#include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/irq.h>
  #include <linux/spinlock.h>

  #include <linux/device.h>
  #include <linux/err.h>
  #include <linux/debugfs.h>
  #include <linux/seq_file.h>
  #include <linux/gpio.h>

  
  
  /* Optional implementation infrastructure for GPIO interfaces.
   *
   * Platforms may want to use this if they tend to use very many GPIOs
   * that aren't part of a System-On-Chip core; or across I2C/SPI/etc.
   *
   * When kernel footprint or instruction count is an issue, simpler
   * implementations may be preferred.  The GPIO programming interface
   * allows for inlining speed-critical get/set operations for common
   * cases, so that access to SOC-integrated GPIOs can sometimes cost
   * only an instruction or two per bit.
   */
  
  
  /* When debugging, extend minimal trust to callers and platform code.
   * Also emit diagnostic messages that may help initial bringup, when
   * board setup or driver bugs are most common.
   *
   * Otherwise, minimize overhead in what may be bitbanging codepaths.
   */
  #ifdef	DEBUG
  #define	extra_checks	1
  #else
  #define	extra_checks	0
  #endif
  
  /* 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.
   */
  static DEFINE_SPINLOCK(gpio_lock);
  
  struct gpio_desc {
  	struct gpio_chip	*chip;
  	unsigned long		flags;
  /* flag symbols are bit numbers */
  #define FLAG_REQUESTED	0
  #define FLAG_IS_OUT	1

  #define FLAG_RESERVED	2

  #define FLAG_EXPORT	3	/* protected by sysfs_lock */
  #define FLAG_SYSFS	4	/* exported via /sys/class/gpio/control */

  
  #ifdef CONFIG_DEBUG_FS
  	const char		*label;
  #endif
  };
  static struct gpio_desc gpio_desc[ARCH_NR_GPIOS];
  
  static inline void desc_set_label(struct gpio_desc *d, const char *label)
  {
  #ifdef CONFIG_DEBUG_FS
  	d->label = label;
  #endif
  }
  
  /* Warn when drivers omit gpio_request() calls -- legal but ill-advised
   * when setting direction, and otherwise illegal.  Until board setup code
   * and drivers use explicit requests everywhere (which won't happen when
   * those calls have no teeth) we can't avoid autorequesting.  This nag
   * message should motivate switching to explicit requests...
   */
  static void gpio_ensure_requested(struct gpio_desc *desc)
  {
  	if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
  		pr_warning("GPIO-%d autorequested
  ", (int)(desc - gpio_desc));
  		desc_set_label(desc, "[auto]");

  		if (!try_module_get(desc->chip->owner))
  			pr_err("GPIO-%d: module can't be gotten 
  ",
  					(int)(desc - gpio_desc));

  	}
  }
  
  /* caller holds gpio_lock *OR* gpio is marked as requested */
  static inline struct gpio_chip *gpio_to_chip(unsigned gpio)
  {
  	return gpio_desc[gpio].chip;
  }

  /* dynamic allocation of GPIOs, e.g. on a hotplugged device */
  static int gpiochip_find_base(int ngpio)
  {
  	int i;
  	int spare = 0;
  	int base = -ENOSPC;
  
  	for (i = ARCH_NR_GPIOS - 1; i >= 0 ; i--) {

  		struct gpio_desc *desc = &gpio_desc[i];
  		struct gpio_chip *chip = desc->chip;

  		if (!chip && !test_bit(FLAG_RESERVED, &desc->flags)) {

  			spare++;
  			if (spare == ngpio) {
  				base = i;
  				break;
  			}
  		} else {
  			spare = 0;

  			if (chip)
  				i -= chip->ngpio - 1;

  		}
  	}
  
  	if (gpio_is_valid(base))
  		pr_debug("%s: found new base at %d
  ", __func__, base);
  	return base;
  }

  /**

   * gpiochip_reserve() - reserve range of gpios to use with platform code only
   * @start: starting gpio number
   * @ngpio: number of gpios to reserve
   * Context: platform init, potentially before irqs or kmalloc will work
   *
   * Returns a negative errno if any gpio within the range is already reserved
   * or registered, else returns zero as a success code.  Use this function
   * to mark a range of gpios as unavailable for dynamic gpio number allocation,
   * for example because its driver support is not yet loaded.
   */
  int __init gpiochip_reserve(int start, int ngpio)
  {
  	int ret = 0;
  	unsigned long flags;
  	int i;

  	if (!gpio_is_valid(start) || !gpio_is_valid(start + ngpio - 1))

  		return -EINVAL;
  
  	spin_lock_irqsave(&gpio_lock, flags);
  
  	for (i = start; i < start + ngpio; i++) {
  		struct gpio_desc *desc = &gpio_desc[i];
  
  		if (desc->chip || test_bit(FLAG_RESERVED, &desc->flags)) {
  			ret = -EBUSY;
  			goto err;
  		}
  
  		set_bit(FLAG_RESERVED, &desc->flags);
  	}
  
  	pr_debug("%s: reserved gpios from %d to %d
  ",
  		 __func__, start, start + ngpio - 1);
  err:
  	spin_unlock_irqrestore(&gpio_lock, flags);
  
  	return ret;
  }

  #ifdef CONFIG_GPIO_SYSFS
  
  /* lock protects against unexport_gpio() being called while
   * sysfs files are active.
   */
  static DEFINE_MUTEX(sysfs_lock);
  
  /*
   * /sys/class/gpio/gpioN... only for GPIOs that are exported
   *   /direction
   *      * MAY BE OMITTED if kernel won't allow direction changes
   *      * is read/write as "in" or "out"
   *      * may also be written as "high" or "low", initializing
   *        output value as specified ("out" implies "low")
   *   /value
   *      * always readable, subject to hardware behavior
   *      * may be writable, as zero/nonzero
   *
   * REVISIT there will likely be an attribute for configuring async
   * notifications, e.g. to specify polling interval or IRQ trigger type
   * that would for example trigger a poll() on the "value".
   */
  
  static ssize_t gpio_direction_show(struct device *dev,
  		struct device_attribute *attr, char *buf)
  {
  	const struct gpio_desc	*desc = dev_get_drvdata(dev);
  	ssize_t			status;
  
  	mutex_lock(&sysfs_lock);
  
  	if (!test_bit(FLAG_EXPORT, &desc->flags))
  		status = -EIO;
  	else
  		status = sprintf(buf, "%s
  ",
  			test_bit(FLAG_IS_OUT, &desc->flags)
  				? "out" : "in");
  
  	mutex_unlock(&sysfs_lock);
  	return status;
  }
  
  static ssize_t gpio_direction_store(struct device *dev,
  		struct device_attribute *attr, const char *buf, size_t size)
  {
  	const struct gpio_desc	*desc = dev_get_drvdata(dev);
  	unsigned		gpio = desc - gpio_desc;
  	ssize_t			status;
  
  	mutex_lock(&sysfs_lock);
  
  	if (!test_bit(FLAG_EXPORT, &desc->flags))
  		status = -EIO;
  	else if (sysfs_streq(buf, "high"))
  		status = gpio_direction_output(gpio, 1);
  	else if (sysfs_streq(buf, "out") || sysfs_streq(buf, "low"))
  		status = gpio_direction_output(gpio, 0);
  	else if (sysfs_streq(buf, "in"))
  		status = gpio_direction_input(gpio);
  	else
  		status = -EINVAL;
  
  	mutex_unlock(&sysfs_lock);
  	return status ? : size;
  }
  
  static const DEVICE_ATTR(direction, 0644,
  		gpio_direction_show, gpio_direction_store);
  
  static ssize_t gpio_value_show(struct device *dev,
  		struct device_attribute *attr, char *buf)
  {
  	const struct gpio_desc	*desc = dev_get_drvdata(dev);
  	unsigned		gpio = desc - gpio_desc;
  	ssize_t			status;
  
  	mutex_lock(&sysfs_lock);
  
  	if (!test_bit(FLAG_EXPORT, &desc->flags))
  		status = -EIO;
  	else
  		status = sprintf(buf, "%d
  ", gpio_get_value_cansleep(gpio));
  
  	mutex_unlock(&sysfs_lock);
  	return status;
  }
  
  static ssize_t gpio_value_store(struct device *dev,
  		struct device_attribute *attr, const char *buf, size_t size)
  {
  	const struct gpio_desc	*desc = dev_get_drvdata(dev);
  	unsigned		gpio = desc - gpio_desc;
  	ssize_t			status;
  
  	mutex_lock(&sysfs_lock);
  
  	if (!test_bit(FLAG_EXPORT, &desc->flags))
  		status = -EIO;
  	else if (!test_bit(FLAG_IS_OUT, &desc->flags))
  		status = -EPERM;
  	else {
  		long		value;
  
  		status = strict_strtol(buf, 0, &value);
  		if (status == 0) {
  			gpio_set_value_cansleep(gpio, value != 0);
  			status = size;
  		}
  	}
  
  	mutex_unlock(&sysfs_lock);
  	return status;
  }
  
  static /*const*/ DEVICE_ATTR(value, 0644,
  		gpio_value_show, gpio_value_store);
  
  static const struct attribute *gpio_attrs[] = {
  	&dev_attr_direction.attr,
  	&dev_attr_value.attr,
  	NULL,
  };
  
  static const struct attribute_group gpio_attr_group = {
  	.attrs = (struct attribute **) gpio_attrs,
  };
  
  /*
   * /sys/class/gpio/gpiochipN/
   *   /base ... matching gpio_chip.base (N)
   *   /label ... matching gpio_chip.label
   *   /ngpio ... matching gpio_chip.ngpio
   */
  
  static ssize_t chip_base_show(struct device *dev,
  			       struct device_attribute *attr, char *buf)
  {
  	const struct gpio_chip	*chip = dev_get_drvdata(dev);
  
  	return sprintf(buf, "%d
  ", chip->base);
  }
  static DEVICE_ATTR(base, 0444, chip_base_show, NULL);
  
  static ssize_t chip_label_show(struct device *dev,
  			       struct device_attribute *attr, char *buf)
  {
  	const struct gpio_chip	*chip = dev_get_drvdata(dev);
  
  	return sprintf(buf, "%s
  ", chip->label ? : "");
  }
  static DEVICE_ATTR(label, 0444, chip_label_show, NULL);
  
  static ssize_t chip_ngpio_show(struct device *dev,
  			       struct device_attribute *attr, char *buf)
  {
  	const struct gpio_chip	*chip = dev_get_drvdata(dev);
  
  	return sprintf(buf, "%u
  ", chip->ngpio);
  }
  static DEVICE_ATTR(ngpio, 0444, chip_ngpio_show, NULL);
  
  static const struct attribute *gpiochip_attrs[] = {
  	&dev_attr_base.attr,
  	&dev_attr_label.attr,
  	&dev_attr_ngpio.attr,
  	NULL,
  };
  
  static const struct attribute_group gpiochip_attr_group = {
  	.attrs = (struct attribute **) gpiochip_attrs,
  };
  
  /*
   * /sys/class/gpio/export ... write-only
   *	integer N ... number of GPIO to export (full access)
   * /sys/class/gpio/unexport ... write-only
   *	integer N ... number of GPIO to unexport
   */
  static ssize_t export_store(struct class *class, const char *buf, size_t len)
  {
  	long	gpio;
  	int	status;
  
  	status = strict_strtol(buf, 0, &gpio);
  	if (status < 0)
  		goto done;
  
  	/* No extra locking here; FLAG_SYSFS just signifies that the
  	 * request and export were done by on behalf of userspace, so
  	 * they may be undone on its behalf too.
  	 */
  
  	status = gpio_request(gpio, "sysfs");
  	if (status < 0)
  		goto done;
  
  	status = gpio_export(gpio, true);
  	if (status < 0)
  		gpio_free(gpio);
  	else
  		set_bit(FLAG_SYSFS, &gpio_desc[gpio].flags);
  
  done:
  	if (status)
  		pr_debug("%s: status %d
  ", __func__, status);
  	return status ? : len;
  }
  
  static ssize_t unexport_store(struct class *class, const char *buf, size_t len)
  {
  	long	gpio;
  	int	status;
  
  	status = strict_strtol(buf, 0, &gpio);
  	if (status < 0)
  		goto done;
  
  	status = -EINVAL;
  
  	/* reject bogus commands (gpio_unexport ignores them) */
  	if (!gpio_is_valid(gpio))
  		goto done;
  
  	/* No extra locking here; FLAG_SYSFS just signifies that the
  	 * request and export were done by on behalf of userspace, so
  	 * they may be undone on its behalf too.
  	 */
  	if (test_and_clear_bit(FLAG_SYSFS, &gpio_desc[gpio].flags)) {
  		status = 0;
  		gpio_free(gpio);
  	}
  done:
  	if (status)
  		pr_debug("%s: status %d
  ", __func__, status);
  	return status ? : len;
  }
  
  static struct class_attribute gpio_class_attrs[] = {
  	__ATTR(export, 0200, NULL, export_store),
  	__ATTR(unexport, 0200, NULL, unexport_store),
  	__ATTR_NULL,
  };
  
  static struct class gpio_class = {
  	.name =		"gpio",
  	.owner =	THIS_MODULE,
  
  	.class_attrs =	gpio_class_attrs,
  };
  
  
  /**
   * gpio_export - export a GPIO through sysfs
   * @gpio: gpio to make available, already requested
   * @direction_may_change: true if userspace may change gpio direction
   * Context: arch_initcall or later
   *
   * When drivers want to make a GPIO accessible to userspace after they
   * have requested it -- perhaps while debugging, or as part of their
   * public interface -- they may use this routine.  If the GPIO can
   * change direction (some can't) and the caller allows it, userspace
   * will see "direction" sysfs attribute which may be used to change
   * the gpio's direction.  A "value" attribute will always be provided.
   *
   * Returns zero on success, else an error.
   */
  int gpio_export(unsigned gpio, bool direction_may_change)
  {
  	unsigned long		flags;
  	struct gpio_desc	*desc;
  	int			status = -EINVAL;
  
  	/* can't export until sysfs is available ... */
  	if (!gpio_class.p) {
  		pr_debug("%s: called too early!
  ", __func__);
  		return -ENOENT;
  	}
  
  	if (!gpio_is_valid(gpio))
  		goto done;
  
  	mutex_lock(&sysfs_lock);
  
  	spin_lock_irqsave(&gpio_lock, flags);
  	desc = &gpio_desc[gpio];
  	if (test_bit(FLAG_REQUESTED, &desc->flags)
  			&& !test_bit(FLAG_EXPORT, &desc->flags)) {
  		status = 0;
  		if (!desc->chip->direction_input
  				|| !desc->chip->direction_output)
  			direction_may_change = false;
  	}
  	spin_unlock_irqrestore(&gpio_lock, flags);
  
  	if (status == 0) {
  		struct device	*dev;
  
  		dev = device_create(&gpio_class, desc->chip->dev, MKDEV(0, 0),
  					desc, "gpio%d", gpio);
  		if (dev) {
  			if (direction_may_change)
  				status = sysfs_create_group(&dev->kobj,
  						&gpio_attr_group);
  			else
  				status = device_create_file(dev,
  						&dev_attr_value);
  			if (status != 0)
  				device_unregister(dev);
  		} else
  			status = -ENODEV;
  		if (status == 0)
  			set_bit(FLAG_EXPORT, &desc->flags);
  	}
  
  	mutex_unlock(&sysfs_lock);
  
  done:
  	if (status)
  		pr_debug("%s: gpio%d status %d
  ", __func__, gpio, status);
  
  	return status;
  }
  EXPORT_SYMBOL_GPL(gpio_export);
  
  static int match_export(struct device *dev, void *data)
  {
  	return dev_get_drvdata(dev) == data;
  }
  
  /**
   * gpio_unexport - reverse effect of gpio_export()
   * @gpio: gpio to make unavailable
   *
   * This is implicit on gpio_free().
   */
  void gpio_unexport(unsigned gpio)
  {
  	struct gpio_desc	*desc;
  	int			status = -EINVAL;
  
  	if (!gpio_is_valid(gpio))
  		goto done;
  
  	mutex_lock(&sysfs_lock);
  
  	desc = &gpio_desc[gpio];
  	if (test_bit(FLAG_EXPORT, &desc->flags)) {
  		struct device	*dev = NULL;
  
  		dev = class_find_device(&gpio_class, NULL, desc, match_export);
  		if (dev) {
  			clear_bit(FLAG_EXPORT, &desc->flags);
  			put_device(dev);
  			device_unregister(dev);
  			status = 0;
  		} else
  			status = -ENODEV;
  	}
  
  	mutex_unlock(&sysfs_lock);
  done:
  	if (status)
  		pr_debug("%s: gpio%d status %d
  ", __func__, gpio, status);
  }
  EXPORT_SYMBOL_GPL(gpio_unexport);
  
  static int gpiochip_export(struct gpio_chip *chip)
  {
  	int		status;
  	struct device	*dev;
  
  	/* Many systems register gpio chips for SOC support very early,
  	 * before driver model support is available.  In those cases we
  	 * export this later, in gpiolib_sysfs_init() ... here we just
  	 * verify that _some_ field of gpio_class got initialized.
  	 */
  	if (!gpio_class.p)
  		return 0;
  
  	/* use chip->base for the ID; it's already known to be unique */
  	mutex_lock(&sysfs_lock);
  	dev = device_create(&gpio_class, chip->dev, MKDEV(0, 0), chip,
  				"gpiochip%d", chip->base);
  	if (dev) {
  		status = sysfs_create_group(&dev->kobj,
  				&gpiochip_attr_group);
  	} else
  		status = -ENODEV;
  	chip->exported = (status == 0);
  	mutex_unlock(&sysfs_lock);
  
  	if (status) {
  		unsigned long	flags;
  		unsigned	gpio;
  
  		spin_lock_irqsave(&gpio_lock, flags);
  		gpio = chip->base;
  		while (gpio_desc[gpio].chip == chip)
  			gpio_desc[gpio++].chip = NULL;
  		spin_unlock_irqrestore(&gpio_lock, flags);
  
  		pr_debug("%s: chip %s status %d
  ", __func__,
  				chip->label, status);
  	}
  
  	return status;
  }
  
  static void gpiochip_unexport(struct gpio_chip *chip)
  {
  	int			status;
  	struct device		*dev;
  
  	mutex_lock(&sysfs_lock);
  	dev = class_find_device(&gpio_class, NULL, chip, match_export);
  	if (dev) {
  		put_device(dev);
  		device_unregister(dev);
  		chip->exported = 0;
  		status = 0;
  	} else
  		status = -ENODEV;
  	mutex_unlock(&sysfs_lock);
  
  	if (status)
  		pr_debug("%s: chip %s status %d
  ", __func__,
  				chip->label, status);
  }
  
  static int __init gpiolib_sysfs_init(void)
  {
  	int		status;
  	unsigned long	flags;
  	unsigned	gpio;
  
  	status = class_register(&gpio_class);
  	if (status < 0)
  		return status;
  
  	/* Scan and register the gpio_chips which registered very
  	 * early (e.g. before the class_register above was called).
  	 *
  	 * We run before arch_initcall() so chip->dev nodes can have
  	 * registered, and so arch_initcall() can always gpio_export().
  	 */
  	spin_lock_irqsave(&gpio_lock, flags);
  	for (gpio = 0; gpio < ARCH_NR_GPIOS; gpio++) {
  		struct gpio_chip	*chip;
  
  		chip = gpio_desc[gpio].chip;
  		if (!chip || chip->exported)
  			continue;
  
  		spin_unlock_irqrestore(&gpio_lock, flags);
  		status = gpiochip_export(chip);
  		spin_lock_irqsave(&gpio_lock, flags);
  	}
  	spin_unlock_irqrestore(&gpio_lock, flags);
  
  
  	return status;
  }
  postcore_initcall(gpiolib_sysfs_init);
  
  #else
  static inline int gpiochip_export(struct gpio_chip *chip)
  {
  	return 0;
  }
  
  static inline void gpiochip_unexport(struct gpio_chip *chip)
  {
  }
  
  #endif /* CONFIG_GPIO_SYSFS */

  /**

   * gpiochip_add() - register a gpio_chip
   * @chip: the chip to register, with chip->base initialized
   * Context: potentially before irqs or kmalloc will work
   *
   * Returns a negative errno if the chip can't be registered, such as
   * because the chip->base is invalid or already associated with a
   * different chip.  Otherwise it returns zero as a success code.

   *

   * When gpiochip_add() is called very early during boot, so that GPIOs
   * can be freely used, the chip->dev device must be registered before
   * the gpio framework's arch_initcall().  Otherwise sysfs initialization
   * for GPIOs will fail rudely.
   *

   * If chip->base is negative, this requests dynamic assignment of
   * a range of valid GPIOs.

   */
  int gpiochip_add(struct gpio_chip *chip)
  {
  	unsigned long	flags;
  	int		status = 0;
  	unsigned	id;

  	int		base = chip->base;

  	if ((!gpio_is_valid(base) || !gpio_is_valid(base + chip->ngpio - 1))

  			&& base >= 0) {

  		status = -EINVAL;
  		goto fail;
  	}
  
  	spin_lock_irqsave(&gpio_lock, flags);

  	if (base < 0) {
  		base = gpiochip_find_base(chip->ngpio);
  		if (base < 0) {
  			status = base;

  			goto unlock;

  		}
  		chip->base = base;
  	}

  	/* these GPIO numbers must not be managed by another gpio_chip */

  	for (id = base; id < base + chip->ngpio; id++) {

  		if (gpio_desc[id].chip != NULL) {
  			status = -EBUSY;
  			break;
  		}
  	}
  	if (status == 0) {

  		for (id = base; id < base + chip->ngpio; id++) {

  			gpio_desc[id].chip = chip;

  
  			/* REVISIT:  most hardware initializes GPIOs as
  			 * inputs (often with pullups enabled) so power
  			 * usage is minimized.  Linux code should set the
  			 * gpio direction first thing; but until it does,
  			 * we may expose the wrong direction in sysfs.
  			 */
  			gpio_desc[id].flags = !chip->direction_input
  				? (1 << FLAG_IS_OUT)
  				: 0;

  		}
  	}

  unlock:

  	spin_unlock_irqrestore(&gpio_lock, flags);

  	if (status == 0)
  		status = gpiochip_export(chip);

  fail:
  	/* failures here can mean systems won't boot... */
  	if (status)
  		pr_err("gpiochip_add: gpios %d..%d (%s) not registered
  ",

  			chip->base, chip->base + chip->ngpio - 1,

  			chip->label ? : "generic");
  	return status;
  }
  EXPORT_SYMBOL_GPL(gpiochip_add);
  
  /**
   * gpiochip_remove() - unregister a gpio_chip
   * @chip: the chip to unregister
   *
   * A gpio_chip with any GPIOs still requested may not be removed.
   */
  int gpiochip_remove(struct gpio_chip *chip)
  {
  	unsigned long	flags;
  	int		status = 0;
  	unsigned	id;
  
  	spin_lock_irqsave(&gpio_lock, flags);
  
  	for (id = chip->base; id < chip->base + chip->ngpio; id++) {
  		if (test_bit(FLAG_REQUESTED, &gpio_desc[id].flags)) {
  			status = -EBUSY;
  			break;
  		}
  	}
  	if (status == 0) {
  		for (id = chip->base; id < chip->base + chip->ngpio; id++)
  			gpio_desc[id].chip = NULL;
  	}
  
  	spin_unlock_irqrestore(&gpio_lock, flags);

  
  	if (status == 0)
  		gpiochip_unexport(chip);

  	return status;
  }
  EXPORT_SYMBOL_GPL(gpiochip_remove);
  
  
  /* These "optional" allocation calls help prevent drivers from stomping
   * on each other, and help provide better diagnostics in debugfs.
   * They're called even less than the "set direction" calls.
   */
  int gpio_request(unsigned gpio, const char *label)
  {
  	struct gpio_desc	*desc;
  	int			status = -EINVAL;
  	unsigned long		flags;
  
  	spin_lock_irqsave(&gpio_lock, flags);

  	if (!gpio_is_valid(gpio))

  		goto done;
  	desc = &gpio_desc[gpio];
  	if (desc->chip == NULL)
  		goto done;

  	if (!try_module_get(desc->chip->owner))
  		goto done;

  	/* NOTE:  gpio_request() can be called in early boot,
  	 * before IRQs are enabled.
  	 */
  
  	if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
  		desc_set_label(desc, label ? : "?");
  		status = 0;

  	} else {

  		status = -EBUSY;

  		module_put(desc->chip->owner);
  	}

  
  done:
  	if (status)
  		pr_debug("gpio_request: gpio-%d (%s) status %d
  ",
  			gpio, label ? : "?", status);
  	spin_unlock_irqrestore(&gpio_lock, flags);
  	return status;
  }
  EXPORT_SYMBOL_GPL(gpio_request);
  
  void gpio_free(unsigned gpio)
  {
  	unsigned long		flags;
  	struct gpio_desc	*desc;

  	if (!gpio_is_valid(gpio)) {

  		WARN_ON(extra_checks);
  		return;
  	}

  	gpio_unexport(gpio);

  	spin_lock_irqsave(&gpio_lock, flags);
  
  	desc = &gpio_desc[gpio];

  	if (desc->chip && test_and_clear_bit(FLAG_REQUESTED, &desc->flags)) {

  		desc_set_label(desc, NULL);

  		module_put(desc->chip->owner);
  	} else

  		WARN_ON(extra_checks);
  
  	spin_unlock_irqrestore(&gpio_lock, flags);
  }
  EXPORT_SYMBOL_GPL(gpio_free);
  
  
  /**
   * gpiochip_is_requested - return string iff signal was requested
   * @chip: controller managing the signal
   * @offset: of signal within controller's 0..(ngpio - 1) range
   *
   * Returns NULL if the GPIO is not currently requested, else a string.
   * If debugfs support is enabled, the string returned is the label passed
   * to gpio_request(); otherwise it is a meaningless constant.
   *
   * This function is for use by GPIO controller drivers.  The label can
   * help with diagnostics, and knowing that the signal is used as a GPIO
   * can help avoid accidentally multiplexing it to another controller.
   */
  const char *gpiochip_is_requested(struct gpio_chip *chip, unsigned offset)
  {
  	unsigned gpio = chip->base + offset;

  	if (!gpio_is_valid(gpio) || gpio_desc[gpio].chip != chip)

  		return NULL;
  	if (test_bit(FLAG_REQUESTED, &gpio_desc[gpio].flags) == 0)
  		return NULL;
  #ifdef CONFIG_DEBUG_FS
  	return gpio_desc[gpio].label;
  #else
  	return "?";
  #endif
  }
  EXPORT_SYMBOL_GPL(gpiochip_is_requested);
  
  
  /* Drivers MUST set GPIO direction before making get/set calls.  In
   * some cases this is done in early boot, before IRQs are enabled.
   *
   * As a rule these aren't called more than once (except for drivers
   * using the open-drain emulation idiom) so these are natural places
   * to accumulate extra debugging checks.  Note that we can't (yet)
   * rely on gpio_request() having been called beforehand.
   */
  
  int gpio_direction_input(unsigned gpio)
  {
  	unsigned long		flags;
  	struct gpio_chip	*chip;
  	struct gpio_desc	*desc = &gpio_desc[gpio];
  	int			status = -EINVAL;
  
  	spin_lock_irqsave(&gpio_lock, flags);

  	if (!gpio_is_valid(gpio))

  		goto fail;
  	chip = desc->chip;
  	if (!chip || !chip->get || !chip->direction_input)
  		goto fail;
  	gpio -= chip->base;
  	if (gpio >= chip->ngpio)
  		goto fail;
  	gpio_ensure_requested(desc);
  
  	/* now we know the gpio is valid and chip won't vanish */
  
  	spin_unlock_irqrestore(&gpio_lock, flags);
  
  	might_sleep_if(extra_checks && chip->can_sleep);
  
  	status = chip->direction_input(chip, gpio);
  	if (status == 0)
  		clear_bit(FLAG_IS_OUT, &desc->flags);
  	return status;
  fail:
  	spin_unlock_irqrestore(&gpio_lock, flags);
  	if (status)
  		pr_debug("%s: gpio-%d status %d
  ",

  			__func__, gpio, status);

  	return status;
  }
  EXPORT_SYMBOL_GPL(gpio_direction_input);
  
  int gpio_direction_output(unsigned gpio, int value)
  {
  	unsigned long		flags;
  	struct gpio_chip	*chip;
  	struct gpio_desc	*desc = &gpio_desc[gpio];
  	int			status = -EINVAL;
  
  	spin_lock_irqsave(&gpio_lock, flags);

  	if (!gpio_is_valid(gpio))

  		goto fail;
  	chip = desc->chip;
  	if (!chip || !chip->set || !chip->direction_output)
  		goto fail;
  	gpio -= chip->base;
  	if (gpio >= chip->ngpio)
  		goto fail;
  	gpio_ensure_requested(desc);
  
  	/* now we know the gpio is valid and chip won't vanish */
  
  	spin_unlock_irqrestore(&gpio_lock, flags);
  
  	might_sleep_if(extra_checks && chip->can_sleep);
  
  	status = chip->direction_output(chip, gpio, value);
  	if (status == 0)
  		set_bit(FLAG_IS_OUT, &desc->flags);
  	return status;
  fail:
  	spin_unlock_irqrestore(&gpio_lock, flags);
  	if (status)
  		pr_debug("%s: gpio-%d status %d
  ",

  			__func__, gpio, status);

  	return status;
  }
  EXPORT_SYMBOL_GPL(gpio_direction_output);
  
  
  /* I/O calls are only valid after configuration completed; the relevant
   * "is this a valid GPIO" error checks should already have been done.
   *
   * "Get" operations are often inlinable as reading a pin value register,
   * and masking the relevant bit in that register.
   *
   * When "set" operations are inlinable, they involve writing that mask to
   * one register to set a low value, or a different register to set it high.
   * Otherwise locking is needed, so there may be little value to inlining.
   *
   *------------------------------------------------------------------------
   *
   * IMPORTANT!!!  The hot paths -- get/set value -- assume that callers
   * have requested the GPIO.  That can include implicit requesting by
   * a direction setting call.  Marking a gpio as requested locks its chip
   * in memory, guaranteeing that these table lookups need no more locking
   * and that gpiochip_remove() will fail.
   *
   * REVISIT when debugging, consider adding some instrumentation to ensure
   * that the GPIO was actually requested.
   */
  
  /**
   * __gpio_get_value() - return a gpio's value
   * @gpio: gpio whose value will be returned
   * Context: any
   *
   * This is used directly or indirectly to implement gpio_get_value().
   * It returns the zero or nonzero value provided by the associated
   * gpio_chip.get() method; or zero if no such method is provided.
   */
  int __gpio_get_value(unsigned gpio)
  {
  	struct gpio_chip	*chip;
  
  	chip = gpio_to_chip(gpio);
  	WARN_ON(extra_checks && chip->can_sleep);
  	return chip->get ? chip->get(chip, gpio - chip->base) : 0;
  }
  EXPORT_SYMBOL_GPL(__gpio_get_value);
  
  /**
   * __gpio_set_value() - assign a gpio's value
   * @gpio: gpio whose value will be assigned
   * @value: value to assign
   * Context: any
   *
   * This is used directly or indirectly to implement gpio_set_value().
   * It invokes the associated gpio_chip.set() method.
   */
  void __gpio_set_value(unsigned gpio, int value)
  {
  	struct gpio_chip	*chip;
  
  	chip = gpio_to_chip(gpio);
  	WARN_ON(extra_checks && chip->can_sleep);
  	chip->set(chip, gpio - chip->base, value);
  }
  EXPORT_SYMBOL_GPL(__gpio_set_value);
  
  /**
   * __gpio_cansleep() - report whether gpio value access will sleep
   * @gpio: gpio in question
   * Context: any
   *
   * This is used directly or indirectly to implement gpio_cansleep().  It
   * returns nonzero if access reading or writing the GPIO value can sleep.
   */
  int __gpio_cansleep(unsigned gpio)
  {
  	struct gpio_chip	*chip;
  
  	/* only call this on GPIOs that are valid! */
  	chip = gpio_to_chip(gpio);
  
  	return chip->can_sleep;
  }
  EXPORT_SYMBOL_GPL(__gpio_cansleep);
  
  
  
  /* There's no value in making it easy to inline GPIO calls that may sleep.
   * Common examples include ones connected to I2C or SPI chips.
   */
  
  int gpio_get_value_cansleep(unsigned gpio)
  {
  	struct gpio_chip	*chip;
  
  	might_sleep_if(extra_checks);
  	chip = gpio_to_chip(gpio);
  	return chip->get(chip, gpio - chip->base);
  }
  EXPORT_SYMBOL_GPL(gpio_get_value_cansleep);
  
  void gpio_set_value_cansleep(unsigned gpio, int value)
  {
  	struct gpio_chip	*chip;
  
  	might_sleep_if(extra_checks);
  	chip = gpio_to_chip(gpio);
  	chip->set(chip, gpio - chip->base, value);
  }
  EXPORT_SYMBOL_GPL(gpio_set_value_cansleep);
  
  
  #ifdef CONFIG_DEBUG_FS

  static void gpiolib_dbg_show(struct seq_file *s, struct gpio_chip *chip)
  {
  	unsigned		i;
  	unsigned		gpio = chip->base;
  	struct gpio_desc	*gdesc = &gpio_desc[gpio];
  	int			is_out;
  
  	for (i = 0; i < chip->ngpio; i++, gpio++, gdesc++) {
  		if (!test_bit(FLAG_REQUESTED, &gdesc->flags))
  			continue;
  
  		is_out = test_bit(FLAG_IS_OUT, &gdesc->flags);
  		seq_printf(s, " gpio-%-3d (%-12s) %s %s",
  			gpio, gdesc->label,
  			is_out ? "out" : "in ",
  			chip->get
  				? (chip->get(chip, i) ? "hi" : "lo")
  				: "?  ");
  
  		if (!is_out) {
  			int		irq = gpio_to_irq(gpio);
  			struct irq_desc	*desc = irq_desc + irq;
  
  			/* This races with request_irq(), set_irq_type(),
  			 * and set_irq_wake() ... but those are "rare".
  			 *
  			 * More significantly, trigger type flags aren't
  			 * currently maintained by genirq.
  			 */
  			if (irq >= 0 && desc->action) {
  				char *trigger;
  
  				switch (desc->status & IRQ_TYPE_SENSE_MASK) {
  				case IRQ_TYPE_NONE:
  					trigger = "(default)";
  					break;
  				case IRQ_TYPE_EDGE_FALLING:
  					trigger = "edge-falling";
  					break;
  				case IRQ_TYPE_EDGE_RISING:
  					trigger = "edge-rising";
  					break;
  				case IRQ_TYPE_EDGE_BOTH:
  					trigger = "edge-both";
  					break;
  				case IRQ_TYPE_LEVEL_HIGH:
  					trigger = "level-high";
  					break;
  				case IRQ_TYPE_LEVEL_LOW:
  					trigger = "level-low";
  					break;
  				default:
  					trigger = "?trigger?";
  					break;
  				}
  
  				seq_printf(s, " irq-%d %s%s",
  					irq, trigger,
  					(desc->status & IRQ_WAKEUP)
  						? " wakeup" : "");
  			}
  		}
  
  		seq_printf(s, "
  ");
  	}
  }
  
  static int gpiolib_show(struct seq_file *s, void *unused)
  {
  	struct gpio_chip	*chip = NULL;
  	unsigned		gpio;
  	int			started = 0;
  
  	/* REVISIT this isn't locked against gpio_chip removal ... */

  	for (gpio = 0; gpio_is_valid(gpio); gpio++) {

  		struct device *dev;

  		if (chip == gpio_desc[gpio].chip)
  			continue;
  		chip = gpio_desc[gpio].chip;
  		if (!chip)
  			continue;

  		seq_printf(s, "%sGPIOs %d-%d",

  				started ? "
  " : "",

  				chip->base, chip->base + chip->ngpio - 1);
  		dev = chip->dev;
  		if (dev)
  			seq_printf(s, ", %s/%s",
  				dev->bus ? dev->bus->name : "no-bus",
  				dev->bus_id);
  		if (chip->label)
  			seq_printf(s, ", %s", chip->label);
  		if (chip->can_sleep)
  			seq_printf(s, ", can sleep");
  		seq_printf(s, ":
  ");

  		started = 1;
  		if (chip->dbg_show)
  			chip->dbg_show(s, chip);
  		else
  			gpiolib_dbg_show(s, chip);
  	}
  	return 0;
  }
  
  static int gpiolib_open(struct inode *inode, struct file *file)
  {
  	return single_open(file, gpiolib_show, NULL);
  }
  
  static struct file_operations gpiolib_operations = {
  	.open		= gpiolib_open,
  	.read		= seq_read,
  	.llseek		= seq_lseek,
  	.release	= single_release,
  };
  
  static int __init gpiolib_debugfs_init(void)
  {
  	/* /sys/kernel/debug/gpio */
  	(void) debugfs_create_file("gpio", S_IFREG | S_IRUGO,
  				NULL, NULL, &gpiolib_operations);
  	return 0;
  }
  subsys_initcall(gpiolib_debugfs_init);
  
  #endif	/* DEBUG_FS */