ARM: imx_v6_v7_defconfig: Select ADS7846 support

[cascardo/linux.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>
#include <linux/acpi.h>
#include <linux/gpio/driver.h>
#include <linux/gpio/machine.h>
#include <linux/pinctrl/consumer.h>
#include <linux/idr.h>
#include <linux/cdev.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <uapi/linux/gpio.h>

#include "gpiolib.h"

#define CREATE_TRACE_POINTS
#include <trace/events/gpio.h>

/* Implementation infrastructure for GPIO interfaces.
 *
 * 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

/* Device and char device-related information */
static DEFINE_IDA(gpio_ida);
static dev_t gpio_devt;
#define GPIO_DEV_MAX 256 /* 256 GPIO chip devices supported */
static struct bus_type gpio_bus_type = {
        .name = "gpio",
};

/* gpio_lock prevents conflicts during gpio_desc[] table updates.
 * While any GPIO is requested, its gpio_chip is not removable;
 * each GPIO's "requested" flag serves as a lock and refcount.
 */
DEFINE_SPINLOCK(gpio_lock);

static DEFINE_MUTEX(gpio_lookup_lock);
static LIST_HEAD(gpio_lookup_list);
LIST_HEAD(gpio_devices);

static void gpiochip_free_hogs(struct gpio_chip *chip);
static void gpiochip_irqchip_remove(struct gpio_chip *gpiochip);

static bool gpiolib_initialized;

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

/**
 * Convert a GPIO number to its descriptor
 */
struct gpio_desc *gpio_to_desc(unsigned gpio)
{
        struct gpio_device *gdev;
        unsigned long flags;

        spin_lock_irqsave(&gpio_lock, flags);

        list_for_each_entry(gdev, &gpio_devices, list) {
                if (gdev->base <= gpio &&
                    gdev->base + gdev->ngpio > gpio) {
                        spin_unlock_irqrestore(&gpio_lock, flags);
                        return &gdev->descs[gpio - gdev->base];
                }
        }

        spin_unlock_irqrestore(&gpio_lock, flags);

        if (!gpio_is_valid(gpio))
                WARN(1, "invalid GPIO %d\n", gpio);

        return NULL;
}
EXPORT_SYMBOL_GPL(gpio_to_desc);

/**
 * Get the GPIO descriptor corresponding to the given hw number for this chip.
 */
struct gpio_desc *gpiochip_get_desc(struct gpio_chip *chip,
                                    u16 hwnum)
{
        struct gpio_device *gdev = chip->gpiodev;

        if (hwnum >= gdev->ngpio)
                return ERR_PTR(-EINVAL);

        return &gdev->descs[hwnum];
}

/**
 * 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
 */
int desc_to_gpio(const struct gpio_desc *desc)
{
        return desc->gdev->base + (desc - &desc->gdev->descs[0]);
}
EXPORT_SYMBOL_GPL(desc_to_gpio);


/**
 * gpiod_to_chip - Return the GPIO chip to which a GPIO descriptor belongs
 * @desc:       descriptor to return the chip of
 */
struct gpio_chip *gpiod_to_chip(const struct gpio_desc *desc)
{
        if (!desc || !desc->gdev || !desc->gdev->chip)
                return NULL;
        return desc->gdev->chip;
}
EXPORT_SYMBOL_GPL(gpiod_to_chip);

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

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

/**
 * gpiod_get_direction - return the current direction of a GPIO
 * @desc:       GPIO to get the direction of
 *
 * Return GPIOF_DIR_IN or GPIOF_DIR_OUT, or an error code in case of error.
 *
 * This function may sleep if gpiod_cansleep() is true.
 */
int gpiod_get_direction(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;
                clear_bit(FLAG_IS_OUT, &desc->flags);
        }
        if (status == 0) {
                /* GPIOF_DIR_OUT */
                set_bit(FLAG_IS_OUT, &desc->flags);
        }
        return status;
}
EXPORT_SYMBOL_GPL(gpiod_get_direction);

/*
 * Add a new chip to the global chips list, keeping the list of chips sorted
 * by range(means [base, base + ngpio - 1]) order.
 *
 * Return -EBUSY if the new chip overlaps with some other chip's integer
 * space.
 */
static int gpiodev_add_to_list(struct gpio_device *gdev)
{
        struct gpio_device *prev, *next;

        if (list_empty(&gpio_devices)) {
                /* initial entry in list */
                list_add_tail(&gdev->list, &gpio_devices);
                return 0;
        }

        next = list_entry(gpio_devices.next, struct gpio_device, list);
        if (gdev->base + gdev->ngpio <= next->base) {
                /* add before first entry */
                list_add(&gdev->list, &gpio_devices);
                return 0;
        }

        prev = list_entry(gpio_devices.prev, struct gpio_device, list);
        if (prev->base + prev->ngpio <= gdev->base) {
                /* add behind last entry */
                list_add_tail(&gdev->list, &gpio_devices);
                return 0;
        }

        list_for_each_entry_safe(prev, next, &gpio_devices, list) {
                /* at the end of the list */
                if (&next->list == &gpio_devices)
                        break;

                /* add between prev and next */
                if (prev->base + prev->ngpio <= gdev->base
                                && gdev->base + gdev->ngpio <= next->base) {
                        list_add(&gdev->list, &prev->list);
                        return 0;
                }
        }

        dev_err(&gdev->dev, "GPIO integer space overlap, cannot add chip\n");
        return -EBUSY;
}

/**
 * Convert a GPIO name to its descriptor
 */
static struct gpio_desc *gpio_name_to_desc(const char * const name)
{
        struct gpio_device *gdev;
        unsigned long flags;

        spin_lock_irqsave(&gpio_lock, flags);

        list_for_each_entry(gdev, &gpio_devices, list) {
                int i;

                for (i = 0; i != gdev->ngpio; ++i) {
                        struct gpio_desc *desc = &gdev->descs[i];

                        if (!desc->name || !name)
                                continue;

                        if (!strcmp(desc->name, name)) {
                                spin_unlock_irqrestore(&gpio_lock, flags);
                                return desc;
                        }
                }
        }

        spin_unlock_irqrestore(&gpio_lock, flags);

        return NULL;
}

/*
 * Takes the names from gc->names and checks if they are all unique. If they
 * are, they are assigned to their gpio descriptors.
 *
 * Warning if one of the names is already used for a different GPIO.
 */
static int gpiochip_set_desc_names(struct gpio_chip *gc)
{
        struct gpio_device *gdev = gc->gpiodev;
        int i;

        if (!gc->names)
                return 0;

        /* First check all names if they are unique */
        for (i = 0; i != gc->ngpio; ++i) {
                struct gpio_desc *gpio;

                gpio = gpio_name_to_desc(gc->names[i]);
                if (gpio)
                        dev_warn(&gdev->dev,
                                 "Detected name collision for GPIO name '%s'\n",
                                 gc->names[i]);
        }

        /* Then add all names to the GPIO descriptors */
        for (i = 0; i != gc->ngpio; ++i)
                gdev->descs[i].name = gc->names[i];

        return 0;
}

/**
 * gpio_ioctl() - ioctl handler for the GPIO chardev
 */
static long gpio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
        struct gpio_device *gdev = filp->private_data;
        struct gpio_chip *chip = gdev->chip;
        int __user *ip = (int __user *)arg;

        /* We fail any subsequent ioctl():s when the chip is gone */
        if (!chip)
                return -ENODEV;

        /* Fill in the struct and pass to userspace */
        if (cmd == GPIO_GET_CHIPINFO_IOCTL) {
                struct gpiochip_info chipinfo;

                strncpy(chipinfo.name, dev_name(&gdev->dev),
                        sizeof(chipinfo.name));
                chipinfo.name[sizeof(chipinfo.name)-1] = '\0';
                strncpy(chipinfo.label, gdev->label,
                        sizeof(chipinfo.label));
                chipinfo.label[sizeof(chipinfo.label)-1] = '\0';
                chipinfo.lines = gdev->ngpio;
                if (copy_to_user(ip, &chipinfo, sizeof(chipinfo)))
                        return -EFAULT;
                return 0;
        } else if (cmd == GPIO_GET_LINEINFO_IOCTL) {
                struct gpioline_info lineinfo;
                struct gpio_desc *desc;

                if (copy_from_user(&lineinfo, ip, sizeof(lineinfo)))
                        return -EFAULT;
                if (lineinfo.line_offset > gdev->ngpio)
                        return -EINVAL;

                desc = &gdev->descs[lineinfo.line_offset];
                if (desc->name) {
                        strncpy(lineinfo.name, desc->name,
                                sizeof(lineinfo.name));
                        lineinfo.name[sizeof(lineinfo.name)-1] = '\0';
                } else {
                        lineinfo.name[0] = '\0';
                }
                if (desc->label) {
                        strncpy(lineinfo.consumer, desc->label,
                                sizeof(lineinfo.consumer));
                        lineinfo.consumer[sizeof(lineinfo.consumer)-1] = '\0';
                } else {
                        lineinfo.consumer[0] = '\0';
                }

                /*
                 * Userspace only need to know that the kernel is using
                 * this GPIO so it can't use it.
                 */
                lineinfo.flags = 0;
                if (test_bit(FLAG_REQUESTED, &desc->flags) ||
                    test_bit(FLAG_IS_HOGGED, &desc->flags) ||
                    test_bit(FLAG_USED_AS_IRQ, &desc->flags) ||
                    test_bit(FLAG_EXPORT, &desc->flags) ||
                    test_bit(FLAG_SYSFS, &desc->flags))
                        lineinfo.flags |= GPIOLINE_FLAG_KERNEL;
                if (test_bit(FLAG_IS_OUT, &desc->flags))
                        lineinfo.flags |= GPIOLINE_FLAG_IS_OUT;
                if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
                        lineinfo.flags |= GPIOLINE_FLAG_ACTIVE_LOW;
                if (test_bit(FLAG_OPEN_DRAIN, &desc->flags))
                        lineinfo.flags |= GPIOLINE_FLAG_OPEN_DRAIN;
                if (test_bit(FLAG_OPEN_SOURCE, &desc->flags))
                        lineinfo.flags |= GPIOLINE_FLAG_OPEN_SOURCE;

                if (copy_to_user(ip, &lineinfo, sizeof(lineinfo)))
                        return -EFAULT;
                return 0;
        }
        return -EINVAL;
}

/**
 * gpio_chrdev_open() - open the chardev for ioctl operations
 * @inode: inode for this chardev
 * @filp: file struct for storing private data
 * Returns 0 on success
 */
static int gpio_chrdev_open(struct inode *inode, struct file *filp)
{
        struct gpio_device *gdev = container_of(inode->i_cdev,
                                              struct gpio_device, chrdev);

        /* Fail on open if the backing gpiochip is gone */
        if (!gdev || !gdev->chip)
                return -ENODEV;
        get_device(&gdev->dev);
        filp->private_data = gdev;
        return 0;
}

/**
 * gpio_chrdev_release() - close chardev after ioctl operations
 * @inode: inode for this chardev
 * @filp: file struct for storing private data
 * Returns 0 on success
 */
static int gpio_chrdev_release(struct inode *inode, struct file *filp)
{
        struct gpio_device *gdev = container_of(inode->i_cdev,
                                              struct gpio_device, chrdev);

        if (!gdev)
                return -ENODEV;
        put_device(&gdev->dev);
        return 0;
}


static const struct file_operations gpio_fileops = {
        .release = gpio_chrdev_release,
        .open = gpio_chrdev_open,
        .owner = THIS_MODULE,
        .llseek = noop_llseek,
        .unlocked_ioctl = gpio_ioctl,
        .compat_ioctl = gpio_ioctl,
};

static void gpiodevice_release(struct device *dev)
{
        struct gpio_device *gdev = dev_get_drvdata(dev);

        cdev_del(&gdev->chrdev);
        list_del(&gdev->list);
        ida_simple_remove(&gpio_ida, gdev->id);
        kfree(gdev->label);
        kfree(gdev->descs);
        kfree(gdev);
}

static int gpiochip_setup_dev(struct gpio_device *gdev)
{
        int status;

        cdev_init(&gdev->chrdev, &gpio_fileops);
        gdev->chrdev.owner = THIS_MODULE;
        gdev->chrdev.kobj.parent = &gdev->dev.kobj;
        gdev->dev.devt = MKDEV(MAJOR(gpio_devt), gdev->id);
        status = cdev_add(&gdev->chrdev, gdev->dev.devt, 1);
        if (status < 0)
                chip_warn(gdev->chip, "failed to add char device %d:%d\n",
                          MAJOR(gpio_devt), gdev->id);
        else
                chip_dbg(gdev->chip, "added GPIO chardev (%d:%d)\n",
                         MAJOR(gpio_devt), gdev->id);
        status = device_add(&gdev->dev);
        if (status)
                goto err_remove_chardev;

        status = gpiochip_sysfs_register(gdev);
        if (status)
                goto err_remove_device;

        /* From this point, the .release() function cleans up gpio_device */
        gdev->dev.release = gpiodevice_release;
        get_device(&gdev->dev);
        pr_debug("%s: registered GPIOs %d to %d on device: %s (%s)\n",
                 __func__, gdev->base, gdev->base + gdev->ngpio - 1,
                 dev_name(&gdev->dev), gdev->chip->label ? : "generic");

        return 0;

err_remove_device:
        device_del(&gdev->dev);
err_remove_chardev:
        cdev_del(&gdev->chrdev);
        return status;
}

static void gpiochip_setup_devs(void)
{
        struct gpio_device *gdev;
        int err;

        list_for_each_entry(gdev, &gpio_devices, list) {
                err = gpiochip_setup_dev(gdev);
                if (err)
                        pr_err("%s: Failed to initialize gpio device (%d)\n",
                               dev_name(&gdev->dev), err);
        }
}

/**
 * gpiochip_add_data() - register a gpio_chip
 * @chip: the chip to register, with chip->base initialized
 * Context: potentially before irqs 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_data() is called very early during boot, so that GPIOs
 * can be freely used, the chip->parent device must be registered before
 * the gpio framework's arch_initcall().  Otherwise sysfs initialization
 * for GPIOs will fail rudely.
 *
 * gpiochip_add_data() must only be called after gpiolib initialization,
 * ie after core_initcall().
 *
 * If chip->base is negative, this requests dynamic assignment of
 * a range of valid GPIOs.
 */
int gpiochip_add_data(struct gpio_chip *chip, void *data)
{
        unsigned long   flags;
        int             status = 0;
        unsigned        i;
        int             base = chip->base;
        struct gpio_device *gdev;

        /*
         * First: allocate and populate the internal stat container, and
         * set up the struct device.
         */
        gdev = kzalloc(sizeof(*gdev), GFP_KERNEL);
        if (!gdev)
                return -ENOMEM;
        gdev->dev.bus = &gpio_bus_type;
        gdev->chip = chip;
        chip->gpiodev = gdev;
        if (chip->parent) {
                gdev->dev.parent = chip->parent;
                gdev->dev.of_node = chip->parent->of_node;
        } else {
#ifdef CONFIG_OF_GPIO
        /* If the gpiochip has an assigned OF node this takes precedence */
                if (chip->of_node)
                        gdev->dev.of_node = chip->of_node;
#endif
        }
        gdev->id = ida_simple_get(&gpio_ida, 0, 0, GFP_KERNEL);
        if (gdev->id < 0) {
                status = gdev->id;
                goto err_free_gdev;
        }
        dev_set_name(&gdev->dev, "gpiochip%d", gdev->id);
        device_initialize(&gdev->dev);
        dev_set_drvdata(&gdev->dev, gdev);
        if (chip->parent && chip->parent->driver)
                gdev->owner = chip->parent->driver->owner;
        else if (chip->owner)
                /* TODO: remove chip->owner */
                gdev->owner = chip->owner;
        else
                gdev->owner = THIS_MODULE;

        gdev->descs = kcalloc(chip->ngpio, sizeof(gdev->descs[0]), GFP_KERNEL);
        if (!gdev->descs) {
                status = -ENOMEM;
                goto err_free_gdev;
        }

        if (chip->ngpio == 0) {
                chip_err(chip, "tried to insert a GPIO chip with zero lines\n");
                status = -EINVAL;
                goto err_free_descs;
        }

        if (chip->label)
                gdev->label = kstrdup(chip->label, GFP_KERNEL);
        else
                gdev->label = kstrdup("unknown", GFP_KERNEL);
        if (!gdev->label) {
                status = -ENOMEM;
                goto err_free_descs;
        }

        gdev->ngpio = chip->ngpio;
        gdev->data = data;

        spin_lock_irqsave(&gpio_lock, flags);

        /*
         * TODO: this allocates a Linux GPIO number base in the global
         * GPIO numberspace for this chip. In the long run we want to
         * get *rid* of this numberspace and use only descriptors, but
         * it may be a pipe dream. It will not happen before we get rid
         * of the sysfs interface anyways.
         */
        if (base < 0) {
                base = gpiochip_find_base(chip->ngpio);
                if (base < 0) {
                        status = base;
                        spin_unlock_irqrestore(&gpio_lock, flags);
                        goto err_free_label;
                }
                /*
                 * TODO: it should not be necessary to reflect the assigned
                 * base outside of the GPIO subsystem. Go over drivers and
                 * see if anyone makes use of this, else drop this and assign
                 * a poison instead.
                 */
                chip->base = base;
        }
        gdev->base = base;

        status = gpiodev_add_to_list(gdev);
        if (status) {
                spin_unlock_irqrestore(&gpio_lock, flags);
                goto err_free_label;
        }

        for (i = 0; i < chip->ngpio; i++) {
                struct gpio_desc *desc = &gdev->descs[i];

                desc->gdev = gdev;
                /*
                 * 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.
                 */

                if (chip->get_direction) {
                        /*
                         * If we have .get_direction, set up the initial
                         * direction flag from the hardware.
                         */
                        int dir = chip->get_direction(chip, i);

                        if (!dir)
                                set_bit(FLAG_IS_OUT, &desc->flags);
                } else if (!chip->direction_input) {
                        /*
                         * If the chip lacks the .direction_input callback
                         * we logically assume all lines are outputs.
                         */
                        set_bit(FLAG_IS_OUT, &desc->flags);
                }
        }

        spin_unlock_irqrestore(&gpio_lock, flags);

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

        status = gpiochip_set_desc_names(chip);
        if (status)
                goto err_remove_from_list;

        status = of_gpiochip_add(chip);
        if (status)
                goto err_remove_chip;

        acpi_gpiochip_add(chip);

        /*
         * By first adding the chardev, and then adding the device,
         * we get a device node entry in sysfs under
         * /sys/bus/gpio/devices/gpiochipN/dev that can be used for
         * coldplug of device nodes and other udev business.
         * We can do this only if gpiolib has been initialized.
         * Otherwise, defer until later.
         */
        if (gpiolib_initialized) {
                status = gpiochip_setup_dev(gdev);
                if (status)
                        goto err_remove_chip;
        }
        return 0;

err_remove_chip:
        acpi_gpiochip_remove(chip);
        gpiochip_free_hogs(chip);
        of_gpiochip_remove(chip);
err_remove_from_list:
        spin_lock_irqsave(&gpio_lock, flags);
        list_del(&gdev->list);
        spin_unlock_irqrestore(&gpio_lock, flags);
err_free_label:
        kfree(gdev->label);
err_free_descs:
        kfree(gdev->descs);
err_free_gdev:
        ida_simple_remove(&gpio_ida, gdev->id);
        /* failures here can mean systems won't boot... */
        pr_err("%s: GPIOs %d..%d (%s) failed to register\n", __func__,
               gdev->base, gdev->base + gdev->ngpio - 1,
               chip->label ? : "generic");
        kfree(gdev);
        return status;
}
EXPORT_SYMBOL_GPL(gpiochip_add_data);

/**
 * gpiochip_get_data() - get per-subdriver data for the chip
 */
void *gpiochip_get_data(struct gpio_chip *chip)
{
        return chip->gpiodev->data;
}
EXPORT_SYMBOL_GPL(gpiochip_get_data);

/**
 * gpiochip_remove() - unregister a gpio_chip
 * @chip: the chip to unregister
 *
 * A gpio_chip with any GPIOs still requested may not be removed.
 */
void gpiochip_remove(struct gpio_chip *chip)
{
        struct gpio_device *gdev = chip->gpiodev;
        struct gpio_desc *desc;
        unsigned long   flags;
        unsigned        i;
        bool            requested = false;

        /* FIXME: should the legacy sysfs handling be moved to gpio_device? */
        gpiochip_sysfs_unregister(gdev);
        /* Numb the device, cancelling all outstanding operations */
        gdev->chip = NULL;
        gpiochip_irqchip_remove(chip);
        acpi_gpiochip_remove(chip);
        gpiochip_remove_pin_ranges(chip);
        gpiochip_free_hogs(chip);
        of_gpiochip_remove(chip);
        /*
         * We accept no more calls into the driver from this point, so
         * NULL the driver data pointer
         */
        gdev->data = NULL;

        spin_lock_irqsave(&gpio_lock, flags);
        for (i = 0; i < gdev->ngpio; i++) {
                desc = &gdev->descs[i];
                if (test_bit(FLAG_REQUESTED, &desc->flags))
                        requested = true;
        }
        spin_unlock_irqrestore(&gpio_lock, flags);

        if (requested)
                dev_crit(&gdev->dev,
                         "REMOVING GPIOCHIP WITH GPIOS STILL REQUESTED\n");

        /*
         * The gpiochip side puts its use of the device to rest here:
         * if there are no userspace clients, the chardev and device will
         * be removed, else it will be dangling until the last user is
         * gone.
         */
        put_device(&gdev->dev);
}
EXPORT_SYMBOL_GPL(gpiochip_remove);

static void devm_gpio_chip_release(struct device *dev, void *res)
{
        struct gpio_chip *chip = *(struct gpio_chip **)res;

        gpiochip_remove(chip);
}

static int devm_gpio_chip_match(struct device *dev, void *res, void *data)

{
        struct gpio_chip **r = res;

        if (!r || !*r) {
                WARN_ON(!r || !*r);
                return 0;
        }

        return *r == data;
}

/**
 * devm_gpiochip_add_data() - Resource manager piochip_add_data()
 * @dev: the device pointer on which irq_chip belongs to.
 * @chip: the chip to register, with chip->base initialized
 * Context: potentially before irqs 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.
 *
 * The gpio chip automatically be released when the device is unbound.
 */
int devm_gpiochip_add_data(struct device *dev, struct gpio_chip *chip,
                           void *data)
{
        struct gpio_chip **ptr;
        int ret;

        ptr = devres_alloc(devm_gpio_chip_release, sizeof(*ptr),
                             GFP_KERNEL);
        if (!ptr)
                return -ENOMEM;

        ret = gpiochip_add_data(chip, data);
        if (ret < 0) {
                devres_free(ptr);
                return ret;
        }

        *ptr = chip;
        devres_add(dev, ptr);

        return 0;
}
EXPORT_SYMBOL_GPL(devm_gpiochip_add_data);

/**
 * devm_gpiochip_remove() - Resource manager of gpiochip_remove()
 * @dev: device for which which resource was allocated
 * @chip: the chip to remove
 *
 * A gpio_chip with any GPIOs still requested may not be removed.
 */
void devm_gpiochip_remove(struct device *dev, struct gpio_chip *chip)
{
        int ret;

        ret = devres_release(dev, devm_gpio_chip_release,
                             devm_gpio_chip_match, chip);
        if (!ret)
                WARN_ON(ret);
}
EXPORT_SYMBOL_GPL(devm_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_device *gdev;
        struct gpio_chip *chip;
        unsigned long flags;

        spin_lock_irqsave(&gpio_lock, flags);
        list_for_each_entry(gdev, &gpio_devices, list)
                if (match(gdev->chip, data))
                        break;

        /* No match? */
        if (&gdev->list == &gpio_devices)
                chip = NULL;
        else
                chip = gdev->chip;

        spin_unlock_irqrestore(&gpio_lock, flags);

        return chip;
}
EXPORT_SYMBOL_GPL(gpiochip_find);

static int gpiochip_match_name(struct gpio_chip *chip, void *data)
{
        const char *name = data;

        return !strcmp(chip->label, name);
}

static struct gpio_chip *find_chip_by_name(const char *name)
{
        return gpiochip_find((void *)name, gpiochip_match_name);
}

#ifdef CONFIG_GPIOLIB_IRQCHIP

/*
 * The following is irqchip helper code for gpiochips.
 */

/**
 * gpiochip_set_chained_irqchip() - sets a chained irqchip to a gpiochip
 * @gpiochip: the gpiochip to set the irqchip chain to
 * @irqchip: the irqchip to chain to the gpiochip
 * @parent_irq: the irq number corresponding to the parent IRQ for this
 * chained irqchip
 * @parent_handler: the parent interrupt handler for the accumulated IRQ
 * coming out of the gpiochip. If the interrupt is nested rather than
 * cascaded, pass NULL in this handler argument
 */
void gpiochip_set_chained_irqchip(struct gpio_chip *gpiochip,
                                  struct irq_chip *irqchip,
                                  int parent_irq,
                                  irq_flow_handler_t parent_handler)
{
        unsigned int offset;

        if (!gpiochip->irqdomain) {
                chip_err(gpiochip, "called %s before setting up irqchip\n",
                         __func__);
                return;
        }

        if (parent_handler) {
                if (gpiochip->can_sleep) {
                        chip_err(gpiochip,
                                 "you cannot have chained interrupts on a "
                                 "chip that may sleep\n");
                        return;
                }
                /*
                 * The parent irqchip is already using the chip_data for this
                 * irqchip, so our callbacks simply use the handler_data.
                 */
                irq_set_chained_handler_and_data(parent_irq, parent_handler,
                                                 gpiochip);

                gpiochip->irq_parent = parent_irq;
        }

        /* Set the parent IRQ for all affected IRQs */
        for (offset = 0; offset < gpiochip->ngpio; offset++)
                irq_set_parent(irq_find_mapping(gpiochip->irqdomain, offset),
                               parent_irq);
}
EXPORT_SYMBOL_GPL(gpiochip_set_chained_irqchip);

/**
 * gpiochip_irq_map() - maps an IRQ into a GPIO irqchip
 * @d: the irqdomain used by this irqchip
 * @irq: the global irq number used by this GPIO irqchip irq
 * @hwirq: the local IRQ/GPIO line offset on this gpiochip
 *
 * This function will set up the mapping for a certain IRQ line on a
 * gpiochip by assigning the gpiochip as chip data, and using the irqchip
 * stored inside the gpiochip.
 */
static int gpiochip_irq_map(struct irq_domain *d, unsigned int irq,
                            irq_hw_number_t hwirq)
{
        struct gpio_chip *chip = d->host_data;

        irq_set_chip_data(irq, chip);
        /*
         * This lock class tells lockdep that GPIO irqs are in a different
         * category than their parents, so it won't report false recursion.
         */
        irq_set_lockdep_class(irq, chip->lock_key);
        irq_set_chip_and_handler(irq, chip->irqchip, chip->irq_handler);
        /* Chips that can sleep need nested thread handlers */
        if (chip->can_sleep && !chip->irq_not_threaded)
                irq_set_nested_thread(irq, 1);
        irq_set_noprobe(irq);

        /*
         * No set-up of the hardware will happen if IRQ_TYPE_NONE
         * is passed as default type.
         */
        if (chip->irq_default_type != IRQ_TYPE_NONE)
                irq_set_irq_type(irq, chip->irq_default_type);

        return 0;
}

static void gpiochip_irq_unmap(struct irq_domain *d, unsigned int irq)
{
        struct gpio_chip *chip = d->host_data;

        if (chip->can_sleep)
                irq_set_nested_thread(irq, 0);
        irq_set_chip_and_handler(irq, NULL, NULL);
        irq_set_chip_data(irq, NULL);
}

static const struct irq_domain_ops gpiochip_domain_ops = {
        .map    = gpiochip_irq_map,
        .unmap  = gpiochip_irq_unmap,
        /* Virtually all GPIO irqchips are twocell:ed */
        .xlate  = irq_domain_xlate_twocell,
};

static int gpiochip_irq_reqres(struct irq_data *d)
{
        struct gpio_chip *chip = irq_data_get_irq_chip_data(d);

        if (!try_module_get(chip->gpiodev->owner))
                return -ENODEV;

        if (gpiochip_lock_as_irq(chip, d->hwirq)) {
                chip_err(chip,
                        "unable to lock HW IRQ %lu for IRQ\n",
                        d->hwirq);
                module_put(chip->gpiodev->owner);
                return -EINVAL;
        }
        return 0;
}

static void gpiochip_irq_relres(struct irq_data *d)
{
        struct gpio_chip *chip = irq_data_get_irq_chip_data(d);

        gpiochip_unlock_as_irq(chip, d->hwirq);
        module_put(chip->gpiodev->owner);
}

static int gpiochip_to_irq(struct gpio_chip *chip, unsigned offset)
{
        return irq_find_mapping(chip->irqdomain, offset);
}

/**
 * gpiochip_irqchip_remove() - removes an irqchip added to a gpiochip
 * @gpiochip: the gpiochip to remove the irqchip from
 *
 * This is called only from gpiochip_remove()
 */
static void gpiochip_irqchip_remove(struct gpio_chip *gpiochip)
{
        unsigned int offset;

        acpi_gpiochip_free_interrupts(gpiochip);

        if (gpiochip->irq_parent) {
                irq_set_chained_handler(gpiochip->irq_parent, NULL);
                irq_set_handler_data(gpiochip->irq_parent, NULL);
        }

        /* Remove all IRQ mappings and delete the domain */
        if (gpiochip->irqdomain) {
                for (offset = 0; offset < gpiochip->ngpio; offset++)
                        irq_dispose_mapping(
                                irq_find_mapping(gpiochip->irqdomain, offset));
                irq_domain_remove(gpiochip->irqdomain);
        }

        if (gpiochip->irqchip) {
                gpiochip->irqchip->irq_request_resources = NULL;
                gpiochip->irqchip->irq_release_resources = NULL;
                gpiochip->irqchip = NULL;
        }
}

/**
 * gpiochip_irqchip_add() - adds an irqchip to a gpiochip
 * @gpiochip: the gpiochip to add the irqchip to
 * @irqchip: the irqchip to add to the gpiochip
 * @first_irq: if not dynamically assigned, the base (first) IRQ to
 * allocate gpiochip irqs from
 * @handler: the irq handler to use (often a predefined irq core function)
 * @type: the default type for IRQs on this irqchip, pass IRQ_TYPE_NONE
 * to have the core avoid setting up any default type in the hardware.
 * @lock_key: lockdep class
 *
 * This function closely associates a certain irqchip with a certain
 * gpiochip, providing an irq domain to translate the local IRQs to
 * global irqs in the gpiolib core, and making sure that the gpiochip
 * is passed as chip data to all related functions. Driver callbacks
 * need to use gpiochip_get_data() to get their local state containers back
 * from the gpiochip passed as chip data. An irqdomain will be stored
 * in the gpiochip that shall be used by the driver to handle IRQ number
 * translation. The gpiochip will need to be initialized and registered
 * before calling this function.
 *
 * This function will handle two cell:ed simple IRQs and assumes all
 * the pins on the gpiochip can generate a unique IRQ. Everything else
 * need to be open coded.
 */
int _gpiochip_irqchip_add(struct gpio_chip *gpiochip,
                          struct irq_chip *irqchip,
                          unsigned int first_irq,
                          irq_flow_handler_t handler,
                          unsigned int type,
                          struct lock_class_key *lock_key)
{
        struct device_node *of_node;
        unsigned int offset;
        unsigned irq_base = 0;

        if (!gpiochip || !irqchip)
                return -EINVAL;

        if (!gpiochip->parent) {
                pr_err("missing gpiochip .dev parent pointer\n");
                return -EINVAL;
        }
        of_node = gpiochip->parent->of_node;
#ifdef CONFIG_OF_GPIO
        /*
         * If the gpiochip has an assigned OF node this takes precedence
         * FIXME: get rid of this and use gpiochip->parent->of_node
         * everywhere
         */
        if (gpiochip->of_node)
                of_node = gpiochip->of_node;
#endif
        gpiochip->irqchip = irqchip;
        gpiochip->irq_handler = handler;
        gpiochip->irq_default_type = type;
        gpiochip->to_irq = gpiochip_to_irq;
        gpiochip->lock_key = lock_key;
        gpiochip->irqdomain = irq_domain_add_simple(of_node,
                                        gpiochip->ngpio, first_irq,
                                        &gpiochip_domain_ops, gpiochip);
        if (!gpiochip->irqdomain) {
                gpiochip->irqchip = NULL;
                return -EINVAL;
        }

        /*
         * It is possible for a driver to override this, but only if the
         * alternative functions are both implemented.
         */
        if (!irqchip->irq_request_resources &&
            !irqchip->irq_release_resources) {
                irqchip->irq_request_resources = gpiochip_irq_reqres;
                irqchip->irq_release_resources = gpiochip_irq_relres;
        }

        /*
         * Prepare the mapping since the irqchip shall be orthogonal to
         * any gpiochip calls. If the first_irq was zero, this is
         * necessary to allocate descriptors for all IRQs.
         */
        for (offset = 0; offset < gpiochip->ngpio; offset++) {
                irq_base = irq_create_mapping(gpiochip->irqdomain, offset);
                if (offset == 0)
                        /*
                         * Store the base into the gpiochip to be used when
                         * unmapping the irqs.
                         */
                        gpiochip->irq_base = irq_base;
        }

        acpi_gpiochip_request_interrupts(gpiochip);

        return 0;
}
EXPORT_SYMBOL_GPL(_gpiochip_irqchip_add);

#else /* CONFIG_GPIOLIB_IRQCHIP */

static void gpiochip_irqchip_remove(struct gpio_chip *gpiochip) {}

#endif /* CONFIG_GPIOLIB_IRQCHIP */

/**
 * gpiochip_generic_request() - request the gpio function for a pin
 * @chip: the gpiochip owning the GPIO
 * @offset: the offset of the GPIO to request for GPIO function
 */
int gpiochip_generic_request(struct gpio_chip *chip, unsigned offset)
{
        return pinctrl_request_gpio(chip->gpiodev->base + offset);
}
EXPORT_SYMBOL_GPL(gpiochip_generic_request);

/**
 * gpiochip_generic_free() - free the gpio function from a pin
 * @chip: the gpiochip to request the gpio function for
 * @offset: the offset of the GPIO to free from GPIO function
 */
void gpiochip_generic_free(struct gpio_chip *chip, unsigned offset)
{
        pinctrl_free_gpio(chip->gpiodev->base + offset);
}
EXPORT_SYMBOL_GPL(gpiochip_generic_free);

#ifdef CONFIG_PINCTRL

/**
 * gpiochip_add_pingroup_range() - add a range for GPIO <-> pin mapping
 * @chip: the gpiochip to add the range for
 * @pctldev: the pin controller to map to
 * @gpio_offset: the start offset in the current gpio_chip number space
 * @pin_group: name of the pin group inside the pin controller
 */
int gpiochip_add_pingroup_range(struct gpio_chip *chip,
                        struct pinctrl_dev *pctldev,
                        unsigned int gpio_offset, const char *pin_group)
{
        struct gpio_pin_range *pin_range;
        struct gpio_device *gdev = chip->gpiodev;
        int ret;

        pin_range = kzalloc(sizeof(*pin_range), GFP_KERNEL);
        if (!pin_range) {
                chip_err(chip, "failed to allocate pin ranges\n");
                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 = gdev->base + gpio_offset;
        pin_range->pctldev = pctldev;

        ret = pinctrl_get_group_pins(pctldev, pin_group,
                                        &pin_range->range.pins,
                                        &pin_range->range.npins);
        if (ret < 0) {
                kfree(pin_range);
                return ret;
        }

        pinctrl_add_gpio_range(pctldev, &pin_range->range);

        chip_dbg(chip, "created GPIO range %d->%d ==> %s PINGRP %s\n",
                 gpio_offset, gpio_offset + pin_range->range.npins - 1,
                 pinctrl_dev_get_devname(pctldev), pin_group);

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

        return 0;
}
EXPORT_SYMBOL_GPL(gpiochip_add_pingroup_range);

/**
 * 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;
        struct gpio_device *gdev = chip->gpiodev;
        int ret;

        pin_range = kzalloc(sizeof(*pin_range), GFP_KERNEL);
        if (!pin_range) {
                chip_err(chip, "failed to allocate pin ranges\n");
                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 = gdev->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);
                chip_err(chip, "could not create pin range\n");
                kfree(pin_range);
                return ret;
        }
        chip_dbg(chip, "created GPIO range %d->%d ==> %s PIN %d->%d\n",
                 gpio_offset, gpio_offset + npins - 1,
                 pinctl_name,
                 pin_offset, pin_offset + npins - 1);

        list_add_tail(&pin_range->node, &gdev->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;
        struct gpio_device *gdev = chip->gpiodev;

        list_for_each_entry_safe(pin_range, tmp, &gdev->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 = desc->gdev->chip;
        int                     status;
        unsigned long           flags;

        spin_lock_irqsave(&gpio_lock, flags);

        /* 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;
                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);
                        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 < 0) {
                /* Clear flags that might have been set by the caller before
                 * requesting the GPIO.
                 */
                clear_bit(FLAG_ACTIVE_LOW, &desc->flags);
                clear_bit(FLAG_OPEN_DRAIN, &desc->flags);
                clear_bit(FLAG_OPEN_SOURCE, &desc->flags);
        }
        spin_unlock_irqrestore(&gpio_lock, flags);
        return status;
}

/*
 * This descriptor validation needs to be inserted verbatim into each
 * function taking a descriptor, so we need to use a preprocessor
 * macro to avoid endless duplication.
 */
#define VALIDATE_DESC(desc) do { \
        if (!desc || !desc->gdev) { \
                pr_warn("%s: invalid GPIO\n", __func__); \
                return -EINVAL; \
        } \
        if ( !desc->gdev->chip ) { \
                dev_warn(&desc->gdev->dev, \
                         "%s: backing chip is gone\n", __func__); \
                return 0; \
        } } while (0)

#define VALIDATE_DESC_VOID(desc) do { \
        if (!desc || !desc->gdev) { \
                pr_warn("%s: invalid GPIO\n", __func__); \
                return; \
        } \
        if (!desc->gdev->chip) { \
                dev_warn(&desc->gdev->dev, \
                         "%s: backing chip is gone\n", __func__); \
                return; \
        } } while (0)


int gpiod_request(struct gpio_desc *desc, const char *label)
{
        int status = -EPROBE_DEFER;
        struct gpio_device *gdev;

        VALIDATE_DESC(desc);
        gdev = desc->gdev;

        if (try_module_get(gdev->owner)) {
                status = __gpiod_request(desc, label);
                if (status < 0)
                        module_put(gdev->owner);
                else
                        get_device(&gdev->dev);
        }

        if (status)
                gpiod_dbg(desc, "%s: status %d\n", __func__, status);

        return status;
}

static bool __gpiod_free(struct gpio_desc *desc)
{
        bool                    ret = false;
        unsigned long           flags;
        struct gpio_chip        *chip;

        might_sleep();

        gpiod_unexport(desc);

        spin_lock_irqsave(&gpio_lock, flags);

        chip = desc->gdev->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);
                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);
                clear_bit(FLAG_IS_HOGGED, &desc->flags);
                ret = true;
        }

        spin_unlock_irqrestore(&gpio_lock, flags);
        return ret;
}

void gpiod_free(struct gpio_desc *desc)
{
        if (desc && desc->gdev && __gpiod_free(desc)) {
                module_put(desc->gdev->owner);
                put_device(&desc->gdev->dev);
        } else {
                WARN_ON(extra_checks);
        }
}

/**
 * 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.
 * The string returned is the label passed to gpio_request(); if none has been
 * passed it is a meaningless, non-NULL 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 (offset >= chip->ngpio)
                return NULL;

        desc = &chip->gpiodev->descs[offset];

        if (test_bit(FLAG_REQUESTED, &desc->flags) == 0)
                return NULL;
        return desc->label;
}
EXPORT_SYMBOL_GPL(gpiochip_is_requested);

/**
 * gpiochip_request_own_desc - Allow GPIO chip to request its own descriptor
 * @desc: GPIO descriptor to request
 * @label: label for the GPIO
 *
 * Function allows GPIO chip drivers to request and use their own GPIO
 * descriptors via gpiolib API. Difference to gpiod_request() is that this
 * function will not increase reference count of the GPIO chip module. This
 * allows the GPIO chip module to be unloaded as needed (we assume that the
 * GPIO chip driver handles freeing the GPIOs it has requested).
 */
struct gpio_desc *gpiochip_request_own_desc(struct gpio_chip *chip, u16 hwnum,
                                            const char *label)
{
        struct gpio_desc *desc = gpiochip_get_desc(chip, hwnum);
        int err;

        if (IS_ERR(desc)) {
                chip_err(chip, "failed to get GPIO descriptor\n");
                return desc;
        }

        err = __gpiod_request(desc, label);
        if (err < 0)
                return ERR_PTR(err);

        return desc;
}
EXPORT_SYMBOL_GPL(gpiochip_request_own_desc);

/**
 * gpiochip_free_own_desc - Free GPIO requested by the chip driver
 * @desc: GPIO descriptor to free
 *
 * Function frees the given GPIO requested previously with
 * gpiochip_request_own_desc().
 */
void gpiochip_free_own_desc(struct gpio_desc *desc)
{
        if (desc)
                __gpiod_free(desc);
}
EXPORT_SYMBOL_GPL(gpiochip_free_own_desc);

/*
 * 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.
 */

/**
 * gpiod_direction_input - set the GPIO direction to input
 * @desc:       GPIO to set to input
 *
 * Set the direction of the passed GPIO to input, such as gpiod_get_value() can
 * be called safely on it.
 *
 * Return 0 in case of success, else an error code.
 */
int gpiod_direction_input(struct gpio_desc *desc)
{
        struct gpio_chip        *chip;
        int                     status = -EINVAL;

        VALIDATE_DESC(desc);
        chip = desc->gdev->chip;

        if (!chip->get || !chip->direction_input) {
                gpiod_warn(desc,
                        "%s: missing get() or direction_input() operations\n",
                        __func__);
                return -EIO;
        }

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

        trace_gpio_direction(desc_to_gpio(desc), 1, status);

        return status;
}
EXPORT_SYMBOL_GPL(gpiod_direction_input);

static int _gpiod_direction_output_raw(struct gpio_desc *desc, int value)
{
        struct gpio_chip *gc = desc->gdev->chip;
        int ret;

        /* GPIOs used for IRQs shall not be set as output */
        if (test_bit(FLAG_USED_AS_IRQ, &desc->flags)) {
                gpiod_err(desc,
                          "%s: tried to set a GPIO tied to an IRQ as output\n",
                          __func__);
                return -EIO;
        }

        if (test_bit(FLAG_OPEN_DRAIN, &desc->flags)) {
                /* First see if we can enable open drain in hardware */
                if (gc->set_single_ended) {
                        ret = gc->set_single_ended(gc, gpio_chip_hwgpio(desc),
                                                   LINE_MODE_OPEN_DRAIN);
                        if (!ret)
                                goto set_output_value;
                }
                /* Emulate open drain by not actively driving the line high */
                if (value)
                        return gpiod_direction_input(desc);
        }
        else if (test_bit(FLAG_OPEN_SOURCE, &desc->flags)) {
                if (gc->set_single_ended) {
                        ret = gc->set_single_ended(gc, gpio_chip_hwgpio(desc),
                                                   LINE_MODE_OPEN_SOURCE);
                        if (!ret)
                                goto set_output_value;
                }
                /* Emulate open source by not actively driving the line low */
                if (!value)
                        return gpiod_direction_input(desc);
        } else {
                /* Make sure to disable open drain/source hardware, if any */
                if (gc->set_single_ended)
                        gc->set_single_ended(gc,
                                             gpio_chip_hwgpio(desc),
                                             LINE_MODE_PUSH_PULL);
        }

set_output_value:
        if (!gc->set || !gc->direction_output) {
                gpiod_warn(desc,
                       "%s: missing set() or direction_output() operations\n",
                       __func__);
                return -EIO;
        }

        ret = gc->direction_output(gc, gpio_chip_hwgpio(desc), value);
        if (!ret)
                set_bit(FLAG_IS_OUT, &desc->flags);
        trace_gpio_value(desc_to_gpio(desc), 0, value);
        trace_gpio_direction(desc_to_gpio(desc), 0, ret);
        return ret;
}

/**
 * gpiod_direction_output_raw - set the GPIO direction to output
 * @desc:       GPIO to set to output
 * @value:      initial output value of the GPIO
 *
 * Set the direction of the passed GPIO to output, such as gpiod_set_value() can
 * be called safely on it. The initial value of the output must be specified
 * as raw value on the physical line without regard for the ACTIVE_LOW status.
 *
 * Return 0 in case of success, else an error code.
 */
int gpiod_direction_output_raw(struct gpio_desc *desc, int value)
{
        VALIDATE_DESC(desc);
        return _gpiod_direction_output_raw(desc, value);
}
EXPORT_SYMBOL_GPL(gpiod_direction_output_raw);

/**
 * gpiod_direction_output - set the GPIO direction to output
 * @desc:       GPIO to set to output
 * @value:      initial output value of the GPIO
 *
 * Set the direction of the passed GPIO to output, such as gpiod_set_value() can
 * be called safely on it. The initial value of the output must be specified
 * as the logical value of the GPIO, i.e. taking its ACTIVE_LOW status into
 * account.
 *
 * Return 0 in case of success, else an error code.
 */
int gpiod_direction_output(struct gpio_desc *desc, int value)
{
        VALIDATE_DESC(desc);
        if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
                value = !value;
        return _gpiod_direction_output_raw(desc, value);
}
EXPORT_SYMBOL_GPL(gpiod_direction_output);

/**
 * gpiod_set_debounce - sets @debounce time for a @gpio
 * @gpio: the gpio to set debounce time
 * @debounce: debounce time is microseconds
 *
 * returns -ENOTSUPP if the controller does not support setting
 * debounce.
 */
int gpiod_set_debounce(struct gpio_desc *desc, unsigned debounce)
{
        struct gpio_chip        *chip;

        VALIDATE_DESC(desc);
        chip = desc->gdev->chip;
        if (!chip->set || !chip->set_debounce) {
                gpiod_dbg(desc,
                          "%s: missing set() or set_debounce() operations\n",
                          __func__);
                return -ENOTSUPP;
        }

        return chip->set_debounce(chip, gpio_chip_hwgpio(desc), debounce);
}
EXPORT_SYMBOL_GPL(gpiod_set_debounce);

/**
 * gpiod_is_active_low - test whether a GPIO is active-low or not
 * @desc: the gpio descriptor to test
 *
 * Returns 1 if the GPIO is active-low, 0 otherwise.
 */
int gpiod_is_active_low(const struct gpio_desc *desc)
{
        VALIDATE_DESC(desc);
        return test_bit(FLAG_ACTIVE_LOW, &desc->flags);
}
EXPORT_SYMBOL_GPL(gpiod_is_active_low);

/* 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.
 */

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

        chip = desc->gdev->chip;
        offset = gpio_chip_hwgpio(desc);
        value = chip->get ? chip->get(chip, offset) : -EIO;
        value = value < 0 ? value : !!value;
        trace_gpio_value(desc_to_gpio(desc), 1, value);
        return value;
}

/**
 * gpiod_get_raw_value() - return a gpio's raw value
 * @desc: gpio whose value will be returned
 *
 * Return the GPIO's raw value, i.e. the value of the physical line disregarding
 * its ACTIVE_LOW status, or negative errno on failure.
 *
 * This function should be called from contexts where we cannot sleep, and will
 * complain if the GPIO chip functions potentially sleep.
 */
int gpiod_get_raw_value(const struct gpio_desc *desc)
{
        VALIDATE_DESC(desc);
        /* Should be using gpio_get_value_cansleep() */
        WARN_ON(desc->gdev->chip->can_sleep);
        return _gpiod_get_raw_value(desc);
}
EXPORT_SYMBOL_GPL(gpiod_get_raw_value);

/**
 * gpiod_get_value() - return a gpio's value
 * @desc: gpio whose value will be returned
 *
 * Return the GPIO's logical value, i.e. taking the ACTIVE_LOW status into
 * account, or negative errno on failure.
 *
 * This function should be called from contexts where we cannot sleep, and will
 * complain if the GPIO chip functions potentially sleep.
 */
int gpiod_get_value(const struct gpio_desc *desc)
{
        int value;

        VALIDATE_DESC(desc);
        /* Should be using gpio_get_value_cansleep() */
        WARN_ON(desc->gdev->chip->can_sleep);

        value = _gpiod_get_raw_value(desc);
        if (value < 0)
                return value;

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

        return value;
}
EXPORT_SYMBOL_GPL(gpiod_get_value);

/*
 *  _gpio_set_open_drain_value() - Set the open drain gpio's value.
 * @desc: gpio descriptor whose state need to be set.
 * @value: Non-zero for setting it HIGH otherwise it will set to LOW.
 */
static void _gpio_set_open_drain_value(struct gpio_desc *desc, bool value)
{
        int err = 0;
        struct gpio_chip *chip = desc->gdev->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)
                gpiod_err(desc,
                          "%s: Error in set_value for open drain err %d\n",
                          __func__, err);
}

/*
 *  _gpio_set_open_source_value() - Set the open source gpio's value.
 * @desc: gpio descriptor whose state need to be set.
 * @value: Non-zero for setting it HIGH otherwise it will set to LOW.
 */
static void _gpio_set_open_source_value(struct gpio_desc *desc, bool value)
{
        int err = 0;
        struct gpio_chip *chip = desc->gdev->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)
                gpiod_err(desc,
                          "%s: Error in set_value for open source err %d\n",
                          __func__, err);
}

static void _gpiod_set_raw_value(struct gpio_desc *desc, bool value)
{
        struct gpio_chip        *chip;

        chip = desc->gdev->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);
}

/*
 * set multiple outputs on the same chip;
 * use the chip's set_multiple function if available;
 * otherwise set the outputs sequentially;
 * @mask: bit mask array; one bit per output; BITS_PER_LONG bits per word
 *        defines which outputs are to be changed
 * @bits: bit value array; one bit per output; BITS_PER_LONG bits per word
 *        defines the values the outputs specified by mask are to be set to
 */
static void gpio_chip_set_multiple(struct gpio_chip *chip,
                                   unsigned long *mask, unsigned long *bits)
{
        if (chip->set_multiple) {
                chip->set_multiple(chip, mask, bits);
        } else {
                int i;
                for (i = 0; i < chip->ngpio; i++) {
                        if (mask[BIT_WORD(i)] == 0) {
                                /* no more set bits in this mask word;
                                 * skip ahead to the next word */
                                i = (BIT_WORD(i) + 1) * BITS_PER_LONG - 1;
                                continue;
                        }
                        /* set outputs if the corresponding mask bit is set */
                        if (__test_and_clear_bit(i, mask))
                                chip->set(chip, i, test_bit(i, bits));
                }
        }
}

void gpiod_set_array_value_complex(bool raw, bool can_sleep,
                                   unsigned int array_size,
                                   struct gpio_desc **desc_array,
                                   int *value_array)
{
        int i = 0;

        while (i < array_size) {
                struct gpio_chip *chip = desc_array[i]->gdev->chip;
                unsigned long mask[BITS_TO_LONGS(chip->ngpio)];
                unsigned long bits[BITS_TO_LONGS(chip->ngpio)];
                int count = 0;

                if (!can_sleep)
                        WARN_ON(chip->can_sleep);

                memset(mask, 0, sizeof(mask));
                do {
                        struct gpio_desc *desc = desc_array[i];
                        int hwgpio = gpio_chip_hwgpio(desc);
                        int value = value_array[i];

                        if (!raw && test_bit(FLAG_ACTIVE_LOW, &desc->flags))
                                value = !value;
                        trace_gpio_value(desc_to_gpio(desc), 0, value);
                        /*
                         * collect all normal outputs belonging to the same chip
                         * open drain and open source outputs are set individually
                         */
                        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 {
                                __set_bit(hwgpio, mask);
                                if (value)
                                        __set_bit(hwgpio, bits);
                                else
                                        __clear_bit(hwgpio, bits);
                                count++;
                        }
                        i++;
                } while ((i < array_size) &&
                         (desc_array[i]->gdev->chip == chip));
                /* push collected bits to outputs */
                if (count != 0)
                        gpio_chip_set_multiple(chip, mask, bits);
        }
}

/**
 * gpiod_set_raw_value() - assign a gpio's raw value
 * @desc: gpio whose value will be assigned
 * @value: value to assign
 *
 * Set the raw value of the GPIO, i.e. the value of its physical line without
 * regard for its ACTIVE_LOW status.
 *
 * This function should be called from contexts where we cannot sleep, and will
 * complain if the GPIO chip functions potentially sleep.
 */
void gpiod_set_raw_value(struct gpio_desc *desc, int value)
{
        VALIDATE_DESC_VOID(desc);
        /* Should be using gpiod_set_value_cansleep() */
        WARN_ON(desc->gdev->chip->can_sleep);
        _gpiod_set_raw_value(desc, value);
}
EXPORT_SYMBOL_GPL(gpiod_set_raw_value);

/**
 * gpiod_set_value() - assign a gpio's value
 * @desc: gpio whose value will be assigned
 * @value: value to assign
 *
 * Set the logical value of the GPIO, i.e. taking its ACTIVE_LOW status into
 * account
 *
 * This function should be called from contexts where we cannot sleep, and will
 * complain if the GPIO chip functions potentially sleep.
 */
void gpiod_set_value(struct gpio_desc *desc, int value)
{
        VALIDATE_DESC_VOID(desc);
        /* Should be using gpiod_set_value_cansleep() */
        WARN_ON(desc->gdev->chip->can_sleep);
        if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
                value = !value;
        _gpiod_set_raw_value(desc, value);
}
EXPORT_SYMBOL_GPL(gpiod_set_value);

/**
 * gpiod_set_raw_array_value() - assign values to an array of GPIOs
 * @array_size: number of elements in the descriptor / value arrays
 * @desc_array: array of GPIO descriptors whose values will be assigned
 * @value_array: array of values to assign
 *
 * Set the raw values of the GPIOs, i.e. the values of the physical lines
 * without regard for their ACTIVE_LOW status.
 *
 * This function should be called from contexts where we cannot sleep, and will
 * complain if the GPIO chip functions potentially sleep.
 */
void gpiod_set_raw_array_value(unsigned int array_size,
                         struct gpio_desc **desc_array, int *value_array)
{
        if (!desc_array)
                return;
        gpiod_set_array_value_complex(true, false, array_size, desc_array,
                                      value_array);
}
EXPORT_SYMBOL_GPL(gpiod_set_raw_array_value);

/**
 * gpiod_set_array_value() - assign values to an array of GPIOs
 * @array_size: number of elements in the descriptor / value arrays
 * @desc_array: array of GPIO descriptors whose values will be assigned
 * @value_array: array of values to assign
 *
 * Set the logical values of the GPIOs, i.e. taking their ACTIVE_LOW status
 * into account.
 *
 * This function should be called from contexts where we cannot sleep, and will
 * complain if the GPIO chip functions potentially sleep.
 */
void gpiod_set_array_value(unsigned int array_size,
                           struct gpio_desc **desc_array, int *value_array)
{
        if (!desc_array)
                return;
        gpiod_set_array_value_complex(false, false, array_size, desc_array,
                                      value_array);
}
EXPORT_SYMBOL_GPL(gpiod_set_array_value);

/**
 * gpiod_cansleep() - report whether gpio value access may sleep
 * @desc: gpio to check
 *
 */
int gpiod_cansleep(const struct gpio_desc *desc)
{
        VALIDATE_DESC(desc);
        return desc->gdev->chip->can_sleep;
}
EXPORT_SYMBOL_GPL(gpiod_cansleep);

/**
 * gpiod_to_irq() - return the IRQ corresponding to a GPIO
 * @desc: gpio whose IRQ will be returned (already requested)
 *
 * Return the IRQ corresponding to the passed GPIO, or an error code in case of
 * error.
 */
int gpiod_to_irq(const struct gpio_desc *desc)
{
        struct gpio_chip *chip;
        int offset;

        VALIDATE_DESC(desc);
        chip = desc->gdev->chip;
        offset = gpio_chip_hwgpio(desc);
        if (chip->to_irq) {
                int retirq = chip->to_irq(chip, offset);

                /* Zero means NO_IRQ */
                if (!retirq)
                        return -ENXIO;

                return retirq;
        }
        return -ENXIO;
}
EXPORT_SYMBOL_GPL(gpiod_to_irq);

/**
 * gpiochip_lock_as_irq() - lock a GPIO to be used as IRQ
 * @chip: the chip the GPIO to lock belongs to
 * @offset: the offset of the GPIO to lock as IRQ
 *
 * This is used directly by GPIO drivers that want to lock down
 * a certain GPIO line to be used for IRQs.
 */
int gpiochip_lock_as_irq(struct gpio_chip *chip, unsigned int offset)
{
        if (offset >= chip->ngpio)
                return -EINVAL;

        if (test_bit(FLAG_IS_OUT, &chip->gpiodev->descs[offset].flags)) {
                chip_err(chip,
                          "%s: tried to flag a GPIO set as output for IRQ\n",
                          __func__);
                return -EIO;
        }

        set_bit(FLAG_USED_AS_IRQ, &chip->gpiodev->descs[offset].flags);
        return 0;
}
EXPORT_SYMBOL_GPL(gpiochip_lock_as_irq);

/**
 * gpiochip_unlock_as_irq() - unlock a GPIO used as IRQ
 * @chip: the chip the GPIO to lock belongs to
 * @offset: the offset of the GPIO to lock as IRQ
 *
 * This is used directly by GPIO drivers that want to indicate
 * that a certain GPIO is no longer used exclusively for IRQ.
 */
void gpiochip_unlock_as_irq(struct gpio_chip *chip, unsigned int offset)
{
        if (offset >= chip->ngpio)
                return;

        clear_bit(FLAG_USED_AS_IRQ, &chip->gpiodev->descs[offset].flags);
}
EXPORT_SYMBOL_GPL(gpiochip_unlock_as_irq);

bool gpiochip_line_is_irq(struct gpio_chip *chip, unsigned int offset)
{
        if (offset >= chip->ngpio)
                return false;

        return test_bit(FLAG_USED_AS_IRQ, &chip->gpiodev->descs[offset].flags);
}
EXPORT_SYMBOL_GPL(gpiochip_line_is_irq);

bool gpiochip_line_is_open_drain(struct gpio_chip *chip, unsigned int offset)
{
        if (offset >= chip->ngpio)
                return false;

        return test_bit(FLAG_OPEN_DRAIN, &chip->gpiodev->descs[offset].flags);
}
EXPORT_SYMBOL_GPL(gpiochip_line_is_open_drain);

bool gpiochip_line_is_open_source(struct gpio_chip *chip, unsigned int offset)
{
        if (offset >= chip->ngpio)
                return false;

        return test_bit(FLAG_OPEN_SOURCE, &chip->gpiodev->descs[offset].flags);
}
EXPORT_SYMBOL_GPL(gpiochip_line_is_open_source);

/**
 * gpiod_get_raw_value_cansleep() - return a gpio's raw value
 * @desc: gpio whose value will be returned
 *
 * Return the GPIO's raw value, i.e. the value of the physical line disregarding
 * its ACTIVE_LOW status, or negative errno on failure.
 *
 * This function is to be called from contexts that can sleep.
 */
int gpiod_get_raw_value_cansleep(const struct gpio_desc *desc)
{
        might_sleep_if(extra_checks);
        VALIDATE_DESC(desc);
        return _gpiod_get_raw_value(desc);
}
EXPORT_SYMBOL_GPL(gpiod_get_raw_value_cansleep);

/**
 * gpiod_get_value_cansleep() - return a gpio's value
 * @desc: gpio whose value will be returned
 *
 * Return the GPIO's logical value, i.e. taking the ACTIVE_LOW status into
 * account, or negative errno on failure.
 *
 * This function is to be called from contexts that can sleep.
 */
int gpiod_get_value_cansleep(const struct gpio_desc *desc)
{
        int value;

        might_sleep_if(extra_checks);
        VALIDATE_DESC(desc);
        value = _gpiod_get_raw_value(desc);
        if (value < 0)
                return value;

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

        return value;
}
EXPORT_SYMBOL_GPL(gpiod_get_value_cansleep);

/**
 * gpiod_set_raw_value_cansleep() - assign a gpio's raw value
 * @desc: gpio whose value will be assigned
 * @value: value to assign
 *
 * Set the raw value of the GPIO, i.e. the value of its physical line without
 * regard for its ACTIVE_LOW status.
 *
 * This function is to be called from contexts that can sleep.
 */
void gpiod_set_raw_value_cansleep(struct gpio_desc *desc, int value)
{
        might_sleep_if(extra_checks);
        VALIDATE_DESC_VOID(desc);
        _gpiod_set_raw_value(desc, value);
}
EXPORT_SYMBOL_GPL(gpiod_set_raw_value_cansleep);

/**
 * gpiod_set_value_cansleep() - assign a gpio's value
 * @desc: gpio whose value will be assigned
 * @value: value to assign
 *
 * Set the logical value of the GPIO, i.e. taking its ACTIVE_LOW status into
 * account
 *
 * This function is to be called from contexts that can sleep.
 */
void gpiod_set_value_cansleep(struct gpio_desc *desc, int value)
{
        might_sleep_if(extra_checks);
        VALIDATE_DESC_VOID(desc);
        if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
                value = !value;
        _gpiod_set_raw_value(desc, value);
}
EXPORT_SYMBOL_GPL(gpiod_set_value_cansleep);

/**
 * gpiod_set_raw_array_value_cansleep() - assign values to an array of GPIOs
 * @array_size: number of elements in the descriptor / value arrays
 * @desc_array: array of GPIO descriptors whose values will be assigned
 * @value_array: array of values to assign
 *
 * Set the raw values of the GPIOs, i.e. the values of the physical lines
 * without regard for their ACTIVE_LOW status.
 *
 * This function is to be called from contexts that can sleep.
 */
void gpiod_set_raw_array_value_cansleep(unsigned int array_size,
                                        struct gpio_desc **desc_array,
                                        int *value_array)
{
        might_sleep_if(extra_checks);
        if (!desc_array)
                return;
        gpiod_set_array_value_complex(true, true, array_size, desc_array,
                                      value_array);
}
EXPORT_SYMBOL_GPL(gpiod_set_raw_array_value_cansleep);

/**
 * gpiod_set_array_value_cansleep() - assign values to an array of GPIOs
 * @array_size: number of elements in the descriptor / value arrays
 * @desc_array: array of GPIO descriptors whose values will be assigned
 * @value_array: array of values to assign
 *
 * Set the logical values of the GPIOs, i.e. taking their ACTIVE_LOW status
 * into account.
 *
 * This function is to be called from contexts that can sleep.
 */
void gpiod_set_array_value_cansleep(unsigned int array_size,
                                    struct gpio_desc **desc_array,
                                    int *value_array)
{
        might_sleep_if(extra_checks);
        if (!desc_array)
                return;
        gpiod_set_array_value_complex(false, true, array_size, desc_array,
                                      value_array);
}
EXPORT_SYMBOL_GPL(gpiod_set_array_value_cansleep);

/**
 * gpiod_add_lookup_table() - register GPIO device consumers
 * @table: table of consumers to register
 */
void gpiod_add_lookup_table(struct gpiod_lookup_table *table)
{
        mutex_lock(&gpio_lookup_lock);

        list_add_tail(&table->list, &gpio_lookup_list);

        mutex_unlock(&gpio_lookup_lock);
}

/**
 * gpiod_remove_lookup_table() - unregister GPIO device consumers
 * @table: table of consumers to unregister
 */
void gpiod_remove_lookup_table(struct gpiod_lookup_table *table)
{
        mutex_lock(&gpio_lookup_lock);

        list_del(&table->list);

        mutex_unlock(&gpio_lookup_lock);
}

static struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id,
                                      unsigned int idx,
                                      enum gpio_lookup_flags *flags)
{
        char prop_name[32]; /* 32 is max size of property name */
        enum of_gpio_flags of_flags;
        struct gpio_desc *desc;
        unsigned int i;

        for (i = 0; i < ARRAY_SIZE(gpio_suffixes); i++) {
                if (con_id)
                        snprintf(prop_name, sizeof(prop_name), "%s-%s", con_id,
                                 gpio_suffixes[i]);
                else
                        snprintf(prop_name, sizeof(prop_name), "%s",
                                 gpio_suffixes[i]);

                desc = of_get_named_gpiod_flags(dev->of_node, prop_name, idx,
                                                &of_flags);
                if (!IS_ERR(desc) || (PTR_ERR(desc) == -EPROBE_DEFER))
                        break;
        }

        if (IS_ERR(desc))
                return desc;

        if (of_flags & OF_GPIO_ACTIVE_LOW)
                *flags |= GPIO_ACTIVE_LOW;

        if (of_flags & OF_GPIO_SINGLE_ENDED) {
                if (of_flags & OF_GPIO_ACTIVE_LOW)
                        *flags |= GPIO_OPEN_DRAIN;
                else
                        *flags |= GPIO_OPEN_SOURCE;
        }

        return desc;
}

static struct gpio_desc *acpi_find_gpio(struct device *dev,
                                        const char *con_id,
                                        unsigned int idx,
                                        enum gpiod_flags flags,
                                        enum gpio_lookup_flags *lookupflags)
{
        struct acpi_device *adev = ACPI_COMPANION(dev);
        struct acpi_gpio_info info;
        struct gpio_desc *desc;
        char propname[32];
        int i;

        /* Try first from _DSD */
        for (i = 0; i < ARRAY_SIZE(gpio_suffixes); i++) {
                if (con_id && strcmp(con_id, "gpios")) {
                        snprintf(propname, sizeof(propname), "%s-%s",
                                 con_id, gpio_suffixes[i]);
                } else {
                        snprintf(propname, sizeof(propname), "%s",
                                 gpio_suffixes[i]);
                }

                desc = acpi_get_gpiod_by_index(adev, propname, idx, &info);
                if (!IS_ERR(desc) || (PTR_ERR(desc) == -EPROBE_DEFER))
                        break;
        }

        /* Then from plain _CRS GPIOs */
        if (IS_ERR(desc)) {
                if (!acpi_can_fallback_to_crs(adev, con_id))
                        return ERR_PTR(-ENOENT);

                desc = acpi_get_gpiod_by_index(adev, NULL, idx, &info);
                if (IS_ERR(desc))
                        return desc;

                if ((flags == GPIOD_OUT_LOW || flags == GPIOD_OUT_HIGH) &&
                    info.gpioint) {
                        dev_dbg(dev, "refusing GpioInt() entry when doing GPIOD_OUT_* lookup\n");
                        return ERR_PTR(-ENOENT);
                }
        }

        if (info.polarity == GPIO_ACTIVE_LOW)
                *lookupflags |= GPIO_ACTIVE_LOW;

        return desc;
}

static struct gpiod_lookup_table *gpiod_find_lookup_table(struct device *dev)
{
        const char *dev_id = dev ? dev_name(dev) : NULL;
        struct gpiod_lookup_table *table;

        mutex_lock(&gpio_lookup_lock);

        list_for_each_entry(table, &gpio_lookup_list, list) {
                if (table->dev_id && dev_id) {
                        /*
                         * Valid strings on both ends, must be identical to have
                         * a match
                         */
                        if (!strcmp(table->dev_id, dev_id))
                                goto found;
                } else {
                        /*
                         * One of the pointers is NULL, so both must be to have
                         * a match
                         */
                        if (dev_id == table->dev_id)
                                goto found;
                }
        }
        table = NULL;

found:
        mutex_unlock(&gpio_lookup_lock);
        return table;
}

static struct gpio_desc *gpiod_find(struct device *dev, const char *con_id,
                                    unsigned int idx,
                                    enum gpio_lookup_flags *flags)
{
        struct gpio_desc *desc = ERR_PTR(-ENOENT);
        struct gpiod_lookup_table *table;
        struct gpiod_lookup *p;

        table = gpiod_find_lookup_table(dev);
        if (!table)
                return desc;

        for (p = &table->table[0]; p->chip_label; p++) {
                struct gpio_chip *chip;

                /* idx must always match exactly */
                if (p->idx != idx)
                        continue;

                /* If the lookup entry has a con_id, require exact match */
                if (p->con_id && (!con_id || strcmp(p->con_id, con_id)))
                        continue;

                chip = find_chip_by_name(p->chip_label);

                if (!chip) {
                        dev_err(dev, "cannot find GPIO chip %s\n",
                                p->chip_label);
                        return ERR_PTR(-ENODEV);
                }

                if (chip->ngpio <= p->chip_hwnum) {
                        dev_err(dev,
                                "requested GPIO %d is out of range [0..%d] for chip %s\n",
                                idx, chip->ngpio, chip->label);
                        return ERR_PTR(-EINVAL);
                }

                desc = gpiochip_get_desc(chip, p->chip_hwnum);
                *flags = p->flags;

                return desc;
        }

        return desc;
}

static int dt_gpio_count(struct device *dev, const char *con_id)
{
        int ret;
        char propname[32];
        unsigned int i;

        for (i = 0; i < ARRAY_SIZE(gpio_suffixes); i++) {
                if (con_id)
                        snprintf(propname, sizeof(propname), "%s-%s",
                                 con_id, gpio_suffixes[i]);
                else
                        snprintf(propname, sizeof(propname), "%s",
                                 gpio_suffixes[i]);

                ret = of_gpio_named_count(dev->of_node, propname);
                if (ret >= 0)
                        break;
        }
        return ret;
}

static int platform_gpio_count(struct device *dev, const char *con_id)
{
        struct gpiod_lookup_table *table;
        struct gpiod_lookup *p;
        unsigned int count = 0;

        table = gpiod_find_lookup_table(dev);
        if (!table)
                return -ENOENT;

        for (p = &table->table[0]; p->chip_label; p++) {
                if ((con_id && p->con_id && !strcmp(con_id, p->con_id)) ||
                    (!con_id && !p->con_id))
                        count++;
        }
        if (!count)
                return -ENOENT;

        return count;
}

/**
 * gpiod_count - return the number of GPIOs associated with a device / function
 *              or -ENOENT if no GPIO has been assigned to the requested function
 * @dev:        GPIO consumer, can be NULL for system-global GPIOs
 * @con_id:     function within the GPIO consumer
 */
int gpiod_count(struct device *dev, const char *con_id)
{
        int count = -ENOENT;

        if (IS_ENABLED(CONFIG_OF) && dev && dev->of_node)
                count = dt_gpio_count(dev, con_id);
        else if (IS_ENABLED(CONFIG_ACPI) && dev && ACPI_HANDLE(dev))
                count = acpi_gpio_count(dev, con_id);

        if (count < 0)
                count = platform_gpio_count(dev, con_id);

        return count;
}
EXPORT_SYMBOL_GPL(gpiod_count);

/**
 * gpiod_get - obtain a GPIO for a given GPIO function
 * @dev:        GPIO consumer, can be NULL for system-global GPIOs
 * @con_id:     function within the GPIO consumer
 * @flags:      optional GPIO initialization flags
 *
 * Return the GPIO descriptor corresponding to the function con_id of device
 * dev, -ENOENT if no GPIO has been assigned to the requested function, or
 * another IS_ERR() code if an error occurred while trying to acquire the GPIO.
 */
struct gpio_desc *__must_check gpiod_get(struct device *dev, const char *con_id,
                                         enum gpiod_flags flags)
{
        return gpiod_get_index(dev, con_id, 0, flags);
}
EXPORT_SYMBOL_GPL(gpiod_get);

/**
 * gpiod_get_optional - obtain an optional GPIO for a given GPIO function
 * @dev: GPIO consumer, can be NULL for system-global GPIOs
 * @con_id: function within the GPIO consumer
 * @flags: optional GPIO initialization flags
 *
 * This is equivalent to gpiod_get(), except that when no GPIO was assigned to
 * the requested function it will return NULL. This is convenient for drivers
 * that need to handle optional GPIOs.
 */
struct gpio_desc *__must_check gpiod_get_optional(struct device *dev,
                                                  const char *con_id,
                                                  enum gpiod_flags flags)
{
        return gpiod_get_index_optional(dev, con_id, 0, flags);
}
EXPORT_SYMBOL_GPL(gpiod_get_optional);

/**
 * gpiod_parse_flags - helper function to parse GPIO lookup flags
 * @desc:       gpio to be setup
 * @lflags:     gpio_lookup_flags - returned from of_find_gpio() or
 *              of_get_gpio_hog()
 *
 * Set the GPIO descriptor flags based on the given GPIO lookup flags.
 */
static void gpiod_parse_flags(struct gpio_desc *desc, unsigned long lflags)
{
        if (lflags & GPIO_ACTIVE_LOW)
                set_bit(FLAG_ACTIVE_LOW, &desc->flags);
        if (lflags & GPIO_OPEN_DRAIN)
                set_bit(FLAG_OPEN_DRAIN, &desc->flags);
        if (lflags & GPIO_OPEN_SOURCE)
                set_bit(FLAG_OPEN_SOURCE, &desc->flags);
}

/**
 * gpiod_configure_flags - helper function to configure a given GPIO
 * @desc:       gpio whose value will be assigned
 * @con_id:     function within the GPIO consumer
 * @dflags:     gpiod_flags - optional GPIO initialization flags
 *
 * Return 0 on success, -ENOENT if no GPIO has been assigned to the
 * requested function and/or index, or another IS_ERR() code if an error
 * occurred while trying to acquire the GPIO.
 */
static int gpiod_configure_flags(struct gpio_desc *desc, const char *con_id,
                                 enum gpiod_flags dflags)
{
        int status;

        /* No particular flag request, return here... */
        if (!(dflags & GPIOD_FLAGS_BIT_DIR_SET)) {
                pr_debug("no flags found for %s\n", con_id);
                return 0;
        }

        /* Process flags */
        if (dflags & GPIOD_FLAGS_BIT_DIR_OUT)
                status = gpiod_direction_output(desc,
                                              dflags & GPIOD_FLAGS_BIT_DIR_VAL);
        else
                status = gpiod_direction_input(desc);

        return status;
}

/**
 * gpiod_get_index - obtain a GPIO from a multi-index GPIO function
 * @dev:        GPIO consumer, can be NULL for system-global GPIOs
 * @con_id:     function within the GPIO consumer
 * @idx:        index of the GPIO to obtain in the consumer
 * @flags:      optional GPIO initialization flags
 *
 * This variant of gpiod_get() allows to access GPIOs other than the first
 * defined one for functions that define several GPIOs.
 *
 * Return a valid GPIO descriptor, -ENOENT if no GPIO has been assigned to the
 * requested function and/or index, or another IS_ERR() code if an error
 * occurred while trying to acquire the GPIO.
 */
struct gpio_desc *__must_check gpiod_get_index(struct device *dev,
                                               const char *con_id,
                                               unsigned int idx,
                                               enum gpiod_flags flags)
{
        struct gpio_desc *desc = NULL;
        int status;
        enum gpio_lookup_flags lookupflags = 0;

        dev_dbg(dev, "GPIO lookup for consumer %s\n", con_id);

        if (dev) {
                /* Using device tree? */
                if (IS_ENABLED(CONFIG_OF) && dev->of_node) {
                        dev_dbg(dev, "using device tree for GPIO lookup\n");
                        desc = of_find_gpio(dev, con_id, idx, &lookupflags);
                } else if (ACPI_COMPANION(dev)) {
                        dev_dbg(dev, "using ACPI for GPIO lookup\n");
                        desc = acpi_find_gpio(dev, con_id, idx, flags, &lookupflags);
                }
        }

        /*
         * Either we are not using DT or ACPI, or their lookup did not return
         * a result. In that case, use platform lookup as a fallback.
         */
        if (!desc || desc == ERR_PTR(-ENOENT)) {
                dev_dbg(dev, "using lookup tables for GPIO lookup\n");
                desc = gpiod_find(dev, con_id, idx, &lookupflags);
        }

        if (IS_ERR(desc)) {
                dev_dbg(dev, "lookup for GPIO %s failed\n", con_id);
                return desc;
        }

        gpiod_parse_flags(desc, lookupflags);

        status = gpiod_request(desc, con_id);
        if (status < 0)
                return ERR_PTR(status);

        status = gpiod_configure_flags(desc, con_id, flags);
        if (status < 0) {
                dev_dbg(dev, "setup of GPIO %s failed\n", con_id);
                gpiod_put(desc);
                return ERR_PTR(status);
        }

        return desc;
}
EXPORT_SYMBOL_GPL(gpiod_get_index);

/**
 * fwnode_get_named_gpiod - obtain a GPIO from firmware node
 * @fwnode:     handle of the firmware node
 * @propname:   name of the firmware property representing the GPIO
 *
 * This function can be used for drivers that get their configuration
 * from firmware.
 *
 * Function properly finds the corresponding GPIO using whatever is the
 * underlying firmware interface and then makes sure that the GPIO
 * descriptor is requested before it is returned to the caller.
 *
 * In case of error an ERR_PTR() is returned.
 */
struct gpio_desc *fwnode_get_named_gpiod(struct fwnode_handle *fwnode,
                                         const char *propname)
{
        struct gpio_desc *desc = ERR_PTR(-ENODEV);
        bool active_low = false;
        bool single_ended = false;
        int ret;

        if (!fwnode)
                return ERR_PTR(-EINVAL);

        if (is_of_node(fwnode)) {
                enum of_gpio_flags flags;

                desc = of_get_named_gpiod_flags(to_of_node(fwnode), propname, 0,
                                                &flags);
                if (!IS_ERR(desc)) {
                        active_low = flags & OF_GPIO_ACTIVE_LOW;
                        single_ended = flags & OF_GPIO_SINGLE_ENDED;
                }
        } else if (is_acpi_node(fwnode)) {
                struct acpi_gpio_info info;

                desc = acpi_node_get_gpiod(fwnode, propname, 0, &info);
                if (!IS_ERR(desc))
                        active_low = info.polarity == GPIO_ACTIVE_LOW;
        }

        if (IS_ERR(desc))
                return desc;

        if (active_low)
                set_bit(FLAG_ACTIVE_LOW, &desc->flags);

        if (single_ended) {
                if (active_low)
                        set_bit(FLAG_OPEN_DRAIN, &desc->flags);
                else
                        set_bit(FLAG_OPEN_SOURCE, &desc->flags);
        }

        ret = gpiod_request(desc, NULL);
        if (ret)
                return ERR_PTR(ret);

        return desc;
}
EXPORT_SYMBOL_GPL(fwnode_get_named_gpiod);

/**
 * gpiod_get_index_optional - obtain an optional GPIO from a multi-index GPIO
 *                            function
 * @dev: GPIO consumer, can be NULL for system-global GPIOs
 * @con_id: function within the GPIO consumer
 * @index: index of the GPIO to obtain in the consumer
 * @flags: optional GPIO initialization flags
 *
 * This is equivalent to gpiod_get_index(), except that when no GPIO with the
 * specified index was assigned to the requested function it will return NULL.
 * This is convenient for drivers that need to handle optional GPIOs.
 */
struct gpio_desc *__must_check gpiod_get_index_optional(struct device *dev,
                                                        const char *con_id,
                                                        unsigned int index,
                                                        enum gpiod_flags flags)
{
        struct gpio_desc *desc;

        desc = gpiod_get_index(dev, con_id, index, flags);
        if (IS_ERR(desc)) {
                if (PTR_ERR(desc) == -ENOENT)
                        return NULL;
        }

        return desc;
}
EXPORT_SYMBOL_GPL(gpiod_get_index_optional);

/**
 * gpiod_hog - Hog the specified GPIO desc given the provided flags
 * @desc:       gpio whose value will be assigned
 * @name:       gpio line name
 * @lflags:     gpio_lookup_flags - returned from of_find_gpio() or
 *              of_get_gpio_hog()
 * @dflags:     gpiod_flags - optional GPIO initialization flags
 */
int gpiod_hog(struct gpio_desc *desc, const char *name,
              unsigned long lflags, enum gpiod_flags dflags)
{
        struct gpio_chip *chip;
        struct gpio_desc *local_desc;
        int hwnum;
        int status;

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

        gpiod_parse_flags(desc, lflags);

        local_desc = gpiochip_request_own_desc(chip, hwnum, name);
        if (IS_ERR(local_desc)) {
                status = PTR_ERR(local_desc);
                pr_err("requesting hog GPIO %s (chip %s, offset %d) failed, %d\n",
                       name, chip->label, hwnum, status);
                return status;
        }

        status = gpiod_configure_flags(desc, name, dflags);
        if (status < 0) {
                pr_err("setup of hog GPIO %s (chip %s, offset %d) failed, %d\n",
                       name, chip->label, hwnum, status);
                gpiochip_free_own_desc(desc);
                return status;
        }

        /* Mark GPIO as hogged so it can be identified and removed later */
        set_bit(FLAG_IS_HOGGED, &desc->flags);

        pr_info("GPIO line %d (%s) hogged as %s%s\n",
                desc_to_gpio(desc), name,
                (dflags&GPIOD_FLAGS_BIT_DIR_OUT) ? "output" : "input",
                (dflags&GPIOD_FLAGS_BIT_DIR_OUT) ?
                  (dflags&GPIOD_FLAGS_BIT_DIR_VAL) ? "/high" : "/low":"");

        return 0;
}

/**
 * gpiochip_free_hogs - Scan gpio-controller chip and release GPIO hog
 * @chip:       gpio chip to act on
 *
 * This is only used by of_gpiochip_remove to free hogged gpios
 */
static void gpiochip_free_hogs(struct gpio_chip *chip)
{
        int id;

        for (id = 0; id < chip->ngpio; id++) {
                if (test_bit(FLAG_IS_HOGGED, &chip->gpiodev->descs[id].flags))
                        gpiochip_free_own_desc(&chip->gpiodev->descs[id]);
        }
}

/**
 * gpiod_get_array - obtain multiple GPIOs from a multi-index GPIO function
 * @dev:        GPIO consumer, can be NULL for system-global GPIOs
 * @con_id:     function within the GPIO consumer
 * @flags:      optional GPIO initialization flags
 *
 * This function acquires all the GPIOs defined under a given function.
 *
 * Return a struct gpio_descs containing an array of descriptors, -ENOENT if
 * no GPIO has been assigned to the requested function, or another IS_ERR()
 * code if an error occurred while trying to acquire the GPIOs.
 */
struct gpio_descs *__must_check gpiod_get_array(struct device *dev,
                                                const char *con_id,
                                                enum gpiod_flags flags)
{
        struct gpio_desc *desc;
        struct gpio_descs *descs;
        int count;

        count = gpiod_count(dev, con_id);
        if (count < 0)
                return ERR_PTR(count);

        descs = kzalloc(sizeof(*descs) + sizeof(descs->desc[0]) * count,
                        GFP_KERNEL);
        if (!descs)
                return ERR_PTR(-ENOMEM);

        for (descs->ndescs = 0; descs->ndescs < count; ) {
                desc = gpiod_get_index(dev, con_id, descs->ndescs, flags);
                if (IS_ERR(desc)) {
                        gpiod_put_array(descs);
                        return ERR_CAST(desc);
                }
                descs->desc[descs->ndescs] = desc;
                descs->ndescs++;
        }
        return descs;
}
EXPORT_SYMBOL_GPL(gpiod_get_array);

/**
 * gpiod_get_array_optional - obtain multiple GPIOs from a multi-index GPIO
 *                            function
 * @dev:        GPIO consumer, can be NULL for system-global GPIOs
 * @con_id:     function within the GPIO consumer
 * @flags:      optional GPIO initialization flags
 *
 * This is equivalent to gpiod_get_array(), except that when no GPIO was
 * assigned to the requested function it will return NULL.
 */
struct gpio_descs *__must_check gpiod_get_array_optional(struct device *dev,
                                                        const char *con_id,
                                                        enum gpiod_flags flags)
{
        struct gpio_descs *descs;

        descs = gpiod_get_array(dev, con_id, flags);
        if (IS_ERR(descs) && (PTR_ERR(descs) == -ENOENT))
                return NULL;

        return descs;
}
EXPORT_SYMBOL_GPL(gpiod_get_array_optional);

/**
 * gpiod_put - dispose of a GPIO descriptor
 * @desc:       GPIO descriptor to dispose of
 *
 * No descriptor can be used after gpiod_put() has been called on it.
 */
void gpiod_put(struct gpio_desc *desc)
{
        gpiod_free(desc);
}
EXPORT_SYMBOL_GPL(gpiod_put);

/**
 * gpiod_put_array - dispose of multiple GPIO descriptors
 * @descs:      struct gpio_descs containing an array of descriptors
 */
void gpiod_put_array(struct gpio_descs *descs)
{
        unsigned int i;

        for (i = 0; i < descs->ndescs; i++)
                gpiod_put(descs->desc[i]);

        kfree(descs);
}
EXPORT_SYMBOL_GPL(gpiod_put_array);

static int __init gpiolib_dev_init(void)
{
        int ret;

        /* Register GPIO sysfs bus */
        ret  = bus_register(&gpio_bus_type);
        if (ret < 0) {
                pr_err("gpiolib: could not register GPIO bus type\n");
                return ret;
        }

        ret = alloc_chrdev_region(&gpio_devt, 0, GPIO_DEV_MAX, "gpiochip");
        if (ret < 0) {
                pr_err("gpiolib: failed to allocate char dev region\n");
                bus_unregister(&gpio_bus_type);
        } else {
                gpiolib_initialized = true;
                gpiochip_setup_devs();
        }
        return ret;
}
core_initcall(gpiolib_dev_init);

#ifdef CONFIG_DEBUG_FS

static void gpiolib_dbg_show(struct seq_file *s, struct gpio_device *gdev)
{
        unsigned                i;
        struct gpio_chip        *chip = gdev->chip;
        unsigned                gpio = gdev->base;
        struct gpio_desc        *gdesc = &gdev->descs[0];
        int                     is_out;
        int                     is_irq;

        for (i = 0; i < gdev->ngpio; i++, gpio++, gdesc++) {
                if (!test_bit(FLAG_REQUESTED, &gdesc->flags)) {
                        if (gdesc->name) {
                                seq_printf(s, " gpio-%-3d (%-20.20s)\n",
                                           gpio, gdesc->name);
                        }
                        continue;
                }

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

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

        s->private = "";

        spin_lock_irqsave(&gpio_lock, flags);
        list_for_each_entry(gdev, &gpio_devices, list)
                if (index-- == 0) {
                        spin_unlock_irqrestore(&gpio_lock, flags);
                        return gdev;
                }
        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_device *gdev = v;
        void *ret = NULL;

        spin_lock_irqsave(&gpio_lock, flags);
        if (list_is_last(&gdev->list, &gpio_devices))
                ret = NULL;
        else
                ret = list_entry(gdev->list.next, struct gpio_device, 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_device *gdev = v;
        struct gpio_chip *chip = gdev->chip;
        struct device *parent;

        if (!chip) {
                seq_printf(s, "%s%s: (dangling chip)", (char *)s->private,
                           dev_name(&gdev->dev));
                return 0;
        }

        seq_printf(s, "%s%s: GPIOs %d-%d", (char *)s->private,
                   dev_name(&gdev->dev),
                   gdev->base, gdev->base + gdev->ngpio - 1);
        parent = chip->parent;
        if (parent)
                seq_printf(s, ", parent: %s/%s",
                           parent->bus ? parent->bus->name : "no-bus",
                           dev_name(parent));
        if (chip->label)
                seq_printf(s, ", %s", chip->label);
        if (chip->can_sleep)
                seq_printf(s, ", can sleep");
        seq_printf(s, ":\n");

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

        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 */