/*
 * 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/vmalloc.h>
#include <linux/mm.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"

enum evdev_clock_type {
        EV_CLK_REAL = 0,
        EV_CLK_MONO,
        EV_CLK_BOOT,
        EV_CLK_MAX
};

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;
        unsigned int clk_type;
        bool revoked;
        unsigned long *evmasks[EV_CNT];
        unsigned int bufsize;
        struct input_event buffer[];
};

static size_t evdev_get_mask_cnt(unsigned int type)
{
        static const size_t counts[EV_CNT] = {
                /* EV_SYN==0 is EV_CNT, _not_ SYN_CNT, see EVIOCGBIT */
                [EV_SYN]        = EV_CNT,
                [EV_KEY]        = KEY_CNT,
                [EV_REL]        = REL_CNT,
                [EV_ABS]        = ABS_CNT,
                [EV_MSC]        = MSC_CNT,
                [EV_SW]         = SW_CNT,
                [EV_LED]        = LED_CNT,
                [EV_SND]        = SND_CNT,
                [EV_FF]         = FF_CNT,
        };

        return (type < EV_CNT) ? counts[type] : 0;
}

/* requires the buffer lock to be held */
static bool __evdev_is_filtered(struct evdev_client *client,
                                unsigned int type,
                                unsigned int code)
{
        unsigned long *mask;
        size_t cnt;

        /* EV_SYN and unknown codes are never filtered */
        if (type == EV_SYN || type >= EV_CNT)
                return false;

        /* first test whether the type is filtered */
        mask = client->evmasks[0];
        if (mask && !test_bit(type, mask))
                return true;

        /* unknown values are never filtered */
        cnt = evdev_get_mask_cnt(type);
        if (!cnt || code >= cnt)
                return false;

        mask = client->evmasks[type];
        return mask && !test_bit(code, mask);
}

/* flush queued events of type @type, caller must hold client->buffer_lock */
static void __evdev_flush_queue(struct evdev_client *client, unsigned int type)
{
        unsigned int i, head, num;
        unsigned int mask = client->bufsize - 1;
        bool is_report;
        struct input_event *ev;

        BUG_ON(type == EV_SYN);

        head = client->tail;
        client->packet_head = client->tail;

        /* init to 1 so a leading SYN_REPORT will not be dropped */
        num = 1;

        for (i = client->tail; i != client->head; i = (i + 1) & mask) {
                ev = &client->buffer[i];
                is_report = ev->type == EV_SYN && ev->code == SYN_REPORT;

                if (ev->type == type) {
                        /* drop matched entry */
                        continue;
                } else if (is_report && !num) {
                        /* drop empty SYN_REPORT groups */
                        continue;
                } else if (head != i) {
                        /* move entry to fill the gap */
                        client->buffer[head] = *ev;
                }

                num++;
                head = (head + 1) & mask;

                if (is_report) {
                        num = 0;
                        client->packet_head = head;
                }
        }

        client->head = head;
}

static void __evdev_queue_syn_dropped(struct evdev_client *client)
{
        struct input_event ev;
        ktime_t time;
        struct timespec64 ts;

        time = client->clk_type == EV_CLK_REAL ?
                        ktime_get_real() :
                        client->clk_type == EV_CLK_MONO ?
                                ktime_get() :
                                ktime_get_boottime();

        ts = ktime_to_timespec64(time);
        ev.input_event_sec = ts.tv_sec;
        ev.input_event_usec = ts.tv_nsec / NSEC_PER_USEC;
        ev.type = EV_SYN;
        ev.code = SYN_DROPPED;
        ev.value = 0;

        client->buffer[client->head++] = ev;
        client->head &= client->bufsize - 1;

        if (unlikely(client->head == client->tail)) {
                /* drop queue but keep our SYN_DROPPED event */
                client->tail = (client->head - 1) & (client->bufsize - 1);
                client->packet_head = client->tail;
        }
}

static void evdev_queue_syn_dropped(struct evdev_client *client)
{
        unsigned long flags;

        spin_lock_irqsave(&client->buffer_lock, flags);
        __evdev_queue_syn_dropped(client);
        spin_unlock_irqrestore(&client->buffer_lock, flags);
}

static int evdev_set_clk_type(struct evdev_client *client, unsigned int clkid)
{
        unsigned long flags;
        unsigned int clk_type;

        switch (clkid) {

        case CLOCK_REALTIME:
                clk_type = EV_CLK_REAL;
                break;
        case CLOCK_MONOTONIC:
                clk_type = EV_CLK_MONO;
                break;
        case CLOCK_BOOTTIME:
                clk_type = EV_CLK_BOOT;
                break;
        default:
                return -EINVAL;
        }

        if (client->clk_type != clk_type) {
                client->clk_type = clk_type;

                /*
                 * Flush pending events and queue SYN_DROPPED event,
                 * but only if the queue is not empty.
                 */
                spin_lock_irqsave(&client->buffer_lock, flags);

                if (client->head != client->tail) {
                        client->packet_head = client->head = client->tail;
                        __evdev_queue_syn_dropped(client);
                }

                spin_unlock_irqrestore(&client->buffer_lock, flags);
        }

        return 0;
}

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].input_event_sec =
                                                event->input_event_sec;
                client->buffer[client->tail].input_event_usec =
                                                event->input_event_usec;
                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 *ev_time)
{
        struct evdev *evdev = client->evdev;
        const struct input_value *v;
        struct input_event event;
        struct timespec64 ts;
        bool wakeup = false;

        if (client->revoked)
                return;

        ts = ktime_to_timespec64(ev_time[client->clk_type]);
        event.input_event_sec = ts.tv_sec;
        event.input_event_usec = ts.tv_nsec / NSEC_PER_USEC;

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

        for (v = vals; v != vals + count; v++) {
                if (__evdev_is_filtered(client, v->type, v->code))
                        continue;

                if (v->type == EV_SYN && v->code == SYN_REPORT) {
                        /* drop empty SYN_REPORT */
                        if (client->packet_head == client->head)
                                continue;

                        wakeup = true;
                }

                event.type = v->type;
                event.code = v->code;
                event.value = v->value;
                __pass_event(client, &event);
        }

        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 ev_time[EV_CLK_MAX];

        ev_time[EV_CLK_MONO] = ktime_get();
        ev_time[EV_CLK_REAL] = ktime_mono_to_real(ev_time[EV_CLK_MONO]);
        ev_time[EV_CLK_BOOT] = ktime_mono_to_any(ev_time[EV_CLK_MONO],
                                                 TK_OFFS_BOOT);

        rcu_read_lock();

        client = rcu_dereference(evdev->grab);

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

        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;

        mutex_lock(&evdev->mutex);

        if (evdev->exist && !client->revoked)
                input_flush_device(&evdev->handle, file);

        mutex_unlock(&evdev->mutex);
        return 0;
}

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;
        unsigned int i;

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

        evdev_detach_client(evdev, client);

        for (i = 0; i < EV_CNT; ++i)
                bitmap_free(client->evmasks[i]);

        kvfree(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);
        unsigned int size = sizeof(struct evdev_client) +
                                        bufsize * sizeof(struct input_event);
        struct evdev_client *client;
        int error;

        client = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
        if (!client)
                client = vzalloc(size);
        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);
        kvfree(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 || client->revoked) {
                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);
                cond_resched();
        }

 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 || client->revoked)
                        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 || client->revoked);
                        if (error)
                                return error;
                }
        }

        return read;
}

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

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

        if (evdev->exist && !client->revoked)
                mask = EPOLLOUT | EPOLLWRNORM;
        else
                mask = EPOLLHUP | EPOLLERR;

        if (client->packet_head != client->tail)
                mask |= EPOLLIN | EPOLLRDNORM;

        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;
}

static int bits_from_user(unsigned long *bits, unsigned int maxbit,
                          unsigned int maxlen, const void __user *p, int compat)
{
        int len, i;

        if (compat) {
                if (maxlen % sizeof(compat_long_t))
                        return -EINVAL;

                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_from_user((compat_long_t *) bits +
                                                i + 1 - ((i % 2) << 1),
                                           (compat_long_t __user *) p + i,
                                           sizeof(compat_long_t)))
                                return -EFAULT;
                if (i % 2)
                        *((compat_long_t *) bits + i - 1) = 0;

        } else {
                if (maxlen % sizeof(long))
                        return -EINVAL;

                len = BITS_TO_LONGS(maxbit) * sizeof(long);
                if (len > maxlen)
                        len = maxlen;

                if (copy_from_user(bits, p, 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;
}

static int bits_from_user(unsigned long *bits, unsigned int maxbit,
                          unsigned int maxlen, const void __user *p, int compat)
{
        size_t chunk_size = compat ? sizeof(compat_long_t) : sizeof(long);
        int len;

        if (maxlen % chunk_size)
                return -EINVAL;

        len = compat ? BITS_TO_LONGS_COMPAT(maxbit) : BITS_TO_LONGS(maxbit);
        len *= chunk_size;
        if (len > maxlen)
                len = maxlen;

        return copy_from_user(bits, p, 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;
}

static int bits_from_user(unsigned long *bits, unsigned int maxbit,
                          unsigned int maxlen, const void __user *p, int compat)
{
        int len;

        if (maxlen % sizeof(long))
                return -EINVAL;

        len = BITS_TO_LONGS(maxbit) * sizeof(long);
        if (len > maxlen)
                len = maxlen;

        return copy_from_user(bits, p, 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;
}

static int handle_eviocgbit(struct input_dev *dev,
                            unsigned int type, unsigned int size,
                            void __user *p, int compat_mode)
{
        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;
        }

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

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);
}

/*
 * If we transfer state to the user, we should flush all pending events
 * of the same type from the client's queue. Otherwise, they might end up
 * with duplicate events, which can screw up client's state tracking.
 * If bits_to_user fails after flushing the queue, we queue a SYN_DROPPED
 * event so user-space will notice missing events.
 *
 * LOCKING:
 * We need to take event_lock before buffer_lock to avoid dead-locks. But we
 * need the even_lock only to guarantee consistent state. We can safely release
 * it while flushing the queue. This allows input-core to handle filters while
 * we flush the queue.
 */
static int evdev_handle_get_val(struct evdev_client *client,
                                struct input_dev *dev, unsigned int type,
                                unsigned long *bits, unsigned int maxbit,
                                unsigned int maxlen, void __user *p,
                                int compat)
{
        int ret;
        unsigned long *mem;

        mem = bitmap_alloc(maxbit, GFP_KERNEL);
        if (!mem)
                return -ENOMEM;

        spin_lock_irq(&dev->event_lock);
        spin_lock(&client->buffer_lock);

        bitmap_copy(mem, bits, maxbit);

        spin_unlock(&dev->event_lock);

        __evdev_flush_queue(client, type);

        spin_unlock_irq(&client->buffer_lock);

        ret = bits_to_user(mem, maxbit, maxlen, p, compat);
        if (ret < 0)
                evdev_queue_syn_dropped(client);

        bitmap_free(mem);

        return ret;
}

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 int evdev_revoke(struct evdev *evdev, struct evdev_client *client,
                        struct file *file)
{
        client->revoked = true;
        evdev_ungrab(evdev, client);
        input_flush_device(&evdev->handle, file);
        wake_up_interruptible(&evdev->wait);

        return 0;
}

/* must be called with evdev-mutex held */
static int evdev_set_mask(struct evdev_client *client,
                          unsigned int type,
                          const void __user *codes,
                          u32 codes_size,
                          int compat)
{
        unsigned long flags, *mask, *oldmask;
        size_t cnt;
        int error;

        /* we allow unknown types and 'codes_size > size' for forward-compat */

        cnt = evdev_get_mask_cnt(type);
        if (!cnt)
                return 0;

        mask = bitmap_zalloc(cnt, GFP_KERNEL);
        if (!mask)
                return -ENOMEM;

        error = bits_from_user(mask, cnt - 1, codes_size, codes, compat);
        if (error < 0) {
                bitmap_free(mask);
                return error;
        }

        spin_lock_irqsave(&client->buffer_lock, flags);
        oldmask = client->evmasks[type];
        client->evmasks[type] = mask;
        spin_unlock_irqrestore(&client->buffer_lock, flags);

        bitmap_free(oldmask);

        return 0;
}

/* must be called with evdev-mutex held */
static int evdev_get_mask(struct evdev_client *client,
                          unsigned int type,
                          void __user *codes,
                          u32 codes_size,
                          int compat)
{
        unsigned long *mask;
        size_t cnt, size, xfer_size;
        int i;
        int error;

        /* we allow unknown types and 'codes_size > size' for forward-compat */
        cnt = evdev_get_mask_cnt(type);
        size = sizeof(unsigned long) * BITS_TO_LONGS(cnt);
        xfer_size = min_t(size_t, codes_size, size);

        if (cnt > 0) {
                mask = client->evmasks[type];
                if (mask) {
                        error = bits_to_user(mask, cnt - 1,
                                             xfer_size, codes, compat);
                        if (error < 0)
                                return error;
                } else {
                        /* fake mask with all bits set */
                        for (i = 0; i < xfer_size; i++)
                                if (put_user(0xffU, (u8 __user *)codes + i))
                                        return -EFAULT;
                }
        }

        if (xfer_size < codes_size)
                if (clear_user(codes + xfer_size, codes_size - xfer_size))
                        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 input_mask mask;
        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 EVIOCREVOKE:
                if (p)
                        return -EINVAL;
                else
                        return evdev_revoke(evdev, client, file);

        case EVIOCGMASK: {
                void __user *codes_ptr;

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

                codes_ptr = (void __user *)(unsigned long)mask.codes_ptr;
                return evdev_get_mask(client,
                                      mask.type, codes_ptr, mask.codes_size,
                                      compat_mode);
        }

        case EVIOCSMASK: {
                const void __user *codes_ptr;

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

                codes_ptr = (const void __user *)(unsigned long)mask.codes_ptr;
                return evdev_set_mask(client,
                                      mask.type, codes_ptr, mask.codes_size,
                                      compat_mode);
        }

        case EVIOCSCLOCKID:
                if (copy_from_user(&i, p, sizeof(unsigned int)))
                        return -EFAULT;

                return evdev_set_clk_type(client, i);

        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 evdev_handle_get_val(client, dev, EV_KEY, dev->key,
                                            KEY_MAX, size, p, compat_mode);

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

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

        case EVIOCGSW(0):
                return evdev_handle_get_val(client, dev, EV_SW, 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 (error)
                        return error;

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

                return 0;
        }

        /* 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 || client->revoked) {
                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);

        /* 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);

        error = cdev_device_add(&evdev->cdev, &evdev->dev);
        if (error)
                goto err_cleanup_evdev;

        return 0;

 err_cleanup_evdev:
        evdev_cleanup(evdev);
        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;

        cdev_device_del(&evdev->cdev, &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 <vojtech@ucw.cz>");
MODULE_DESCRIPTION("Input driver event char devices");
MODULE_LICENSE("GPL");