path: root/drivers/input/evdev.c

/*
 * 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.h>
#include <linux/major.h>
#include <linux/device.h>
#include "input-compat.h"

struct evdev {
	int open;
	int minor;
	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;
	bool exist;
};

struct evdev_client {
	int head;
	int tail;
	spinlock_t buffer_lock; /* protects access to buffer, head and tail */
	struct fasync_struct *fasync;
	struct evdev *evdev;
	struct list_head node;
	int bufsize;
	struct input_event buffer[];
};

static struct evdev *evdev_table[EVDEV_MINORS];
static DEFINE_MUTEX(evdev_table_mutex);

static void evdev_pass_event(struct evdev_client *client,
			     struct input_event *event)
{
	/*
	 * Interrupts are disabled, just acquire the lock.
	 * Make sure we don't leave with the client buffer
	 * "empty" by having client->head == client->tail.
	 */
	spin_lock(&client->buffer_lock);
	do {
		client->buffer[client->head++] = *event;
		client->head &= client->bufsize - 1;
	} while (client->head == client->tail);
	spin_unlock(&client->buffer_lock);

	if (event->type == EV_SYN)
		kill_fasync(&client->fasync, SIGIO, POLL_IN);
}

/*
 * Pass incoming event to all connected clients.
 */
static void evdev_event(struct input_handle *handle,
			unsigned int type, unsigned int code, int value)
{
	struct evdev *evdev = handle->private;
	struct evdev_client *client;
	struct input_event event;

	do_gettimeofday(&event.time);
	event.type = type;
	event.code = code;
	event.value = value;

	rcu_read_lock();

	client = rcu_dereference(evdev->grab);
	if (client)
		evdev_pass_event(client, &event);
	else
		list_for_each_entry_rcu(client, &evdev->client_list, node)
			evdev_pass_event(client, &event);

	rcu_read_unlock();

	wake_up_interruptible(&evdev->wait);
}

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);
	synchronize_rcu();

	return 0;
}

static int evdev_ungrab(struct evdev *evdev, struct evdev_client *client)
{
	if (evdev->grab != client)
		return  -EINVAL;

	rcu_assign_pointer(evdev