From ff2b1359229927563addbf2f5ad480660c350903 Mon Sep 17 00:00:00 2001
From: Linus Walleij <linus.walleij@linaro.org>
Date: Tue, 20 Oct 2015 11:10:38 +0200
Subject: gpio: make the gpiochip a real device

GPIO chips have been around for years, but were never real devices,
instead they were piggy-backing on a parent device (such as a
platform_device or amba_device) but this was always optional.
GPIO chips could also exist without any device at all, with its
struct device *parent (ex *dev) pointer being set to null.

When sysfs was in use, a mock device would be created, with the
optional parent assigned, or just floating orphaned with NULL
as parent.

If sysfs is active, it will use this device as parent.

We now create a gpio_device struct containing a real
struct device and move the subsystem over to using that. The
list of struct gpio_chip:s is augmented to hold struct
gpio_device:s and we find gpio_chips:s by first looking up
the struct gpio_device.

The struct gpio_device is designed to stay around even if the
gpio_chip is removed, so as to satisfy users in userspace
that need a backing data structure to hold the state of the
session initiated with e.g. a character device even if there is
no physical chip anymore.

From this point on, gpiochips are devices.

Cc: Johan Hovold <johan@kernel.org>
Cc: Michael Welling <mwelling@ieee.org>
Cc: Markus Pargmann <mpa@pengutronix.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
 drivers/gpio/gpiolib-sysfs.c |  12 ++-
 drivers/gpio/gpiolib.c       | 232 ++++++++++++++++++++++++++++++-------------
 drivers/gpio/gpiolib.h       |  27 ++++-
 include/linux/gpio/driver.h  |   7 +-
 4 files changed, 201 insertions(+), 77 deletions(-)

diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index 405dfcaadc4c..28d3bf2328aa 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -547,6 +547,7 @@ static struct class gpio_class = {
 int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
 {
 	struct gpio_chip	*chip;
+	struct gpio_device	*gdev;
 	struct gpiod_data	*data;
 	unsigned long		flags;
 	int			status;
@@ -566,6 +567,7 @@ int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
 	}
 
 	chip = desc->chip;
+	gdev = chip->gpiodev;
 
 	mutex_lock(&sysfs_lock);
 
@@ -605,7 +607,7 @@ int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
 	if (chip->names && chip->names[offset])
 		ioname = chip->names[offset];
 
-	dev = device_create_with_groups(&gpio_class, chip->parent,
+	dev = device_create_with_groups(&gpio_class, &gdev->dev,
 					MKDEV(0, 0), data, gpio_groups,
 					ioname ? ioname : "gpio%u",
 					desc_to_gpio(desc));
@@ -771,7 +773,7 @@ static int __init gpiolib_sysfs_init(void)
 {
 	int		status;
 	unsigned long	flags;
-	struct gpio_chip *chip;
+	struct gpio_device *gdev;
 
 	status = class_register(&gpio_class);
 	if (status < 0)
@@ -784,8 +786,8 @@ static int __init gpiolib_sysfs_init(void)
 	 * registered, and so arch_initcall() can always gpio_export().
 	 */
 	spin_lock_irqsave(&gpio_lock, flags);
-	list_for_each_entry(chip, &gpio_chips, list) {
-		if (chip->cdev)
+	list_for_each_entry(gdev, &gpio_devices, list) {
+		if (gdev->chip->cdev)
 			continue;
 
 		/*
@@ -798,7 +800,7 @@ static int __init gpiolib_sysfs_init(void)
 		 * gpio_lock prevents us from doing this.
 		 */
 		spin_unlock_irqrestore(&gpio_lock, flags);
-		status = gpiochip_sysfs_register(chip);
+		status = gpiochip_sysfs_register(gdev->chip);
 		spin_lock_irqsave(&gpio_lock, flags);
 	}
 	spin_unlock_irqrestore(&gpio_lock, flags);
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 5c1ba879f889..3a073ab5e863 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -16,6 +16,7 @@
 #include <linux/gpio/driver.h>
 #include <linux/gpio/machine.h>
 #include <linux/pinctrl/consumer.h>
+#include <linux/idr.h>
 
 #include "gpiolib.h"
 
@@ -42,6 +43,9 @@
 #define	extra_checks	0
 #endif
 
+/* Device and char device-related information */
+static DEFINE_IDA(gpio_ida);
+
 /* gpio_lock prevents conflicts during gpio_desc[] table updates.
  * While any GPIO is requested, its gpio_chip is not removable;
  * each GPIO's "requested" flag serves as a lock and refcount.
@@ -50,8 +54,7 @@ DEFINE_SPINLOCK(gpio_lock);
 
 static DEFINE_MUTEX(gpio_lookup_lock);
 static LIST_HEAD(gpio_lookup_list);
-LIST_HEAD(gpio_chips);
-
+LIST_HEAD(gpio_devices);
 
 static void gpiochip_free_hogs(struct gpio_chip *chip);
 static void gpiochip_irqchip_remove(struct gpio_chip *gpiochip);
@@ -67,15 +70,16 @@ static inline void desc_set_label(struct gpio_desc *d, const char *label)
  */
 struct gpio_desc *gpio_to_desc(unsigned gpio)
 {
-	struct gpio_chip *chip;
+	struct gpio_device *gdev;
 	unsigned long flags;
 
 	spin_lock_irqsave(&gpio_lock, flags);
 
-	list_for_each_entry(chip, &gpio_chips, list) {
-		if (chip->base <= gpio && chip->base + chip->ngpio > gpio) {
+	list_for_each_entry(gdev, &gpio_devices, list) {
+		if (gdev->chip->base <= gpio &&
+		    gdev->chip->base + gdev->chip->ngpio > gpio) {
 			spin_unlock_irqrestore(&gpio_lock, flags);
-			return &chip->desc[gpio - chip->base];
+			return &gdev->chip->desc[gpio - gdev->chip->base];
 		}
 	}
 
@@ -125,16 +129,16 @@ EXPORT_SYMBOL_GPL(gpiod_to_chip);
 /* dynamic allocation of GPIOs, e.g. on a hotplugged device */
 static int gpiochip_find_base(int ngpio)
 {
-	struct gpio_chip *chip;
+	struct gpio_device *gdev;
 	int base = ARCH_NR_GPIOS - ngpio;
 
-	list_for_each_entry_reverse(chip, &gpio_chips, list) {
+	list_for_each_entry_reverse(gdev, &gpio_devices, list) {
 		/* found a free space? */
-		if (chip->base + chip->ngpio <= base)
+		if (gdev->chip->base + gdev->chip->ngpio <= base)
 			break;
 		else
 			/* nope, check the space right before the chip */
-			base = chip->base - ngpio;
+			base = gdev->chip->base - ngpio;
 	}
 
 	if (gpio_is_valid(base)) {
@@ -187,18 +191,28 @@ EXPORT_SYMBOL_GPL(gpiod_get_direction);
  * Return -EBUSY if the new chip overlaps with some other chip's integer
  * space.
  */
-static int gpiochip_add_to_list(struct gpio_chip *chip)
+static int gpiodev_add_to_list(struct gpio_device *gdev)
 {
-	struct gpio_chip *iterator;
-	struct gpio_chip *previous = NULL;
+	struct gpio_device *iterator;
+	struct gpio_device *previous = NULL;
+
+	if (!gdev->chip)
+		return -EINVAL;
 
-	if (list_empty(&gpio_chips)) {
-		list_add_tail(&chip->list, &gpio_chips);
+	if (list_empty(&gpio_devices)) {
+		list_add_tail(&gdev->list, &gpio_devices);
 		return 0;
 	}
 
-	list_for_each_entry(iterator, &gpio_chips, list) {
-		if (iterator->base >= chip->base + chip->ngpio) {
+	list_for_each_entry(iterator, &gpio_devices, list) {
+		/*
+		 * The list may contain dangling GPIO devices with no
+		 * live chip assigned.
+		 */
+		if (!iterator->chip)
+			continue;
+		if (iterator->chip->base >=
+		    gdev->chip->base + gdev->chip->ngpio) {
 			/*
 			 * Iterator is the first GPIO chip so there is no
 			 * previous one
@@ -211,8 +225,8 @@ static int gpiochip_add_to_list(struct gpio_chip *chip)
 				 * [base, base + ngpio - 1]) between previous
 				 * and iterator chip.
 				 */
-				if (previous->base + previous->ngpio
-						<= chip->base)
+				if (previous->chip->base + previous->chip->ngpio
+						<= gdev->chip->base)
 					goto found;
 			}
 		}
@@ -225,18 +239,18 @@ static int gpiochip_add_to_list(struct gpio_chip *chip)
 	 * Let iterator point to the last chip in the list.
 	 */
 
-	iterator = list_last_entry(&gpio_chips, struct gpio_chip, list);
-	if (iterator->base + iterator->ngpio <= chip->base) {
-		list_add(&chip->list, &iterator->list);
+	iterator = list_last_entry(&gpio_devices, struct gpio_device, list);
+	if (iterator->chip->base + iterator->chip->ngpio <= gdev->chip->base) {
+		list_add(&gdev->list, &iterator->list);
 		return 0;
 	}
 
-	dev_err(chip->parent,
+	dev_err(&gdev->dev,
 	       "GPIO integer space overlap, cannot add chip\n");
 	return -EBUSY;
 
 found:
-	list_add_tail(&chip->list, &iterator->list);
+	list_add_tail(&gdev->list, &iterator->list);
 	return 0;
 }
 
@@ -245,16 +259,16 @@ found:
  */
 static struct gpio_desc *gpio_name_to_desc(const char * const name)
 {
-	struct gpio_chip *chip;
+	struct gpio_device *gdev;
 	unsigned long flags;
 
 	spin_lock_irqsave(&gpio_lock, flags);
 
-	list_for_each_entry(chip, &gpio_chips, list) {
+	list_for_each_entry(gdev, &gpio_devices, list) {
 		int i;
 
-		for (i = 0; i != chip->ngpio; ++i) {
-			struct gpio_desc *gpio = &chip->desc[i];
+		for (i = 0; i != gdev->chip->ngpio; ++i) {
+			struct gpio_desc *gpio = &gdev->chip->desc[i];
 
 			if (!gpio->name || !name)
 				continue;
@@ -302,6 +316,14 @@ static int gpiochip_set_desc_names(struct gpio_chip *gc)
 	return 0;
 }
 
+static void gpiodevice_release(struct device *dev)
+{
+	struct gpio_device *gdev = dev_get_drvdata(dev);
+
+	list_del(&gdev->list);
+	ida_simple_remove(&gpio_ida, gdev->id);
+}
+
 /**
  * gpiochip_add_data() - register a gpio_chip
  * @chip: the chip to register, with chip->base initialized
@@ -323,19 +345,60 @@ int gpiochip_add_data(struct gpio_chip *chip, void *data)
 {
 	unsigned long	flags;
 	int		status = 0;
-	unsigned	id;
+	unsigned	i;
 	int		base = chip->base;
 	struct gpio_desc *descs;
+	struct gpio_device *gdev;
 
-	descs = kcalloc(chip->ngpio, sizeof(descs[0]), GFP_KERNEL);
-	if (!descs)
+	/*
+	 * First: allocate and populate the internal stat container, and
+	 * set up the struct device.
+	 */
+	gdev = kmalloc(sizeof(*gdev), GFP_KERNEL);
+	if (!gdev)
 		return -ENOMEM;
+	gdev->chip = chip;
+	chip->gpiodev = gdev;
+	if (chip->parent) {
+		gdev->dev.parent = chip->parent;
+		gdev->dev.of_node = chip->parent->of_node;
+	} else {
+#ifdef CONFIG_OF_GPIO
+	/* If the gpiochip has an assigned OF node this takes precedence */
+		if (chip->of_node)
+			gdev->dev.of_node = chip->of_node;
+#endif
+	}
+	gdev->id = ida_simple_get(&gpio_ida, 0, 0, GFP_KERNEL);
+	if (gdev->id < 0) {
+		status = gdev->id;
+		goto err_free_gdev;
+	}
+	dev_set_name(&gdev->dev, "gpiochip%d", gdev->id);
+	device_initialize(&gdev->dev);
+	dev_set_drvdata(&gdev->dev, gdev);
+	if (chip->parent && chip->parent->driver)
+		gdev->owner = chip->parent->driver->owner;
+	else if (chip->owner)
+		/* TODO: remove chip->owner */
+		gdev->owner = chip->owner;
+	else
+		gdev->owner = THIS_MODULE;
 
+	/* FIXME: devm_kcalloc() these and move to gpio_device */
+	descs = kcalloc(chip->ngpio, sizeof(descs[0]), GFP_KERNEL);
+	if (!descs) {
+		status = -ENOMEM;
+		goto err_free_gdev;
+	}
+
+	/* FIXME: move driver data into gpio_device dev_set_drvdata() */
 	chip->data = data;
 
 	if (chip->ngpio == 0) {
 		chip_err(chip, "tried to insert a GPIO chip with zero lines\n");
-		return -EINVAL;
+		status = -EINVAL;
+		goto err_free_descs;
 	}
 
 	spin_lock_irqsave(&gpio_lock, flags);
@@ -350,15 +413,16 @@ int gpiochip_add_data(struct gpio_chip *chip, void *data)
 		chip->base = base;
 	}
 
-	status = gpiochip_add_to_list(chip);
+	status = gpiodev_add_to_list(gdev);
 	if (status) {
 		spin_unlock_irqrestore(&gpio_lock, flags);
 		goto err_free_descs;
 	}
 
-	for (id = 0; id < chip->ngpio; id++) {
-		struct gpio_desc *desc = &descs[id];
+	for (i = 0; i < chip->ngpio; i++) {
+		struct gpio_desc *desc = &descs[i];
 
+		/* REVISIT: maybe a pointer to gpio_device is better */
 		desc->chip = chip;
 
 		/* REVISIT: most hardware initializes GPIOs as inputs (often
@@ -369,18 +433,15 @@ int gpiochip_add_data(struct gpio_chip *chip, void *data)
 		 */
 		desc->flags = !chip->direction_input ? (1 << FLAG_IS_OUT) : 0;
 	}
-
 	chip->desc = descs;
 
 	spin_unlock_irqrestore(&gpio_lock, flags);
 
 #ifdef CONFIG_PINCTRL
+	/* FIXME: move pin ranges to gpio_device */
 	INIT_LIST_HEAD(&chip->pin_ranges);
 #endif
 
-	if (!chip->owner && chip->parent && chip->parent->driver)
-		chip->owner = chip->parent->driver->owner;
-
 	status = gpiochip_set_desc_names(chip);
 	if (status)
 		goto err_remove_from_list;
@@ -391,28 +452,39 @@ int gpiochip_add_data(struct gpio_chip *chip, void *data)
 
 	acpi_gpiochip_add(chip);
 
-	status = gpiochip_sysfs_register(chip);
+	status = device_add(&gdev->dev);
 	if (status)
 		goto err_remove_chip;
 
+	status = gpiochip_sysfs_register(chip);
+	if (status)
+		goto err_remove_device;
+
+	/* From this point, the .release() function cleans up gpio_device */
+	gdev->dev.release = gpiodevice_release;
+	get_device(&gdev->dev);
 	pr_debug("%s: registered GPIOs %d to %d on device: %s\n", __func__,
 		chip->base, chip->base + chip->ngpio - 1,
 		chip->label ? : "generic");
 
 	return 0;
 
+err_remove_device:
+	device_del(&gdev->dev);
 err_remove_chip:
 	acpi_gpiochip_remove(chip);
 	gpiochip_free_hogs(chip);
 	of_gpiochip_remove(chip);
 err_remove_from_list:
 	spin_lock_irqsave(&gpio_lock, flags);
-	list_del(&chip->list);
+	list_del(&gdev->list);
 	spin_unlock_irqrestore(&gpio_lock, flags);
 	chip->desc = NULL;
 err_free_descs:
 	kfree(descs);
-
+err_free_gdev:
+	ida_simple_remove(&gpio_ida, gdev->id);
+	kfree(gdev);
 	/* failures here can mean systems won't boot... */
 	pr_err("%s: GPIOs %d..%d (%s) failed to register\n", __func__,
 		chip->base, chip->base + chip->ngpio - 1,
@@ -429,15 +501,18 @@ EXPORT_SYMBOL_GPL(gpiochip_add_data);
  */
 void gpiochip_remove(struct gpio_chip *chip)
 {
+	struct gpio_device *gdev = chip->gpiodev;
 	struct gpio_desc *desc;
 	unsigned long	flags;
 	unsigned	id;
 	bool		requested = false;
 
-	gpiochip_sysfs_unregister(chip);
+	/* Numb the device, cancelling all outstanding operations */
+	gdev->chip = NULL;
 
+	/* FIXME: should the legacy sysfs handling be moved to gpio_device? */
+	gpiochip_sysfs_unregister(chip);
 	gpiochip_irqchip_remove(chip);
-
 	acpi_gpiochip_remove(chip);
 	gpiochip_remove_pin_ranges(chip);
 	gpiochip_free_hogs(chip);
@@ -450,15 +525,23 @@ void gpiochip_remove(struct gpio_chip *chip)
 		if (test_bit(FLAG_REQUESTED, &desc->flags))
 			requested = true;
 	}
-	list_del(&chip->list);
 	spin_unlock_irqrestore(&gpio_lock, flags);
 
 	if (requested)
 		dev_crit(chip->parent,
 			 "REMOVING GPIOCHIP WITH GPIOS STILL REQUESTED\n");
 
+	/* FIXME: need to be moved to gpio_device and held there */
 	kfree(chip->desc);
 	chip->desc = NULL;
+
+	/*
+	 * The gpiochip side puts its use of the device to rest here:
+	 * if there are no userspace clients, the chardev and device will
+	 * be removed, else it will be dangling until the last user is
+	 * gone.
+	 */
+	put_device(&gdev->dev);
 }
 EXPORT_SYMBOL_GPL(gpiochip_remove);
 
@@ -477,17 +560,21 @@ struct gpio_chip *gpiochip_find(void *data,
 				int (*match)(struct gpio_chip *chip,
 					     void *data))
 {
+	struct gpio_device *gdev;
 	struct gpio_chip *chip;
 	unsigned long flags;
 
 	spin_lock_irqsave(&gpio_lock, flags);
-	list_for_each_entry(chip, &gpio_chips, list)
-		if (match(chip, data))
+	list_for_each_entry(gdev, &gpio_devices, list)
+		if (match(gdev->chip, data))
 			break;
 
 	/* No match? */
-	if (&chip->list == &gpio_chips)
+	if (&gdev->list == &gpio_devices)
 		chip = NULL;
+	else
+		chip = gdev->chip;
+
 	spin_unlock_irqrestore(&gpio_lock, flags);
 
 	return chip;
@@ -617,14 +704,14 @@ static int gpiochip_irq_reqres(struct irq_data *d)
 {
 	struct gpio_chip *chip = irq_data_get_irq_chip_data(d);
 
-	if (!try_module_get(chip->owner))
+	if (!try_module_get(chip->gpiodev->owner))
 		return -ENODEV;
 
 	if (gpiochip_lock_as_irq(chip, d->hwirq)) {
 		chip_err(chip,
 			"unable to lock HW IRQ %lu for IRQ\n",
 			d->hwirq);
-		module_put(chip->owner);
+		module_put(chip->gpiodev->owner);
 		return -EINVAL;
 	}
 	return 0;
@@ -635,7 +722,7 @@ static void gpiochip_irq_relres(struct irq_data *d)
 	struct gpio_chip *chip = irq_data_get_irq_chip_data(d);
 
 	gpiochip_unlock_as_irq(chip, d->hwirq);
-	module_put(chip->owner);
+	module_put(chip->gpiodev->owner);
 }
 
 static int gpiochip_to_irq(struct gpio_chip *chip, unsigned offset)
@@ -985,10 +1072,10 @@ int gpiod_request(struct gpio_desc *desc, const char *label)
 	if (!chip)
 		goto done;
 
-	if (try_module_get(chip->owner)) {
+	if (try_module_get(chip->gpiodev->owner)) {
 		status = __gpiod_request(desc, label);
 		if (status < 0)
-			module_put(chip->owner);
+			module_put(chip->gpiodev->owner);
 	}
 
 done:
@@ -1034,7 +1121,7 @@ static bool __gpiod_free(struct gpio_desc *desc)
 void gpiod_free(struct gpio_desc *desc)
 {
 	if (desc && __gpiod_free(desc))
-		module_put(desc->chip->owner);
+		module_put(desc->chip->gpiodev->owner);
 	else
 		WARN_ON(extra_checks);
 }
@@ -2492,16 +2579,16 @@ static void gpiolib_dbg_show(struct seq_file *s, struct gpio_chip *chip)
 static void *gpiolib_seq_start(struct seq_file *s, loff_t *pos)
 {
 	unsigned long flags;
-	struct gpio_chip *chip = NULL;
+	struct gpio_device *gdev = NULL;
 	loff_t index = *pos;
 
 	s->private = "";
 
 	spin_lock_irqsave(&gpio_lock, flags);
-	list_for_each_entry(chip, &gpio_chips, list)
+	list_for_each_entry(gdev, &gpio_devices, list)
 		if (index-- == 0) {
 			spin_unlock_irqrestore(&gpio_lock, flags);
-			return chip;
+			return gdev;
 		}
 	spin_unlock_irqrestore(&gpio_lock, flags);
 
@@ -2511,14 +2598,14 @@ static void *gpiolib_seq_start(struct seq_file *s, loff_t *pos)
 static void *gpiolib_seq_next(struct seq_file *s, void *v, loff_t *pos)
 {
 	unsigned long flags;
-	struct gpio_chip *chip = v;
+	struct gpio_device *gdev = v;
 	void *ret = NULL;
 
 	spin_lock_irqsave(&gpio_lock, flags);
-	if (list_is_last(&chip->list, &gpio_chips))
+	if (list_is_last(&gdev->list, &gpio_devices))
 		ret = NULL;
 	else
-		ret = list_entry(chip->list.next, struct gpio_chip, list);
+		ret = list_entry(gdev->list.next, struct gpio_device, list);
 	spin_unlock_irqrestore(&gpio_lock, flags);
 
 	s->private = "\n";
@@ -2533,15 +2620,24 @@ static void gpiolib_seq_stop(struct seq_file *s, void *v)
 
 static int gpiolib_seq_show(struct seq_file *s, void *v)
 {
-	struct gpio_chip *chip = v;
-	struct device *dev;
+	struct gpio_device *gdev = v;
+	struct gpio_chip *chip = gdev->chip;
+	struct device *parent;
+
+	if (!chip) {
+		seq_printf(s, "%s%s: (dangling chip)", (char *)s->private,
+			   dev_name(&gdev->dev));
+		return 0;
+	}
 
-	seq_printf(s, "%sGPIOs %d-%d", (char *)s->private,
-			chip->base, chip->base + chip->ngpio - 1);
-	dev = chip->parent;
-	if (dev)
-		seq_printf(s, ", %s/%s", dev->bus ? dev->bus->name : "no-bus",
-			dev_name(dev));
+	seq_printf(s, "%s%s: GPIOs %d-%d", (char *)s->private,
+		   dev_name(&gdev->dev),
+		   chip->base, chip->base + chip->ngpio - 1);
+	parent = chip->parent;
+	if (parent)
+		seq_printf(s, ", parent: %s/%s",
+			   parent->bus ? parent->bus->name : "no-bus",
+			   dev_name(parent));
 	if (chip->label)
 		seq_printf(s, ", %s", chip->label);
 	if (chip->can_sleep)
diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index 99ed3b00ffe9..feea2c823e47 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -12,13 +12,38 @@
 #ifndef GPIOLIB_H
 #define GPIOLIB_H
 
+#include <linux/gpio/driver.h>
 #include <linux/err.h>
 #include <linux/device.h>
+#include <linux/module.h>
+#include <linux/cdev.h>
 
 enum of_gpio_flags;
 enum gpiod_flags;
 struct acpi_device;
 
+/**
+ * struct gpio_device - internal state container for GPIO devices
+ * @id: numerical ID number for the GPIO chip
+ * @dev: the GPIO device struct
+ * @owner: helps prevent removal of modules exporting active GPIOs
+ * @chip: pointer to the corresponding gpiochip, holding static
+ * data for this device
+ * @list: links gpio_device:s together for traversal
+ *
+ * This state container holds most of the runtime variable data
+ * for a GPIO device and can hold references and live on after the
+ * GPIO chip has been removed, if it is still being used from
+ * userspace.
+ */
+struct gpio_device {
+	int			id;
+	struct device		dev;
+	struct module		*owner;
+	struct gpio_chip	*chip;
+	struct list_head        list;
+};
+
 /**
  * struct acpi_gpio_info - ACPI GPIO specific information
  * @gpioint: if %true this GPIO is of type GpioInt otherwise type is GpioIo
@@ -90,7 +115,7 @@ struct gpio_desc *of_get_named_gpiod_flags(struct device_node *np,
 struct gpio_desc *gpiochip_get_desc(struct gpio_chip *chip, u16 hwnum);
 
 extern struct spinlock gpio_lock;
-extern struct list_head gpio_chips;
+extern struct list_head gpio_devices;
 
 struct gpio_desc {
 	struct gpio_chip	*chip;
diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index 82fda487453f..f3f1dbd43c9b 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -1,6 +1,7 @@
 #ifndef __LINUX_GPIO_DRIVER_H
 #define __LINUX_GPIO_DRIVER_H
 
+#include <linux/device.h>
 #include <linux/types.h>
 #include <linux/module.h>
 #include <linux/irq.h>
@@ -10,22 +11,22 @@
 #include <linux/pinctrl/pinctrl.h>
 #include <linux/kconfig.h>
 
-struct device;
 struct gpio_desc;
 struct of_phandle_args;
 struct device_node;
 struct seq_file;
+struct gpio_device;
 
 #ifdef CONFIG_GPIOLIB
 
 /**
  * struct gpio_chip - abstract a GPIO controller
  * @label: for diagnostics
+ * @gpiodev: the internal state holder, opaque struct
  * @parent: optional parent device providing the GPIOs
  * @cdev: class device used by sysfs interface (may be NULL)
  * @owner: helps prevent removal of modules exporting active GPIOs
  * @data: per-instance data assigned by the driver
- * @list: links gpio_chips together for traversal
  * @request: optional hook for chip-specific activation, such as
  *	enabling module power and clock; may sleep
  * @free: optional hook for chip-specific deactivation, such as
@@ -107,11 +108,11 @@ struct seq_file;
  */
 struct gpio_chip {
 	const char		*label;
+	struct gpio_device	*gpiodev;
 	struct device		*parent;
 	struct device		*cdev;
 	struct module		*owner;
 	void			*data;
-	struct list_head        list;
 
 	int			(*request)(struct gpio_chip *chip,
 						unsigned offset);
-- 
cgit 


From 34ffd85d9c46cde3dc987cac82bff370a937ac4b Mon Sep 17 00:00:00 2001
From: Linus Walleij <linus.walleij@linaro.org>
Date: Tue, 20 Oct 2015 11:31:54 +0200
Subject: gpio: refer to gpio device in prints and debugfs

We use the new struct device inside gpio_chip to related debug
prints and warnings, and we also add it to the debugfs dump.

Cc: Johan Hovold <johan@kernel.org>
Cc: Michael Welling <mwelling@ieee.org>
Cc: Markus Pargmann <mpa@pengutronix.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
 drivers/gpio/gpiolib.c |  6 +++---
 drivers/gpio/gpiolib.h | 12 ++++++------
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 3a073ab5e863..4b94e31a50af 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -304,8 +304,8 @@ static int gpiochip_set_desc_names(struct gpio_chip *gc)
 
 		gpio = gpio_name_to_desc(gc->names[i]);
 		if (gpio)
-			dev_warn(gc->parent, "Detected name collision for "
-				 "GPIO name '%s'\n",
+			dev_warn(&gc->gpiodev->dev,
+				 "Detected name collision for GPIO name '%s'\n",
 				 gc->names[i]);
 	}
 
@@ -528,7 +528,7 @@ void gpiochip_remove(struct gpio_chip *chip)
 	spin_unlock_irqrestore(&gpio_lock, flags);
 
 	if (requested)
-		dev_crit(chip->parent,
+		dev_crit(&chip->gpiodev->dev,
 			 "REMOVING GPIOCHIP WITH GPIOS STILL REQUESTED\n");
 
 	/* FIXME: need to be moved to gpio_device and held there */
diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index feea2c823e47..3f329c922f5b 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -174,17 +174,17 @@ static int __maybe_unused gpio_chip_hwgpio(const struct gpio_desc *desc)
 /* With chip prefix */
 
 #define chip_emerg(chip, fmt, ...)					\
-	pr_emerg("GPIO chip %s: " fmt, chip->label, ##__VA_ARGS__)
+	dev_emerg(&chip->gpiodev->dev, "(%s): " fmt, chip->label, ##__VA_ARGS__)
 #define chip_crit(chip, fmt, ...)					\
-	pr_crit("GPIO chip %s: " fmt, chip->label, ##__VA_ARGS__)
+	dev_crit(&chip->gpiodev->dev, "(%s): " fmt, chip->label, ##__VA_ARGS__)
 #define chip_err(chip, fmt, ...)					\
-	pr_err("GPIO chip %s: " fmt, chip->label, ##__VA_ARGS__)
+	dev_err(&chip->gpiodev->dev, "(%s): " fmt, chip->label, ##__VA_ARGS__)
 #define chip_warn(chip, fmt, ...)					\
-	pr_warn("GPIO chip %s: " fmt, chip->label, ##__VA_ARGS__)
+	dev_warn(&chip->gpiodev->dev, "(%s): " fmt, chip->label, ##__VA_ARGS__)
 #define chip_info(chip, fmt, ...)					\
-	pr_info("GPIO chip %s: " fmt, chip->label, ##__VA_ARGS__)
+	dev_info(&chip->gpiodev->dev, "(%s): " fmt, chip->label, ##__VA_ARGS__)
 #define chip_dbg(chip, fmt, ...)					\
-	pr_debug("GPIO chip %s: " fmt, chip->label, ##__VA_ARGS__)
+	dev_dbg(&chip->gpiodev->dev, "(%s): " fmt, chip->label, ##__VA_ARGS__)
 
 #ifdef CONFIG_GPIO_SYSFS
 
-- 
cgit 


From 3c702e9987e261042a07e43460a8148be254412e Mon Sep 17 00:00:00 2001
From: Linus Walleij <linus.walleij@linaro.org>
Date: Wed, 21 Oct 2015 15:29:53 +0200
Subject: gpio: add a userspace chardev ABI for GPIOs

A new chardev that is to be used for userspace GPIO access is
added in this patch. It is intended to gradually replace the
horribly broken sysfs ABI.

Using a chardev has many upsides:

- All operations are per-gpiochip, which is the actual
  device underlying the GPIOs, making us tie in to the
  kernel device model properly.

- Hotpluggable GPIO controllers can come and go, as this
  kind of problem has been know to userspace for character
  devices since ages, and if a gpiochip handle is held in
  userspace we know we will break something, whereas the
  sysfs is stateless.

- The one-value-per-file rule of sysfs is really hard to
  maintain when you want to twist more than one knob at a time,
  for example have in-kernel APIs to switch several GPIO
  lines at the same time, and this will be possible to do
  with a single ioctl() from userspace, saving a lot of
  context switching.

We also need to add a new bus type for GPIO. This is
necessary for example for userspace coldplug, where sysfs is
traversed to find the boot-time device nodes and create the
character devices in /dev.

This new chardev ABI is *non* *optional* and can be counted
on to be present in the future, emphasizing the preference
of this ABI.

The ABI only implements one single ioctl() to get the name
and number of GPIO lines of a chip. Even this is debatable:
see it as a minimal example for review. This ABI shall be
ruthlessly reviewed and etched in stone.

The old /sys/class/gpio is still optional to compile in,
but will be deprecated.

Unique device IDs are created using IDR, which is overkill
and insanely scalable, but also well tested.

Cc: Johan Hovold <johan@kernel.org>
Cc: Michael Welling <mwelling@ieee.org>
Cc: Markus Pargmann <mpa@pengutronix.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
 MAINTAINERS               |   1 +
 drivers/gpio/gpiolib.c    | 125 +++++++++++++++++++++++++++++++++++++++++++++-
 drivers/gpio/gpiolib.h    |   2 +
 include/uapi/linux/Kbuild |   1 +
 include/uapi/linux/gpio.h |  28 +++++++++++
 5 files changed, 156 insertions(+), 1 deletion(-)
 create mode 100644 include/uapi/linux/gpio.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 30aca4aa5467..76986c3ab4ff 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4819,6 +4819,7 @@ F:	drivers/gpio/
 F:	include/linux/gpio/
 F:	include/linux/gpio.h
 F:	include/asm-generic/gpio.h
+F:	include/uapi/linux/gpio.h
 
 GRE DEMULTIPLEXER DRIVER
 M:	Dmitry Kozlov <xeb@mail.ru>
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 4b94e31a50af..70e0fff0a8a7 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -17,6 +17,10 @@
 #include <linux/gpio/machine.h>
 #include <linux/pinctrl/consumer.h>
 #include <linux/idr.h>
+#include <linux/cdev.h>
+#include <linux/fs.h>
+#include <linux/uaccess.h>
+#include <uapi/linux/gpio.h>
 
 #include "gpiolib.h"
 
@@ -45,6 +49,11 @@
 
 /* Device and char device-related information */
 static DEFINE_IDA(gpio_ida);
+static dev_t gpio_devt;
+#define GPIO_DEV_MAX 256 /* 256 GPIO chip devices supported */
+static struct bus_type gpio_bus_type = {
+	.name = "gpio",
+};
 
 /* gpio_lock prevents conflicts during gpio_desc[] table updates.
  * While any GPIO is requested, its gpio_chip is not removable;
@@ -316,10 +325,84 @@ static int gpiochip_set_desc_names(struct gpio_chip *gc)
 	return 0;
 }
 
+/**
+ * gpio_ioctl() - ioctl handler for the GPIO chardev
+ */
+static long gpio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+{
+	struct gpio_device *gdev = filp->private_data;
+	struct gpio_chip *chip = gdev->chip;
+	int __user *ip = (int __user *)arg;
+	struct gpiochip_info chipinfo;
+
+	/* We fail any subsequent ioctl():s when the chip is gone */
+	if (!chip)
+		return -ENODEV;
+
+	if (cmd == GPIO_GET_CHIPINFO_IOCTL) {
+		/* Fill in the struct and pass to userspace */
+		strncpy(chipinfo.name, dev_name(&gdev->dev),
+			sizeof(chipinfo.name));
+		chipinfo.name[sizeof(chipinfo.name)-1] = '\0';
+		chipinfo.lines = chip->ngpio;
+		if (copy_to_user(ip, &chipinfo, sizeof(chipinfo)))
+			return -EFAULT;
+		return 0;
+	}
+	return -EINVAL;
+}
+
+/**
+ * gpio_chrdev_open() - open the chardev for ioctl operations
+ * @inode: inode for this chardev
+ * @filp: file struct for storing private data
+ * Returns 0 on success
+ */
+static int gpio_chrdev_open(struct inode *inode, struct file *filp)
+{
+	struct gpio_device *gdev = container_of(inode->i_cdev,
+					      struct gpio_device, chrdev);
+
+	/* Fail on open if the backing gpiochip is gone */
+	if (!gdev || !gdev->chip)
+		return -ENODEV;
+	get_device(&gdev->dev);
+	filp->private_data = gdev;
+	return 0;
+}
+
+/**
+ * gpio_chrdev_release() - close chardev after ioctl operations
+ * @inode: inode for this chardev
+ * @filp: file struct for storing private data
+ * Returns 0 on success
+ */
+static int gpio_chrdev_release(struct inode *inode, struct file *filp)
+{
+	struct gpio_device *gdev = container_of(inode->i_cdev,
+					      struct gpio_device, chrdev);
+
+	if (!gdev)
+		return -ENODEV;
+	put_device(&gdev->dev);
+	return 0;
+}
+
+
+static const struct file_operations gpio_fileops = {
+	.release = gpio_chrdev_release,
+	.open = gpio_chrdev_open,
+	.owner = THIS_MODULE,
+	.llseek = noop_llseek,
+	.unlocked_ioctl = gpio_ioctl,
+	.compat_ioctl = gpio_ioctl,
+};
+
 static void gpiodevice_release(struct device *dev)
 {
 	struct gpio_device *gdev = dev_get_drvdata(dev);
 
+	cdev_del(&gdev->chrdev);
 	list_del(&gdev->list);
 	ida_simple_remove(&gpio_ida, gdev->id);
 }
@@ -357,6 +440,7 @@ int gpiochip_add_data(struct gpio_chip *chip, void *data)
 	gdev = kmalloc(sizeof(*gdev), GFP_KERNEL);
 	if (!gdev)
 		return -ENOMEM;
+	gdev->dev.bus = &gpio_bus_type;
 	gdev->chip = chip;
 	chip->gpiodev = gdev;
 	if (chip->parent) {
@@ -452,9 +536,26 @@ int gpiochip_add_data(struct gpio_chip *chip, void *data)
 
 	acpi_gpiochip_add(chip);
 
+	/*
+	 * By first adding the chardev, and then adding the device,
+	 * we get a device node entry in sysfs under
+	 * /sys/bus/gpio/devices/gpiochipN/dev that can be used for
+	 * coldplug of device nodes and other udev business.
+	 */
+	cdev_init(&gdev->chrdev, &gpio_fileops);
+	gdev->chrdev.owner = THIS_MODULE;
+	gdev->chrdev.kobj.parent = &gdev->dev.kobj;
+	gdev->dev.devt = MKDEV(MAJOR(gpio_devt), gdev->id);
+	status = cdev_add(&gdev->chrdev, gdev->dev.devt, 1);
+	if (status < 0)
+		chip_warn(chip, "failed to add char device %d:%d\n",
+			  MAJOR(gpio_devt), gdev->id);
+	else
+		chip_dbg(chip, "added GPIO chardev (%d:%d)\n",
+			 MAJOR(gpio_devt), gdev->id);
 	status = device_add(&gdev->dev);
 	if (status)
-		goto err_remove_chip;
+		goto err_remove_chardev;
 
 	status = gpiochip_sysfs_register(chip);
 	if (status)
@@ -471,6 +572,8 @@ int gpiochip_add_data(struct gpio_chip *chip, void *data)
 
 err_remove_device:
 	device_del(&gdev->dev);
+err_remove_chardev:
+	cdev_del(&gdev->chrdev);
 err_remove_chip:
 	acpi_gpiochip_remove(chip);
 	gpiochip_free_hogs(chip);
@@ -2543,6 +2646,26 @@ void gpiod_put_array(struct gpio_descs *descs)
 }
 EXPORT_SYMBOL_GPL(gpiod_put_array);
 
+static int __init gpiolib_dev_init(void)
+{
+	int ret;
+
+	/* Register GPIO sysfs bus */
+	ret  = bus_register(&gpio_bus_type);
+	if (ret < 0) {
+		pr_err("gpiolib: could not register GPIO bus type\n");
+		return ret;
+	}
+
+	ret = alloc_chrdev_region(&gpio_devt, 0, GPIO_DEV_MAX, "gpiochip");
+	if (ret < 0) {
+		pr_err("gpiolib: failed to allocate char dev region\n");
+		bus_unregister(&gpio_bus_type);
+	}
+	return ret;
+}
+core_initcall(gpiolib_dev_init);
+
 #ifdef CONFIG_DEBUG_FS
 
 static void gpiolib_dbg_show(struct seq_file *s, struct gpio_chip *chip)
diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index 3f329c922f5b..1524ba0ca99d 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -26,6 +26,7 @@ struct acpi_device;
  * struct gpio_device - internal state container for GPIO devices
  * @id: numerical ID number for the GPIO chip
  * @dev: the GPIO device struct
+ * @chrdev: character device for the GPIO device
  * @owner: helps prevent removal of modules exporting active GPIOs
  * @chip: pointer to the corresponding gpiochip, holding static
  * data for this device
@@ -39,6 +40,7 @@ struct acpi_device;
 struct gpio_device {
 	int			id;
 	struct device		dev;
+	struct cdev		chrdev;
 	struct module		*owner;
 	struct gpio_chip	*chip;
 	struct list_head        list;
diff --git a/include/uapi/linux/Kbuild b/include/uapi/linux/Kbuild
index ebd10e624598..5c9ae6a9b7f5 100644
--- a/include/uapi/linux/Kbuild
+++ b/include/uapi/linux/Kbuild
@@ -138,6 +138,7 @@ header-y += genetlink.h
 header-y += gen_stats.h
 header-y += gfs2_ondisk.h
 header-y += gigaset_dev.h
+header-y += gpio.h
 header-y += gsmmux.h
 header-y += hdlcdrv.h
 header-y += hdlc.h
diff --git a/include/uapi/linux/gpio.h b/include/uapi/linux/gpio.h
new file mode 100644
index 000000000000..3188a87bdaa0
--- /dev/null
+++ b/include/uapi/linux/gpio.h
@@ -0,0 +1,28 @@
+/*
+ * <linux/gpio.h> - userspace ABI for the GPIO character devices
+ *
+ * Copyright (C) 2015 Linus Walleij
+ *
+ * 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 _UAPI_GPIO_H_
+#define _UAPI_GPIO_H_
+
+#include <linux/ioctl.h>
+#include <linux/types.h>
+
+/**
+ * struct gpiochip_info - Information about a certain GPIO chip
+ * @name: the name of this GPIO chip
+ * @lines: number of GPIO lines on this chip
+ */
+struct gpiochip_info {
+	char name[32];
+	__u32 lines;
+};
+
+#define GPIO_GET_CHIPINFO_IOCTL _IOR('o', 0x01, struct gpiochip_info)
+
+#endif /* _UAPI_GPIO_H_ */
-- 
cgit 


From 6d591c46bce037696d173bd5c8461b2b4bb680ad Mon Sep 17 00:00:00 2001
From: Linus Walleij <linus.walleij@linaro.org>
Date: Wed, 21 Oct 2015 15:45:54 +0200
Subject: tools/gpio: create GPIO tools

This creates GPIO tools under tools/gpio/* and adds a single
example program to list the GPIOs on a system. When proper
devices are created it provides this minimal output:

Cc: Johan Hovold <johan@kernel.org>
Cc: Michael Welling <mwelling@ieee.org>
Cc: Markus Pargmann <mpa@pengutronix.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
 MAINTAINERS             |   1 +
 tools/Makefile          |   8 +--
 tools/gpio/Makefile     |  12 +++++
 tools/gpio/gpio-utils.c |  11 +++++
 tools/gpio/gpio-utils.h |  25 ++++++++++
 tools/gpio/lsgpio.c     | 128 ++++++++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 182 insertions(+), 3 deletions(-)
 create mode 100644 tools/gpio/Makefile
 create mode 100644 tools/gpio/gpio-utils.c
 create mode 100644 tools/gpio/gpio-utils.h
 create mode 100644 tools/gpio/lsgpio.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 76986c3ab4ff..4d3d1b817873 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4820,6 +4820,7 @@ F:	include/linux/gpio/
 F:	include/linux/gpio.h
 F:	include/asm-generic/gpio.h
 F:	include/uapi/linux/gpio.h
+F:	tools/gpio/
 
 GRE DEMULTIPLEXER DRIVER
 M:	Dmitry Kozlov <xeb@mail.ru>
diff --git a/tools/Makefile b/tools/Makefile
index 6339f6ac3ccb..f41e7c6ea23e 100644
--- a/tools/Makefile
+++ b/tools/Makefile
@@ -13,6 +13,7 @@ help:
 	@echo '  cpupower               - a tool for all things x86 CPU power'
 	@echo '  firewire               - the userspace part of nosy, an IEEE-1394 traffic sniffer'
 	@echo '  freefall               - laptop accelerometer program for disk protection'
+	@echo '  gpio                   - GPIO tools'
 	@echo '  hv                     - tools used when in Hyper-V clients'
 	@echo '  iio                    - IIO tools'
 	@echo '  lguest                 - a minimal 32-bit x86 hypervisor'
@@ -53,7 +54,7 @@ acpi: FORCE
 cpupower: FORCE
 	$(call descend,power/$@)
 
-cgroup firewire hv guest spi usb virtio vm net iio: FORCE
+cgroup firewire hv guest spi usb virtio vm net iio gpio: FORCE
 	$(call descend,$@)
 
 liblockdep: FORCE
@@ -119,7 +120,7 @@ acpi_clean:
 cpupower_clean:
 	$(call descend,power/cpupower,clean)
 
-cgroup_clean hv_clean firewire_clean lguest_clean spi_clean usb_clean virtio_clean vm_clean net_clean iio_clean:
+cgroup_clean hv_clean firewire_clean lguest_clean spi_clean usb_clean virtio_clean vm_clean net_clean iio_clean gpio_clean:
 	$(call descend,$(@:_clean=),clean)
 
 liblockdep_clean:
@@ -155,6 +156,7 @@ build_clean:
 clean: acpi_clean cgroup_clean cpupower_clean hv_clean firewire_clean lguest_clean \
 		perf_clean selftests_clean turbostat_clean spi_clean usb_clean virtio_clean \
 		vm_clean net_clean iio_clean x86_energy_perf_policy_clean tmon_clean \
-		freefall_clean build_clean libbpf_clean libsubcmd_clean liblockdep_clean
+		freefall_clean build_clean libbpf_clean libsubcmd_clean liblockdep_clean \
+		gpio_clean
 
 .PHONY: FORCE
diff --git a/tools/gpio/Makefile b/tools/gpio/Makefile
new file mode 100644
index 000000000000..4d198d5c4203
--- /dev/null
+++ b/tools/gpio/Makefile
@@ -0,0 +1,12 @@
+CC = $(CROSS_COMPILE)gcc
+CFLAGS += -Wall -g -D_GNU_SOURCE
+
+all: lsgpio
+
+lsgpio: lsgpio.o gpio-utils.o
+
+%.o: %.c gpio-utils.h
+
+.PHONY: clean
+clean:
+	rm -f *.o lsgpio
diff --git a/tools/gpio/gpio-utils.c b/tools/gpio/gpio-utils.c
new file mode 100644
index 000000000000..8208718f2c99
--- /dev/null
+++ b/tools/gpio/gpio-utils.c
@@ -0,0 +1,11 @@
+/*
+ * GPIO tools - helpers library for the GPIO tools
+ *
+ * Copyright (C) 2015 Linus Walleij
+ *
+ * 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 "gpio-utils.h"
diff --git a/tools/gpio/gpio-utils.h b/tools/gpio/gpio-utils.h
new file mode 100644
index 000000000000..b18209a45ad3
--- /dev/null
+++ b/tools/gpio/gpio-utils.h
@@ -0,0 +1,25 @@
+/*
+ * GPIO tools - utility helpers library for the GPIO tools
+ *
+ * Copyright (C) 2015 Linus Walleij
+ *
+ * Portions copied from iio_utils and lssio:
+ * Copyright (c) 2010 Manuel Stahl <manuel.stahl@iis.fraunhofer.de>
+ * Copyright (c) 2008 Jonathan Cameron
+ * *
+ * 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 _GPIO_UTILS_H_
+#define _GPIO_UTILS_H_
+
+#include <string.h>
+
+static inline int check_prefix(const char *str, const char *prefix)
+{
+	return strlen(str) > strlen(prefix) &&
+		strncmp(str, prefix, strlen(prefix)) == 0;
+}
+
+#endif /* _GPIO_UTILS_H_ */
diff --git a/tools/gpio/lsgpio.c b/tools/gpio/lsgpio.c
new file mode 100644
index 000000000000..4cfe29da279b
--- /dev/null
+++ b/tools/gpio/lsgpio.c
@@ -0,0 +1,128 @@
+/*
+ * lsgpio - example on how to list the GPIO lines on a system
+ *
+ * Copyright (C) 2015 Linus Walleij
+ *
+ * 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.
+ *
+ * Usage:
+ *	lsgpio <-n device-name>
+ */
+
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <dirent.h>
+#include <errno.h>
+#include <string.h>
+#include <poll.h>
+#include <fcntl.h>
+#include <getopt.h>
+#include <sys/ioctl.h>
+#include <linux/gpio.h>
+
+#include "gpio-utils.h"
+
+int list_device(const char *device_name)
+{
+	struct gpiochip_info cinfo;
+	char *chrdev_name;
+	int fd;
+	int ret;
+
+	ret = asprintf(&chrdev_name, "/dev/%s", device_name);
+	if (ret < 0)
+		return -ENOMEM;
+
+	fd = open(chrdev_name, 0);
+	if (fd == -1) {
+		ret = -errno;
+		fprintf(stderr, "Failed to open %s\n", chrdev_name);
+		goto free_chrdev_name;
+	}
+
+	/* Inspect this GPIO chip */
+	ret = ioctl(fd, GPIO_GET_CHIPINFO_IOCTL, &cinfo);
+	if (ret == -1) {
+		ret = -errno;
+		fprintf(stderr, "Failed to retrieve GPIO fd\n");
+		if (close(fd) == -1)
+			perror("Failed to close GPIO character device file");
+
+		goto free_chrdev_name;
+	}
+	fprintf(stdout, "GPIO chip: %s, %u GPIO lines\n",
+		cinfo.name, cinfo.lines);
+
+	if (close(fd) == -1)  {
+		ret = -errno;
+		goto free_chrdev_name;
+	}
+
+free_chrdev_name:
+	free(chrdev_name);
+
+	return ret;
+
+}
+
+void print_usage(void)
+{
+	fprintf(stderr, "Usage: lsgpio [options]...\n"
+		"List GPIO chips, lines and states\n"
+		"  -n <name>  List GPIOs on a named device\n"
+		"  -?         This helptext\n"
+	);
+}
+
+int main(int argc, char **argv)
+{
+	const char *device_name;
+	int ret;
+	int c;
+
+	while ((c = getopt(argc, argv, "n:")) != -1) {
+		switch (c) {
+		case 'n':
+			device_name = optarg;
+			break;
+		case '?':
+			print_usage();
+			return -1;
+		}
+	}
+
+	if (device_name)
+		ret = list_device(device_name);
+	else {
+		const struct dirent *ent;
+		DIR *dp;
+
+		/* List all GPIO devices one at a time */
+		dp = opendir("/dev");
+		if (!dp) {
+			ret = -errno;
+			goto error_out;
+		}
+
+		ret = -ENOENT;
+		while (ent = readdir(dp), ent) {
+			if (check_prefix(ent->d_name, "gpiochip")) {
+				ret = list_device(ent->d_name);
+				if (ret)
+					break;
+			}
+		}
+
+		ret = 0;
+		if (closedir(dp) == -1) {
+			perror("scanning devices: Failed to close directory");
+			ret = -errno;
+		}
+	}
+error_out:
+	return ret;
+}
-- 
cgit 


From 40c159b776f882f2e2cbe20c9e29832841e5c0f9 Mon Sep 17 00:00:00 2001
From: Linus Walleij <linus.walleij@linaro.org>
Date: Thu, 22 Oct 2015 10:21:57 +0200
Subject: gpio: add a userspace character device ABI

Put in some documentation for the new character device ABI
so we can properly etch it in stone.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
 Documentation/ABI/testing/gpio-cdev | 26 ++++++++++++++++++++++++++
 MAINTAINERS                         |  1 +
 2 files changed, 27 insertions(+)
 create mode 100644 Documentation/ABI/testing/gpio-cdev

diff --git a/Documentation/ABI/testing/gpio-cdev b/Documentation/ABI/testing/gpio-cdev
new file mode 100644
index 000000000000..7b265fbb47e3
--- /dev/null
+++ b/Documentation/ABI/testing/gpio-cdev
@@ -0,0 +1,26 @@
+What:		/dev/gpiochip[0-9]+
+Date:		November 2015
+KernelVersion:	4.4
+Contact:	linux-gpio@vger.kernel.org
+Description:
+		The character device files /dev/gpiochip* are the interface
+		between GPIO chips and userspace.
+
+		The ioctl(2)-based ABI is defined and documented in
+		[include/uapi]<linux/gpio.h>.
+
+		The following file operations are supported:
+
+		open(2)
+		Currently the only useful flags are O_RDWR.
+
+		ioctl(2)
+		Initiate various actions.
+		See the inline documentation in [include/uapi]<linux/gpio.h>
+		for descriptions of all ioctls.
+
+		close(2)
+		Stops and free up the I/O contexts that was associated
+		with the file descriptor.
+
+Users:		TBD
diff --git a/MAINTAINERS b/MAINTAINERS
index 4d3d1b817873..a85cd6dcb5de 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4815,6 +4815,7 @@ L:	linux-gpio@vger.kernel.org
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-gpio.git
 S:	Maintained
 F:	Documentation/gpio/
+F:	Documentation/ABI/testing/gpio-cdev
 F:	drivers/gpio/
 F:	include/linux/gpio/
 F:	include/linux/gpio.h
-- 
cgit 


From fe95046e960b4b76e73dc1486955d93f47276134 Mon Sep 17 00:00:00 2001
From: Linus Walleij <linus.walleij@linaro.org>
Date: Thu, 22 Oct 2015 09:58:34 +0200
Subject: gpio: ABI: mark the sysfs ABI as obsolete

This marks the (optional) sysfs GPIO ABI as obsolete and schedules
it for removal in 2020.

Cc: Johan Hovold <johan@kernel.org>
Cc: Michael Welling <mwelling@ieee.org>
Cc: Markus Pargmann <mpa@pengutronix.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
 Documentation/ABI/obsolete/sysfs-gpio | 30 ++++++++++++++++++++++++++++++
 Documentation/ABI/testing/sysfs-gpio  | 28 ----------------------------
 MAINTAINERS                           |  1 +
 3 files changed, 31 insertions(+), 28 deletions(-)
 create mode 100644 Documentation/ABI/obsolete/sysfs-gpio
 delete mode 100644 Documentation/ABI/testing/sysfs-gpio

diff --git a/Documentation/ABI/obsolete/sysfs-gpio b/Documentation/ABI/obsolete/sysfs-gpio
new file mode 100644
index 000000000000..867c1fab20e2
--- /dev/null
+++ b/Documentation/ABI/obsolete/sysfs-gpio
@@ -0,0 +1,30 @@
+What:		/sys/class/gpio/
+Date:		July 2008
+KernelVersion:	2.6.27
+Contact:	Linus Walleij <linusw@kernel.org>
+Description:
+
+  As a Kconfig option, individual GPIO signals may be accessed from
+  userspace.  GPIOs are only made available to userspace by an explicit
+  "export" operation.  If a given GPIO is not claimed for use by
+  kernel code, it may be exported by userspace (and unexported later).
+  Kernel code may export it for complete or partial access.
+
+  GPIOs are identified as they are inside the kernel, using integers in
+  the range 0..INT_MAX.  See Documentation/gpio.txt for more information.
+
+    /sys/class/gpio
+	/export ... asks the kernel to export a GPIO to userspace
+	/unexport ... to return a GPIO to the kernel
+	/gpioN ... for each exported GPIO #N OR
+	/<LINE-NAME> ... for a properly named GPIO line
+	    /value ... always readable, writes fail for input GPIOs
+	    /direction ... r/w as: in, out (default low); write: high, low
+	    /edge ... r/w as: none, falling, rising, both
+	/gpiochipN ... for each gpiochip; #N is its first GPIO
+	    /base ... (r/o) same as N
+	    /label ... (r/o) descriptive, not necessarily unique
+	    /ngpio ... (r/o) number of GPIOs; numbered N to N + (ngpio - 1)
+
+  This ABI is deprecated and will be removed after 2020. It is
+  replaced with the GPIO character device.
diff --git a/Documentation/ABI/testing/sysfs-gpio b/Documentation/ABI/testing/sysfs-gpio
deleted file mode 100644
index 55ffa2df1c10..000000000000
--- a/Documentation/ABI/testing/sysfs-gpio
+++ /dev/null
@@ -1,28 +0,0 @@
-What:		/sys/class/gpio/
-Date:		July 2008
-KernelVersion:	2.6.27
-Contact:	David Brownell <dbrownell@users.sourceforge.net>
-Description:
-
-  As a Kconfig option, individual GPIO signals may be accessed from
-  userspace.  GPIOs are only made available to userspace by an explicit
-  "export" operation.  If a given GPIO is not claimed for use by
-  kernel code, it may be exported by userspace (and unexported later).
-  Kernel code may export it for complete or partial access.
-
-  GPIOs are identified as they are inside the kernel, using integers in
-  the range 0..INT_MAX.  See Documentation/gpio.txt for more information.
-
-    /sys/class/gpio
-	/export ... asks the kernel to export a GPIO to userspace
-	/unexport ... to return a GPIO to the kernel
-	/gpioN ... for each exported GPIO #N OR
-	/<LINE-NAME> ... for a properly named GPIO line
-	    /value ... always readable, writes fail for input GPIOs
-	    /direction ... r/w as: in, out (default low); write: high, low
-	    /edge ... r/w as: none, falling, rising, both
-	/gpiochipN ... for each gpiochip; #N is its first GPIO
-	    /base ... (r/o) same as N
-	    /label ... (r/o) descriptive, not necessarily unique
-	    /ngpio ... (r/o) number of GPIOs; numbered N to N + (ngpio - 1)
-
diff --git a/MAINTAINERS b/MAINTAINERS
index a85cd6dcb5de..7df638be28e2 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4816,6 +4816,7 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-gpio.git
 S:	Maintained
 F:	Documentation/gpio/
 F:	Documentation/ABI/testing/gpio-cdev
+F:	Documentation/ABI/obsolete/sysfs-gpio
 F:	drivers/gpio/
 F:	include/linux/gpio/
 F:	include/linux/gpio.h
-- 
cgit