |  | dev |
+    .------------.                '-----'  '-----'
+    | SoC        |                   |        |
+    |            |          .--------+--------'
+    |   .------. |  .------+    child bus A, on MUX value set to 0
+    |   | I2C  |-|--| Mux  |
+    |   '------' |  '--+---+    child bus B, on MUX value set to 1
+    |   .------. |     |    '----------+--------+--------.
+    |   | MUX- | |     |               |        |        |
+    |   | Ctrl |-|-----+            .-----.  .-----.  .-----.
+    |   '------' |                  | dev |  | dev |  | dev |
+    '------------'                  '-----'  '-----'  '-----'
+
+Required properties:
+- compatible: i2c-mux-simple,mux-locked or i2c-mux-simple,parent-locked
+- i2c-parent: The phandle of the I2C bus that this multiplexer's master-side
+  port is connected to.
+- control-muxes : Node of the multiplexer that controls "Mux".
+- control-mux-names : Should be "mux".
+* Standard I2C mux properties. See i2c-mux.txt in this directory.
+* I2C child bus nodes. See i2c-mux.txt in this directory.
+
+Optional properties:
+- idle-state: value to set the muxer to when idle. When no value is
+  given, it defaults to the last value used.
+
+For each i2c child node, an I2C child bus will be created. They will
+be numbered based on their order in the device tree.
+
+Whenever an access is made to a device on a child bus, the value set
+in the relevant node's reg property will be fed to the mux controller.
+
+If an idle state is defined, using the idle-state (optional) property,
+whenever an access is not being made to a device on a child bus, the
+mux controller will be set according to the idle value.
+
+If an idle state is not defined, the most recently used value will be
+left programmed into hardware whenever no access is being made to a
+device on a child bus.
+
+Example:
+	control_i2c_mux: control-i2c-mux {
+		compatible = "mux-gpio";
+
+		mux-gpios = <&pioA 0 GPIO_ACTIVE_HIGH>,
+			    <&pioA 1 GPIO_ACTIVE_HIGH>;
+	};
+
+	i2c-mux {
+		compatible = "i2c-mux-simple,mux-locked";
+		i2c-parent = <&i2c1>;
+
+		control-muxes = <&control_i2c_mux>;
+		control-mux-names = "mux";
+
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		i2c@1 {
+			reg = <1>;
+			#address-cells = <1>;
+			#size-cells = <0>;
+
+			ssd1307: oled@3c {
+				compatible = "solomon,ssd1307fb-i2c";
+				reg = <0x3c>;
+				pwms = <&pwm 4 3000>;
+				reset-gpios = <&gpio2 7 1>;
+				reset-active-low;
+			};
+		};
+
+		i2c@3 {
+			reg = <3>;
+			#address-cells = <1>;
+			#size-cells = <0>;
+
+			pca9555: pca9555@20 {
+				compatible = "nxp,pca9555";
+				gpio-controller;
+				#gpio-cells = <2>;
+				reg = <0x20>;
+			};
+		};
+	};
-- 
2.1.4

[RFC PATCH 6/7] dt-bindings: i2c: i2c-mux-simple: document i2c-mux-simple bindings

[Peter Rosin]

---
 .../devicetree/bindings/i2c/i2c-mux-simple.txt     | 91 ++++++++++++++++++++++
 1 file changed, 91 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/i2c/i2c-mux-simple.txt

diff --git a/Documentation/devicetree/bindings/i2c/i2c-mux-simple.txt b/Documentation/devicetree/bindings/i2c/i2c-mux-simple.txt
new file mode 100644
index 000000000000..fec1ab39ad64
--- /dev/null
+++ b/Documentation/devicetree/bindings/i2c/i2c-mux-simple.txt
@@ -0,0 +1,91 @@
+Simple I2C Bus Mux
+
+This binding describes an I2C bus multiplexer that uses GPIOs to
+route the I2C signals.
+
+                                  .-----.  .-----.
+                                  | dev |  | dev |
+    .------------.                '-----'  '-----'
+    | SoC        |                   |        |
+    |            |          .--------+--------'
+    |   .------. |  .------+    child bus A, on MUX value set to 0
+    |   | I2C  |-|--| Mux  |
+    |   '------' |  '--+---+    child bus B, on MUX value set to 1
+    |   .------. |     |    '----------+--------+--------.
+    |   | MUX- | |     |               |        |        |
+    |   | Ctrl |-|-----+            .-----.  .-----.  .-----.
+    |   '------' |                  | dev |  | dev |  | dev |
+    '------------'                  '-----'  '-----'  '-----'
+
+Required properties:
+- compatible: i2c-mux-simple,mux-locked or i2c-mux-simple,parent-locked
+- i2c-parent: The phandle of the I2C bus that this multiplexer's master-side
+  port is connected to.
+- control-muxes : Node of the multiplexer that controls "Mux".
+- control-mux-names : Should be "mux".
+* Standard I2C mux properties. See i2c-mux.txt in this directory.
+* I2C child bus nodes. See i2c-mux.txt in this directory.
+
+Optional properties:
+- idle-state: value to set the muxer to when idle. When no value is
+  given, it defaults to the last value used.
+
+For each i2c child node, an I2C child bus will be created. They will
+be numbered based on their order in the device tree.
+
+Whenever an access is made to a device on a child bus, the value set
+in the relevant node's reg property will be fed to the mux controller.
+
+If an idle state is defined, using the idle-state (optional) property,
+whenever an access is not being made to a device on a child bus, the
+mux controller will be set according to the idle value.
+
+If an idle state is not defined, the most recently used value will be
+left programmed into hardware whenever no access is being made to a
+device on a child bus.
+
+Example:
+	control_i2c_mux: control-i2c-mux {
+		compatible = "mux-gpio";
+
+		mux-gpios = <&pioA 0 GPIO_ACTIVE_HIGH>,
+			    <&pioA 1 GPIO_ACTIVE_HIGH>;
+	};
+
+	i2c-mux {
+		compatible = "i2c-mux-simple,mux-locked";
+		i2c-parent = <&i2c1>;
+
+		control-muxes = <&control_i2c_mux>;
+		control-mux-names = "mux";
+
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		i2c@1 {
+			reg = <1>;
+			#address-cells = <1>;
+			#size-cells = <0>;
+
+			ssd1307: oled@3c {
+				compatible = "solomon,ssd1307fb-i2c";
+				reg = <0x3c>;
+				pwms = <&pwm 4 3000>;
+				reset-gpios = <&gpio2 7 1>;
+				reset-active-low;
+			};
+		};
+
+		i2c@3 {
+			reg = <3>;
+			#address-cells = <1>;
+			#size-cells = <0>;
+
+			pca9555: pca9555@20 {
+				compatible = "nxp,pca9555";
+				gpio-controller;
+				#gpio-cells = <2>;
+				reg = <0x20>;
+			};
+		};
+	};
-- 
2.1.4

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[RFC PATCH 7/7] i2c: i2c-mux-simple: new driver

[Peter Rosin]

This is a generic simple i2c mux that uses the generic multiplexer
subsystem to do the muxing.

The user can select if the mux is to be mux-locked and parent-locked
as described in Documentation/i2c/i2c-topology.
---
 drivers/i2c/muxes/Kconfig          |  12 +++
 drivers/i2c/muxes/Makefile         |   1 +
 drivers/i2c/muxes/i2c-mux-simple.c | 172 +++++++++++++++++++++++++++++++++++++
 3 files changed, 185 insertions(+)
 create mode 100644 drivers/i2c/muxes/i2c-mux-simple.c

diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
index e280c8ecc0b5..45e80ad2d4ab 100644
--- a/drivers/i2c/muxes/Kconfig
+++ b/drivers/i2c/muxes/Kconfig
@@ -72,6 +72,18 @@ config I2C_MUX_REG
 	  This driver can also be built as a module.  If so, the module
 	  will be called i2c-mux-reg.
 
+config I2C_MUX_SIMPLE
+	tristate "Simple I2C multiplexer"
+	depends on OF
+	help
+	  If you say yes to this option, support will be included for a
+	  simple generic I2C multiplexer. This driver provides access to
+	  I2C busses connected through a MUX, which is controlled
+	  by a generic MUX controller.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called i2c-mux-simple.
+
 config I2C_DEMUX_PINCTRL
 	tristate "pinctrl-based I2C demultiplexer"
 	depends on PINCTRL && OF
diff --git a/drivers/i2c/muxes/Makefile b/drivers/i2c/muxes/Makefile
index 7c267c29b191..eea1fb9e6466 100644
--- a/drivers/i2c/muxes/Makefile
+++ b/drivers/i2c/muxes/Makefile
@@ -10,5 +10,6 @@ obj-$(CONFIG_I2C_MUX_PCA9541)	+= i2c-mux-pca9541.o
 obj-$(CONFIG_I2C_MUX_PCA954x)	+= i2c-mux-pca954x.o
 obj-$(CONFIG_I2C_MUX_PINCTRL)	+= i2c-mux-pinctrl.o
 obj-$(CONFIG_I2C_MUX_REG)	+= i2c-mux-reg.o
+obj-$(CONFIG_I2C_MUX_SIMPLE)	+= i2c-mux-simple.o
 
 ccflags-$(CONFIG_I2C_DEBUG_BUS) := -DDEBUG
diff --git a/drivers/i2c/muxes/i2c-mux-simple.c b/drivers/i2c/muxes/i2c-mux-simple.c
new file mode 100644
index 000000000000..308ecbf9d66c
--- /dev/null
+++ b/drivers/i2c/muxes/i2c-mux-simple.c
@@ -0,0 +1,172 @@
+/*
+ * Generic simple I2C multiplexer
+ *
+ * Peter Rosin <peda@axentia.se>
+ *
+ * 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.
+ */
+
+#include <linux/i2c.h>
+#include <linux/i2c-mux.h>
+#include <linux/module.h>
+#include <linux/mux.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+
+struct mux {
+	struct mux_control *control;
+
+	int parent;
+	int n_values;
+	u32 *values;
+};
+
+static int i2c_mux_select(struct i2c_mux_core *muxc, u32 chan)
+{
+	struct mux *mux = i2c_mux_priv(muxc);
+
+	return mux_control_select(mux->control, chan);
+}
+
+static int i2c_mux_deselect(struct i2c_mux_core *muxc, u32 chan)
+{
+	struct mux *mux = i2c_mux_priv(muxc);
+
+	return mux_control_deselect(mux->control);
+}
+
+static int i2c_mux_probe_dt(struct mux *mux,
+			    struct device *dev)
+{
+	struct device_node *np = dev->of_node;
+	struct device_node *adapter_np, *child;
+	struct i2c_adapter *adapter;
+	int i = 0;
+
+	if (!np)
+		return -ENODEV;
+
+	adapter_np = of_parse_phandle(np, "i2c-parent", 0);
+	if (!adapter_np) {
+		dev_err(dev, "Cannot parse i2c-parent\n");
+		return -ENODEV;
+	}
+	adapter = of_find_i2c_adapter_by_node(adapter_np);
+	of_node_put(adapter_np);
+	if (!adapter)
+		return -EPROBE_DEFER;
+
+	mux->parent = i2c_adapter_id(adapter);
+	put_device(&adapter->dev);
+
+	mux->control = devm_mux_control_get(dev, "mux");
+	if (IS_ERR(mux->control)) {
+		if (PTR_ERR(mux->control) != -EPROBE_DEFER)
+			dev_err(dev, "failed to get control-mux\n");
+		return PTR_ERR(mux->control);
+	}
+
+	mux->n_values = of_get_child_count(np);
+
+	mux->values = devm_kzalloc(dev,
+				   sizeof(*mux->values) * mux->n_values,
+				   GFP_KERNEL);
+	if (!mux->values)
+		return -ENOMEM;
+
+	for_each_child_of_node(np, child) {
+		of_property_read_u32(child, "reg", mux->values + i);
+		i++;
+	}
+
+	return 0;
+}
+
+static const struct of_device_id i2c_mux_of_match[] = {
+	{ .compatible = "i2c-mux-simple,parent-locked",
+	  .data = (void *)0, },
+	{ .compatible = "i2c-mux-simple,mux-locked",
+	  .data = (void *)1, },
+	{},
+};
+MODULE_DEVICE_TABLE(of, i2c_mux_of_match);
+
+static int i2c_mux_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	const struct of_device_id *match;
+	struct i2c_mux_core *muxc;
+	struct mux *mux;
+	struct i2c_adapter *parent;
+	int i, ret;
+
+	mux = devm_kzalloc(dev, sizeof(*mux), GFP_KERNEL);
+	if (!mux)
+		return -ENOMEM;
+
+	ret = i2c_mux_probe_dt(mux, dev);
+	if (ret < 0)
+		return ret;
+
+	parent = i2c_get_adapter(mux->parent);
+	if (!parent)
+		return -EPROBE_DEFER;
+
+	muxc = i2c_mux_alloc(parent, dev, mux->n_values, 0, 0,
+			     i2c_mux_select, i2c_mux_deselect);
+	if (!muxc) {
+		ret = -ENOMEM;
+		goto alloc_failed;
+	}
+	muxc->priv = mux;
+
+	platform_set_drvdata(pdev, muxc);
+
+	match = of_match_device(of_match_ptr(i2c_mux_of_match), dev);
+	if (match)
+		muxc->mux_locked = !!of_device_get_match_data(dev);
+
+	for (i = 0; i < mux->n_values; i++) {
+		ret = i2c_mux_add_adapter(muxc, 0, mux->values[i], 0);
+		if (ret)
+			goto add_adapter_failed;
+	}
+
+	dev_info(dev, "%d port mux on %s adapter\n",
+		 mux->n_values, parent->name);
+
+	return 0;
+
+add_adapter_failed:
+	i2c_mux_del_adapters(muxc);
+alloc_failed:
+	i2c_put_adapter(parent);
+
+	return ret;
+}
+
+static int i2c_mux_remove(struct platform_device *pdev)
+{
+	struct i2c_mux_core *muxc = platform_get_drvdata(pdev);
+
+	i2c_mux_del_adapters(muxc);
+	i2c_put_adapter(muxc->parent);
+
+	return 0;
+}
+
+static struct platform_driver i2c_mux_driver = {
+	.probe	= i2c_mux_probe,
+	.remove	= i2c_mux_remove,
+	.driver	= {
+		.name	= "i2c-mux-simple",
+		.of_match_table = i2c_mux_of_match,
+	},
+};
+module_platform_driver(i2c_mux_driver);
+
+MODULE_DESCRIPTION("Simple I2C multiplexer driver");
+MODULE_AUTHOR("Peter Rosin <peda@axentia.se>");
+MODULE_LICENSE("GPL v2");
-- 
2.1.4

[RFC PATCH 7/7] i2c: i2c-mux-simple: new driver

[Peter Rosin]

This is a generic simple i2c mux that uses the generic multiplexer
subsystem to do the muxing.

The user can select if the mux is to be mux-locked and parent-locked
as described in Documentation/i2c/i2c-topology.
---
 drivers/i2c/muxes/Kconfig          |  12 +++
 drivers/i2c/muxes/Makefile         |   1 +
 drivers/i2c/muxes/i2c-mux-simple.c | 172 +++++++++++++++++++++++++++++++++++++
 3 files changed, 185 insertions(+)
 create mode 100644 drivers/i2c/muxes/i2c-mux-simple.c

diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
index e280c8ecc0b5..45e80ad2d4ab 100644
--- a/drivers/i2c/muxes/Kconfig
+++ b/drivers/i2c/muxes/Kconfig
@@ -72,6 +72,18 @@ config I2C_MUX_REG
 	  This driver can also be built as a module.  If so, the module
 	  will be called i2c-mux-reg.
 
+config I2C_MUX_SIMPLE
+	tristate "Simple I2C multiplexer"
+	depends on OF
+	help
+	  If you say yes to this option, support will be included for a
+	  simple generic I2C multiplexer. This driver provides access to
+	  I2C busses connected through a MUX, which is controlled
+	  by a generic MUX controller.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called i2c-mux-simple.
+
 config I2C_DEMUX_PINCTRL
 	tristate "pinctrl-based I2C demultiplexer"
 	depends on PINCTRL && OF
diff --git a/drivers/i2c/muxes/Makefile b/drivers/i2c/muxes/Makefile
index 7c267c29b191..eea1fb9e6466 100644
--- a/drivers/i2c/muxes/Makefile
+++ b/drivers/i2c/muxes/Makefile
@@ -10,5 +10,6 @@ obj-$(CONFIG_I2C_MUX_PCA9541)	+= i2c-mux-pca9541.o
 obj-$(CONFIG_I2C_MUX_PCA954x)	+= i2c-mux-pca954x.o
 obj-$(CONFIG_I2C_MUX_PINCTRL)	+= i2c-mux-pinctrl.o
 obj-$(CONFIG_I2C_MUX_REG)	+= i2c-mux-reg.o
+obj-$(CONFIG_I2C_MUX_SIMPLE)	+= i2c-mux-simple.o
 
 ccflags-$(CONFIG_I2C_DEBUG_BUS) := -DDEBUG
diff --git a/drivers/i2c/muxes/i2c-mux-simple.c b/drivers/i2c/muxes/i2c-mux-simple.c
new file mode 100644
index 000000000000..308ecbf9d66c
--- /dev/null
+++ b/drivers/i2c/muxes/i2c-mux-simple.c
@@ -0,0 +1,172 @@
+/*
+ * Generic simple I2C multiplexer
+ *
+ * Peter Rosin <peda-koto5C5qi+TLoDKTGw+V6w@public.gmane.org>
+ *
+ * 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.
+ */
+
+#include <linux/i2c.h>
+#include <linux/i2c-mux.h>
+#include <linux/module.h>
+#include <linux/mux.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+
+struct mux {
+	struct mux_control *control;
+
+	int parent;
+	int n_values;
+	u32 *values;
+};
+
+static int i2c_mux_select(struct i2c_mux_core *muxc, u32 chan)
+{
+	struct mux *mux = i2c_mux_priv(muxc);
+
+	return mux_control_select(mux->control, chan);
+}
+
+static int i2c_mux_deselect(struct i2c_mux_core *muxc, u32 chan)
+{
+	struct mux *mux = i2c_mux_priv(muxc);
+
+	return mux_control_deselect(mux->control);
+}
+
+static int i2c_mux_probe_dt(struct mux *mux,
+			    struct device *dev)
+{
+	struct device_node *np = dev->of_node;
+	struct device_node *adapter_np, *child;
+	struct i2c_adapter *adapter;
+	int i = 0;
+
+	if (!np)
+		return -ENODEV;
+
+	adapter_np = of_parse_phandle(np, "i2c-parent", 0);
+	if (!adapter_np) {
+		dev_err(dev, "Cannot parse i2c-parent\n");
+		return -ENODEV;
+	}
+	adapter = of_find_i2c_adapter_by_node(adapter_np);
+	of_node_put(adapter_np);
+	if (!adapter)
+		return -EPROBE_DEFER;
+
+	mux->parent = i2c_adapter_id(adapter);
+	put_device(&adapter->dev);
+
+	mux->control = devm_mux_control_get(dev, "mux");
+	if (IS_ERR(mux->control)) {
+		if (PTR_ERR(mux->control) != -EPROBE_DEFER)
+			dev_err(dev, "failed to get control-mux\n");
+		return PTR_ERR(mux->control);
+	}
+
+	mux->n_values = of_get_child_count(np);
+
+	mux->values = devm_kzalloc(dev,
+				   sizeof(*mux->values) * mux->n_values,
+				   GFP_KERNEL);
+	if (!mux->values)
+		return -ENOMEM;
+
+	for_each_child_of_node(np, child) {
+		of_property_read_u32(child, "reg", mux->values + i);
+		i++;
+	}
+
+	return 0;
+}
+
+static const struct of_device_id i2c_mux_of_match[] = {
+	{ .compatible = "i2c-mux-simple,parent-locked",
+	  .data = (void *)0, },
+	{ .compatible = "i2c-mux-simple,mux-locked",
+	  .data = (void *)1, },
+	{},
+};
+MODULE_DEVICE_TABLE(of, i2c_mux_of_match);
+
+static int i2c_mux_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	const struct of_device_id *match;
+	struct i2c_mux_core *muxc;
+	struct mux *mux;
+	struct i2c_adapter *parent;
+	int i, ret;
+
+	mux = devm_kzalloc(dev, sizeof(*mux), GFP_KERNEL);
+	if (!mux)
+		return -ENOMEM;
+
+	ret = i2c_mux_probe_dt(mux, dev);
+	if (ret < 0)
+		return ret;
+
+	parent = i2c_get_adapter(mux->parent);
+	if (!parent)
+		return -EPROBE_DEFER;
+
+	muxc = i2c_mux_alloc(parent, dev, mux->n_values, 0, 0,
+			     i2c_mux_select, i2c_mux_deselect);
+	if (!muxc) {
+		ret = -ENOMEM;
+		goto alloc_failed;
+	}
+	muxc->priv = mux;
+
+	platform_set_drvdata(pdev, muxc);
+
+	match = of_match_device(of_match_ptr(i2c_mux_of_match), dev);
+	if (match)
+		muxc->mux_locked = !!of_device_get_match_data(dev);
+
+	for (i = 0; i < mux->n_values; i++) {
+		ret = i2c_mux_add_adapter(muxc, 0, mux->values[i], 0);
+		if (ret)
+			goto add_adapter_failed;
+	}
+
+	dev_info(dev, "%d port mux on %s adapter\n",
+		 mux->n_values, parent->name);
+
+	return 0;
+
+add_adapter_failed:
+	i2c_mux_del_adapters(muxc);
+alloc_failed:
+	i2c_put_adapter(parent);
+
+	return ret;
+}
+
+static int i2c_mux_remove(struct platform_device *pdev)
+{
+	struct i2c_mux_core *muxc = platform_get_drvdata(pdev);
+
+	i2c_mux_del_adapters(muxc);
+	i2c_put_adapter(muxc->parent);
+
+	return 0;
+}
+
+static struct platform_driver i2c_mux_driver = {
+	.probe	= i2c_mux_probe,
+	.remove	= i2c_mux_remove,
+	.driver	= {
+		.name	= "i2c-mux-simple",
+		.of_match_table = i2c_mux_of_match,
+	},
+};
+module_platform_driver(i2c_mux_driver);
+
+MODULE_DESCRIPTION("Simple I2C multiplexer driver");
+MODULE_AUTHOR("Peter Rosin <peda-koto5C5qi+TLoDKTGw+V6w@public.gmane.org>");
+MODULE_LICENSE("GPL v2");
-- 
2.1.4

Re: [RFC PATCH 0/7] mux controller astraction and iio/i2c muxes

[Peter Rosin]

On 2016-11-17 00:48, Peter Rosin wrote:
> Hi!
> 
> This is work in progress, I'm asking for early feedback.

Forgot to mention, sorry, but this series depends on some
stuff not in mainline yet (the _available work in iio [1]),
but it is in linux-next.

Cheers,
Peter

[1] Specifically these patches:
51239600074b "iio:core: add a callback to allow drivers to provide _available attributes"
00c5f80c2fad "iio: inkern: add helpers to query available values from channels"

Re: [RFC PATCH 0/7] mux controller astraction and iio/i2c muxes

[Peter Rosin]

On 2016-11-17 00:48, Peter Rosin wrote:
> Hi!
> 
> This is work in progress, I'm asking for early feedback.

Forgot to mention, sorry, but this series depends on some
stuff not in mainline yet (the _available work in iio [1]),
but it is in linux-next.

Cheers,
Peter

[1] Specifically these patches:
51239600074b "iio:core: add a callback to allow drivers to provide _available attributes"
00c5f80c2fad "iio: inkern: add helpers to query available values from channels"
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Re: [RFC PATCH 4/7] dt-bindings: iio: iio-mux: document iio-mux bindings

[Lars-Peter Clausen]

On 11/17/2016 12:48 AM, Peter Rosin wrote:
> ---
>  .../bindings/iio/multiplexer/iio-mux.txt           | 59 ++++++++++++++++++++++
>  1 file changed, 59 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/multiplexer/iio-mux.txt
> 
> diff --git a/Documentation/devicetree/bindings/iio/multiplexer/iio-mux.txt b/Documentation/devicetree/bindings/iio/multiplexer/iio-mux.txt
> new file mode 100644
> index 000000000000..2f5c7fc35a42
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/multiplexer/iio-mux.txt
> @@ -0,0 +1,59 @@
> +IIO multiplexer bindings
> +
> +If a multiplexer is used to select when hardware signal is fed to
> +e.g. an ADC channel, these bindings describe that situation.
> +
> +Required properties:
> +- compatible : "iio-mux"
> +- io-channels : Channel node of the parent channel that has multiplexed
> +		input.
> +- io-channel-names : Should be "parent".
> +- control-muxes : Node of the multiplexer that controls the input signal.
> +- control-mux-names : Should be "mux".
> +- #address-cells = <1>;
> +- #size-cells = <0>;
> +
> +Required properties for iio-mux child nodes:
> +- reg : The multiplexer number.
> +
> +Optional properties for iio-mux child nodes:
> +- iio-ext-info : Array of string pairs, the first item in each pair is the
> +		 iio ext_info attribute name, and the second item in each
> +		 pair is the iio ext_info value for that attribute. The
> +		 mux will write these ext_info values to the corresponding
> +		 ext_info attributes on every multiplexer switch.

This can't go into the devicetree in its current form as it exposes
implementation details of the Linux kernel drivers.