Merge branch 'chardev' into devel

14 files changed, 578 insertions, 90 deletions

diff --git a/Documentation/ABI/testing/sysfs-gpio b/Documentation/ABI/obsolete/sysfs-gpio
index 55ffa2d..867c1fa 100644
--- a/Documentation/ABI/testing/sysfs-gpio
+++ b/Documentation/ABI/obsolete/sysfs-gpio
@@ -1,7 +1,7 @@
 What:		/sys/class/gpio/
 Date:		July 2008
 KernelVersion:	2.6.27
-Contact:	David Brownell <dbrownell@users.sourceforge.net>
+Contact:	Linus Walleij <linusw@kernel.org>
 Description:
 
   As a Kconfig option, individual GPIO signals may be accessed from
@@ -26,3 +26,5 @@ Description:
 	    /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/gpio-cdev b/Documentation/ABI/testing/gpio-cdev
new file mode 100644
index 0000000..7b265fbb
--- /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 f043e95..7b8c058 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4821,10 +4821,14 @@ 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:	Documentation/ABI/obsolete/sysfs-gpio
 F:	drivers/gpio/
 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/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index 405dfca..28d3bf2 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 5c1ba87..70e0fff 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -16,6 +16,11 @@
 #include <linux/gpio/driver.h>
 #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"
 
@@ -42,6 +47,14 @@
 #define	extra_checks	0
 #endif
 
+/* 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;
  * each GPIO's "requested" flag serves as a lock and refcount.
@@ -50,8 +63,7 @@ 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 +79,16 @@ 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 +138,16 @@ 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 +200,28 @@ 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 (list_empty(&gpio_chips)) {
-		list_add_tail(&chip->list, &gpio_chips);
+	if (!gdev->chip)
+		return -EINVAL;
+
+	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 +234,8 @@ 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 +248,18 @@ 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 +268,16 @@ 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;
@@ -290,8 +313,8 @@ 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]);
 	}
 
@@ -303,6 +326,88 @@ static int gpiochip_set_desc_names(struct gpio_chip *gc)
 }
 
 /**
+ * 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);
+}
+
+/**
  * gpiochip_add_data() - register a gpio_chip
  * @chip: the chip to register, with chip->base initialized
  * Context: potentially before irqs will work
@@ -323,19 +428,61 @@ 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->dev.bus = &gpio_bus_type;
+	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 +497,16 @@ 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 +517,15 @@ 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 +536,58 @@ 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_chardev;
+
 	status = gpiochip_sysfs_register(chip);
 	if (status)
-		goto err_remove_chip;
+		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_chardev:
+	cdev_del(&gdev->chrdev);
 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 +604,18 @@ 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 +628,23 @@ 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,
+		dev_crit(&chip->gpiodev->dev,
 			 "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 +663,21 @@ 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 +807,14 @@ 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 +825,7 @@ 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 +1175,10 @@ 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 +1224,7 @@ 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);
 }
@@ -2456,6 +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)
@@ -2492,16 +2702,16 @@ 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 +2721,14 @@ 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 +2743,24 @@ 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 99ed3b0..1524ba0 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -12,14 +12,41 @@
 #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
+ * @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
+ * @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 cdev		chrdev;
+	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
  * @active_low: in case of @gpioint, the pin is active low
@@ -90,7 +117,7 @@ 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;
@@ -149,17 +176,17 @@ 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
 
diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index 82fda48..f3f1dbd 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);
diff --git a/include/uapi/linux/Kbuild b/include/uapi/linux/Kbuild
index ebd10e6..5c9ae6a 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 0000000..3188a87
--- /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_ */
diff --git a/tools/Makefile b/tools/Makefile
index 6339f6a..f41e7c6 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 0000000..4d198d5
--- /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 0000000..8208718
--- /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 0000000..b18209a
--- /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 0000000..4cfe29d
--- /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;
+}