hdmi: move show sink info to debug node.

[firefly-linux-kernel-4.4.55.git] / drivers / gpio / gpiolib.c

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/spinlock.h>
#include <linux/list.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>
#include <linux/gpio.h>
#include <linux/of_gpio.h>
#include <linux/idr.h>
#include <linux/slab.h>

#define CREATE_TRACE_POINTS
#include <trace/events/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_EXPORT     2       /* protected by sysfs_lock */
#define FLAG_SYSFS      3       /* exported via /sys/class/gpio/control */
#define FLAG_TRIG_FALL  4       /* trigger on falling edge */
#define FLAG_TRIG_RISE  5       /* trigger on rising edge */
#define FLAG_ACTIVE_LOW 6       /* sysfs value has active low */
#define FLAG_OPEN_DRAIN 7       /* Gpio is open drain type */
#define FLAG_OPEN_SOURCE 8      /* Gpio is open source type */

#define ID_SHIFT        16      /* add new flags before this one */

#define GPIO_FLAGS_MASK         ((1 << ID_SHIFT) - 1)
#define GPIO_TRIGGER_MASK       (BIT(FLAG_TRIG_FALL) | BIT(FLAG_TRIG_RISE))

#ifdef CONFIG_DEBUG_FS
        const char              *label;
#endif
};
static struct gpio_desc gpio_desc[ARCH_NR_GPIOS];

#define GPIO_OFFSET_VALID(chip, offset) (offset >= 0 && offset < chip->ngpio)

static LIST_HEAD(gpio_chips);

#ifdef CONFIG_GPIO_SYSFS
static DEFINE_IDR(dirent_idr);
#endif

/*
 * Internal gpiod_* API using descriptors instead of the integer namespace.
 * Most of this should eventually go public.
 */
static int gpiod_request(struct gpio_desc *desc, const char *label);
static void gpiod_free(struct gpio_desc *desc);
static int gpiod_direction_input(struct gpio_desc *desc);
static int gpiod_direction_output(struct gpio_desc *desc, int value);
static int gpiod_get_direction(const struct gpio_desc *desc);
static int gpiod_set_debounce(struct gpio_desc *desc, unsigned debounce);
static int gpiod_get_value_cansleep(const struct gpio_desc *desc);
static void gpiod_set_value_cansleep(struct gpio_desc *desc, int value);
static int gpiod_get_value(const struct gpio_desc *desc);
static void gpiod_set_value(struct gpio_desc *desc, int value);
static int gpiod_cansleep(const struct gpio_desc *desc);
static int gpiod_to_irq(const struct gpio_desc *desc);
static int gpiod_export(struct gpio_desc *desc, bool direction_may_change);
static int gpiod_export_link(struct device *dev, const char *name,
                             struct gpio_desc *desc);
static int gpiod_sysfs_set_active_low(struct gpio_desc *desc, int value);
static void gpiod_unexport(struct gpio_desc *desc);


static inline void desc_set_label(struct gpio_desc *d, const char *label)
{
#ifdef CONFIG_DEBUG_FS
        d->label = label;
#endif
}

/*
 * Return the GPIO number of the passed descriptor relative to its chip
 */
static int gpio_chip_hwgpio(const struct gpio_desc *desc)
{
        return desc - &desc->chip->desc[0];
}

/**
 * Convert a GPIO number to its descriptor
 */
static struct gpio_desc *gpio_to_desc(unsigned gpio)
{
        if (WARN(!gpio_is_valid(gpio), "invalid GPIO %d\n", gpio))
                return NULL;
        else
                return &gpio_desc[gpio];
}

/**
 * Convert a GPIO descriptor to the integer namespace.
 * This should disappear in the future but is needed since we still
 * use GPIO numbers for error messages and sysfs nodes
 */
static int desc_to_gpio(const struct gpio_desc *desc)
{
        return desc - &gpio_desc[0];
}


/* 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... so should
 * the weaker cleanup after faults, compared to gpio_request().
 *
 * NOTE: the autorequest mechanism is going away; at this point it's
 * only "legal" in the sense that (old) code using it won't break yet,
 * but instead only triggers a WARN() stack dump.
 */
static int gpio_ensure_requested(struct gpio_desc *desc)
{
        const struct gpio_chip *chip = desc->chip;
        const int gpio = desc_to_gpio(desc);

        if (WARN(test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0,
                        "autorequest GPIO-%d\n", gpio)) {
                if (!try_module_get(chip->owner)) {
                        pr_err("GPIO-%d: module can't be gotten \n", gpio);
                        clear_bit(FLAG_REQUESTED, &desc->flags);
                        /* lose */
                        return -EIO;
                }
                desc_set_label(desc, "[auto]");
                /* caller must chip->request() w/o spinlock */
                if (chip->request)
                        return 1;
        }
        return 0;
}

static struct gpio_chip *gpiod_to_chip(const struct gpio_desc *desc)
{
        return desc ? desc->chip : NULL;
}

/* caller holds gpio_lock *OR* gpio is marked as requested */
struct gpio_chip *gpio_to_chip(unsigned gpio)
{
        return gpiod_to_chip(gpio_to_desc(gpio));
}

/* dynamic allocation of GPIOs, e.g. on a hotplugged device */
static int gpiochip_find_base(int ngpio)
{
        struct gpio_chip *chip;
        int base = ARCH_NR_GPIOS - ngpio;

        list_for_each_entry_reverse(chip, &gpio_chips, list) {
                /* found a free space? */
                if (chip->base + chip->ngpio <= base)
                        break;
                else
                        /* nope, check the space right before the chip */
                        base = chip->base - ngpio;
        }

        if (gpio_is_valid(base)) {
                pr_debug("%s: found new base at %d\n", __func__, base);
                return base;
        } else {
                pr_err("%s: cannot find free range\n", __func__);
                return -ENOSPC;
        }
}

/* caller ensures gpio is valid and requested, chip->get_direction may sleep  */
static int gpiod_get_direction(const struct gpio_desc *desc)
{
        struct gpio_chip        *chip;
        unsigned                offset;
        int                     status = -EINVAL;

        chip = gpiod_to_chip(desc);
        offset = gpio_chip_hwgpio(desc);

        if (!chip->get_direction)
                return status;

        status = chip->get_direction(chip, offset);
        if (status > 0) {
                /* GPIOF_DIR_IN, or other positive */
                status = 1;
                /* FLAG_IS_OUT is just a cache of the result of get_direction(),
                 * so it does not affect constness per se */
                clear_bit(FLAG_IS_OUT, &((struct gpio_desc *)desc)->flags);
        }
        if (status == 0) {
                /* GPIOF_DIR_OUT */
                set_bit(FLAG_IS_OUT, &((struct gpio_desc *)desc)->flags);
        }
        return status;
}

#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
 *   /edge
 *      * configures behavior of poll(2) on /value
 *      * available only if pin can generate IRQs on input
 *      * is read/write as "none", "falling", "rising", or "both"
 *   /active_low
 *      * configures polarity of /value
 *      * is read/write as zero/nonzero
 *      * also affects existing and subsequent "falling" and "rising"
 *        /edge configuration
 */

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 {
                gpiod_get_direction(desc);
                status = sprintf(buf, "%s\n",
                        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)
{
        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 if (sysfs_streq(buf, "high"))
                status = gpiod_direction_output(desc, 1);
        else if (sysfs_streq(buf, "out") || sysfs_streq(buf, "low"))
                status = gpiod_direction_output(desc, 0);
        else if (sysfs_streq(buf, "in"))
                status = gpiod_direction_input(desc);
        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)
{
        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 {
                int value;

                value = !!gpiod_get_value_cansleep(desc);
                if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
                        value = !value;

                status = sprintf(buf, "%d\n", value);
        }

        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)
{
        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 if (!test_bit(FLAG_IS_OUT, &desc->flags))
                status = -EPERM;
        else {
                long            value;

                status = strict_strtol(buf, 0, &value);
                if (status == 0) {
                        if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
                                value = !value;
                        gpiod_set_value_cansleep(desc, value != 0);
                        status = size;
                }
        }

        mutex_unlock(&sysfs_lock);
        return status;
}

static DEVICE_ATTR(value, 0644,
                gpio_value_show, gpio_value_store);

static irqreturn_t gpio_sysfs_irq(int irq, void *priv)
{
        struct sysfs_dirent     *value_sd = priv;

        sysfs_notify_dirent(value_sd);
        return IRQ_HANDLED;
}

static int gpio_setup_irq(struct gpio_desc *desc, struct device *dev,
                unsigned long gpio_flags)
{
        struct sysfs_dirent     *value_sd;
        unsigned long           irq_flags;
        int                     ret, irq, id;

        if ((desc->flags & GPIO_TRIGGER_MASK) == gpio_flags)
                return 0;

        irq = gpiod_to_irq(desc);
        if (irq < 0)
                return -EIO;

        id = desc->flags >> ID_SHIFT;
        value_sd = idr_find(&dirent_idr, id);
        if (value_sd)
                free_irq(irq, value_sd);

        desc->flags &= ~GPIO_TRIGGER_MASK;

        if (!gpio_flags) {
                ret = 0;
                goto free_id;
        }

        irq_flags = IRQF_SHARED;
        if (test_bit(FLAG_TRIG_FALL, &gpio_flags))
                irq_flags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
                        IRQF_TRIGGER_RISING : IRQF_TRIGGER_FALLING;
        if (test_bit(FLAG_TRIG_RISE, &gpio_flags))
                irq_flags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
                        IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING;

        if (!value_sd) {
                value_sd = sysfs_get_dirent(dev->kobj.sd, NULL, "value");
                if (!value_sd) {
                        ret = -ENODEV;
                        goto err_out;
                }

                ret = idr_alloc(&dirent_idr, value_sd, 1, 0, GFP_KERNEL);
                if (ret < 0)
                        goto free_sd;
                id = ret;

                desc->flags &= GPIO_FLAGS_MASK;
                desc->flags |= (unsigned long)id << ID_SHIFT;

                if (desc->flags >> ID_SHIFT != id) {
                        ret = -ERANGE;
                        goto free_id;
                }
        }

        ret = request_any_context_irq(irq, gpio_sysfs_irq, irq_flags,
                                "gpiolib", value_sd);
        if (ret < 0)
                goto free_id;

        desc->flags |= gpio_flags;
        return 0;

free_id:
        idr_remove(&dirent_idr, id);
        desc->flags &= GPIO_FLAGS_MASK;
free_sd:
        if (value_sd)
                sysfs_put(value_sd);
err_out:
        return ret;
}

static const struct {
        const char *name;
        unsigned long flags;
} trigger_types[] = {
        { "none",    0 },
        { "falling", BIT(FLAG_TRIG_FALL) },
        { "rising",  BIT(FLAG_TRIG_RISE) },
        { "both",    BIT(FLAG_TRIG_FALL) | BIT(FLAG_TRIG_RISE) },
};

static ssize_t gpio_edge_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 {
                int i;

                status = 0;
                for (i = 0; i < ARRAY_SIZE(trigger_types); i++)
                        if ((desc->flags & GPIO_TRIGGER_MASK)
                                        == trigger_types[i].flags) {
                                status = sprintf(buf, "%s\n",
                                                 trigger_types[i].name);
                                break;
                        }
        }

        mutex_unlock(&sysfs_lock);
        return status;
}

static ssize_t gpio_edge_store(struct device *dev,
                struct device_attribute *attr, const char *buf, size_t size)
{
        struct gpio_desc        *desc = dev_get_drvdata(dev);
        ssize_t                 status;
        int                     i;

        for (i = 0; i < ARRAY_SIZE(trigger_types); i++)
                if (sysfs_streq(trigger_types[i].name, buf))
                        goto found;
        return -EINVAL;

found:
        mutex_lock(&sysfs_lock);

        if (!test_bit(FLAG_EXPORT, &desc->flags))
                status = -EIO;
        else {
                status = gpio_setup_irq(desc, dev, trigger_types[i].flags);
                if (!status)
                        status = size;
        }

        mutex_unlock(&sysfs_lock);

        return status;
}

static DEVICE_ATTR(edge, 0644, gpio_edge_show, gpio_edge_store);

static int sysfs_set_active_low(struct gpio_desc *desc, struct device *dev,
                                int value)
{
        int                     status = 0;

        if (!!test_bit(FLAG_ACTIVE_LOW, &desc->flags) == !!value)
                return 0;

        if (value)
                set_bit(FLAG_ACTIVE_LOW, &desc->flags);
        else
                clear_bit(FLAG_ACTIVE_LOW, &desc->flags);

        /* reconfigure poll(2) support if enabled on one edge only */
        if (dev != NULL && (!!test_bit(FLAG_TRIG_RISE, &desc->flags) ^
                                !!test_bit(FLAG_TRIG_FALL, &desc->flags))) {
                unsigned long trigger_flags = desc->flags & GPIO_TRIGGER_MASK;

                gpio_setup_irq(desc, dev, 0);
                status = gpio_setup_irq(desc, dev, trigger_flags);
        }

        return status;
}

static ssize_t gpio_active_low_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, "%d\n",
                                !!test_bit(FLAG_ACTIVE_LOW, &desc->flags));

        mutex_unlock(&sysfs_lock);

        return status;
}

static ssize_t gpio_active_low_store(struct device *dev,
                struct device_attribute *attr, const char *buf, size_t size)
{
        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 {
                long            value;

                status = strict_strtol(buf, 0, &value);
                if (status == 0)
                        status = sysfs_set_active_low(desc, dev, value != 0);
        }

        mutex_unlock(&sysfs_lock);

        return status ? : size;
}

static DEVICE_ATTR(active_low, 0644,
                gpio_active_low_show, gpio_active_low_store);

static struct attribute *gpio_attrs[] = {
        &dev_attr_value.attr,
        &dev_attr_active_low.attr,
        NULL,
};

static const struct attribute_group gpio_attr_group = {
        .attrs = 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\n", 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\n", 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\n", chip->ngpio);
}
static DEVICE_ATTR(ngpio, 0444, chip_ngpio_show, NULL);

static 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 = 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,
                                struct class_attribute *attr,
                                const char *buf, size_t len)
{
        long                    gpio;
        struct gpio_desc        *desc;
        int                     status;

        status = strict_strtol(buf, 0, &gpio);
        if (status < 0)
                goto done;

        desc = gpio_to_desc(gpio);
        /* reject invalid GPIOs */
        if (!desc) {
                pr_warn("%s: invalid GPIO %ld\n", __func__, gpio);
                return -EINVAL;
        }

        /* 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 = gpiod_request(desc, "sysfs");
        if (status < 0) {
                if (status == -EPROBE_DEFER)
                        status = -ENODEV;
                goto done;
        }
        status = gpiod_export(desc, true);
        if (status < 0)
                gpiod_free(desc);
        else
                set_bit(FLAG_SYSFS, &desc->flags);

done:
        if (status)
                pr_debug("%s: status %d\n", __func__, status);
        return status ? : len;
}

static ssize_t unexport_store(struct class *class,
                                struct class_attribute *attr,
                                const char *buf, size_t len)
{
        long                    gpio;
        struct gpio_desc        *desc;
        int                     status;

        status = strict_strtol(buf, 0, &gpio);
        if (status < 0)
                goto done;

        desc = gpio_to_desc(gpio);
        /* reject bogus commands (gpio_unexport ignores them) */
        if (!desc) {
                pr_warn("%s: invalid GPIO %ld\n", __func__, gpio);
                return -EINVAL;
        }

        status = -EINVAL;

        /* 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, &desc->flags)) {
                status = 0;
                gpiod_free(desc);
        }
done:
        if (status)
                pr_debug("%s: status %d\n", __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.
 */
static int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
{
        struct gpio_chip        *chip;
        unsigned long           flags;
        int                     status;
        const char              *ioname = NULL;
        struct device           *dev;
        int                     offset;

        /* can't export until sysfs is available ... */
        if (!gpio_class.p) {
                pr_debug("%s: called too early!\n", __func__);
                return -ENOENT;
        }

        if (!desc) {
                pr_debug("%s: invalid gpio descriptor\n", __func__);
                return -EINVAL;
        }

        chip = desc->chip;

        mutex_lock(&sysfs_lock);

        /* check if chip is being removed */
        if (!chip || !chip->exported) {
                status = -ENODEV;
                goto fail_unlock;
        }

        spin_lock_irqsave(&gpio_lock, flags);
        if (!test_bit(FLAG_REQUESTED, &desc->flags) ||
             test_bit(FLAG_EXPORT, &desc->flags)) {
                spin_unlock_irqrestore(&gpio_lock, flags);
                pr_debug("%s: gpio %d unavailable (requested=%d, exported=%d)\n",
                                __func__, desc_to_gpio(desc),
                                test_bit(FLAG_REQUESTED, &desc->flags),
                                test_bit(FLAG_EXPORT, &desc->flags));
                status = -EPERM;
                goto fail_unlock;
        }

        if (!desc->chip->direction_input || !desc->chip->direction_output)
                direction_may_change = false;
        spin_unlock_irqrestore(&gpio_lock, flags);

        offset = gpio_chip_hwgpio(desc);
        if (desc->chip->names && desc->chip->names[offset])
                ioname = desc->chip->names[offset];

        dev = device_create(&gpio_class, desc->chip->dev, MKDEV(0, 0),
                            desc, ioname ? ioname : "gpio%u",
                            desc_to_gpio(desc));
        if (IS_ERR(dev)) {
                status = PTR_ERR(dev);
                goto fail_unlock;
        }

        status = sysfs_create_group(&dev->kobj, &gpio_attr_group);
        if (status)
                goto fail_unregister_device;

        if (direction_may_change) {
                status = device_create_file(dev, &dev_attr_direction);
                if (status)
                        goto fail_remove_attr_group;
        }

        if (gpiod_to_irq(desc) >= 0 && (direction_may_change ||
                                       !test_bit(FLAG_IS_OUT, &desc->flags))) {
                status = device_create_file(dev, &dev_attr_edge);
                if (status)
                        goto fail_remove_attr_direction;
        }

        set_bit(FLAG_EXPORT, &desc->flags);
        mutex_unlock(&sysfs_lock);
        return 0;

fail_remove_attr_direction:
        device_remove_file(dev, &dev_attr_direction);
fail_remove_attr_group:
        sysfs_remove_group(&dev->kobj, &gpio_attr_group);
fail_unregister_device:
        device_unregister(dev);
fail_unlock:
        mutex_unlock(&sysfs_lock);
        pr_debug("%s: gpio%d status %d\n", __func__, desc_to_gpio(desc),
                 status);
        return status;
}

int gpio_export(unsigned gpio, bool direction_may_change)
{
        return gpiod_export(gpio_to_desc(gpio), direction_may_change);
}
EXPORT_SYMBOL_GPL(gpio_export);

static int match_export(struct device *dev, const void *data)
{
        return dev_get_drvdata(dev) == data;
}

/**
 * gpio_export_link - create a sysfs link to an exported GPIO node
 * @dev: device under which to create symlink
 * @name: name of the symlink
 * @gpio: gpio to create symlink to, already exported
 *
 * Set up a symlink from /sys/.../dev/name to /sys/class/gpio/gpioN
 * node. Caller is responsible for unlinking.
 *
 * Returns zero on success, else an error.
 */
static int gpiod_export_link(struct device *dev, const char *name,
                             struct gpio_desc *desc)
{
        int                     status = -EINVAL;

        if (!desc) {
                pr_warn("%s: invalid GPIO\n", __func__);
                return -EINVAL;
        }

        mutex_lock(&sysfs_lock);

        if (test_bit(FLAG_EXPORT, &desc->flags)) {
                struct device *tdev;

                tdev = class_find_device(&gpio_class, NULL, desc, match_export);
                if (tdev != NULL) {
                        status = sysfs_create_link(&dev->kobj, &tdev->kobj,
                                                name);
                        put_device(tdev);
                } else {
                        status = -ENODEV;
                }
        }

        mutex_unlock(&sysfs_lock);

        if (status)
                pr_debug("%s: gpio%d status %d\n", __func__, desc_to_gpio(desc),
                         status);

        return status;
}

int gpio_export_link(struct device *dev, const char *name, unsigned gpio)
{
        return gpiod_export_link(dev, name, gpio_to_desc(gpio));
}
EXPORT_SYMBOL_GPL(gpio_export_link);

/**
 * gpio_sysfs_set_active_low - set the polarity of gpio sysfs value
 * @gpio: gpio to change
 * @value: non-zero to use active low, i.e. inverted values
 *
 * Set the polarity of /sys/class/gpio/gpioN/value sysfs attribute.
 * The GPIO does not have to be exported yet.  If poll(2) support has
 * been enabled for either rising or falling edge, it will be
 * reconfigured to follow the new polarity.
 *
 * Returns zero on success, else an error.
 */
static int gpiod_sysfs_set_active_low(struct gpio_desc *desc, int value)
{
        struct device           *dev = NULL;
        int                     status = -EINVAL;

        if (!desc) {
                pr_warn("%s: invalid GPIO\n", __func__);
                return -EINVAL;
        }

        mutex_lock(&sysfs_lock);

        if (test_bit(FLAG_EXPORT, &desc->flags)) {
                dev = class_find_device(&gpio_class, NULL, desc, match_export);
                if (dev == NULL) {
                        status = -ENODEV;
                        goto unlock;
                }
        }

        status = sysfs_set_active_low(desc, dev, value);
        put_device(dev);
unlock:
        mutex_unlock(&sysfs_lock);

        if (status)
                pr_debug("%s: gpio%d status %d\n", __func__, desc_to_gpio(desc),
                         status);

        return status;
}

int gpio_sysfs_set_active_low(unsigned gpio, int value)
{
        return gpiod_sysfs_set_active_low(gpio_to_desc(gpio), value);
}
EXPORT_SYMBOL_GPL(gpio_sysfs_set_active_low);

/**
 * gpio_unexport - reverse effect of gpio_export()
 * @gpio: gpio to make unavailable
 *
 * This is implicit on gpio_free().
 */
static void gpiod_unexport(struct gpio_desc *desc)
{
        int                     status = 0;
        struct device           *dev = NULL;

        if (!desc) {
                pr_warn("%s: invalid GPIO\n", __func__);
                return;
        }

        mutex_lock(&sysfs_lock);

        if (test_bit(FLAG_EXPORT, &desc->flags)) {

                dev = class_find_device(&gpio_class, NULL, desc, match_export);
                if (dev) {
                        gpio_setup_irq(desc, dev, 0);
                        clear_bit(FLAG_EXPORT, &desc->flags);
                } else
                        status = -ENODEV;
        }

        mutex_unlock(&sysfs_lock);

        if (dev) {
                device_remove_file(dev, &dev_attr_edge);
                device_remove_file(dev, &dev_attr_direction);
                sysfs_remove_group(&dev->kobj, &gpio_attr_group);
                device_unregister(dev);
                put_device(dev);
        }

        if (status)
                pr_debug("%s: gpio%d status %d\n", __func__, desc_to_gpio(desc),
                         status);
}

void gpio_unexport(unsigned gpio)
{
        gpiod_unexport(gpio_to_desc(gpio));
}
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 (!IS_ERR(dev)) {
                status = sysfs_create_group(&dev->kobj,
                                &gpiochip_attr_group);
        } else
                status = PTR_ERR(dev);
        chip->exported = (status == 0);
        mutex_unlock(&sysfs_lock);

        if (status) {
                unsigned long   flags;
                unsigned        gpio;

                spin_lock_irqsave(&gpio_lock, flags);
                gpio = 0;
                while (gpio < chip->ngpio)
                        chip->desc[gpio++].chip = NULL;
                spin_unlock_irqrestore(&gpio_lock, flags);

                pr_debug("%s: chip %s status %d\n", __func__,
                                chip->label, status);
        }

        return status;
}

static void gpiochip_unexport(struct gpio_chip *chip)
{
        int                     status;
        struct device           *dev;
        struct gpio_desc *desc;
        unsigned int i;

        mutex_lock(&sysfs_lock);
        dev = class_find_device(&gpio_class, NULL, chip, match_export);
        if (dev) {
                sysfs_remove_group(&dev->kobj, &gpiochip_attr_group);
                put_device(dev);
                device_unregister(dev);
                /* prevent further gpiod exports */
                chip->exported = 0;
                status = 0;
        } else
                status = -ENODEV;
        mutex_unlock(&sysfs_lock);

        if (status)
                pr_debug("%s: chip %s status %d\n", __func__,
                                chip->label, status);

        /* unregister gpiod class devices owned by sysfs */
        for (i = 0; i < chip->ngpio; i++) {
                desc = &chip->desc[i];
                if (test_and_clear_bit(FLAG_SYSFS, &desc->flags))
                        gpiod_free(desc);
        }
}

static int __init gpiolib_sysfs_init(void)
{
        int             status;
        unsigned long   flags;
        struct gpio_chip *chip;

        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);
        list_for_each_entry(chip, &gpio_chips, list) {
                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)
{
}

static inline int gpiod_export(struct gpio_desc *desc,
                               bool direction_may_change)
{
        return -ENOSYS;
}

static inline int gpiod_export_link(struct device *dev, const char *name,
                                    struct gpio_desc *desc)
{
        return -ENOSYS;
}

static inline int gpiod_sysfs_set_active_low(struct gpio_desc *desc, int value)
{
        return -ENOSYS;
}

static inline void gpiod_unexport(struct gpio_desc *desc)
{
}

#endif /* CONFIG_GPIO_SYSFS */

/*
 * Add a new chip to the global chips list, keeping the list of chips sorted
 * by base order.
 *
 * Return -EBUSY if the new chip overlaps with some other chip's integer
 * space.
 */
static int gpiochip_add_to_list(struct gpio_chip *chip)
{
        struct list_head *pos = &gpio_chips;
        struct gpio_chip *_chip;
        int err = 0;

        /* find where to insert our chip */
        list_for_each(pos, &gpio_chips) {
                _chip = list_entry(pos, struct gpio_chip, list);
                /* shall we insert before _chip? */
                if (_chip->base >= chip->base + chip->ngpio)
                        break;
        }

        /* are we stepping on the chip right before? */
        if (pos != &gpio_chips && pos->prev != &gpio_chips) {
                _chip = list_entry(pos->prev, struct gpio_chip, list);
                if (_chip->base + _chip->ngpio > chip->base) {
                        dev_err(chip->dev,
                               "GPIO integer space overlap, cannot add chip\n");
                        err = -EBUSY;
                }
        }

        if (!err)
                list_add_tail(&chip->list, pos);

        return err;
}

/**
 * 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;
        }

        status = gpiochip_add_to_list(chip);

        if (status == 0) {
                chip->desc = &gpio_desc[chip->base];

                for (id = 0; id < chip->ngpio; id++) {
                        struct gpio_desc *desc = &chip->desc[id];
                        desc->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,
                         * and in case chip->get_direction is not set,
                         * we may expose the wrong direction in sysfs.
                         */
                        desc->flags = !chip->direction_input
                                ? (1 << FLAG_IS_OUT)
                                : 0;
                }
        }

        spin_unlock_irqrestore(&gpio_lock, flags);

#ifdef CONFIG_PINCTRL
        INIT_LIST_HEAD(&chip->pin_ranges);
#endif

        of_gpiochip_add(chip);

        if (status)
                goto fail;

        status = gpiochip_export(chip);
        if (status)
                goto fail;

        pr_debug("gpiochip_add: registered GPIOs %d to %d on device: %s\n",
                chip->base, chip->base + chip->ngpio - 1,
                chip->label ? : "generic");

        return 0;

unlock:
        spin_unlock_irqrestore(&gpio_lock, flags);
fail:
        /* failures here can mean systems won't boot... */
        pr_err("gpiochip_add: gpios %d..%d (%s) failed to register\n",
                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;

        gpiochip_unexport(chip);

        spin_lock_irqsave(&gpio_lock, flags);

        gpiochip_remove_pin_ranges(chip);
        of_gpiochip_remove(chip);

        for (id = 0; id < chip->ngpio; id++) {
                if (test_bit(FLAG_REQUESTED, &chip->desc[id].flags)) {
                        status = -EBUSY;
                        break;
                }
        }
        if (status == 0) {
                for (id = 0; id < chip->ngpio; id++)
                        chip->desc[id].chip = NULL;

                list_del(&chip->list);
        }

        spin_unlock_irqrestore(&gpio_lock, flags);

        return status;
}
EXPORT_SYMBOL_GPL(gpiochip_remove);

/**
 * gpiochip_find() - iterator for locating a specific gpio_chip
 * @data: data to pass to match function
 * @callback: Callback function to check gpio_chip
 *
 * Similar to bus_find_device.  It returns a reference to a gpio_chip as
 * determined by a user supplied @match callback.  The callback should return
 * 0 if the device doesn't match and non-zero if it does.  If the callback is
 * non-zero, this function will return to the caller and not iterate over any
 * more gpio_chips.
 */
struct gpio_chip *gpiochip_find(void *data,
                                int (*match)(struct gpio_chip *chip,
                                             void *data))
{
        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))
                        break;

        /* No match? */
        if (&chip->list == &gpio_chips)
                chip = NULL;
        spin_unlock_irqrestore(&gpio_lock, flags);

        return chip;
}
EXPORT_SYMBOL_GPL(gpiochip_find);

#ifdef CONFIG_PINCTRL

/**
 * gpiochip_add_pin_range() - add a range for GPIO <-> pin mapping
 * @chip: the gpiochip to add the range for
 * @pinctrl_name: the dev_name() of the pin controller to map to
 * @gpio_offset: the start offset in the current gpio_chip number space
 * @pin_offset: the start offset in the pin controller number space
 * @npins: the number of pins from the offset of each pin space (GPIO and
 *      pin controller) to accumulate in this range
 */
int gpiochip_add_pin_range(struct gpio_chip *chip, const char *pinctl_name,
                           unsigned int gpio_offset, unsigned int pin_offset,
                           unsigned int npins)
{
        struct gpio_pin_range *pin_range;
        int ret;

        pin_range = kzalloc(sizeof(*pin_range), GFP_KERNEL);
        if (!pin_range) {
                pr_err("%s: GPIO chip: failed to allocate pin ranges\n",
                                chip->label);
                return -ENOMEM;
        }

        /* Use local offset as range ID */
        pin_range->range.id = gpio_offset;
        pin_range->range.gc = chip;
        pin_range->range.name = chip->label;
        pin_range->range.base = chip->base + gpio_offset;
        pin_range->range.pin_base = pin_offset;
        pin_range->range.npins = npins;
        pin_range->pctldev = pinctrl_find_and_add_gpio_range(pinctl_name,
                        &pin_range->range);
        if (IS_ERR(pin_range->pctldev)) {
                ret = PTR_ERR(pin_range->pctldev);
                pr_err("%s: GPIO chip: could not create pin range\n",
                       chip->label);
                kfree(pin_range);
                return ret;
        }
        pr_debug("GPIO chip %s: created GPIO range %d->%d ==> %s PIN %d->%d\n",
                 chip->label, gpio_offset, gpio_offset + npins - 1,
                 pinctl_name,
                 pin_offset, pin_offset + npins - 1);

        list_add_tail(&pin_range->node, &chip->pin_ranges);

        return 0;
}
EXPORT_SYMBOL_GPL(gpiochip_add_pin_range);

/**
 * gpiochip_remove_pin_ranges() - remove all the GPIO <-> pin mappings
 * @chip: the chip to remove all the mappings for
 */
void gpiochip_remove_pin_ranges(struct gpio_chip *chip)
{
        struct gpio_pin_range *pin_range, *tmp;

        list_for_each_entry_safe(pin_range, tmp, &chip->pin_ranges, node) {
                list_del(&pin_range->node);
                pinctrl_remove_gpio_range(pin_range->pctldev,
                                &pin_range->range);
                kfree(pin_range);
        }
}
EXPORT_SYMBOL_GPL(gpiochip_remove_pin_ranges);

#endif /* CONFIG_PINCTRL */

/* 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.
 */
static int gpiod_request(struct gpio_desc *desc, const char *label)
{
        struct gpio_chip        *chip;
        int                     status = -EPROBE_DEFER;
        unsigned long           flags;

        if (!desc) {
                pr_warn("%s: invalid GPIO\n", __func__);
                return -EINVAL;
        }

        spin_lock_irqsave(&gpio_lock, flags);

        chip = desc->chip;
        if (chip == NULL)
                goto done;

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

        /* NOTE:  gpio_request() can be called in early boot,
         * before IRQs are enabled, for non-sleeping (SOC) GPIOs.
         */

        if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
                desc_set_label(desc, label ? : "?");
                status = 0;
        } else {
                status = -EBUSY;
                module_put(chip->owner);
                goto done;
        }

        if (chip->request) {
                /* chip->request may sleep */
                spin_unlock_irqrestore(&gpio_lock, flags);
                status = chip->request(chip, gpio_chip_hwgpio(desc));
                spin_lock_irqsave(&gpio_lock, flags);

                if (status < 0) {
                        desc_set_label(desc, NULL);
                        module_put(chip->owner);
                        clear_bit(FLAG_REQUESTED, &desc->flags);
                        goto done;
                }
        }
        if (chip->get_direction) {
                /* chip->get_direction may sleep */
                spin_unlock_irqrestore(&gpio_lock, flags);
                gpiod_get_direction(desc);
                spin_lock_irqsave(&gpio_lock, flags);
        }
done:
        if (status)
                pr_debug("_gpio_request: gpio-%d (%s) status %d\n",
                         desc_to_gpio(desc), label ? : "?", status);
        spin_unlock_irqrestore(&gpio_lock, flags);
        return status;
}

int gpio_request(unsigned gpio, const char *label)
{
        return gpiod_request(gpio_to_desc(gpio), label);
}
EXPORT_SYMBOL_GPL(gpio_request);

static void gpiod_free(struct gpio_desc *desc)
{
        unsigned long           flags;
        struct gpio_chip        *chip;

        might_sleep();

        if (!desc) {
                WARN_ON(extra_checks);
                return;
        }

        gpiod_unexport(desc);

        spin_lock_irqsave(&gpio_lock, flags);

        chip = desc->chip;
        if (chip && test_bit(FLAG_REQUESTED, &desc->flags)) {
                if (chip->free) {
                        spin_unlock_irqrestore(&gpio_lock, flags);
                        might_sleep_if(chip->can_sleep);
                        chip->free(chip, gpio_chip_hwgpio(desc));
                        spin_lock_irqsave(&gpio_lock, flags);
                }
                desc_set_label(desc, NULL);
                module_put(desc->chip->owner);
                clear_bit(FLAG_ACTIVE_LOW, &desc->flags);
                clear_bit(FLAG_REQUESTED, &desc->flags);
                clear_bit(FLAG_OPEN_DRAIN, &desc->flags);
                clear_bit(FLAG_OPEN_SOURCE, &desc->flags);
        } else
                WARN_ON(extra_checks);

        spin_unlock_irqrestore(&gpio_lock, flags);
}

void gpio_free(unsigned gpio)
{
        gpiod_free(gpio_to_desc(gpio));
}
EXPORT_SYMBOL_GPL(gpio_free);

/**
 * gpio_request_one - request a single GPIO with initial configuration
 * @gpio:       the GPIO number
 * @flags:      GPIO configuration as specified by GPIOF_*
 * @label:      a literal description string of this GPIO
 */
int gpio_request_one(unsigned gpio, unsigned long flags, const char *label)
{
        struct gpio_desc *desc;
        int err;

        desc = gpio_to_desc(gpio);

        err = gpiod_request(desc, label);
        if (err)
                return err;

        if (flags & GPIOF_OPEN_DRAIN)
                set_bit(FLAG_OPEN_DRAIN, &desc->flags);

        if (flags & GPIOF_OPEN_SOURCE)
                set_bit(FLAG_OPEN_SOURCE, &desc->flags);

        if (flags & GPIOF_DIR_IN)
                err = gpiod_direction_input(desc);
        else
                err = gpiod_direction_output(desc,
                                (flags & GPIOF_INIT_HIGH) ? 1 : 0);

        if (err)
                goto free_gpio;

        if (flags & GPIOF_EXPORT) {
                err = gpiod_export(desc, flags & GPIOF_EXPORT_CHANGEABLE);
                if (err)
                        goto free_gpio;
        }

        return 0;

 free_gpio:
        gpiod_free(desc);
        return err;
}
EXPORT_SYMBOL_GPL(gpio_request_one);

/**
 * gpio_request_array - request multiple GPIOs in a single call
 * @array:      array of the 'struct gpio'
 * @num:        how many GPIOs in the array
 */
int gpio_request_array(const struct gpio *array, size_t num)
{
        int i, err;

        for (i = 0; i < num; i++, array++) {
                err = gpio_request_one(array->gpio, array->flags, array->label);
                if (err)
                        goto err_free;
        }
        return 0;

err_free:
        while (i--)
                gpio_free((--array)->gpio);
        return err;
}
EXPORT_SYMBOL_GPL(gpio_request_array);

/**
 * gpio_free_array - release multiple GPIOs in a single call
 * @array:      array of the 'struct gpio'
 * @num:        how many GPIOs in the array
 */
void gpio_free_array(const struct gpio *array, size_t num)
{
        while (num--)
                gpio_free((array++)->gpio);
}
EXPORT_SYMBOL_GPL(gpio_free_array);

/**
 * 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)
{
        struct gpio_desc *desc;

        if (!GPIO_OFFSET_VALID(chip, offset))
                return NULL;

        desc = &chip->desc[offset];

        if (test_bit(FLAG_REQUESTED, &desc->flags) == 0)
                return NULL;
#ifdef CONFIG_DEBUG_FS
        return desc->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.
 */

static int gpiod_direction_input(struct gpio_desc *desc)
{
        unsigned long           flags;
        struct gpio_chip        *chip;
        int                     status = -EINVAL;
        int                     offset;

        if (!desc) {
                pr_warn("%s: invalid GPIO\n", __func__);
                return -EINVAL;
        }

        spin_lock_irqsave(&gpio_lock, flags);

        chip = desc->chip;
        if (!chip || !chip->get || !chip->direction_input)
                goto fail;
        status = gpio_ensure_requested(desc);
        if (status < 0)
                goto fail;

        /* now we know the gpio is valid and chip won't vanish */

        spin_unlock_irqrestore(&gpio_lock, flags);

        might_sleep_if(chip->can_sleep);

        offset = gpio_chip_hwgpio(desc);
        if (status) {
                status = chip->request(chip, offset);
                if (status < 0) {
                        pr_debug("GPIO-%d: chip request fail, %d\n",
                                desc_to_gpio(desc), status);
                        /* and it's not available to anyone else ...
                         * gpio_request() is the fully clean solution.
                         */
                        goto lose;
                }
        }

        status = chip->direction_input(chip, offset);
        if (status == 0)
                clear_bit(FLAG_IS_OUT, &desc->flags);

        trace_gpio_direction(desc_to_gpio(desc), 1, status);
lose:
        return status;
fail:
        spin_unlock_irqrestore(&gpio_lock, flags);
        if (status)
                pr_debug("%s: gpio-%d status %d\n", __func__,
                         desc_to_gpio(desc), status);
        return status;
}

int gpio_direction_input(unsigned gpio)
{
        return gpiod_direction_input(gpio_to_desc(gpio));
}
EXPORT_SYMBOL_GPL(gpio_direction_input);

static int gpiod_direction_output(struct gpio_desc *desc, int value)
{
        unsigned long           flags;
        struct gpio_chip        *chip;
        int                     status = -EINVAL;
        int offset;

        if (!desc) {
                pr_warn("%s: invalid GPIO\n", __func__);
                return -EINVAL;
        }

        /* Open drain pin should not be driven to 1 */
        if (value && test_bit(FLAG_OPEN_DRAIN,  &desc->flags))
                return gpiod_direction_input(desc);

        /* Open source pin should not be driven to 0 */
        if (!value && test_bit(FLAG_OPEN_SOURCE,  &desc->flags))
                return gpiod_direction_input(desc);

        spin_lock_irqsave(&gpio_lock, flags);

        chip = desc->chip;
        if (!chip || !chip->set || !chip->direction_output)
                goto fail;
        status = gpio_ensure_requested(desc);
        if (status < 0)
                goto fail;

        /* now we know the gpio is valid and chip won't vanish */

        spin_unlock_irqrestore(&gpio_lock, flags);

        might_sleep_if(chip->can_sleep);

        offset = gpio_chip_hwgpio(desc);
        if (status) {
                status = chip->request(chip, offset);
                if (status < 0) {
                        pr_debug("GPIO-%d: chip request fail, %d\n",
                                desc_to_gpio(desc), status);
                        /* and it's not available to anyone else ...
                         * gpio_request() is the fully clean solution.
                         */
                        goto lose;
                }
        }

        status = chip->direction_output(chip, offset, value);
        if (status == 0)
                set_bit(FLAG_IS_OUT, &desc->flags);
        trace_gpio_value(desc_to_gpio(desc), 0, value);
        trace_gpio_direction(desc_to_gpio(desc), 0, status);
lose:
        return status;
fail:
        spin_unlock_irqrestore(&gpio_lock, flags);
        if (status)
                pr_debug("%s: gpio-%d status %d\n", __func__,
                         desc_to_gpio(desc), status);
        return status;
}

int gpio_direction_output(unsigned gpio, int value)
{
        return gpiod_direction_output(gpio_to_desc(gpio), value);
}
EXPORT_SYMBOL_GPL(gpio_direction_output);

/**
 * gpio_set_debounce - sets @debounce time for a @gpio
 * @gpio: the gpio to set debounce time
 * @debounce: debounce time is microseconds
 */
static int gpiod_set_debounce(struct gpio_desc *desc, unsigned debounce)
{
        unsigned long           flags;
        struct gpio_chip        *chip;
        int                     status = -EINVAL;
        int                     offset;

        if (!desc) {
                pr_warn("%s: invalid GPIO\n", __func__);
                return -EINVAL;
        }

        spin_lock_irqsave(&gpio_lock, flags);

        chip = desc->chip;
        if (!chip || !chip->set || !chip->set_debounce)
                goto fail;

        status = gpio_ensure_requested(desc);
        if (status < 0)
                goto fail;

        /* now we know the gpio is valid and chip won't vanish */

        spin_unlock_irqrestore(&gpio_lock, flags);

        might_sleep_if(chip->can_sleep);

        offset = gpio_chip_hwgpio(desc);
        return chip->set_debounce(chip, offset, debounce);

fail:
        spin_unlock_irqrestore(&gpio_lock, flags);
        if (status)
                pr_debug("%s: gpio-%d status %d\n", __func__,
                         desc_to_gpio(desc), status);

        return status;
}

int gpio_set_debounce(unsigned gpio, unsigned debounce)
{
        return gpiod_set_debounce(gpio_to_desc(gpio), debounce);
}
EXPORT_SYMBOL_GPL(gpio_set_debounce);

/* 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.
 */
static int gpiod_get_value(const struct gpio_desc *desc)
{
        struct gpio_chip        *chip;
        int value;
        int offset;

        if (!desc)
                return 0;
        chip = desc->chip;
        offset = gpio_chip_hwgpio(desc);
        /* Should be using gpio_get_value_cansleep() */
        WARN_ON(chip->can_sleep);
        value = chip->get ? chip->get(chip, offset) : 0;
        trace_gpio_value(desc_to_gpio(desc), 1, value);
        return value;
}

int __gpio_get_value(unsigned gpio)
{
        return gpiod_get_value(gpio_to_desc(gpio));
}
EXPORT_SYMBOL_GPL(__gpio_get_value);

/*
 *  _gpio_set_open_drain_value() - Set the open drain gpio's value.
 * @gpio: Gpio whose state need to be set.
 * @chip: Gpio chip.
 * @value: Non-zero for setting it HIGH otherise it will set to LOW.
 */
static void _gpio_set_open_drain_value(struct gpio_desc *desc, int value)
{
        int err = 0;
        struct gpio_chip *chip = desc->chip;
        int offset = gpio_chip_hwgpio(desc);

        if (value) {
                err = chip->direction_input(chip, offset);
                if (!err)
                        clear_bit(FLAG_IS_OUT, &desc->flags);
        } else {
                err = chip->direction_output(chip, offset, 0);
                if (!err)
                        set_bit(FLAG_IS_OUT, &desc->flags);
        }
        trace_gpio_direction(desc_to_gpio(desc), value, err);
        if (err < 0)
                pr_err("%s: Error in set_value for open drain gpio%d err %d\n",
                                        __func__, desc_to_gpio(desc), err);
}

/*
 *  _gpio_set_open_source() - Set the open source gpio's value.
 * @gpio: Gpio whose state need to be set.
 * @chip: Gpio chip.
 * @value: Non-zero for setting it HIGH otherise it will set to LOW.
 */
static void _gpio_set_open_source_value(struct gpio_desc *desc, int value)
{
        int err = 0;
        struct gpio_chip *chip = desc->chip;
        int offset = gpio_chip_hwgpio(desc);

        if (value) {
                err = chip->direction_output(chip, offset, 1);
                if (!err)
                        set_bit(FLAG_IS_OUT, &desc->flags);
        } else {
                err = chip->direction_input(chip, offset);
                if (!err)
                        clear_bit(FLAG_IS_OUT, &desc->flags);
        }
        trace_gpio_direction(desc_to_gpio(desc), !value, err);
        if (err < 0)
                pr_err("%s: Error in set_value for open source gpio%d err %d\n",
                                        __func__, desc_to_gpio(desc), err);
}

/**
 * __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.
 */
static void gpiod_set_value(struct gpio_desc *desc, int value)
{
        struct gpio_chip        *chip;

        if (!desc)
                return;
        chip = desc->chip;
        /* Should be using gpio_set_value_cansleep() */
        WARN_ON(chip->can_sleep);
        trace_gpio_value(desc_to_gpio(desc), 0, value);
        if (test_bit(FLAG_OPEN_DRAIN, &desc->flags))
                _gpio_set_open_drain_value(desc, value);
        else if (test_bit(FLAG_OPEN_SOURCE, &desc->flags))
                _gpio_set_open_source_value(desc, value);
        else
                chip->set(chip, gpio_chip_hwgpio(desc), value);
}

void __gpio_set_value(unsigned gpio, int value)
{
        return gpiod_set_value(gpio_to_desc(gpio), 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.
 */
static int gpiod_cansleep(const struct gpio_desc *desc)
{
        if (!desc)
                return 0;
        /* only call this on GPIOs that are valid! */
        return desc->chip->can_sleep;
}

int __gpio_cansleep(unsigned gpio)
{
        return gpiod_cansleep(gpio_to_desc(gpio));
}
EXPORT_SYMBOL_GPL(__gpio_cansleep);

/**
 * __gpio_to_irq() - return the IRQ corresponding to a GPIO
 * @gpio: gpio whose IRQ will be returned (already requested)
 * Context: any
 *
 * This is used directly or indirectly to implement gpio_to_irq().
 * It returns the number of the IRQ signaled by this (input) GPIO,
 * or a negative errno.
 */
static int gpiod_to_irq(const struct gpio_desc *desc)
{
        struct gpio_chip        *chip;
        int                     offset;

        if (!desc)
                return -EINVAL;
        chip = desc->chip;
        offset = gpio_chip_hwgpio(desc);
        return chip->to_irq ? chip->to_irq(chip, offset) : -ENXIO;
}

int __gpio_to_irq(unsigned gpio)
{
        return gpiod_to_irq(gpio_to_desc(gpio));
}
EXPORT_SYMBOL_GPL(__gpio_to_irq);


/* 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.
 */

static int gpiod_get_value_cansleep(const struct gpio_desc *desc)
{
        struct gpio_chip        *chip;
        int value;
        int offset;

        might_sleep_if(extra_checks);
        if (!desc)
                return 0;
        chip = desc->chip;
        offset = gpio_chip_hwgpio(desc);
        value = chip->get ? chip->get(chip, offset) : 0;
        trace_gpio_value(desc_to_gpio(desc), 1, value);
        return value;
}

int gpio_get_value_cansleep(unsigned gpio)
{
        return gpiod_get_value_cansleep(gpio_to_desc(gpio));
}
EXPORT_SYMBOL_GPL(gpio_get_value_cansleep);

static void gpiod_set_value_cansleep(struct gpio_desc *desc, int value)
{
        struct gpio_chip        *chip;

        might_sleep_if(extra_checks);
        if (!desc)
                return;
        chip = desc->chip;
        trace_gpio_value(desc_to_gpio(desc), 0, value);
        if (test_bit(FLAG_OPEN_DRAIN,  &desc->flags))
                _gpio_set_open_drain_value(desc, value);
        else if (test_bit(FLAG_OPEN_SOURCE,  &desc->flags))
                _gpio_set_open_source_value(desc, value);
        else
                chip->set(chip, gpio_chip_hwgpio(desc), value);
}

void gpio_set_value_cansleep(unsigned gpio, int value)
{
        return gpiod_set_value_cansleep(gpio_to_desc(gpio), 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 = &chip->desc[0];
        int                     is_out;

        for (i = 0; i < chip->ngpio; i++, gpio++, gdesc++) {
                if (!test_bit(FLAG_REQUESTED, &gdesc->flags))
                        continue;

                gpiod_get_direction(gdesc);
                is_out = test_bit(FLAG_IS_OUT, &gdesc->flags);
                seq_printf(s, " gpio-%-3d (%-20.20s) %s %s",
                        gpio, gdesc->label,
                        is_out ? "out" : "in ",
                        chip->get
                                ? (chip->get(chip, i) ? "hi" : "lo")
                                : "?  ");
                seq_printf(s, "\n");
        }
}

static void *gpiolib_seq_start(struct seq_file *s, loff_t *pos)
{
        unsigned long flags;
        struct gpio_chip *chip = NULL;
        loff_t index = *pos;

        s->private = "";

        spin_lock_irqsave(&gpio_lock, flags);
        list_for_each_entry(chip, &gpio_chips, list)
                if (index-- == 0) {
                        spin_unlock_irqrestore(&gpio_lock, flags);
                        return chip;
                }
        spin_unlock_irqrestore(&gpio_lock, flags);

        return NULL;
}

static void *gpiolib_seq_next(struct seq_file *s, void *v, loff_t *pos)
{
        unsigned long flags;
        struct gpio_chip *chip = v;
        void *ret = NULL;

        spin_lock_irqsave(&gpio_lock, flags);
        if (list_is_last(&chip->list, &gpio_chips))
                ret = NULL;
        else
                ret = list_entry(chip->list.next, struct gpio_chip, list);
        spin_unlock_irqrestore(&gpio_lock, flags);

        s->private = "\n";
        ++*pos;

        return ret;
}

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;

        seq_printf(s, "%sGPIOs %d-%d", (char *)s->private,
                        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_name(dev));
        if (chip->label)
                seq_printf(s, ", %s", chip->label);
        if (chip->can_sleep)
                seq_printf(s, ", can sleep");
        seq_printf(s, ":\n");

        if (chip->dbg_show)
                chip->dbg_show(s, chip);
        else
                gpiolib_dbg_show(s, chip);

        return 0;
}

static const struct seq_operations gpiolib_seq_ops = {
        .start = gpiolib_seq_start,
        .next = gpiolib_seq_next,
        .stop = gpiolib_seq_stop,
        .show = gpiolib_seq_show,
};

static int gpiolib_open(struct inode *inode, struct file *file)
{
        return seq_open(file, &gpiolib_seq_ops);
}

static const struct file_operations gpiolib_operations = {
        .owner          = THIS_MODULE,
        .open           = gpiolib_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = seq_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 */