gpio: move gpio_ensure_requested() into legacy C file

[karo-tx-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 "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

/* 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 struct gpio_desc gpio_desc[ARCH_NR_GPIOS];

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

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

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)
{
        if (WARN(!gpio_is_valid(gpio), "invalid GPIO %d\n", gpio))
                return NULL;
        else
                return &gpio_desc[gpio];
}
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)
{
        if (hwnum >= chip->ngpio)
                return ERR_PTR(-EINVAL);

        return &chip->desc[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 - &gpio_desc[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)
{
        return desc ? desc->chip : NULL;
}
EXPORT_SYMBOL_GPL(gpiod_to_chip);

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

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

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

/**
 * 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(const struct gpio_desc *desc)
{
        struct gpio_chip        *chip;
        unsigned                offset;
        int                     status = -EINVAL;

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

        if (!chip->get_direction)
                return status;

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

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

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

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

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

        return err;
}

/**
 * gpiochip_add() - register a gpio_chip
 * @chip: the chip to register, with chip->base initialized
 * Context: potentially before irqs or kmalloc will work
 *
 * Returns a negative errno if the chip can't be registered, such as
 * because the chip->base is invalid or already associated with a
 * different chip.  Otherwise it returns zero as a success code.
 *
 * When gpiochip_add() is called very early during boot, so that GPIOs
 * can be freely used, the chip->dev device must be registered before
 * the gpio framework's arch_initcall().  Otherwise sysfs initialization
 * for GPIOs will fail rudely.
 *
 * If chip->base is negative, this requests dynamic assignment of
 * a range of valid GPIOs.
 */
int gpiochip_add(struct gpio_chip *chip)
{
        unsigned long   flags;
        int             status = 0;
        unsigned        id;
        int             base = chip->base;

        if ((!gpio_is_valid(base) || !gpio_is_valid(base + chip->ngpio - 1))
                        && base >= 0) {
                status = -EINVAL;
                goto fail;
        }

        spin_lock_irqsave(&gpio_lock, flags);

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

        status = gpiochip_add_to_list(chip);

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

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

                        /* REVISIT:  most hardware initializes GPIOs as
                         * inputs (often with pullups enabled) so power
                         * usage is minimized.  Linux code should set the
                         * gpio direction first thing; but until it does,
                         * and in case chip->get_direction is not set,
                         * we may expose the wrong direction in sysfs.
                         */
                        desc->flags = !chip->direction_input
                                ? (1 << FLAG_IS_OUT)
                                : 0;
                }
        }

        spin_unlock_irqrestore(&gpio_lock, flags);

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

        of_gpiochip_add(chip);
        acpi_gpiochip_add(chip);

        if (status)
                goto fail;

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

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

        return 0;

unlock:
        spin_unlock_irqrestore(&gpio_lock, flags);
fail:
        /* failures here can mean systems won't boot... */
        pr_err("%s: GPIOs %d..%d (%s) failed to register\n", __func__,
                chip->base, chip->base + chip->ngpio - 1,
                chip->label ? : "generic");
        return status;
}
EXPORT_SYMBOL_GPL(gpiochip_add);

/* Forward-declaration */
static void gpiochip_irqchip_remove(struct gpio_chip *gpiochip);

/**
 * gpiochip_remove() - unregister a gpio_chip
 * @chip: the chip to unregister
 *
 * A gpio_chip with any GPIOs still requested may not be removed.
 */
int gpiochip_remove(struct gpio_chip *chip)
{
        unsigned long   flags;
        int             status = 0;
        unsigned        id;

        acpi_gpiochip_remove(chip);

        spin_lock_irqsave(&gpio_lock, flags);

        gpiochip_irqchip_remove(chip);
        gpiochip_remove_pin_ranges(chip);
        of_gpiochip_remove(chip);

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

                list_del(&chip->list);
        }

        spin_unlock_irqrestore(&gpio_lock, flags);

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

        return status;
}
EXPORT_SYMBOL_GPL(gpiochip_remove);

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

        spin_lock_irqsave(&gpio_lock, flags);
        list_for_each_entry(chip, &gpio_chips, list)
                if (match(chip, data))
                        break;

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

        return chip;
}
EXPORT_SYMBOL_GPL(gpiochip_find);

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_add_chained_irqchip() - adds a chained irqchip to a gpiochip
 * @gpiochip: the gpiochip to add the irqchip to
 * @irqchip: the irqchip to add 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
 */
void gpiochip_set_chained_irqchip(struct gpio_chip *gpiochip,
                                  struct irq_chip *irqchip,
                                  int parent_irq,
                                  irq_flow_handler_t parent_handler)
{
        if (gpiochip->can_sleep) {
                chip_err(gpiochip, "you cannot have chained interrupts on a chip that may sleep\n");
                return;
        }

        irq_set_chained_handler(parent_irq, parent_handler);
        /*
         * The parent irqchip is already using the chip_data for this
         * irqchip, so our callbacks simply use the handler_data.
         */
        irq_set_handler_data(parent_irq, gpiochip);
}
EXPORT_SYMBOL_GPL(gpiochip_set_chained_irqchip);

/*
 * This lock class tells lockdep that GPIO irqs are in a different
 * category than their parents, so it won't report false recursion.
 */
static struct lock_class_key gpiochip_irq_lock_class;

/**
 * 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);
        irq_set_lockdep_class(irq, &gpiochip_irq_lock_class);
        irq_set_chip_and_handler(irq, chip->irqchip, chip->irq_handler);
        /* Chips that can sleep need nested thread handlers */
        if (chip->can_sleep)
                irq_set_nested_thread(irq, 1);
#ifdef CONFIG_ARM
        set_irq_flags(irq, IRQF_VALID);
#else
        irq_set_noprobe(irq);
#endif
        /*
         * 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;

#ifdef CONFIG_ARM
        set_irq_flags(irq, 0);
#endif
        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 (gpio_lock_as_irq(chip, d->hwirq)) {
                chip_err(chip,
                        "unable to lock HW IRQ %lu for IRQ\n",
                        d->hwirq);
                return -EINVAL;
        }
        return 0;
}

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

        gpio_unlock_as_irq(chip, d->hwirq);
}

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;

        /* Remove all IRQ mappings and delete the domain */
        if (gpiochip->irqdomain) {
                for (offset = 0; offset < gpiochip->ngpio; offset++)
                        irq_dispose_mapping(gpiochip->irq_base + 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.
 *
 * 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 container_of() 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 device_node *of_node;
        unsigned int offset;
        unsigned irq_base = 0;

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

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

        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 */

#ifdef CONFIG_PINCTRL

/**
 * gpiochip_add_pingroup_range() - add a range for GPIO <-> pin mapping
 * @chip: the gpiochip to add the range for
 * @pinctrl: the dev_name() of 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;
        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 = chip->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, &chip->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;
        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 = chip->base + gpio_offset;
        pin_range->range.pin_base = pin_offset;
        pin_range->range.npins = npins;
        pin_range->pctldev = pinctrl_find_and_add_gpio_range(pinctl_name,
                        &pin_range->range);
        if (IS_ERR(pin_range->pctldev)) {
                ret = PTR_ERR(pin_range->pctldev);
                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, &chip->pin_ranges);

        return 0;
}
EXPORT_SYMBOL_GPL(gpiochip_add_pin_range);

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

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

#endif /* CONFIG_PINCTRL */

/* These "optional" allocation calls help prevent drivers from stomping
 * on each other, and help provide better diagnostics in debugfs.
 * They're called even less than the "set direction" calls.
 */
static int __gpiod_request(struct gpio_desc *desc, const char *label)
{
        struct gpio_chip        *chip = desc->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:
        spin_unlock_irqrestore(&gpio_lock, flags);
        return status;
}

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

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

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

        if (try_module_get(chip->owner)) {
                status = __gpiod_request(desc, label);
                if (status < 0)
                        module_put(chip->owner);
        }

done:
        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->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);
                ret = true;
        }

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

void gpiod_free(struct gpio_desc *desc)
{
        if (desc && __gpiod_free(desc))
                module_put(desc->chip->owner);
        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 (!GPIO_OFFSET_VALID(chip, offset))
                return NULL;

        desc = &chip->desc[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).
 */
int gpiochip_request_own_desc(struct gpio_desc *desc, const char *label)
{
        if (!desc || !desc->chip)
                return -EINVAL;

        return __gpiod_request(desc, label);
}

/**
 * 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);
}

/* 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;

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

        chip = desc->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        *chip;
        int                     status = -EINVAL;

        /* 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;
        }

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

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

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

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

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

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

        chip = desc->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)
{
        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 bool _gpiod_get_raw_value(const struct gpio_desc *desc)
{
        struct gpio_chip        *chip;
        bool value;
        int offset;

        chip = desc->chip;
        offset = gpio_chip_hwgpio(desc);
        value = chip->get ? chip->get(chip, offset) : false;
        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.
 *
 * 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)
{
        if (!desc)
                return 0;
        /* Should be using gpio_get_value_cansleep() */
        WARN_ON(desc->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.
 *
 * 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;
        if (!desc)
                return 0;
        /* Should be using gpio_get_value_cansleep() */
        WARN_ON(desc->chip->can_sleep);

        value = _gpiod_get_raw_value(desc);
        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 otherise 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->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 otherise 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->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->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);
}

/**
 * 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)
{
        if (!desc)
                return;
        /* Should be using gpio_set_value_cansleep() */
        WARN_ON(desc->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)
{
        if (!desc)
                return;
        /* Should be using gpio_set_value_cansleep() */
        WARN_ON(desc->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_cansleep() - report whether gpio value access may sleep
 * @desc: gpio to check
 *
 */
int gpiod_cansleep(const struct gpio_desc *desc)
{
        if (!desc)
                return 0;
        return desc->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;

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

/**
 * gpio_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 gpio_lock_as_irq(struct gpio_chip *chip, unsigned int offset)
{
        if (offset >= chip->ngpio)
                return -EINVAL;

        if (test_bit(FLAG_IS_OUT, &chip->desc[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->desc[offset].flags);
        return 0;
}
EXPORT_SYMBOL_GPL(gpio_lock_as_irq);

/**
 * gpio_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 gpio_unlock_as_irq(struct gpio_chip *chip, unsigned int offset)
{
        if (offset >= chip->ngpio)
                return;

        clear_bit(FLAG_USED_AS_IRQ, &chip->desc[offset].flags);
}
EXPORT_SYMBOL_GPL(gpio_unlock_as_irq);

/**
 * 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.
 *
 * 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);
        if (!desc)
                return 0;
        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.
 *
 * 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);
        if (!desc)
                return 0;

        value = _gpiod_get_raw_value(desc);
        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);
        if (!desc)
                return;
        _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);
        if (!desc)
                return;

        if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
                value = !value;
        _gpiod_set_raw_value(desc, value);
}
EXPORT_SYMBOL_GPL(gpiod_set_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);
}

static struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id,
                                      unsigned int idx,
                                      enum gpio_lookup_flags *flags)
{
        static const char *suffixes[] = { "gpios", "gpio" };
        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(suffixes); i++) {
                if (con_id)
                        snprintf(prop_name, 32, "%s-%s", con_id, suffixes[i]);
                else
                        snprintf(prop_name, 32, "%s", 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;

        return desc;
}

static struct gpio_desc *acpi_find_gpio(struct device *dev, const char *con_id,
                                        unsigned int idx,
                                        enum gpio_lookup_flags *flags)
{
        struct acpi_gpio_info info;
        struct gpio_desc *desc;

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

        if (info.gpioint && info.active_low)
                *flags |= 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;
}

/**
 * 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
 *
 * 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 occured while trying to acquire the GPIO.
 */
struct gpio_desc *__must_check gpiod_get(struct device *dev, const char *con_id)
{
        return gpiod_get_index(dev, con_id, 0);
}
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
 *
 * 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)
{
        return gpiod_get_index_optional(dev, con_id, 0);
}
EXPORT_SYMBOL_GPL(gpiod_get_optional);

/**
 * 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
 *
 * 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
 * occured while trying to acquire the GPIO.
 */
struct gpio_desc *__must_check gpiod_get_index(struct device *dev,
                                               const char *con_id,
                                               unsigned int idx)
{
        struct gpio_desc *desc = NULL;
        int status;
        enum gpio_lookup_flags flags = 0;

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

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

        /*
         * 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");
                desc = gpiod_find(dev, con_id, idx, &flags);
        }

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

        status = gpiod_request(desc, con_id);

        if (status < 0)
                return ERR_PTR(status);

        if (flags & GPIO_ACTIVE_LOW)
                set_bit(FLAG_ACTIVE_LOW, &desc->flags);
        if (flags & GPIO_OPEN_DRAIN)
                set_bit(FLAG_OPEN_DRAIN, &desc->flags);
        if (flags & GPIO_OPEN_SOURCE)
                set_bit(FLAG_OPEN_SOURCE, &desc->flags);

        return desc;
}
EXPORT_SYMBOL_GPL(gpiod_get_index);

/**
 * 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
 *
 * 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)
{
        struct gpio_desc *desc;

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

        return desc;
}
EXPORT_SYMBOL_GPL(gpiod_get_index_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);

#ifdef CONFIG_DEBUG_FS

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

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

                gpiod_get_direction(gdesc);
                is_out = test_bit(FLAG_IS_OUT, &gdesc->flags);
                is_irq = test_bit(FLAG_USED_AS_IRQ, &gdesc->flags);
                seq_printf(s, " gpio-%-3d (%-20.20s) %s %s %s",
                        gpio, 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_chip *chip = NULL;
        loff_t index = *pos;

        s->private = "";

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

        return NULL;
}

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

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

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

        return ret;
}

static void gpiolib_seq_stop(struct seq_file *s, void *v)
{
}

static int gpiolib_seq_show(struct seq_file *s, void *v)
{
        struct gpio_chip *chip = v;
        struct device *dev;

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

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

        return 0;
}

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

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

static const struct file_operations gpiolib_operations = {
        .owner          = THIS_MODULE,
        .open           = gpiolib_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = seq_release,
};

static int __init gpiolib_debugfs_init(void)
{
        /* /sys/kernel/debug/gpio */
        (void) debugfs_create_file("gpio", S_IFREG | S_IRUGO,
                                NULL, NULL, &gpiolib_operations);
        return 0;
}
subsys_initcall(gpiolib_debugfs_init);

#endif  /* DEBUG_FS */