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/mt.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 {
	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 struct evdev *evdev_table[EVDEV_MINORS];
static DEFINE_MUTEX(evdev_table_mutex);

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