evdev.c

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/*
 * 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 EVDEV_MINOR_BASE	64
#define EVDEV_MINORS		32
#define EVDEV_BUFFER_SIZE	64

#include <linux/poll.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 <linux/compat.h>

struct evdev {
	int exist;
	int open;
	int minor;
	char name[16];
	struct input_handle handle;
	wait_queue_head_t wait;
	struct evdev_client *grab;
	struct list_head client_list;
	spinlock_t client_lock; /* protects client_list */
	struct mutex mutex;
	struct device dev;
};

struct evdev_client {
	struct input_event buffer[EVDEV_BUFFER_SIZE];
	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;
};

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
	 */
	spin_lock(&client->buffer_lock);
	client->buffer[client->head++] = *event;
	client->head &= EVDEV_BUFFER_SIZE - 1;
	spin_unlock(&client->buffer_lock);

	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;
	int retval;

	retval = fasync_helper(fd, file, on, &client->fasync);

	return retval < 0 ? retval : 0;
}

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);

	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->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);
	synchronize_rcu();
}

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);
	if (evdev->grab == client)
		evdev_ungrab(evdev, client);
	mutex_unlock(&evdev->mutex);

	evdev_fasync(-1, file, 0);
	evdev_detach_client(evdev, client);
	kfree(client);

	evdev_close_device(evdev);
	put_device(&evdev->dev);

	return 0;
}

static int evdev_open(struct inode *inode, struct file *file)
{
	struct evdev *evdev;
	struct evdev_client *client;
	int i = iminor(inode) - EVDEV_MINOR_BASE;
	int error;

	if (i >= EVDEV_MINORS)
		return -ENODEV;

	error = mutex_lock_interruptible(&evdev_table_mutex);
	if (error)
		return error;
	evdev = evdev_table[i];
	if (evdev)
		get_device(&evdev->dev);
	mutex_unlock(&evdev_table_mutex);

	if (!evdev)
		return -ENODEV;

	client = kzalloc(sizeof(struct evdev_client), GFP_KERNEL);
	if (!client) {
		error = -ENOMEM;
		goto err_put_evdev;
	}

	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;
	return 0;

 err_free_client:
	evdev_detach_client(evdev, client);
	kfree(client);
 err_put_evdev:
	put_device(&evdev->dev);
	return error;
}

#ifdef CONFIG_COMPAT

struct input_event_compat {
	struct compat_timeval time;
	__u16 type;
	__u16 code;
	__s32 value;
};

/* Note to the author of this code: did it ever occur to
   you why the ifdefs are needed? Think about it again. -AK */
#ifdef CONFIG_X86_64
#  define COMPAT_TEST is_compat_task()
#elif defined(CONFIG_IA64)
#  define COMPAT_TEST IS_IA32_PROCESS(task_pt_regs(current))
#elif defined(CONFIG_S390)
#  define COMPAT_TEST test_thread_flag(TIF_31BIT)
#elif defined(CONFIG_MIPS)
#  define COMPAT_TEST test_thread_flag(TIF_32BIT_ADDR)
#else
#  define COMPAT_TEST test_thread_flag(TIF_32BIT)
#endif

static inline size_t evdev_event_size(void)
{
	return COMPAT_TEST ?
		sizeof(struct input_event_compat) : sizeof(struct input_event);
}

static int evdev_event_from_user(const char __user *buffer,
				 struct input_event *event)
{
	if (COMPAT_TEST) {
		struct input_event_compat compat_event;

		if (copy_from_user(&compat_event, buffer,
				   sizeof(struct input_event_compat)))
			return -EFAULT;

		event->time.tv_sec = compat_event.time.tv_sec;
		event->time.tv_usec = compat_event.time.tv_usec;
		event->type = compat_event.type;
		event->code = compat_event.code;
		event->value = compat_event.value;

	} else {
		if (copy_from_user(event, buffer, sizeof(struct input_event)))
			return -EFAULT;
	}

	return 0;
}

static int evdev_event_to_user(char __user *buffer,
				const struct input_event *event)
{
	if (COMPAT_TEST) {
		struct input_event_compat compat_event;

		compat_event.time.tv_sec = event->time.tv_sec;
		compat_event.time.tv_usec = event->time.tv_usec;
		compat_event.type = event->type;
		compat_event.code = event->code;
		compat_event.value = event->value;

		if (copy_to_user(buffer, &compat_event,
				 sizeof(struct input_event_compat)))
			return -EFAULT;

	} else {
		if (copy_to_user(buffer, event, sizeof(struct input_event)))
			return -EFAULT;
	}

	return 0;
}

#else

static inline size_t evdev_event_size(void)
{
	return sizeof(struct input_event);
}

static int evdev_event_from_user(const char __user *buffer,
				 struct input_event *event)
{
	if (copy_from_user(event, buffer, sizeof(struct input_event)))
		return -EFAULT;

	return 0;
}

static int evdev_event_to_user(char __user *buffer,
				const struct input_event *event)
{
	if (copy_to_user(buffer, event, sizeof(struct input_event)))
		return -EFAULT;

	return 0;
}

#endif /* CONFIG_COMPAT */

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;

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

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

	while (retval < count) {

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

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

 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->head != client->tail;
	if (have_event) {
		*event = client->buffer[client->tail++];
		client->tail &= EVDEV_BUFFER_SIZE - 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;
	int retval;

	if (count < evdev_event_size())
		return -EINVAL;

	if (client->head == client->tail && evdev->exist &&
	    (file->f_flags & O_NONBLOCK))
		return -EAGAIN;

	retval = wait_event_interruptible(evdev->wait,
		client->head != client->tail || !evdev->exist);
	if (retval)
		return retval;

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

	while (retval + evdev_event_size() <= count &&
	       evdev_fetch_next_event(client, &event)) {

		if (evdev_event_to_user(buffer + retval, &event))
			return -EFAULT;

		retval += evdev_event_size();
	}

	return retval;
}

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