evdev.c

Go to the documentation of this file.

/*
 * Event char devices, giving access to raw input device events.
 *
 * Copyright (c) 1999-2002 Vojtech Pavlik
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#define EVDEV_MINOR_BASE    64
#define EVDEV_MINORS        32
#define EVDEV_MIN_BUFFER_SIZE   64U
#define EVDEV_BUF_PACKETS   8

#include <linux/poll.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/input/mt.h>
#include <linux/major.h>
#include <linux/device.h>
#include <linux/cdev.h>
#include "input-compat.h"

struct evdev {
    int open;
    struct input_handle handle;
    wait_queue_head_t wait;
    struct evdev_client __rcu *grab;
    struct list_head client_list;
    spinlock_t client_lock; /* protects client_list */
    struct mutex mutex;
    struct device dev;
    struct cdev cdev;
    bool exist;
};

struct evdev_client {
    unsigned int head;
    unsigned int tail;
    unsigned int packet_head; /* [future] position of the first element of next packet */
    spinlock_t buffer_lock; /* protects access to buffer, head and tail */
    struct fasync_struct *fasync;
    struct evdev *evdev;
    struct list_head node;
    int clkid;
    unsigned int bufsize;
    struct input_event buffer[];
};

static void __pass_event(struct evdev_client *client,
             const struct input_event *event)
{
    client->buffer[client->head++] = *event;
    client->head &= client->bufsize - 1;

    if (unlikely(client->head == client->tail)) {
        /*
         * This effectively "drops" all unconsumed events, leaving
         * EV_SYN/SYN_DROPPED plus the newest event in the queue.
         */
        client->tail = (client->head - 2) & (client->bufsize - 1);

        client->buffer[client->tail].time = event->time;
        client->buffer[client->tail].type = EV_SYN;
        client->buffer[client->tail].code = SYN_DROPPED;
        client->buffer[client->tail].value = 0;

        client->packet_head = client->tail;
    }

    if (event->type == EV_SYN && event->code == SYN_REPORT) {
        client->packet_head = client->head;
        kill_fasync(&client->fasync, SIGIO, POLL_IN);
    }
}

static void evdev_pass_values(struct evdev_client *client,
            const struct input_value *vals, unsigned int count,
            ktime_t mono, ktime_t real)
{
    struct evdev *evdev = client->evdev;
    const struct input_value *v;
    struct input_event event;
    bool wakeup = false;

    event.time = ktime_to_timeval(client->clkid == CLOCK_MONOTONIC ?
                      mono : real);

    /* Interrupts are disabled, just acquire the lock. */
    spin_lock(&client->buffer_lock);

    for (v = vals; v != vals + count; v++) {
        event.type = v->type;
        event.code = v->code;
        event.value = v->value;
        __pass_event(client, &event);
        if (v->type == EV_SYN && v->code == SYN_REPORT)
            wakeup = true;
    }

    spin_unlock(&client->buffer_lock);

    if (wakeup)
        wake_up_interruptible(&evdev->wait);
}

/*
 * Pass incoming events to all connected clients.
 */
static void evdev_events(struct input_handle *handle,
             const struct input_value *vals, unsigned int count)
{
    struct evdev *evdev = handle->private;
    struct evdev_client *client;
    ktime_t time_mono, time_real;

    time_mono = ktime_get();
    time_real = ktime_sub(time_mono, ktime_get_monotonic_offset());

    rcu_read_lock();

    client = rcu_dereference(evdev->grab);

    if (client)
        evdev_pass_values(client, vals, count, time_mono, time_real);
    else
        list_for_each_entry_rcu(client, &evdev->client_list, node)
            evdev_pass_values(client, vals, count,
                      time_mono, time_real);

    rcu_read_unlock();
}

/*
 * Pass incoming event to all connected clients.
 */
static void evdev_event(struct input_handle *handle,
            unsigned int type, unsigned int code, int value)
{
    struct input_value vals[] = { { type, code, value } };

    evdev_events(handle, vals, 1);
}

static int evdev_fasync(int fd, struct file *file, int on)
{
    struct evdev_client *client = file->private_data;

    return fasync_helper(fd, file, on, &client->fasync);
}

static int evdev_flush(struct file *file, fl_owner_t id)
{
    struct evdev_client *client = file->private_data;
    struct evdev *evdev = client->evdev;
    int retval;

    retval = mutex_lock_interruptible(&evdev->mutex);
    if (retval)
        return retval;

    if (!evdev->exist)
        retval = -ENODEV;
    else
        retval = input_flush_device(&evdev->handle, file);

    mutex_unlock(&evdev->mutex);
    return retval;
}

static void evdev_free(struct device *dev)
{
    struct evdev *evdev = container_of(dev, struct evdev, dev);

    input_put_device(evdev->handle.dev);
    kfree(evdev);
}

/*
 * Grabs an event device (along with underlying input device).
 * This function is called with evdev->mutex taken.
 */
static int evdev_grab(struct evdev *evdev, struct evdev_client *client)
{
    int error;

    if (evdev->grab)
        return -EBUSY;

    error = input_grab_device(&evdev->handle);
    if (error)
        return error;

    rcu_assign_pointer(evdev->grab, client);

    return 0;
}

static int evdev_ungrab(struct evdev *evdev, struct evdev_client *client)
{
    struct evdev_client *grab = rcu_dereference_protected(evdev->grab,
                    lockdep_is_held(&evdev->mutex));

    if (grab != client)
        return  -EINVAL;

    rcu_assign_pointer(evdev->grab, NULL);
    synchronize_rcu();
    input_release_device(&evdev->handle);

    return 0;
}

static void evdev_attach_client(struct evdev *evdev,
                struct evdev_client *client)
{
    spin_lock(&evdev->client_lock);
    list_add_tail_rcu(&client->node, &evdev->client_list);
    spin_unlock(&evdev->client_lock);
}

static void evdev_detach_client(struct evdev *evdev,
                struct evdev_client *client)
{
    spin_lock(&evdev->client_lock);
    list_del_rcu(&client->node);
    spin_unlock(&evdev->client_lock);
    synchronize_rcu();
}

static int evdev_open_device(struct evdev *evdev)
{
    int retval;

    retval = mutex_lock_interruptible(&evdev->mutex);
    if (retval)
        return retval;

    if (!evdev->exist)
        retval = -ENODEV;
    else if (!evdev->open++) {
        retval = input_open_device(&evdev->handle);
        if (retval)
            evdev->open--;
    }

    mutex_unlock(&evdev->mutex);
    return retval;
}

static void evdev_close_device(struct evdev *evdev)
{
    mutex_lock(&evdev->mutex);

    if (evdev->exist && !--evdev->open)
        input_close_device(&evdev->handle);

    mutex_unlock(&evdev->mutex);
}

/*
 * Wake up users waiting for IO so they can disconnect from
 * dead device.
 */
static void evdev_hangup(struct evdev *evdev)
{
    struct evdev_client *client;

    spin_lock(&evdev->client_lock);
    list_for_each_entry(client, &evdev->client_list, node)
        kill_fasync(&client->fasync, SIGIO, POLL_HUP);
    spin_unlock(&evdev->client_lock);

    wake_up_interruptible(&evdev->wait);
}

static int evdev_release(struct inode *inode, struct file *file)
{
    struct evdev_client *client = file->private_data;
    struct evdev *evdev = client->evdev;

    mutex_lock(&evdev->mutex);
    evdev_ungrab(evdev, client);
    mutex_unlock(&evdev->mutex);

    evdev_detach_client(evdev, client);
    kfree(client);

    evdev_close_device(evdev);

    return 0;
}

static unsigned int evdev_compute_buffer_size(struct input_dev *dev)
{
    unsigned int n_events =
        max(dev->hint_events_per_packet * EVDEV_BUF_PACKETS,
            EVDEV_MIN_BUFFER_SIZE);

    return roundup_pow_of_two(n_events);
}

static int evdev_open(struct inode *inode, struct file *file)
{
    struct evdev *evdev = container_of(inode->i_cdev, struct evdev, cdev);
    unsigned int bufsize = evdev_compute_buffer_size(evdev->handle.dev);
    struct evdev_client *client;
    int error;

    client = kzalloc(sizeof(struct evdev_client) +
                bufsize * sizeof(struct input_event),
             GFP_KERNEL);
    if (!client)
        return -ENOMEM;

    client->bufsize = bufsize;
    spin_lock_init(&client->buffer_lock);
    client->evdev = evdev;
    evdev_attach_client(evdev, client);

    error = evdev_open_device(evdev);
    if (error)
        goto err_free_client;

    file->private_data = client;
    nonseekable_open(inode, file);

    return 0;

 err_free_client:
    evdev_detach_client(evdev, client);
    kfree(client);
    return error;
}

static ssize_t evdev_write(struct file *file, const char __user *buffer,
               size_t count, loff_t *ppos)
{
    struct evdev_client *client = file->private_data;
    struct evdev *evdev = client->evdev;
    struct input_event event;
    int retval = 0;

    if (count != 0 && count < input_event_size())
        return -EINVAL;

    retval = mutex_lock_interruptible(&evdev->mutex);
    if (retval)
        return retval;

    if (!evdev->exist) {
        retval = -ENODEV;
        goto out;
    }

    while (retval + input_event_size() <= count) {

        if (input_event_from_user(buffer + retval, &event)) {
            retval = -EFAULT;
            goto out;
        }
        retval += input_event_size();

        input_inject_event(&evdev->handle,
                   event.type, event.code, event.value);
    }

 out:
    mutex_unlock(&evdev->mutex);
    return retval;
}

static int evdev_fetch_next_event(struct evdev_client *client,
                  struct input_event *event)
{
    int have_event;

    spin_lock_irq(&client->buffer_lock);

    have_event = client->packet_head != client->tail;
    if (have_event) {
        *event = client->buffer[client->tail++];
        client->tail &= client->bufsize - 1;
    }

    spin_unlock_irq(&client->buffer_lock);

    return have_event;
}

static ssize_t evdev_read(struct file *file, char __user *buffer,
              size_t count, loff_t *ppos)
{
    struct evdev_client *client = file->private_data;
    struct evdev *evdev = client->evdev;
    struct input_event event;
    size_t read = 0;
    int error;

    if (count != 0 && count < input_event_size())
        return -EINVAL;

    for (;;) {
        if (!evdev->exist)
            return -ENODEV;

        if (client->packet_head == client->tail &&
            (file->f_flags & O_NONBLOCK))
            return -EAGAIN;

        /*
         * count == 0 is special - no IO is done but we check
         * for error conditions (see above).
         */
        if (count == 0)
            break;

        while (read + input_event_size() <= count &&
               evdev_fetch_next_event(client, &event)) {

            if (input_event_to_user(buffer + read, &event))
                return -EFAULT;

            read += input_event_size();
        }

        if (read)
            break;

        if (!(file->f_flags & O_NONBLOCK)) {
            error = wait_event_interruptible(evdev->wait,
                    client->packet_head != client->tail ||
                    !evdev->exist);
            if (error)
                return error;
        }
    }

    return read;
}

/* No kernel lock - fine */
static unsigned int evdev_poll(struct file *file, poll_table *wait)
{
    struct evdev_client *client = file->private_data;
    struct evdev *evdev = client->evdev;
    unsigned int mask;

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

    mask = evdev->exist ? POLLOUT | POLLWRNORM : POLLHUP | POLLERR;
    if (client->packet_head != client->tail)
        mask |= POLLIN | POLLRDNORM;

    return mask;
}

#ifdef CONFIG_COMPAT

#define BITS_PER_LONG_COMPAT (sizeof(compat_long_t) * 8)
#define BITS_TO_LONGS_COMPAT(x) ((((x) - 1) / BITS_PER_LONG_COMPAT) + 1)

#ifdef __BIG_ENDIAN
static int bits_to_user(unsigned long *bits, unsigned int maxbit,
            unsigned int maxlen, void __user *p, int compat)
{
    int len, i;

    if (compat) {
        len = BITS_TO_LONGS_COMPAT(maxbit) * sizeof(compat_long_t);
        if (len > maxlen)
            len = maxlen;

        for (i = 0; i < len / sizeof(compat_long_t); i++)
            if (copy_to_user((compat_long_t __user *) p + i,
                     (compat_long_t *) bits +
                        i + 1 - ((i % 2) << 1),
                     sizeof(compat_long_t)))
                return -EFAULT;
    } else {
        len = BITS_TO_LONGS(maxbit) * sizeof(long);
        if (len > maxlen)
            len = maxlen;

        if (copy_to_user(p, bits, len))
            return -EFAULT;
    }

    return len;
}
#else
static int bits_to_user(unsigned long *bits, unsigned int maxbit,
            unsigned int maxlen, void __user *p, int compat)
{
    int len = compat ?
            BITS_TO_LONGS_COMPAT(maxbit) * sizeof(compat_long_t) :
            BITS_TO_LONGS(maxbit) * sizeof(long);

    if (len > maxlen)
        len = maxlen;

    return copy_to_user(p, bits, len) ? -EFAULT : len;
}
#endif /* __BIG_ENDIAN */

#else

static int bits_to_user(unsigned long *bits, unsigned int maxbit,
            unsigned int maxlen, void __user *p, int compat)
{
    int len = BITS_TO_LONGS(maxbit) * sizeof(long);

    if (len > maxlen)
        len = maxlen;

    return copy_to_user(p, bits, len) ? -EFAULT : len;
}

#endif /* CONFIG_COMPAT */

static int str_to_user(const char *str, unsigned int maxlen, void __user *p)
{
    int len;

    if (!str)
        return -ENOENT;

    len = strlen(str) + 1;
    if (len > maxlen)
        len = maxlen;

    return copy_to_user(p, str, len) ? -EFAULT : len;
}

#define OLD_KEY_MAX 0x1ff
static int handle_eviocgbit(struct input_dev *dev,
                unsigned int type, unsigned int size,
                void __user *p, int compat_mode)
{
    static unsigned long keymax_warn_time;
    unsigned long *bits;
    int len;

    switch (type) {

    case      0: bits = dev->evbit;  len = EV_MAX;  break;
    case EV_KEY: bits = dev->keybit; len = KEY_MAX; break;
    case EV_REL: bits = dev->relbit; len = REL_MAX; break;
    case EV_ABS: bits = dev->absbit; len = ABS_MAX; break;
    case EV_MSC: bits = dev->mscbit; len = MSC_MAX; break;
    case EV_LED: bits = dev->ledbit; len = LED_MAX; break;
    case EV_SND: bits = dev->sndbit; len = SND_MAX; break;
    case EV_FF:  bits = dev->ffbit;  len = FF_MAX;  break;
    case EV_SW:  bits = dev->swbit;  len = SW_MAX;  break;
    default: return -EINVAL;
    }

    /*
     * Work around bugs in userspace programs that like to do
     * EVIOCGBIT(EV_KEY, KEY_MAX) and not realize that 'len'
     * should be in bytes, not in bits.
     */
    if (type == EV_KEY && size == OLD_KEY_MAX) {
        len = OLD_KEY_MAX;
        if (printk_timed_ratelimit(&keymax_warn_time, 10 * 1000))
            pr_warning("(EVIOCGBIT): Suspicious buffer size %u, "
                   "limiting output to %zu bytes. See "
                   "http://userweb.kernel.org/~dtor/eviocgbit-bug.html\n",
                   OLD_KEY_MAX,
                   BITS_TO_LONGS(OLD_KEY_MAX) * sizeof(long));
    }

    return bits_to_user(bits, len, size, p, compat_mode);
}
#undef OLD_KEY_MAX

static int evdev_handle_get_keycode(struct input_dev *dev, void __user *p)
{
    struct input_keymap_entry ke = {
        .len    = sizeof(unsigned int),
        .flags  = 0,
    };
    int __user *ip = (int __user *)p;
    int error;

    /* legacy case */
    if (copy_from_user(ke.scancode, p, sizeof(unsigned int)))
        return -EFAULT;

    error = input_get_keycode(dev, &ke);
    if (error)
        return error;

    if (put_user(ke.keycode, ip + 1))
        return -EFAULT;

    return 0;
}

static int evdev_handle_get_keycode_v2(struct input_dev *dev, void __user *p)
{
    struct input_keymap_entry ke;
    int error;

    if (copy_from_user(&ke, p, sizeof(ke)))
        return -EFAULT;

    error = input_get_keycode(dev, &ke);
    if (error)
        return error;

    if (copy_to_user(p, &ke, sizeof(ke)))
        return -EFAULT;

    return 0;
}

static int evdev_handle_set_keycode(struct input_dev *dev, void __user *p)
{
    struct input_keymap_entry ke = {
        .len    = sizeof(unsigned int),
        .flags  = 0,
    };
    int __user *ip = (int __user *)p;

    if (copy_from_user(ke.scancode, p, sizeof(unsigned int)))
        return -EFAULT;

    if (get_user(ke.keycode, ip + 1))
        return -EFAULT;

    return input_set_keycode(dev, &ke);
}

static int evdev_handle_set_keycode_v2(struct input_dev *dev, void __user *p)
{
    struct input_keymap_entry ke;

    if (copy_from_user(&ke, p, sizeof(ke)))
        return -EFAULT;

    if (ke.len > sizeof(ke.scancode))
        return -EINVAL;

    return input_set_keycode(dev, &ke);
}

static int evdev_handle_mt_request(struct input_dev *dev,
                   unsigned int size,
                   int __user *ip)
{
    const struct input_mt *mt = dev->mt;
    unsigned int code;
    int max_slots;
    int i;

    if (get_user(code, &ip[0]))
        return -EFAULT;
    if (!mt || !input_is_mt_value(code))
        return -EINVAL;

    max_slots = (size - sizeof(__u32)) / sizeof(__s32);
    for (i = 0; i < mt->num_slots && i < max_slots; i++) {
        int value = input_mt_get_value(&mt->slots[i], code);
        if (put_user(value, &ip[1 + i]))
            return -EFAULT;
    }

    return 0;
}

static long evdev_do_ioctl(struct file *file, unsigned int cmd,
               void __user *p, int compat_mode)
{
    struct evdev_client *client = file->private_data;
    struct evdev *evdev = client->evdev;
    struct input_dev *dev = evdev->handle.dev;
    struct input_absinfo abs;
    struct ff_effect effect;
    int __user *ip = (int __user *)p;
    unsigned int i, t, u, v;
    unsigned int size;
    int error;

    /* First we check for fixed-length commands */
    switch (cmd) {

    case EVIOCGVERSION:
        return put_user(EV_VERSION, ip);

    case EVIOCGID:
        if (copy_to_user(p, &dev->id, sizeof(struct input_id)))
            return -EFAULT;
        return 0;

    case EVIOCGREP:
        if (!test_bit(EV_REP, dev->evbit))
            return -ENOSYS;
        if (put_user(dev->rep[REP_DELAY], ip))
            return -EFAULT;
        if (put_user(dev->rep[REP_PERIOD], ip + 1))
            return -EFAULT;
        return 0;

    case EVIOCSREP:
        if (!test_bit(EV_REP, dev->evbit))
            return -ENOSYS;
        if (get_user(u, ip))
            return -EFAULT;
        if (get_user(v, ip + 1))
            return -EFAULT;

        input_inject_event(&evdev->handle, EV_REP, REP_DELAY, u);
        input_inject_event(&evdev->handle, EV_REP, REP_PERIOD, v);

        return 0;

    case EVIOCRMFF:
        return input_ff_erase(dev, (int)(unsigned long) p, file);

    case EVIOCGEFFECTS:
        i = test_bit(EV_FF, dev->evbit) ?
                dev->ff->max_effects : 0;
        if (put_user(i, ip))
            return -EFAULT;
        return 0;

    case EVIOCGRAB:
        if (p)
            return evdev_grab(evdev, client);
        else
            return evdev_ungrab(evdev, client);

    case EVIOCSCLOCKID:
        if (copy_from_user(&i, p, sizeof(unsigned int)))
            return -EFAULT;
        if (i != CLOCK_MONOTONIC && i != CLOCK_REALTIME)
            return -EINVAL;
        client->clkid = i;
        return 0;

    case EVIOCGKEYCODE:
        return evdev_handle_get_keycode(dev, p);

    case EVIOCSKEYCODE:
        return evdev_handle_set_keycode(dev, p);

    case EVIOCGKEYCODE_V2:
        return evdev_handle_get_keycode_v2(dev, p);

    case EVIOCSKEYCODE_V2:
        return evdev_handle_set_keycode_v2(dev, p);
    }

    size = _IOC_SIZE(cmd);

    /* Now check variable-length commands */
#define EVIOC_MASK_SIZE(nr) ((nr) & ~(_IOC_SIZEMASK << _IOC_SIZESHIFT))
    switch (EVIOC_MASK_SIZE(cmd)) {

    case EVIOCGPROP(0):
        return bits_to_user(dev->propbit, INPUT_PROP_MAX,
                    size, p, compat_mode);

    case EVIOCGMTSLOTS(0):
        return evdev_handle_mt_request(dev, size, ip);

    case EVIOCGKEY(0):
        return bits_to_user(dev->key, KEY_MAX, size, p, compat_mode);

    case EVIOCGLED(0):
        return bits_to_user(dev->led, LED_MAX, size, p, compat_mode);

    case EVIOCGSND(0):
        return bits_to_user(dev->snd, SND_MAX, size, p, compat_mode);

    case EVIOCGSW(0):
        return bits_to_user(dev->sw, SW_MAX, size, p, compat_mode);

    case EVIOCGNAME(0):
        return str_to_user(dev->name, size, p);

    case EVIOCGPHYS(0):
        return str_to_user(dev->phys, size, p);

    case EVIOCGUNIQ(0):
        return str_to_user(dev->uniq, size, p);

    case EVIOC_MASK_SIZE(EVIOCSFF):
        if (input_ff_effect_from_user(p, size, &effect))
            return -EFAULT;

        error = input_ff_upload(dev, &effect, file);

        if (put_user(effect.id, &(((struct ff_effect __user *)p)->id)))
            return -EFAULT;

        return error;
    }

    /* Multi-number variable-length handlers */
    if (_IOC_TYPE(cmd) != 'E')
        return -EINVAL;

    if (_IOC_DIR(cmd) == _IOC_READ) {

        if ((_IOC_NR(cmd) & ~EV_MAX) == _IOC_NR(EVIOCGBIT(0, 0)))
            return handle_eviocgbit(dev,
                        _IOC_NR(cmd) & EV_MAX, size,
                        p, compat_mode);

        if ((_IOC_NR(cmd) & ~ABS_MAX) == _IOC_NR(EVIOCGABS(0))) {

            if (!dev->absinfo)
                return -EINVAL;

            t = _IOC_NR(cmd) & ABS_MAX;
            abs = dev->absinfo[t];

            if (copy_to_user(p, &abs, min_t(size_t,
                    size, sizeof(struct input_absinfo))))
                return -EFAULT;

            return 0;
        }
    }

    if (_IOC_DIR(cmd) == _IOC_WRITE) {

        if ((_IOC_NR(cmd) & ~ABS_MAX) == _IOC_NR(EVIOCSABS(0))) {

            if (!dev->absinfo)
                return -EINVAL;

            t = _IOC_NR(cmd) & ABS_MAX;

            if (copy_from_user(&abs, p, min_t(size_t,
                    size, sizeof(struct input_absinfo))))
                return -EFAULT;

            if (size < sizeof(struct input_absinfo))
                abs.resolution = 0;

            /* We can't change number of reserved MT slots */
            if (t == ABS_MT_SLOT)
                return -EINVAL;

            /*
             * Take event lock to ensure that we are not
             * changing device parameters in the middle
             * of event.
             */
            spin_lock_irq(&dev->event_lock);
            dev->absinfo[t] = abs;
            spin_unlock_irq(&dev->event_lock);

            return 0;
        }
    }

    return -EINVAL;
}

static long evdev_ioctl_handler(struct file *file, unsigned int cmd,
                void __user *p, int compat_mode)
{
    struct evdev_client *client = file->private_data;
    struct evdev *evdev = client->evdev;
    int retval;

    retval = mutex_lock_interruptible(&evdev->mutex);
    if (retval)
        return retval;

    if (!evdev->exist) {
        retval = -ENODEV;
        goto out;
    }

    retval = evdev_do_ioctl(file, cmd, p, compat_mode);

 out:
    mutex_unlock(&evdev->mutex);
    return retval;
}

static long evdev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
    return evdev_ioctl_handler(file, cmd, (void __user *)arg, 0);
}

#ifdef CONFIG_COMPAT
static long evdev_ioctl_compat(struct file *file,
                unsigned int cmd, unsigned long arg)
{
    return evdev_ioctl_handler(file, cmd, compat_ptr(arg), 1);
}
#endif

static const struct file_operations evdev_fops = {
    .owner      = THIS_MODULE,
    .read       = evdev_read,
    .write      = evdev_write,
    .poll       = evdev_poll,
    .open       = evdev_open,
    .release    = evdev_release,
    .unlocked_ioctl = evdev_ioctl,
#ifdef CONFIG_COMPAT
    .compat_ioctl   = evdev_ioctl_compat,
#endif
    .fasync     = evdev_fasync,
    .flush      = evdev_flush,
    .llseek     = no_llseek,
};

/*
 * Mark device non-existent. This disables writes, ioctls and
 * prevents new users from opening the device. Already posted
 * blocking reads will stay, however new ones will fail.
 */
static void evdev_mark_dead(struct evdev *evdev)
{
    mutex_lock(&evdev->mutex);
    evdev->exist = false;
    mutex_unlock(&evdev->mutex);
}

static void evdev_cleanup(struct evdev *evdev)
{
    struct input_handle *handle = &evdev->handle;

    evdev_mark_dead(evdev);
    evdev_hangup(evdev);

    cdev_del(&evdev->cdev);

    /* evdev is marked dead so no one else accesses evdev->open */
    if (evdev->open) {
        input_flush_device(handle, NULL);
        input_close_device(handle);
    }
}

/*
 * Create new evdev device. Note that input core serializes calls
 * to connect and disconnect.
 */
static int evdev_connect(struct input_handler *handler, struct input_dev *dev,
             const struct input_device_id *id)
{
    struct evdev *evdev;
    int minor;
    int dev_no;
    int error;

    minor = input_get_new_minor(EVDEV_MINOR_BASE, EVDEV_MINORS, true);
    if (minor < 0) {
        error = minor;
        pr_err("failed to reserve new minor: %d\n", error);
        return error;
    }

    evdev = kzalloc(sizeof(struct evdev), GFP_KERNEL);
    if (!evdev) {
        error = -ENOMEM;
        goto err_free_minor;
    }

    INIT_LIST_HEAD(&evdev->client_list);
    spin_lock_init(&evdev->client_lock);
    mutex_init(&evdev->mutex);
    init_waitqueue_head(&evdev->wait);
    evdev->exist = true;

    dev_no = minor;
    /* Normalize device number if it falls into legacy range */
    if (dev_no < EVDEV_MINOR_BASE + EVDEV_MINORS)
        dev_no -= EVDEV_MINOR_BASE;
    dev_set_name(&evdev->dev, "event%d", dev_no);

    evdev->handle.dev = input_get_device(dev);
    evdev->handle.name = dev_name(&evdev->dev);
    evdev->handle.handler = handler;
    evdev->handle.private = evdev;

    evdev->dev.devt = MKDEV(INPUT_MAJOR, minor);
    evdev->dev.class = &input_class;
    evdev->dev.parent = &dev->dev;
    evdev->dev.release = evdev_free;
    device_initialize(&evdev->dev);

    error = input_register_handle(&evdev->handle);
    if (error)
        goto err_free_evdev;

    cdev_init(&evdev->cdev, &evdev_fops);
    evdev->cdev.kobj.parent = &evdev->dev.kobj;
    error = cdev_add(&evdev->cdev, evdev->dev.devt, 1);
    if (error)
        goto err_unregister_handle;

    error = device_add(&evdev->dev);
    if (error)
        goto err_cleanup_evdev;

    return 0;

 err_cleanup_evdev:
    evdev_cleanup(evdev);
 err_unregister_handle:
    input_unregister_handle(&evdev->handle);
 err_free_evdev:
    put_device(&evdev->dev);
 err_free_minor:
    input_free_minor(minor);
    return error;
}

static void evdev_disconnect(struct input_handle *handle)
{
    struct evdev *evdev = handle->private;

    device_del(&evdev->dev);
    evdev_cleanup(evdev);
    input_free_minor(MINOR(evdev->dev.devt));
    input_unregister_handle(handle);
    put_device(&evdev->dev);
}

static const struct input_device_id evdev_ids[] = {
    { .driver_info = 1 },   /* Matches all devices */
    { },            /* Terminating zero entry */
};

MODULE_DEVICE_TABLE(input, evdev_ids);

static struct input_handler evdev_handler = {
    .event      = evdev_event,
    .events     = evdev_events,
    .connect    = evdev_connect,
    .disconnect = evdev_disconnect,
    .legacy_minors  = true,
    .minor      = EVDEV_MINOR_BASE,
    .name       = "evdev",
    .id_table   = evdev_ids,
};

static int __init evdev_init(void)
{
    return input_register_handler(&evdev_handler);
}

static void __exit evdev_exit(void)
{
    input_unregister_handler(&evdev_handler);
}

module_init(evdev_init);
module_exit(evdev_exit);

MODULE_AUTHOR("Vojtech Pavlik <[email protected]>");
MODULE_DESCRIPTION("Input driver event char devices");
MODULE_LICENSE("GPL");