// SPDX-License-Identifier: GPL-2.0

#include <linux/anon_inodes.h>
#include <linux/atomic.h>
#include <linux/bitmap.h>
#include <linux/build_bug.h>
#include <linux/cdev.h>
#include <linux/compat.h>
#include <linux/compiler.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/file.h>
#include <linux/gpio.h>
#include <linux/gpio/driver.h>
#include <linux/interrupt.h>
#include <linux/irqreturn.h>
#include <linux/kernel.h>
#include <linux/kfifo.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/pinctrl/consumer.h>
#include <linux/poll.h>
#include <linux/spinlock.h>
#include <linux/timekeeping.h>
#include <linux/uaccess.h>
#include <linux/workqueue.h>
#include <uapi/linux/gpio.h>

#include "gpiolib.h"
#include "gpiolib-cdev.h"

/*
 * Array sizes must ensure 64-bit alignment and not create holes in the
 * struct packing.
 */
static_assert(IS_ALIGNED(GPIO_V2_LINES_MAX, 2));
static_assert(IS_ALIGNED(GPIO_MAX_NAME_SIZE, 8));

/*
 * Check that uAPI structs are 64-bit aligned for 32/64-bit compatibility
 */
static_assert(IS_ALIGNED(sizeof(struct gpio_v2_line_attribute), 8));
static_assert(IS_ALIGNED(sizeof(struct gpio_v2_line_config_attribute), 8));
static_assert(IS_ALIGNED(sizeof(struct gpio_v2_line_config), 8));
static_assert(IS_ALIGNED(sizeof(struct gpio_v2_line_request), 8));
static_assert(IS_ALIGNED(sizeof(struct gpio_v2_line_info), 8));
static_assert(IS_ALIGNED(sizeof(struct gpio_v2_line_info_changed), 8));
static_assert(IS_ALIGNED(sizeof(struct gpio_v2_line_event), 8));
static_assert(IS_ALIGNED(sizeof(struct gpio_v2_line_values), 8));

/* Character device interface to GPIO.
 *
 * The GPIO character device, /dev/gpiochipN, provides userspace an
 * interface to gpiolib GPIOs via ioctl()s.
 */

/*
 * GPIO line handle management
 */

#ifdef CONFIG_GPIO_CDEV_V1
/**
 * struct linehandle_state - contains the state of a userspace handle
 * @gdev: the GPIO device the handle pertains to
 * @label: consumer label used to tag descriptors
 * @descs: the GPIO descriptors held by this handle
 * @num_descs: the number of descriptors held in the descs array
 */
struct linehandle_state {
        struct gpio_device *gdev;
        const char *label;
        struct gpio_desc *descs[GPIOHANDLES_MAX];
        u32 num_descs;
};

#define GPIOHANDLE_REQUEST_VALID_FLAGS \
        (GPIOHANDLE_REQUEST_INPUT | \
        GPIOHANDLE_REQUEST_OUTPUT | \
        GPIOHANDLE_REQUEST_ACTIVE_LOW | \
        GPIOHANDLE_REQUEST_BIAS_PULL_UP | \
        GPIOHANDLE_REQUEST_BIAS_PULL_DOWN | \
        GPIOHANDLE_REQUEST_BIAS_DISABLE | \
        GPIOHANDLE_REQUEST_OPEN_DRAIN | \
        GPIOHANDLE_REQUEST_OPEN_SOURCE)

static int linehandle_validate_flags(u32 flags)
{
        /* Return an error if an unknown flag is set */
        if (flags & ~GPIOHANDLE_REQUEST_VALID_FLAGS)
                return -EINVAL;

        /*
         * Do not allow both INPUT & OUTPUT flags to be set as they are
         * contradictory.
         */
        if ((flags & GPIOHANDLE_REQUEST_INPUT) &&
            (flags & GPIOHANDLE_REQUEST_OUTPUT))
                return -EINVAL;

        /*
         * Do not allow OPEN_SOURCE & OPEN_DRAIN flags in a single request. If
         * the hardware actually supports enabling both at the same time the
         * electrical result would be disastrous.
         */
        if ((flags & GPIOHANDLE_REQUEST_OPEN_DRAIN) &&
            (flags & GPIOHANDLE_REQUEST_OPEN_SOURCE))
                return -EINVAL;

        /* OPEN_DRAIN and OPEN_SOURCE flags only make sense for output mode. */
        if (!(flags & GPIOHANDLE_REQUEST_OUTPUT) &&
            ((flags & GPIOHANDLE_REQUEST_OPEN_DRAIN) ||
             (flags & GPIOHANDLE_REQUEST_OPEN_SOURCE)))
                return -EINVAL;

        /* Bias flags only allowed for input or output mode. */
        if (!((flags & GPIOHANDLE_REQUEST_INPUT) ||
              (flags & GPIOHANDLE_REQUEST_OUTPUT)) &&
            ((flags & GPIOHANDLE_REQUEST_BIAS_DISABLE) ||
             (flags & GPIOHANDLE_REQUEST_BIAS_PULL_UP) ||
             (flags & GPIOHANDLE_REQUEST_BIAS_PULL_DOWN)))
                return -EINVAL;

        /* Only one bias flag can be set. */
        if (((flags & GPIOHANDLE_REQUEST_BIAS_DISABLE) &&
             (flags & (GPIOHANDLE_REQUEST_BIAS_PULL_DOWN |
                       GPIOHANDLE_REQUEST_BIAS_PULL_UP))) ||
            ((flags & GPIOHANDLE_REQUEST_BIAS_PULL_DOWN) &&
             (flags & GPIOHANDLE_REQUEST_BIAS_PULL_UP)))
                return -EINVAL;

        return 0;
}

static void linehandle_flags_to_desc_flags(u32 lflags, unsigned long *flagsp)
{
        assign_bit(FLAG_ACTIVE_LOW, flagsp,
                   lflags & GPIOHANDLE_REQUEST_ACTIVE_LOW);
        assign_bit(FLAG_OPEN_DRAIN, flagsp,
                   lflags & GPIOHANDLE_REQUEST_OPEN_DRAIN);
        assign_bit(FLAG_OPEN_SOURCE, flagsp,
                   lflags & GPIOHANDLE_REQUEST_OPEN_SOURCE);
        assign_bit(FLAG_PULL_UP, flagsp,
                   lflags & GPIOHANDLE_REQUEST_BIAS_PULL_UP);
        assign_bit(FLAG_PULL_DOWN, flagsp,
                   lflags & GPIOHANDLE_REQUEST_BIAS_PULL_DOWN);
        assign_bit(FLAG_BIAS_DISABLE, flagsp,
                   lflags & GPIOHANDLE_REQUEST_BIAS_DISABLE);
}

static long linehandle_set_config(struct linehandle_state *lh,
                                  void __user *ip)
{
        struct gpiohandle_config gcnf;
        struct gpio_desc *desc;
        int i, ret;
        u32 lflags;

        if (copy_from_user(&gcnf, ip, sizeof(gcnf)))
                return -EFAULT;

        lflags = gcnf.flags;
        ret = linehandle_validate_flags(lflags);
        if (ret)
                return ret;

        for (i = 0; i < lh->num_descs; i++) {
                desc = lh->descs[i];
                linehandle_flags_to_desc_flags(gcnf.flags, &desc->flags);

                /*
                 * Lines have to be requested explicitly for input
                 * or output, else the line will be treated "as is".
                 */
                if (lflags & GPIOHANDLE_REQUEST_OUTPUT) {
                        int val = !!gcnf.default_values[i];

                        ret = gpiod_direction_output(desc, val);
                        if (ret)
                                return ret;
                } else if (lflags & GPIOHANDLE_REQUEST_INPUT) {
                        ret = gpiod_direction_input(desc);
                        if (ret)
                                return ret;
                }

                blocking_notifier_call_chain(&desc->gdev->notifier,
                                             GPIO_V2_LINE_CHANGED_CONFIG,
                                             desc);
        }
        return 0;
}

static long linehandle_ioctl(struct file *file, unsigned int cmd,
                             unsigned long arg)
{
        struct linehandle_state *lh = file->private_data;
        void __user *ip = (void __user *)arg;
        struct gpiohandle_data ghd;
        DECLARE_BITMAP(vals, GPIOHANDLES_MAX);
        int i;

        if (cmd == GPIOHANDLE_GET_LINE_VALUES_IOCTL) {
                /* NOTE: It's ok to read values of output lines. */
                int ret = gpiod_get_array_value_complex(false,
                                                        true,
                                                        lh->num_descs,
                                                        lh->descs,
                                                        NULL,
                                                        vals);
                if (ret)
                        return ret;

                memset(&ghd, 0, sizeof(ghd));
                for (i = 0; i < lh->num_descs; i++)
                        ghd.values[i] = test_bit(i, vals);

                if (copy_to_user(ip, &ghd, sizeof(ghd)))
                        return -EFAULT;

                return 0;
        } else if (cmd == GPIOHANDLE_SET_LINE_VALUES_IOCTL) {
                /*
                 * All line descriptors were created at once with the same
                 * flags so just check if the first one is really output.
                 */
                if (!test_bit(FLAG_IS_OUT, &lh->descs[0]->flags))
                        return -EPERM;

                if (copy_from_user(&ghd, ip, sizeof(ghd)))
                        return -EFAULT;

                /* Clamp all values to [0,1] */
                for (i = 0; i < lh->num_descs; i++)
                        __assign_bit(i, vals, ghd.values[i]);

                /* Reuse the array setting function */
                return gpiod_set_array_value_complex(false,
                                                     true,
                                                     lh->num_descs,
                                                     lh->descs,
                                                     NULL,
                                                     vals);
        } else if (cmd == GPIOHANDLE_SET_CONFIG_IOCTL) {
                return linehandle_set_config(lh, ip);
        }
        return -EINVAL;
}

#ifdef CONFIG_COMPAT
static long linehandle_ioctl_compat(struct file *file, unsigned int cmd,
                                    unsigned long arg)
{
        return linehandle_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
}
#endif

static void linehandle_free(struct linehandle_state *lh)
{
        int i;

        for (i = 0; i < lh->num_descs; i++)
                if (lh->descs[i])
                        gpiod_free(lh->descs[i]);
        kfree(lh->label);
        put_device(&lh->gdev->dev);
        kfree(lh);
}

static int linehandle_release(struct inode *inode, struct file *file)
{
        linehandle_free(file->private_data);
        return 0;
}

static const struct file_operations linehandle_fileops = {
        .release = linehandle_release,
        .owner = THIS_MODULE,
        .llseek = noop_llseek,
        .unlocked_ioctl = linehandle_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl = linehandle_ioctl_compat,
#endif
};

static int linehandle_create(struct gpio_device *gdev, void __user *ip)
{
        struct gpiohandle_request handlereq;
        struct linehandle_state *lh;
        struct file *file;
        int fd, i, ret;
        u32 lflags;

        if (copy_from_user(&handlereq, ip, sizeof(handlereq)))
                return -EFAULT;
        if ((handlereq.lines == 0) || (handlereq.lines > GPIOHANDLES_MAX))
                return -EINVAL;

        lflags = handlereq.flags;

        ret = linehandle_validate_flags(lflags);
        if (ret)
                return ret;

        lh = kzalloc(sizeof(*lh), GFP_KERNEL);
        if (!lh)
                return -ENOMEM;
        lh->gdev = gdev;
        get_device(&gdev->dev);

        if (handlereq.consumer_label[0] != '\0') {
                /* label is only initialized if consumer_label is set */
                lh->label = kstrndup(handlereq.consumer_label,
                                     sizeof(handlereq.consumer_label) - 1,
                                     GFP_KERNEL);
                if (!lh->label) {
                        ret = -ENOMEM;
                        goto out_free_lh;
                }
        }

        lh->num_descs = handlereq.lines;

        /* Request each GPIO */
        for (i = 0; i < handlereq.lines; i++) {
                u32 offset = handlereq.lineoffsets[i];
                struct gpio_desc *desc = gpiochip_get_desc(gdev->chip, offset);

                if (IS_ERR(desc)) {
                        ret = PTR_ERR(desc);
                        goto out_free_lh;
                }

                ret = gpiod_request(desc, lh->label);
                if (ret)
                        goto out_free_lh;
                lh->descs[i] = desc;
                linehandle_flags_to_desc_flags(handlereq.flags, &desc->flags);

                ret = gpiod_set_transitory(desc, false);
                if (ret < 0)
                        goto out_free_lh;

                /*
                 * Lines have to be requested explicitly for input
                 * or output, else the line will be treated "as is".
                 */
                if (lflags & GPIOHANDLE_REQUEST_OUTPUT) {
                        int val = !!handlereq.default_values[i];

                        ret = gpiod_direction_output(desc, val);
                        if (ret)
                                goto out_free_lh;
                } else if (lflags & GPIOHANDLE_REQUEST_INPUT) {
                        ret = gpiod_direction_input(desc);
                        if (ret)
                                goto out_free_lh;
                }

                blocking_notifier_call_chain(&desc->gdev->notifier,
                                             GPIO_V2_LINE_CHANGED_REQUESTED, desc);

                dev_dbg(&gdev->dev, "registered chardev handle for line %d\n",
                        offset);
        }

        fd = get_unused_fd_flags(O_RDONLY | O_CLOEXEC);
        if (fd < 0) {
                ret = fd;
                goto out_free_lh;
        }

        file = anon_inode_getfile("gpio-linehandle",
                                  &linehandle_fileops,
                                  lh,
                                  O_RDONLY | O_CLOEXEC);
        if (IS_ERR(file)) {
                ret = PTR_ERR(file);
                goto out_put_unused_fd;
        }

        handlereq.fd = fd;
        if (copy_to_user(ip, &handlereq, sizeof(handlereq))) {
                /*
                 * fput() will trigger the release() callback, so do not go onto
                 * the regular error cleanup path here.
                 */
                fput(file);
                put_unused_fd(fd);
                return -EFAULT;
        }

        fd_install(fd, file);

        dev_dbg(&gdev->dev, "registered chardev handle for %d lines\n",
                lh->num_descs);

        return 0;

out_put_unused_fd:
        put_unused_fd(fd);
out_free_lh:
        linehandle_free(lh);
        return ret;
}
#endif /* CONFIG_GPIO_CDEV_V1 */

/**
 * struct line - contains the state of a requested line
 * @desc: the GPIO descriptor for this line.
 * @req: the corresponding line request
 * @irq: the interrupt triggered in response to events on this GPIO
 * @eflags: the edge flags, GPIO_V2_LINE_FLAG_EDGE_RISING and/or
 * GPIO_V2_LINE_FLAG_EDGE_FALLING, indicating the edge detection applied
 * @timestamp_ns: cache for the timestamp storing it between hardirq and
 * IRQ thread, used to bring the timestamp close to the actual event
 * @req_seqno: the seqno for the current edge event in the sequence of
 * events for the corresponding line request. This is drawn from the @req.
 * @line_seqno: the seqno for the current edge event in the sequence of
 * events for this line.
 * @work: the worker that implements software debouncing
 * @sw_debounced: flag indicating if the software debouncer is active
 * @level: the current debounced physical level of the line
 */
struct line {
        struct gpio_desc *desc;
        /*
         * -- edge detector specific fields --
         */
        struct linereq *req;
        unsigned int irq;
        /*
         * eflags is set by edge_detector_setup(), edge_detector_stop() and
         * edge_detector_update(), which are themselves mutually exclusive,
         * and is accessed by edge_irq_thread() and debounce_work_func(),
         * which can both live with a slightly stale value.
         */
        u64 eflags;
        /*
         * timestamp_ns and req_seqno are accessed only by
         * edge_irq_handler() and edge_irq_thread(), which are themselves
         * mutually exclusive, so no additional protection is necessary.
         */
        u64 timestamp_ns;
        u32 req_seqno;
        /*
         * line_seqno is accessed by either edge_irq_thread() or
         * debounce_work_func(), which are themselves mutually exclusive,
         * so no additional protection is necessary.
         */
        u32 line_seqno;
        /*
         * -- debouncer specific fields --
         */
        struct delayed_work work;
        /*
         * sw_debounce is accessed by linereq_set_config(), which is the
         * only setter, and linereq_get_values(), which can live with a
         * slightly stale value.
         */
        unsigned int sw_debounced;
        /*
         * level is accessed by debounce_work_func(), which is the only
         * setter, and linereq_get_values() which can live with a slightly
         * stale value.
         */
        unsigned int level;
};

/**
 * struct linereq - contains the state of a userspace line request
 * @gdev: the GPIO device the line request pertains to
 * @label: consumer label used to tag GPIO descriptors
 * @num_lines: the number of lines in the lines array
 * @wait: wait queue that handles blocking reads of events
 * @event_buffer_size: the number of elements allocated in @events
 * @events: KFIFO for the GPIO events
 * @seqno: the sequence number for edge events generated on all lines in
 * this line request.  Note that this is not used when @num_lines is 1, as
 * the line_seqno is then the same and is cheaper to calculate.
 * @config_mutex: mutex for serializing ioctl() calls to ensure consistency
 * of configuration, particularly multi-step accesses to desc flags.
 * @lines: the lines held by this line request, with @num_lines elements.
 */
struct linereq {
        struct gpio_device *gdev;
        const char *label;
        u32 num_lines;
        wait_queue_head_t wait;
        u32 event_buffer_size;
        DECLARE_KFIFO_PTR(events, struct gpio_v2_line_event);
        atomic_t seqno;
        struct mutex config_mutex;
        struct line lines[];
};

#define GPIO_V2_LINE_BIAS_FLAGS \
        (GPIO_V2_LINE_FLAG_BIAS_PULL_UP | \
         GPIO_V2_LINE_FLAG_BIAS_PULL_DOWN | \
         GPIO_V2_LINE_FLAG_BIAS_DISABLED)

#define GPIO_V2_LINE_DIRECTION_FLAGS \
        (GPIO_V2_LINE_FLAG_INPUT | \
         GPIO_V2_LINE_FLAG_OUTPUT)

#define GPIO_V2_LINE_DRIVE_FLAGS \
        (GPIO_V2_LINE_FLAG_OPEN_DRAIN | \
         GPIO_V2_LINE_FLAG_OPEN_SOURCE)

#define GPIO_V2_LINE_EDGE_FLAGS \
        (GPIO_V2_LINE_FLAG_EDGE_RISING | \
         GPIO_V2_LINE_FLAG_EDGE_FALLING)

#define GPIO_V2_LINE_FLAG_EDGE_BOTH GPIO_V2_LINE_EDGE_FLAGS

#define GPIO_V2_LINE_VALID_FLAGS \
        (GPIO_V2_LINE_FLAG_ACTIVE_LOW | \
         GPIO_V2_LINE_DIRECTION_FLAGS | \
         GPIO_V2_LINE_DRIVE_FLAGS | \
         GPIO_V2_LINE_EDGE_FLAGS | \
         GPIO_V2_LINE_FLAG_EVENT_CLOCK_REALTIME | \
         GPIO_V2_LINE_BIAS_FLAGS)

static void linereq_put_event(struct linereq *lr,
                              struct gpio_v2_line_event *le)
{
        bool overflow = false;

        spin_lock(&lr->wait.lock);
        if (kfifo_is_full(&lr->events)) {
                overflow = true;
                kfifo_skip(&lr->events);
        }
        kfifo_in(&lr->events, le, 1);
        spin_unlock(&lr->wait.lock);
        if (!overflow)
                wake_up_poll(&lr->wait, EPOLLIN);
        else
                pr_debug_ratelimited("event FIFO is full - event dropped\n");
}

static u64 line_event_timestamp(struct line *line)
{
        if (test_bit(FLAG_EVENT_CLOCK_REALTIME, &line->desc->flags))
                return ktime_get_real_ns();

        return ktime_get_ns();
}

static irqreturn_t edge_irq_thread(int irq, void *p)
{
        struct line *line = p;
        struct linereq *lr = line->req;
        struct gpio_v2_line_event le;
        u64 eflags;

        /* Do not leak kernel stack to userspace */
        memset(&le, 0, sizeof(le));

        if (line->timestamp_ns) {
                le.timestamp_ns = line->timestamp_ns;
        } else {
                /*
                 * We may be running from a nested threaded interrupt in
                 * which case we didn't get the timestamp from
                 * edge_irq_handler().
                 */
                le.timestamp_ns = line_event_timestamp(line);
                if (lr->num_lines != 1)
                        line->req_seqno = atomic_inc_return(&lr->seqno);
        }
        line->timestamp_ns = 0;

        eflags = READ_ONCE(line->eflags);
        if (eflags == GPIO_V2_LINE_FLAG_EDGE_BOTH) {
                int level = gpiod_get_value_cansleep(line->desc);

                if (level)
                        /* Emit low-to-high event */
                        le.id = GPIO_V2_LINE_EVENT_RISING_EDGE;
                else
                        /* Emit high-to-low event */
                        le.id = GPIO_V2_LINE_EVENT_FALLING_EDGE;
        } else if (eflags == GPIO_V2_LINE_FLAG_EDGE_RISING) {
                /* Emit low-to-high event */
                le.id = GPIO_V2_LINE_EVENT_RISING_EDGE;
        } else if (eflags == GPIO_V2_LINE_FLAG_EDGE_FALLING) {
                /* Emit high-to-low event */
                le.id = GPIO_V2_LINE_EVENT_FALLING_EDGE;
        } else {
                return IRQ_NONE;
        }
        line->line_seqno++;
        le.line_seqno = line->line_seqno;
        le.seqno = (lr->num_lines == 1) ? le.line_seqno : line->req_seqno;
        le.offset = gpio_chip_hwgpio(line->desc);

        linereq_put_event(lr, &le);

        return IRQ_HANDLED;
}

static irqreturn_t edge_irq_handler(int irq, void *p)
{
        struct line *line = p;
        struct linereq *lr = line->req;

        /*
         * Just store the timestamp in hardirq context so we get it as
         * close in time as possible to the actual event.
         */
        line->timestamp_ns = line_event_timestamp(line);

        if (lr->num_lines != 1)
                line->req_seqno = atomic_inc_return(&lr->seqno);

        return IRQ_WAKE_THREAD;
}

/*
 * returns the current debounced logical value.
 */
static bool debounced_value(struct line *line)
{
        bool value;

        /*
         * minor race - debouncer may be stopped here, so edge_detector_stop()
         * must leave the value unchanged so the following will read the level
         * from when the debouncer was last running.
         */
        value = READ_ONCE(line->level);

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

        return value;
}

static irqreturn_t debounce_irq_handler(int irq, void *p)
{
        struct line *line = p;

        mod_delayed_work(system_wq, &line->work,
                usecs_to_jiffies(READ_ONCE(line->desc->debounce_period_us)));

        return IRQ_HANDLED;
}

static void debounce_work_func(struct work_struct *work)
{
        struct gpio_v2_line_event le;
        struct line *line = container_of(work, struct line, work.work);
        struct linereq *lr;
        int level;
        u64 eflags;

        level = gpiod_get_raw_value_cansleep(line->desc);
        if (level < 0) {
                pr_debug_ratelimited("debouncer failed to read line value\n");
                return;
        }

        if (READ_ONCE(line->level) == level)
                return;

        WRITE_ONCE(line->level, level);

        /* -- edge detection -- */
        eflags = READ_ONCE(line->eflags);
        if (!eflags)
                return;

        /* switch from physical level to logical - if they differ */
        if (test_bit(FLAG_ACTIVE_LOW, &line->desc->flags))
                level = !level;

        /* ignore edges that are not being monitored */
        if (((eflags == GPIO_V2_LINE_FLAG_EDGE_RISING) && !level) ||
            ((eflags == GPIO_V2_LINE_FLAG_EDGE_FALLING) && level))
                return;

        /* Do not leak kernel stack to userspace */
        memset(&le, 0, sizeof(le));

        lr = line->req;
        le.timestamp_ns = line_event_timestamp(line);
        le.offset = gpio_chip_hwgpio(line->desc);
        line->line_seqno++;
        le.line_seqno = line->line_seqno;
        le.seqno = (lr->num_lines == 1) ?
                le.line_seqno : atomic_inc_return(&lr->seqno);

        if (level)
                /* Emit low-to-high event */
                le.id = GPIO_V2_LINE_EVENT_RISING_EDGE;
        else
                /* Emit high-to-low event */
                le.id = GPIO_V2_LINE_EVENT_FALLING_EDGE;

        linereq_put_event(lr, &le);
}

static int debounce_setup(struct line *line,
                          unsigned int debounce_period_us)
{
        unsigned long irqflags;
        int ret, level, irq;

        /* try hardware */
        ret = gpiod_set_debounce(line->desc, debounce_period_us);
        if (!ret) {
                WRITE_ONCE(line->desc->debounce_period_us, debounce_period_us);
                return ret;
        }
        if (ret != -ENOTSUPP)
                return ret;

        if (debounce_period_us) {
                /* setup software debounce */
                level = gpiod_get_raw_value_cansleep(line->desc);
                if (level < 0)
                        return level;

                irq = gpiod_to_irq(line->desc);
                if (irq < 0)
                        return -ENXIO;

                WRITE_ONCE(line->level, level);
                irqflags = IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING;
                ret = request_irq(irq, debounce_irq_handler, irqflags,
                                  line->req->label, line);
                if (ret)
                        return ret;

                WRITE_ONCE(line->sw_debounced, 1);
                line->irq = irq;
        }
        return 0;
}

static bool gpio_v2_line_config_debounced(struct gpio_v2_line_config *lc,
                                          unsigned int line_idx)
{
        unsigned int i;
        u64 mask = BIT_ULL(line_idx);

        for (i = 0; i < lc->num_attrs; i++) {
                if ((lc->attrs[i].attr.id == GPIO_V2_LINE_ATTR_ID_DEBOUNCE) &&
                    (lc->attrs[i].mask & mask))
                        return true;
        }
        return false;
}

static u32 gpio_v2_line_config_debounce_period(struct gpio_v2_line_config *lc,
                                               unsigned int line_idx)
{
        unsigned int i;
        u64 mask = BIT_ULL(line_idx);

        for (i = 0; i < lc->num_attrs; i++) {
                if ((lc->attrs[i].attr.id == GPIO_V2_LINE_ATTR_ID_DEBOUNCE) &&
                    (lc->attrs[i].mask & mask))
                        return lc->attrs[i].attr.debounce_period_us;
        }
        return 0;
}

static void edge_detector_stop(struct line *line)
{
        if (line->irq) {
                free_irq(line->irq, line);
                line->irq = 0;
        }

        cancel_delayed_work_sync(&line->work);
        WRITE_ONCE(line->sw_debounced, 0);
        WRITE_ONCE(line->eflags, 0);
        if (line->desc)
                WRITE_ONCE(line->desc->debounce_period_us, 0);
        /* do not change line->level - see comment in debounced_value() */
}

static int edge_detector_setup(struct line *line,
                               struct gpio_v2_line_config *lc,
                               unsigned int line_idx,
                               u64 eflags)
{
        u32 debounce_period_us;
        unsigned long irqflags = 0;
        int irq, ret;

        if (eflags && !kfifo_initialized(&line->req->events)) {
                ret = kfifo_alloc(&line->req->events,
                                  line->req->event_buffer_size, GFP_KERNEL);
                if (ret)
                        return ret;
        }
        WRITE_ONCE(line->eflags, eflags);
        if (gpio_v2_line_config_debounced(lc, line_idx)) {
                debounce_period_us = gpio_v2_line_config_debounce_period(lc, line_idx);
                ret = debounce_setup(line, debounce_period_us);
                if (ret)
                        return ret;
                WRITE_ONCE(line->desc->debounce_period_us, debounce_period_us);
        }

        /* detection disabled or sw debouncer will provide edge detection */
        if (!eflags || READ_ONCE(line->sw_debounced))
                return 0;

        irq = gpiod_to_irq(line->desc);
        if (irq < 0)
                return -ENXIO;

        if (eflags & GPIO_V2_LINE_FLAG_EDGE_RISING)
                irqflags |= test_bit(FLAG_ACTIVE_LOW, &line->desc->flags) ?
                        IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING;
        if (eflags & GPIO_V2_LINE_FLAG_EDGE_FALLING)
                irqflags |= test_bit(FLAG_ACTIVE_LOW, &line->desc->flags) ?
                        IRQF_TRIGGER_RISING : IRQF_TRIGGER_FALLING;
        irqflags |= IRQF_ONESHOT;

        /* Request a thread to read the events */
        ret = request_threaded_irq(irq, edge_irq_handler, edge_irq_thread,
                                   irqflags, line->req->label, line);
        if (ret)
                return ret;

        line->irq = irq;
        return 0;
}

static int edge_detector_update(struct line *line,
                                struct gpio_v2_line_config *lc,
                                unsigned int line_idx,
                                u64 eflags, bool polarity_change)
{
        unsigned int debounce_period_us =
                gpio_v2_line_config_debounce_period(lc, line_idx);

        if ((READ_ONCE(line->eflags) == eflags) && !polarity_change &&
            (READ_ONCE(line->desc->debounce_period_us) == debounce_period_us))
                return 0;

        /* sw debounced and still will be...*/
        if (debounce_period_us && READ_ONCE(line->sw_debounced)) {
                WRITE_ONCE(line->eflags, eflags);
                WRITE_ONCE(line->desc->debounce_period_us, debounce_period_us);
                return 0;
        }

        /* reconfiguring edge detection or sw debounce being disabled */
        if ((line->irq && !READ_ONCE(line->sw_debounced)) ||
            (!debounce_period_us && READ_ONCE(line->sw_debounced)))
                edge_detector_stop(line);

        return edge_detector_setup(line, lc, line_idx, eflags);
}

static u64 gpio_v2_line_config_flags(struct gpio_v2_line_config *lc,
                                     unsigned int line_idx)
{
        unsigned int i;
        u64 mask = BIT_ULL(line_idx);

        for (i = 0; i < lc->num_attrs; i++) {
                if ((lc->attrs[i].attr.id == GPIO_V2_LINE_ATTR_ID_FLAGS) &&
                    (lc->attrs[i].mask & mask))
                        return lc->attrs[i].attr.flags;
        }
        return lc->flags;
}

static int gpio_v2_line_config_output_value(struct gpio_v2_line_config *lc,
                                            unsigned int line_idx)
{
        unsigned int i;
        u64 mask = BIT_ULL(line_idx);

        for (i = 0; i < lc->num_attrs; i++) {
                if ((lc->attrs[i].attr.id == GPIO_V2_LINE_ATTR_ID_OUTPUT_VALUES) &&
                    (lc->attrs[i].mask & mask))
                        return !!(lc->attrs[i].attr.values & mask);
        }
        return 0;
}

static int gpio_v2_line_flags_validate(u64 flags)
{
        /* Return an error if an unknown flag is set */
        if (flags & ~GPIO_V2_LINE_VALID_FLAGS)
                return -EINVAL;

        /*
         * Do not allow both INPUT and OUTPUT flags to be set as they are
         * contradictory.
         */
        if ((flags & GPIO_V2_LINE_FLAG_INPUT) &&
            (flags & GPIO_V2_LINE_FLAG_OUTPUT))
                return -EINVAL;

        /* Edge detection requires explicit input. */
        if ((flags & GPIO_V2_LINE_EDGE_FLAGS) &&
            !(flags & GPIO_V2_LINE_FLAG_INPUT))
                return -EINVAL;

        /*
         * Do not allow OPEN_SOURCE and OPEN_DRAIN flags in a single
         * request. If the hardware actually supports enabling both at the
         * same time the electrical result would be disastrous.
         */
        if ((flags & GPIO_V2_LINE_FLAG_OPEN_DRAIN) &&
            (flags & GPIO_V2_LINE_FLAG_OPEN_SOURCE))
                return -EINVAL;

        /* Drive requires explicit output direction. */
        if ((flags & GPIO_V2_LINE_DRIVE_FLAGS) &&
            !(flags & GPIO_V2_LINE_FLAG_OUTPUT))
                return -EINVAL;

        /* Bias requires explicit direction. */
        if ((flags & GPIO_V2_LINE_BIAS_FLAGS) &&
            !(flags & GPIO_V2_LINE_DIRECTION_FLAGS))
                return -EINVAL;

        /* Only one bias flag can be set. */
        if (((flags & GPIO_V2_LINE_FLAG_BIAS_DISABLED) &&
             (flags & (GPIO_V2_LINE_FLAG_BIAS_PULL_DOWN |
                       GPIO_V2_LINE_FLAG_BIAS_PULL_UP))) ||
            ((flags & GPIO_V2_LINE_FLAG_BIAS_PULL_DOWN) &&
             (flags & GPIO_V2_LINE_FLAG_BIAS_PULL_UP)))
                return -EINVAL;

        return 0;
}

static int gpio_v2_line_config_validate(struct gpio_v2_line_config *lc,
                                        unsigned int num_lines)
{
        unsigned int i;
        u64 flags;
        int ret;

        if (lc->num_attrs > GPIO_V2_LINE_NUM_ATTRS_MAX)
                return -EINVAL;

        if (memchr_inv(lc->padding, 0, sizeof(lc->padding)))
                return -EINVAL;

        for (i = 0; i < num_lines; i++) {
                flags = gpio_v2_line_config_flags(lc, i);
                ret = gpio_v2_line_flags_validate(flags);
                if (ret)
                        return ret;

                /* debounce requires explicit input */
                if (gpio_v2_line_config_debounced(lc, i) &&
                    !(flags & GPIO_V2_LINE_FLAG_INPUT))
                        return -EINVAL;
        }
        return 0;
}

static void gpio_v2_line_config_flags_to_desc_flags(u64 flags,
                                                    unsigned long *flagsp)
{
        assign_bit(FLAG_ACTIVE_LOW, flagsp,
                   flags & GPIO_V2_LINE_FLAG_ACTIVE_LOW);

        if (flags & GPIO_V2_LINE_FLAG_OUTPUT)
                set_bit(FLAG_IS_OUT, flagsp);
        else if (flags & GPIO_V2_LINE_FLAG_INPUT)
                clear_bit(FLAG_IS_OUT, flagsp);

        assign_bit(FLAG_EDGE_RISING, flagsp,
                   flags & GPIO_V2_LINE_FLAG_EDGE_RISING);
        assign_bit(FLAG_EDGE_FALLING, flagsp,
                   flags & GPIO_V2_LINE_FLAG_EDGE_FALLING);

        assign_bit(FLAG_OPEN_DRAIN, flagsp,
                   flags & GPIO_V2_LINE_FLAG_OPEN_DRAIN);
        assign_bit(FLAG_OPEN_SOURCE, flagsp,
                   flags & GPIO_V2_LINE_FLAG_OPEN_SOURCE);

        assign_bit(FLAG_PULL_UP, flagsp,
                   flags & GPIO_V2_LINE_FLAG_BIAS_PULL_UP);
        assign_bit(FLAG_PULL_DOWN, flagsp,
                   flags & GPIO_V2_LINE_FLAG_BIAS_PULL_DOWN);
        assign_bit(FLAG_BIAS_DISABLE, flagsp,
                   flags & GPIO_V2_LINE_FLAG_BIAS_DISABLED);

        assign_bit(FLAG_EVENT_CLOCK_REALTIME, flagsp,
                   flags & GPIO_V2_LINE_FLAG_EVENT_CLOCK_REALTIME);
}

static long linereq_get_values(struct linereq *lr, void __user *ip)
{
        struct gpio_v2_line_values lv;
        DECLARE_BITMAP(vals, GPIO_V2_LINES_MAX);

        struct gpio_desc **descs;
        unsigned int i, didx, num_get;
        bool val;
        int ret;

        /* NOTE: It's ok to read values of output lines. */
        if (copy_from_user(&lv, ip, sizeof(lv)))
                return -EFAULT;

        for (num_get = 0, i = 0; i < lr->num_lines; i++) {
                if (lv.mask & BIT_ULL(i)) {
                        num_get++;
                        descs = &lr->lines[i].desc;
                }
        }

        if (num_get == 0)
                return -EINVAL;

        if (num_get != 1) {
                descs = kmalloc_array(num_get, sizeof(*descs), GFP_KERNEL);
                if (!descs)
                        return -ENOMEM;
                for (didx = 0, i = 0; i < lr->num_lines; i++) {
                        if (lv.mask & BIT_ULL(i)) {
                                descs[didx] = lr->lines[i].desc;
                                didx++;
                        }
                }
        }
        ret = gpiod_get_array_value_complex(false, true, num_get,
                                            descs, NULL, vals);

        if (num_get != 1)
                kfree(descs);
        if (ret)
                return ret;

        lv.bits = 0;
        for (didx = 0, i = 0; i < lr->num_lines; i++) {
                if (lv.mask & BIT_ULL(i)) {
                        if (lr->lines[i].sw_debounced)
                                val = debounced_value(&lr->lines[i]);
                        else
                                val = test_bit(didx, vals);
                        if (val)
                                lv.bits |= BIT_ULL(i);
                        didx++;
                }
        }

        if (copy_to_user(ip, &lv, sizeof(lv)))
                return -EFAULT;

        return 0;
}

static long linereq_set_values_unlocked(struct linereq *lr,
                                        struct gpio_v2_line_values *lv)
{
        DECLARE_BITMAP(vals, GPIO_V2_LINES_MAX);
        struct gpio_desc **descs;
        unsigned int i, didx, num_set;
        int ret;

        bitmap_zero(vals, GPIO_V2_LINES_MAX);
        for (num_set = 0, i = 0; i < lr->num_lines; i++) {
                if (lv->mask & BIT_ULL(i)) {
                        if (!test_bit(FLAG_IS_OUT, &lr->lines[i].desc->flags))
                                return -EPERM;
                        if (lv->bits & BIT_ULL(i))
                                __set_bit(num_set, vals);
                        num_set++;
                        descs = &lr->lines[i].desc;
                }
        }
        if (num_set == 0)
                return -EINVAL;

        if (num_set != 1) {
                /* build compacted desc array and values */
                descs = kmalloc_array(num_set, sizeof(*descs), GFP_KERNEL);
                if (!descs)
                        return -ENOMEM;
                for (didx = 0, i = 0; i < lr->num_lines; i++) {
                        if (lv->mask & BIT_ULL(i)) {
                                descs[didx] = lr->lines[i].desc;
                                didx++;
                        }
                }
        }
        ret = gpiod_set_array_value_complex(false, true, num_set,
                                            descs, NULL, vals);

        if (num_set != 1)
                kfree(descs);
        return ret;
}

static long linereq_set_values(struct linereq *lr, void __user *ip)
{
        struct gpio_v2_line_values lv;
        int ret;

        if (copy_from_user(&lv, ip, sizeof(lv)))
                return -EFAULT;

        mutex_lock(&lr->config_mutex);

        ret = linereq_set_values_unlocked(lr, &lv);

        mutex_unlock(&lr->config_mutex);

        return ret;
}

static long linereq_set_config_unlocked(struct linereq *lr,
                                        struct gpio_v2_line_config *lc)
{
        struct gpio_desc *desc;
        unsigned int i;
        u64 flags;
        bool polarity_change;
        int ret;

        for (i = 0; i < lr->num_lines; i++) {
                desc = lr->lines[i].desc;
                flags = gpio_v2_line_config_flags(lc, i);
                polarity_change =
                        (!!test_bit(FLAG_ACTIVE_LOW, &desc->flags) !=
                         ((flags & GPIO_V2_LINE_FLAG_ACTIVE_LOW) != 0));

                gpio_v2_line_config_flags_to_desc_flags(flags, &desc->flags);
                /*
                 * Lines have to be requested explicitly for input
                 * or output, else the line will be treated "as is".
                 */
                if (flags & GPIO_V2_LINE_FLAG_OUTPUT) {
                        int val = gpio_v2_line_config_output_value(lc, i);

                        edge_detector_stop(&lr->lines[i]);
                        ret = gpiod_direction_output(desc, val);
                        if (ret)
                                return ret;
                } else if (flags & GPIO_V2_LINE_FLAG_INPUT) {
                        ret = gpiod_direction_input(desc);
                        if (ret)
                                return ret;

                        ret = edge_detector_update(&lr->lines[i], lc, i,
                                        flags & GPIO_V2_LINE_EDGE_FLAGS,
                                        polarity_change);
                        if (ret)
                                return ret;
                }

                blocking_notifier_call_chain(&desc->gdev->notifier,
                                             GPIO_V2_LINE_CHANGED_CONFIG,
                                             desc);
        }
        return 0;
}

static long linereq_set_config(struct linereq *lr, void __user *ip)
{
        struct gpio_v2_line_config lc;
        int ret;

        if (copy_from_user(&lc, ip, sizeof(lc)))
                return -EFAULT;

        ret = gpio_v2_line_config_validate(&lc, lr->num_lines);
        if (ret)
                return ret;

        mutex_lock(&lr->config_mutex);

        ret = linereq_set_config_unlocked(lr, &lc);

        mutex_unlock(&lr->config_mutex);

        return ret;
}

static long linereq_ioctl(struct file *file, unsigned int cmd,
                          unsigned long arg)
{
        struct linereq *lr = file->private_data;
        void __user *ip = (void __user *)arg;

        if (cmd == GPIO_V2_LINE_GET_VALUES_IOCTL)
                return linereq_get_values(lr, ip);
        else if (cmd == GPIO_V2_LINE_SET_VALUES_IOCTL)
                return linereq_set_values(lr, ip);
        else if (cmd == GPIO_V2_LINE_SET_CONFIG_IOCTL)
                return linereq_set_config(lr, ip);

        return -EINVAL;
}

#ifdef CONFIG_COMPAT
static long linereq_ioctl_compat(struct file *file, unsigned int cmd,
                                 unsigned long arg)
{
        return linereq_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
}
#endif

static __poll_t linereq_poll(struct file *file,
                            struct poll_table_struct *wait)
{
        struct linereq *lr = file->private_data;
        __poll_t events = 0;

        poll_wait(file, &lr->wait, wait);

        if (!kfifo_is_empty_spinlocked_noirqsave(&lr->events,
                                                 &lr->wait.lock))
                events = EPOLLIN | EPOLLRDNORM;

        return events;
}

static ssize_t linereq_read(struct file *file,
                            char __user *buf,
                            size_t count,
                            loff_t *f_ps)
{
        struct linereq *lr = file->private_data;
        struct gpio_v2_line_event le;
        ssize_t bytes_read = 0;
        int ret;

        if (count < sizeof(le))
                return -EINVAL;

        do {
                spin_lock(&lr->wait.lock);
                if (kfifo_is_empty(&lr->events)) {
                        if (bytes_read) {
                                spin_unlock(&lr->wait.lock);
                                return bytes_read;
                        }

                        if (file->f_flags & O_NONBLOCK) {
                                spin_unlock(&lr->wait.lock);
                                return -EAGAIN;
                        }

                        ret = wait_event_interruptible_locked(lr->wait,
                                        !kfifo_is_empty(&lr->events));
                        if (ret) {
                                spin_unlock(&lr->wait.lock);
                                return ret;
                        }
                }

                ret = kfifo_out(&lr->events, &le, 1);
                spin_unlock(&lr->wait.lock);
                if (ret != 1) {
                        /*
                         * This should never happen - we were holding the
                         * lock from the moment we learned the fifo is no
                         * longer empty until now.
                         */
                        ret = -EIO;
                        break;
                }

                if (copy_to_user(buf + bytes_read, &le, sizeof(le)))
                        return -EFAULT;
                bytes_read += sizeof(le);
        } while (count >= bytes_read + sizeof(le));

        return bytes_read;
}

static void linereq_free(struct linereq *lr)
{
        unsigned int i;

        for (i = 0; i < lr->num_lines; i++) {
                edge_detector_stop(&lr->lines[i]);
                if (lr->lines[i].desc)
                        gpiod_free(lr->lines[i].desc);
        }
        kfifo_free(&lr->events);
        kfree(lr->label);
        put_device(&lr->gdev->dev);
        kfree(lr);
}

static int linereq_release(struct inode *inode, struct file *file)
{
        struct linereq *lr = file->private_data;

        linereq_free(lr);
        return 0;
}

static const struct file_operations line_fileops = {
        .release = linereq_release,
        .read = linereq_read,
        .poll = linereq_poll,
        .owner = THIS_MODULE,
        .llseek = noop_llseek,
        .unlocked_ioctl = linereq_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl = linereq_ioctl_compat,
#endif
};

static int linereq_create(struct gpio_device *gdev, void __user *ip)
{
        struct gpio_v2_line_request ulr;
        struct gpio_v2_line_config *lc;
        struct linereq *lr;
        struct file *file;
        u64 flags;
        unsigned int i;
        int fd, ret;

        if (copy_from_user(&ulr, ip, sizeof(ulr)))
                return -EFAULT;

        if ((ulr.num_lines == 0) || (ulr.num_lines > GPIO_V2_LINES_MAX))
                return -EINVAL;

        if (memchr_inv(ulr.padding, 0, sizeof(ulr.padding)))
                return -EINVAL;

        lc = &ulr.config;
        ret = gpio_v2_line_config_validate(lc, ulr.num_lines);
        if (ret)
                return ret;

        lr = kzalloc(struct_size(lr, lines, ulr.num_lines), GFP_KERNEL);
        if (!lr)
                return -ENOMEM;

        lr->gdev = gdev;
        get_device(&gdev->dev);

        for (i = 0; i < ulr.num_lines; i++) {
                lr->lines[i].req = lr;
                WRITE_ONCE(lr->lines[i].sw_debounced, 0);
                INIT_DELAYED_WORK(&lr->lines[i].work, debounce_work_func);
        }

        if (ulr.consumer[0] != '\0') {
                /* label is only initialized if consumer is set */
                lr->label = kstrndup(ulr.consumer, sizeof(ulr.consumer) - 1,
                                     GFP_KERNEL);
                if (!lr->label) {
                        ret = -ENOMEM;
                        goto out_free_linereq;
                }
        }

        mutex_init(&lr->config_mutex);
        init_waitqueue_head(&lr->wait);
        lr->event_buffer_size = ulr.event_buffer_size;
        if (lr->event_buffer_size == 0)
                lr->event_buffer_size = ulr.num_lines * 16;
        else if (lr->event_buffer_size > GPIO_V2_LINES_MAX * 16)
                lr->event_buffer_size = GPIO_V2_LINES_MAX * 16;

        atomic_set(&lr->seqno, 0);
        lr->num_lines = ulr.num_lines;

        /* Request each GPIO */
        for (i = 0; i < ulr.num_lines; i++) {
                u32 offset = ulr.offsets[i];
                struct gpio_desc *desc = gpiochip_get_desc(gdev->chip, offset);

                if (IS_ERR(desc)) {
                        ret = PTR_ERR(desc);
                        goto out_free_linereq;
                }

                ret = gpiod_request(desc, lr->label);
                if (ret)
                        goto out_free_linereq;

                lr->lines[i].desc = desc;
                flags = gpio_v2_line_config_flags(lc, i);
                gpio_v2_line_config_flags_to_desc_flags(flags, &desc->flags);

                ret = gpiod_set_transitory(desc, false);
                if (ret < 0)
                        goto out_free_linereq;

                /*
                 * Lines have to be requested explicitly for input
                 * or output, else the line will be treated "as is".
                 */
                if (flags & GPIO_V2_LINE_FLAG_OUTPUT) {
                        int val = gpio_v2_line_config_output_value(lc, i);

                        ret = gpiod_direction_output(desc, val);
                        if (ret)
                                goto out_free_linereq;
                } else if (flags & GPIO_V2_LINE_FLAG_INPUT) {
                        ret = gpiod_direction_input(desc);
                        if (ret)
                                goto out_free_linereq;

                        ret = edge_detector_setup(&lr->lines[i], lc, i,
                                        flags & GPIO_V2_LINE_EDGE_FLAGS);
                        if (ret)
                                goto out_free_linereq;
                }

                blocking_notifier_call_chain(&desc->gdev->notifier,
                                             GPIO_V2_LINE_CHANGED_REQUESTED, desc);

                dev_dbg(&gdev->dev, "registered chardev handle for line %d\n",
                        offset);
        }

        fd = get_unused_fd_flags(O_RDONLY | O_CLOEXEC);
        if (fd < 0) {
                ret = fd;
                goto out_free_linereq;
        }

        file = anon_inode_getfile("gpio-line", &line_fileops, lr,
                                  O_RDONLY | O_CLOEXEC);
        if (IS_ERR(file)) {
                ret = PTR_ERR(file);
                goto out_put_unused_fd;
        }

        ulr.fd = fd;
        if (copy_to_user(ip, &ulr, sizeof(ulr))) {
                /*
                 * fput() will trigger the release() callback, so do not go onto
                 * the regular error cleanup path here.
                 */
                fput(file);
                put_unused_fd(fd);
                return -EFAULT;
        }

        fd_install(fd, file);

        dev_dbg(&gdev->dev, "registered chardev handle for %d lines\n",
                lr->num_lines);

        return 0;

out_put_unused_fd:
        put_unused_fd(fd);
out_free_linereq:
        linereq_free(lr);
        return ret;
}

#ifdef CONFIG_GPIO_CDEV_V1

/*
 * GPIO line event management
 */

/**
 * struct lineevent_state - contains the state of a userspace event
 * @gdev: the GPIO device the event pertains to
 * @label: consumer label used to tag descriptors
 * @desc: the GPIO descriptor held by this event
 * @eflags: the event flags this line was requested with
 * @irq: the interrupt that trigger in response to events on this GPIO
 * @wait: wait queue that handles blocking reads of events
 * @events: KFIFO for the GPIO events
 * @timestamp: cache for the timestamp storing it between hardirq
 * and IRQ thread, used to bring the timestamp close to the actual
 * event
 */
struct lineevent_state {
        struct gpio_device *gdev;
        const char *label;
        struct gpio_desc *desc;
        u32 eflags;
        int irq;
        wait_queue_head_t wait;
        DECLARE_KFIFO(events, struct gpioevent_data, 16);
        u64 timestamp;
};

#define GPIOEVENT_REQUEST_VALID_FLAGS \
        (GPIOEVENT_REQUEST_RISING_EDGE | \
        GPIOEVENT_REQUEST_FALLING_EDGE)

static __poll_t lineevent_poll(struct file *file,
                               struct poll_table_struct *wait)
{
        struct lineevent_state *le = file->private_data;
        __poll_t events = 0;

        poll_wait(file, &le->wait, wait);

        if (!kfifo_is_empty_spinlocked_noirqsave(&le->events, &le->wait.lock))
                events = EPOLLIN | EPOLLRDNORM;

        return events;
}

struct compat_gpioeevent_data {
        compat_u64      timestamp;
        u32             id;
};

static ssize_t lineevent_read(struct file *file,
                              char __user *buf,
                              size_t count,
                              loff_t *f_ps)
{
        struct lineevent_state *le = file->private_data;
        struct gpioevent_data ge;
        ssize_t bytes_read = 0;
        ssize_t ge_size;
        int ret;

        /*
         * When compatible system call is being used the struct gpioevent_data,
         * in case of at least ia32, has different size due to the alignment
         * differences. Because we have first member 64 bits followed by one of
         * 32 bits there is no gap between them. The only difference is the
         * padding at the end of the data structure. Hence, we calculate the
         * actual sizeof() and pass this as an argument to copy_to_user() to
         * drop unneeded bytes from the output.
         */
        if (compat_need_64bit_alignment_fixup())
                ge_size = sizeof(struct compat_gpioeevent_data);
        else
                ge_size = sizeof(struct gpioevent_data);
        if (count < ge_size)
                return -EINVAL;

        do {
                spin_lock(&le->wait.lock);
                if (kfifo_is_empty(&le->events)) {
                        if (bytes_read) {
                                spin_unlock(&le->wait.lock);
                                return bytes_read;
                        }

                        if (file->f_flags & O_NONBLOCK) {
                                spin_unlock(&le->wait.lock);
                                return -EAGAIN;
                        }

                        ret = wait_event_interruptible_locked(le->wait,
                                        !kfifo_is_empty(&le->events));
                        if (ret) {
                                spin_unlock(&le->wait.lock);
                                return ret;
                        }
                }

                ret = kfifo_out(&le->events, &ge, 1);
                spin_unlock(&le->wait.lock);
                if (ret != 1) {
                        /*
                         * This should never happen - we were holding the lock
                         * from the moment we learned the fifo is no longer
                         * empty until now.
                         */
                        ret = -EIO;
                        break;
                }

                if (copy_to_user(buf + bytes_read, &ge, ge_size))
                        return -EFAULT;
                bytes_read += ge_size;
        } while (count >= bytes_read + ge_size);

        return bytes_read;
}

static void lineevent_free(struct lineevent_state *le)
{
        if (le->irq)
                free_irq(le->irq, le);
        if (le->desc)
                gpiod_free(le->desc);
        kfree(le->label);
        put_device(&le->gdev->dev);
        kfree(le);
}

static int lineevent_release(struct inode *inode, struct file *file)
{
        lineevent_free(file->private_data);
        return 0;
}

static long lineevent_ioctl(struct file *file, unsigned int cmd,
                            unsigned long arg)
{
        struct lineevent_state *le = file->private_data;
        void __user *ip = (void __user *)arg;
        struct gpiohandle_data ghd;

        /*
         * We can get the value for an event line but not set it,
         * because it is input by definition.
         */
        if (cmd == GPIOHANDLE_GET_LINE_VALUES_IOCTL) {
                int val;

                memset(&ghd, 0, sizeof(ghd));

                val = gpiod_get_value_cansleep(le->desc);
                if (val < 0)
                        return val;
                ghd.values[0] = val;

                if (copy_to_user(ip, &ghd, sizeof(ghd)))
                        return -EFAULT;

                return 0;
        }
        return -EINVAL;
}

#ifdef CONFIG_COMPAT
static long lineevent_ioctl_compat(struct file *file, unsigned int cmd,
                                   unsigned long arg)
{
        return lineevent_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
}
#endif

static const struct file_operations lineevent_fileops = {
        .release = lineevent_release,
        .read = lineevent_read,
        .poll = lineevent_poll,
        .owner = THIS_MODULE,
        .llseek = noop_llseek,
        .unlocked_ioctl = lineevent_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl = lineevent_ioctl_compat,
#endif
};

static irqreturn_t lineevent_irq_thread(int irq, void *p)
{
        struct lineevent_state *le = p;
        struct gpioevent_data ge;
        int ret;

        /* Do not leak kernel stack to userspace */
        memset(&ge, 0, sizeof(ge));

        /*
         * We may be running from a nested threaded interrupt in which case
         * we didn't get the timestamp from lineevent_irq_handler().
         */
        if (!le->timestamp)
                ge.timestamp = ktime_get_ns();
        else
                ge.timestamp = le->timestamp;

        if (le->eflags & GPIOEVENT_REQUEST_RISING_EDGE
            && le->eflags & GPIOEVENT_REQUEST_FALLING_EDGE) {
                int level = gpiod_get_value_cansleep(le->desc);

                if (level)
                        /* Emit low-to-high event */
                        ge.id = GPIOEVENT_EVENT_RISING_EDGE;
                else
                        /* Emit high-to-low event */
                        ge.id = GPIOEVENT_EVENT_FALLING_EDGE;
        } else if (le->eflags & GPIOEVENT_REQUEST_RISING_EDGE) {
                /* Emit low-to-high event */
                ge.id = GPIOEVENT_EVENT_RISING_EDGE;
        } else if (le->eflags & GPIOEVENT_REQUEST_FALLING_EDGE) {
                /* Emit high-to-low event */
                ge.id = GPIOEVENT_EVENT_FALLING_EDGE;
        } else {
                return IRQ_NONE;
        }

        ret = kfifo_in_spinlocked_noirqsave(&le->events, &ge,
                                            1, &le->wait.lock);
        if (ret)
                wake_up_poll(&le->wait, EPOLLIN);
        else
                pr_debug_ratelimited("event FIFO is full - event dropped\n");

        return IRQ_HANDLED;
}

static irqreturn_t lineevent_irq_handler(int irq, void *p)
{
        struct lineevent_state *le = p;

        /*
         * Just store the timestamp in hardirq context so we get it as
         * close in time as possible to the actual event.
         */
        le->timestamp = ktime_get_ns();

        return IRQ_WAKE_THREAD;
}

static int lineevent_create(struct gpio_device *gdev, void __user *ip)
{
        struct gpioevent_request eventreq;
        struct lineevent_state *le;
        struct gpio_desc *desc;
        struct file *file;
        u32 offset;
        u32 lflags;
        u32 eflags;
        int fd;
        int ret;
        int irq, irqflags = 0;

        if (copy_from_user(&eventreq, ip, sizeof(eventreq)))
                return -EFAULT;

        offset = eventreq.lineoffset;
        lflags = eventreq.handleflags;
        eflags = eventreq.eventflags;

        desc = gpiochip_get_desc(gdev->chip, offset);
        if (IS_ERR(desc))
                return PTR_ERR(desc);

        /* Return an error if a unknown flag is set */
        if ((lflags & ~GPIOHANDLE_REQUEST_VALID_FLAGS) ||
            (eflags & ~GPIOEVENT_REQUEST_VALID_FLAGS))
                return -EINVAL;

        /* This is just wrong: we don't look for events on output lines */
        if ((lflags & GPIOHANDLE_REQUEST_OUTPUT) ||
            (lflags & GPIOHANDLE_REQUEST_OPEN_DRAIN) ||
            (lflags & GPIOHANDLE_REQUEST_OPEN_SOURCE))
                return -EINVAL;

        /* Only one bias flag can be set. */
        if (((lflags & GPIOHANDLE_REQUEST_BIAS_DISABLE) &&
             (lflags & (GPIOHANDLE_REQUEST_BIAS_PULL_DOWN |
                        GPIOHANDLE_REQUEST_BIAS_PULL_UP))) ||
            ((lflags & GPIOHANDLE_REQUEST_BIAS_PULL_DOWN) &&
             (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_UP)))
                return -EINVAL;

        le = kzalloc(sizeof(*le), GFP_KERNEL);
        if (!le)
                return -ENOMEM;
        le->gdev = gdev;
        get_device(&gdev->dev);

        if (eventreq.consumer_label[0] != '\0') {
                /* label is only initialized if consumer_label is set */
                le->label = kstrndup(eventreq.consumer_label,
                                     sizeof(eventreq.consumer_label) - 1,
                                     GFP_KERNEL);
                if (!le->label) {
                        ret = -ENOMEM;
                        goto out_free_le;
                }
        }

        ret = gpiod_request(desc, le->label);
        if (ret)
                goto out_free_le;
        le->desc = desc;
        le->eflags = eflags;

        linehandle_flags_to_desc_flags(lflags, &desc->flags);

        ret = gpiod_direction_input(desc);
        if (ret)
                goto out_free_le;

        blocking_notifier_call_chain(&desc->gdev->notifier,
                                     GPIO_V2_LINE_CHANGED_REQUESTED, desc);

        irq = gpiod_to_irq(desc);
        if (irq <= 0) {
                ret = -ENODEV;
                goto out_free_le;
        }
        le->irq = irq;

        if (eflags & GPIOEVENT_REQUEST_RISING_EDGE)
                irqflags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
                        IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING;
        if (eflags & GPIOEVENT_REQUEST_FALLING_EDGE)
                irqflags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
                        IRQF_TRIGGER_RISING : IRQF_TRIGGER_FALLING;
        irqflags |= IRQF_ONESHOT;

        INIT_KFIFO(le->events);
        init_waitqueue_head(&le->wait);

        /* Request a thread to read the events */
        ret = request_threaded_irq(le->irq,
                                   lineevent_irq_handler,
                                   lineevent_irq_thread,
                                   irqflags,
                                   le->label,
                                   le);
        if (ret)
                goto out_free_le;

        fd = get_unused_fd_flags(O_RDONLY | O_CLOEXEC);
        if (fd < 0) {
                ret = fd;
                goto out_free_le;
        }

        file = anon_inode_getfile("gpio-event",
                                  &lineevent_fileops,
                                  le,
                                  O_RDONLY | O_CLOEXEC);
        if (IS_ERR(file)) {
                ret = PTR_ERR(file);
                goto out_put_unused_fd;
        }

        eventreq.fd = fd;
        if (copy_to_user(ip, &eventreq, sizeof(eventreq))) {
                /*
                 * fput() will trigger the release() callback, so do not go onto
                 * the regular error cleanup path here.
                 */
                fput(file);
                put_unused_fd(fd);
                return -EFAULT;
        }

        fd_install(fd, file);

        return 0;

out_put_unused_fd:
        put_unused_fd(fd);
out_free_le:
        lineevent_free(le);
        return ret;
}

static void gpio_v2_line_info_to_v1(struct gpio_v2_line_info *info_v2,
                                    struct gpioline_info *info_v1)
{
        u64 flagsv2 = info_v2->flags;

        memcpy(info_v1->name, info_v2->name, sizeof(info_v1->name));
        memcpy(info_v1->consumer, info_v2->consumer, sizeof(info_v1->consumer));
        info_v1->line_offset = info_v2->offset;
        info_v1->flags = 0;

        if (flagsv2 & GPIO_V2_LINE_FLAG_USED)
                info_v1->flags |= GPIOLINE_FLAG_KERNEL;

        if (flagsv2 & GPIO_V2_LINE_FLAG_OUTPUT)
                info_v1->flags |= GPIOLINE_FLAG_IS_OUT;

        if (flagsv2 & GPIO_V2_LINE_FLAG_ACTIVE_LOW)
                info_v1->flags |= GPIOLINE_FLAG_ACTIVE_LOW;

        if (flagsv2 & GPIO_V2_LINE_FLAG_OPEN_DRAIN)
                info_v1->flags |= GPIOLINE_FLAG_OPEN_DRAIN;
        if (flagsv2 & GPIO_V2_LINE_FLAG_OPEN_SOURCE)
                info_v1->flags |= GPIOLINE_FLAG_OPEN_SOURCE;

        if (flagsv2 & GPIO_V2_LINE_FLAG_BIAS_PULL_UP)
                info_v1->flags |= GPIOLINE_FLAG_BIAS_PULL_UP;
        if (flagsv2 & GPIO_V2_LINE_FLAG_BIAS_PULL_DOWN)
                info_v1->flags |= GPIOLINE_FLAG_BIAS_PULL_DOWN;
        if (flagsv2 & GPIO_V2_LINE_FLAG_BIAS_DISABLED)
                info_v1->flags |= GPIOLINE_FLAG_BIAS_DISABLE;
}

static void gpio_v2_line_info_changed_to_v1(
                struct gpio_v2_line_info_changed *lic_v2,
                struct gpioline_info_changed *lic_v1)
{
        memset(lic_v1, 0, sizeof(*lic_v1));
        gpio_v2_line_info_to_v1(&lic_v2->info, &lic_v1->info);
        lic_v1->timestamp = lic_v2->timestamp_ns;
        lic_v1->event_type = lic_v2->event_type;
}

#endif /* CONFIG_GPIO_CDEV_V1 */

static void gpio_desc_to_lineinfo(struct gpio_desc *desc,
                                  struct gpio_v2_line_info *info)
{
        struct gpio_chip *gc = desc->gdev->chip;
        bool ok_for_pinctrl;
        unsigned long flags;
        u32 debounce_period_us;
        unsigned int num_attrs = 0;

        memset(info, 0, sizeof(*info));
        info->offset = gpio_chip_hwgpio(desc);

        /*
         * This function takes a mutex so we must check this before taking
         * the spinlock.
         *
         * FIXME: find a non-racy way to retrieve this information. Maybe a
         * lock common to both frameworks?
         */
        ok_for_pinctrl =
                pinctrl_gpio_can_use_line(gc->base + info->offset);

        spin_lock_irqsave(&gpio_lock, flags);

        if (desc->name)
                strscpy(info->name, desc->name, sizeof(info->name));

        if (desc->label)
                strscpy(info->consumer, desc->label, sizeof(info->consumer));

        /*
         * Userspace only need to know that the kernel is using this GPIO so
         * it can't use it.
         */
        info->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) ||
            !gpiochip_line_is_valid(gc, info->offset) ||
            !ok_for_pinctrl)
                info->flags |= GPIO_V2_LINE_FLAG_USED;

        if (test_bit(FLAG_IS_OUT, &desc->flags))
                info->flags |= GPIO_V2_LINE_FLAG_OUTPUT;
        else
                info->flags |= GPIO_V2_LINE_FLAG_INPUT;

        if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
                info->flags |= GPIO_V2_LINE_FLAG_ACTIVE_LOW;

        if (test_bit(FLAG_OPEN_DRAIN, &desc->flags))
                info->flags |= GPIO_V2_LINE_FLAG_OPEN_DRAIN;
        if (test_bit(FLAG_OPEN_SOURCE, &desc->flags))
                info->flags |= GPIO_V2_LINE_FLAG_OPEN_SOURCE;

        if (test_bit(FLAG_BIAS_DISABLE, &desc->flags))
                info->flags |= GPIO_V2_LINE_FLAG_BIAS_DISABLED;
        if (test_bit(FLAG_PULL_DOWN, &desc->flags))
                info->flags |= GPIO_V2_LINE_FLAG_BIAS_PULL_DOWN;
        if (test_bit(FLAG_PULL_UP, &desc->flags))
                info->flags |= GPIO_V2_LINE_FLAG_BIAS_PULL_UP;

        if (test_bit(FLAG_EDGE_RISING, &desc->flags))
                info->flags |= GPIO_V2_LINE_FLAG_EDGE_RISING;
        if (test_bit(FLAG_EDGE_FALLING, &desc->flags))
                info->flags |= GPIO_V2_LINE_FLAG_EDGE_FALLING;

        if (test_bit(FLAG_EVENT_CLOCK_REALTIME, &desc->flags))
                info->flags |= GPIO_V2_LINE_FLAG_EVENT_CLOCK_REALTIME;

        debounce_period_us = READ_ONCE(desc->debounce_period_us);
        if (debounce_period_us) {
                info->attrs[num_attrs].id = GPIO_V2_LINE_ATTR_ID_DEBOUNCE;
                info->attrs[num_attrs].debounce_period_us = debounce_period_us;
                num_attrs++;
        }
        info->num_attrs = num_attrs;

        spin_unlock_irqrestore(&gpio_lock, flags);
}

struct gpio_chardev_data {
        struct gpio_device *gdev;
        wait_queue_head_t wait;
        DECLARE_KFIFO(events, struct gpio_v2_line_info_changed, 32);
        struct notifier_block lineinfo_changed_nb;
        unsigned long *watched_lines;
#ifdef CONFIG_GPIO_CDEV_V1
        atomic_t watch_abi_version;
#endif
};

static int chipinfo_get(struct gpio_chardev_data *cdev, void __user *ip)
{
        struct gpio_device *gdev = cdev->gdev;
        struct gpiochip_info chipinfo;

        memset(&chipinfo, 0, sizeof(chipinfo));

        strscpy(chipinfo.name, dev_name(&gdev->dev), sizeof(chipinfo.name));
        strscpy(chipinfo.label, gdev->label, sizeof(chipinfo.label));
        chipinfo.lines = gdev->ngpio;
        if (copy_to_user(ip, &chipinfo, sizeof(chipinfo)))
                return -EFAULT;
        return 0;
}

#ifdef CONFIG_GPIO_CDEV_V1

/*
 * returns 0 if the versions match, else the previously selected ABI version
 */
static int lineinfo_ensure_abi_version(struct gpio_chardev_data *cdata,
                                       unsigned int version)
{
        int abiv = atomic_cmpxchg(&cdata->watch_abi_version, 0, version);

        if (abiv == version)
                return 0;

        return abiv;
}

static int lineinfo_get_v1(struct gpio_chardev_data *cdev, void __user *ip,
                           bool watch)
{
        struct gpio_desc *desc;
        struct gpioline_info lineinfo;
        struct gpio_v2_line_info lineinfo_v2;

        if (copy_from_user(&lineinfo, ip, sizeof(lineinfo)))
                return -EFAULT;

        /* this doubles as a range check on line_offset */
        desc = gpiochip_get_desc(cdev->gdev->chip, lineinfo.line_offset);
        if (IS_ERR(desc))
                return PTR_ERR(desc);

        if (watch) {
                if (lineinfo_ensure_abi_version(cdev, 1))
                        return -EPERM;

                if (test_and_set_bit(lineinfo.line_offset, cdev->watched_lines))
                        return -EBUSY;
        }

        gpio_desc_to_lineinfo(desc, &lineinfo_v2);
        gpio_v2_line_info_to_v1(&lineinfo_v2, &lineinfo);

        if (copy_to_user(ip, &lineinfo, sizeof(lineinfo))) {
                if (watch)
                        clear_bit(lineinfo.line_offset, cdev->watched_lines);
                return -EFAULT;
        }

        return 0;
}
#endif

static int lineinfo_get(struct gpio_chardev_data *cdev, void __user *ip,
                        bool watch)
{
        struct gpio_desc *desc;
        struct gpio_v2_line_info lineinfo;

        if (copy_from_user(&lineinfo, ip, sizeof(lineinfo)))
                return -EFAULT;

        if (memchr_inv(lineinfo.padding, 0, sizeof(lineinfo.padding)))
                return -EINVAL;

        desc = gpiochip_get_desc(cdev->gdev->chip, lineinfo.offset);
        if (IS_ERR(desc))
                return PTR_ERR(desc);

        if (watch) {
#ifdef CONFIG_GPIO_CDEV_V1
                if (lineinfo_ensure_abi_version(cdev, 2))
                        return -EPERM;
#endif
                if (test_and_set_bit(lineinfo.offset, cdev->watched_lines))
                        return -EBUSY;
        }
        gpio_desc_to_lineinfo(desc, &lineinfo);

        if (copy_to_user(ip, &lineinfo, sizeof(lineinfo))) {
                if (watch)
                        clear_bit(lineinfo.offset, cdev->watched_lines);
                return -EFAULT;
        }

        return 0;
}

static int lineinfo_unwatch(struct gpio_chardev_data *cdev, void __user *ip)
{
        __u32 offset;

        if (copy_from_user(&offset, ip, sizeof(offset)))
                return -EFAULT;

        if (offset >= cdev->gdev->ngpio)
                return -EINVAL;

        if (!test_and_clear_bit(offset, cdev->watched_lines))
                return -EBUSY;

        return 0;
}

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

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

        /* Fill in the struct and pass to userspace */
        if (cmd == GPIO_GET_CHIPINFO_IOCTL) {
                return chipinfo_get(cdev, ip);
#ifdef CONFIG_GPIO_CDEV_V1
        } else if (cmd == GPIO_GET_LINEHANDLE_IOCTL) {
                return linehandle_create(gdev, ip);
        } else if (cmd == GPIO_GET_LINEEVENT_IOCTL) {
                return lineevent_create(gdev, ip);
        } else if (cmd == GPIO_GET_LINEINFO_IOCTL ||
                   cmd == GPIO_GET_LINEINFO_WATCH_IOCTL) {
                return lineinfo_get_v1(cdev, ip,
                                       cmd == GPIO_GET_LINEINFO_WATCH_IOCTL);
#endif /* CONFIG_GPIO_CDEV_V1 */
        } else if (cmd == GPIO_V2_GET_LINEINFO_IOCTL ||
                   cmd == GPIO_V2_GET_LINEINFO_WATCH_IOCTL) {
                return lineinfo_get(cdev, ip,
                                    cmd == GPIO_V2_GET_LINEINFO_WATCH_IOCTL);
        } else if (cmd == GPIO_V2_GET_LINE_IOCTL) {
                return linereq_create(gdev, ip);
        } else if (cmd == GPIO_GET_LINEINFO_UNWATCH_IOCTL) {
                return lineinfo_unwatch(cdev, ip);
        }
        return -EINVAL;
}

#ifdef CONFIG_COMPAT
static long gpio_ioctl_compat(struct file *file, unsigned int cmd,
                              unsigned long arg)
{
        return gpio_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
}
#endif

static struct gpio_chardev_data *
to_gpio_chardev_data(struct notifier_block *nb)
{
        return container_of(nb, struct gpio_chardev_data, lineinfo_changed_nb);
}

static int lineinfo_changed_notify(struct notifier_block *nb,
                                   unsigned long action, void *data)
{
        struct gpio_chardev_data *cdev = to_gpio_chardev_data(nb);
        struct gpio_v2_line_info_changed chg;
        struct gpio_desc *desc = data;
        int ret;

        if (!test_bit(gpio_chip_hwgpio(desc), cdev->watched_lines))
                return NOTIFY_DONE;

        memset(&chg, 0, sizeof(chg));
        chg.event_type = action;
        chg.timestamp_ns = ktime_get_ns();
        gpio_desc_to_lineinfo(desc, &chg.info);

        ret = kfifo_in_spinlocked(&cdev->events, &chg, 1, &cdev->wait.lock);
        if (ret)
                wake_up_poll(&cdev->wait, EPOLLIN);
        else
                pr_debug_ratelimited("lineinfo event FIFO is full - event dropped\n");

        return NOTIFY_OK;
}

static __poll_t lineinfo_watch_poll(struct file *file,
                                    struct poll_table_struct *pollt)
{
        struct gpio_chardev_data *cdev = file->private_data;
        __poll_t events = 0;

        poll_wait(file, &cdev->wait, pollt);

        if (!kfifo_is_empty_spinlocked_noirqsave(&cdev->events,
                                                 &cdev->wait.lock))
                events = EPOLLIN | EPOLLRDNORM;

        return events;
}

static ssize_t lineinfo_watch_read(struct file *file, char __user *buf,
                                   size_t count, loff_t *off)
{
        struct gpio_chardev_data *cdev = file->private_data;
        struct gpio_v2_line_info_changed event;
        ssize_t bytes_read = 0;
        int ret;
        size_t event_size;

#ifndef CONFIG_GPIO_CDEV_V1
        event_size = sizeof(struct gpio_v2_line_info_changed);
        if (count < event_size)
                return -EINVAL;
#endif

        do {
                spin_lock(&cdev->wait.lock);
                if (kfifo_is_empty(&cdev->events)) {
                        if (bytes_read) {
                                spin_unlock(&cdev->wait.lock);
                                return bytes_read;
                        }

                        if (file->f_flags & O_NONBLOCK) {
                                spin_unlock(&cdev->wait.lock);
                                return -EAGAIN;
                        }

                        ret = wait_event_interruptible_locked(cdev->wait,
                                        !kfifo_is_empty(&cdev->events));
                        if (ret) {
                                spin_unlock(&cdev->wait.lock);
                                return ret;
                        }
                }
#ifdef CONFIG_GPIO_CDEV_V1
                /* must be after kfifo check so watch_abi_version is set */
                if (atomic_read(&cdev->watch_abi_version) == 2)
                        event_size = sizeof(struct gpio_v2_line_info_changed);
                else
                        event_size = sizeof(struct gpioline_info_changed);
                if (count < event_size) {
                        spin_unlock(&cdev->wait.lock);
                        return -EINVAL;
                }
#endif
                ret = kfifo_out(&cdev->events, &event, 1);
                spin_unlock(&cdev->wait.lock);
                if (ret != 1) {
                        ret = -EIO;
                        break;
                        /* We should never get here. See lineevent_read(). */
                }

#ifdef CONFIG_GPIO_CDEV_V1
                if (event_size == sizeof(struct gpio_v2_line_info_changed)) {
                        if (copy_to_user(buf + bytes_read, &event, event_size))
                                return -EFAULT;
                } else {
                        struct gpioline_info_changed event_v1;

                        gpio_v2_line_info_changed_to_v1(&event, &event_v1);
                        if (copy_to_user(buf + bytes_read, &event_v1,
                                         event_size))
                                return -EFAULT;
                }
#else
                if (copy_to_user(buf + bytes_read, &event, event_size))
                        return -EFAULT;
#endif
                bytes_read += event_size;
        } while (count >= bytes_read + sizeof(event));

        return bytes_read;
}

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

        /* Fail on open if the backing gpiochip is gone */
        if (!gdev->chip)
                return -ENODEV;

        cdev = kzalloc(sizeof(*cdev), GFP_KERNEL);
        if (!cdev)
                return -ENOMEM;

        cdev->watched_lines = bitmap_zalloc(gdev->chip->ngpio, GFP_KERNEL);
        if (!cdev->watched_lines)
                goto out_free_cdev;

        init_waitqueue_head(&cdev->wait);
        INIT_KFIFO(cdev->events);
        cdev->gdev = gdev;

        cdev->lineinfo_changed_nb.notifier_call = lineinfo_changed_notify;
        ret = blocking_notifier_chain_register(&gdev->notifier,
                                               &cdev->lineinfo_changed_nb);
        if (ret)
                goto out_free_bitmap;

        get_device(&gdev->dev);
        file->private_data = cdev;

        ret = nonseekable_open(inode, file);
        if (ret)
                goto out_unregister_notifier;

        return ret;

out_unregister_notifier:
        blocking_notifier_chain_unregister(&gdev->notifier,
                                           &cdev->lineinfo_changed_nb);
out_free_bitmap:
        bitmap_free(cdev->watched_lines);
out_free_cdev:
        kfree(cdev);
        return ret;
}

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

        bitmap_free(cdev->watched_lines);
        blocking_notifier_chain_unregister(&gdev->notifier,
                                           &cdev->lineinfo_changed_nb);
        put_device(&gdev->dev);
        kfree(cdev);

        return 0;
}

static const struct file_operations gpio_fileops = {
        .release = gpio_chrdev_release,
        .open = gpio_chrdev_open,
        .poll = lineinfo_watch_poll,
        .read = lineinfo_watch_read,
        .owner = THIS_MODULE,
        .llseek = no_llseek,
        .unlocked_ioctl = gpio_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl = gpio_ioctl_compat,
#endif
};

int gpiolib_cdev_register(struct gpio_device *gdev, dev_t devt)
{
        int ret;

        cdev_init(&gdev->chrdev, &gpio_fileops);
        gdev->chrdev.owner = THIS_MODULE;
        gdev->dev.devt = MKDEV(MAJOR(devt), gdev->id);

        ret = cdev_device_add(&gdev->chrdev, &gdev->dev);
        if (ret)
                return ret;

        chip_dbg(gdev->chip, "added GPIO chardev (%d:%d)\n",
                 MAJOR(devt), gdev->id);

        return 0;
}

void gpiolib_cdev_unregister(struct gpio_device *gdev)
{
        cdev_device_del(&gdev->chrdev, &gdev->dev);
}