path: root/drivers/input/misc/uinput.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  User level driver support for input subsystem
 *
 * Heavily based on evdev.c by Vojtech Pavlik
 *
 * Author: Aristeu Sergio Rozanski Filho <aris@cathedrallabs.org>
 *
 * Changes/Revisions:
 *	0.4	01/09/2014 (Benjamin Tissoires <benjamin.tissoires@redhat.com>)
 *		- add UI_GET_SYSNAME ioctl
 *	0.3	09/04/2006 (Anssi Hannula <anssi.hannula@gmail.com>)
 *		- updated ff support for the changes in kernel interface
 *		- added MODULE_VERSION
 *	0.2	16/10/2004 (Micah Dowty <micah@navi.cx>)
 *		- added force feedback support
 *              - added UI_SET_PHYS
 *	0.1	20/06/2002
 *		- first public version
 */
#include <uapi/linux/uinput.h>
#include <linux/poll.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/overflow.h>
#include <linux/input/mt.h>
#include "../input-compat.h"

#define UINPUT_NAME		"uinput"
#define UINPUT_BUFFER_SIZE	16
#define UINPUT_NUM_REQUESTS	16

enum uinput_state { UIST_NEW_DEVICE, UIST_SETUP_COMPLETE, UIST_CREATED };

struct uinput_request {
	unsigned int		id;
	unsigned int		code;	/* UI_FF_UPLOAD, UI_FF_ERASE */

	int			retval;
	struct completion	done;

	union {
		unsigned int	effect_id;
		struct {
			struct ff_effect *effect;
			struct ff_effect *old;
		} upload;
	} u;
};

struct uinput_device {
	struct input_dev	*dev;
	struct mutex		mutex;
	enum uinput_state	state;
	wait_queue_head_t	waitq;
	unsigned char		ready;
	unsigned char		head;
	unsigned char		tail;
	struct input_event	buff[UINPUT_BUFFER_SIZE];
	unsigned int		ff_effects_max;

	struct uinput_request	*requests[UINPUT_NUM_REQUESTS];
	wait_queue_head_t	requests_waitq;
	spinlock_t		requests_lock;
};

static int uinput_dev_event(struct input_dev *dev,
			    unsigned int type, unsigned int code, int value)
{
	struct uinput_device	*udev = input_get_drvdata(dev);
	struct timespec64	ts;

	udev->buff[udev->head].type = type;
	udev->buff[udev->head].code = code;
	udev->buff[udev->head].value = value;
	ktime_get_ts64(&ts);
	udev->buff[udev->head].input_event_sec = ts.tv_sec;
	udev->buff[udev->head].input_event_usec = ts.tv_nsec / NSEC_PER_USEC;
	udev->head = (udev->head + 1) % UINPUT_BUFFER_SIZE;

	wake_up_interruptible(&udev->waitq);

	return 0;
}

/* Atomically allocate an ID for the given request. Returns 0 on success. */
static bool uinput_request_alloc_id(struct uinput_device *udev,
				    struct uinput_request *request)
{
	unsigned int id;
	bool reserved = false;

	spin_lock(&udev->requests_lock);

	for (id = 0; id < UINPUT_NUM_REQUESTS; id++) {
		if (!udev->requests[id]) {
			request->id = id;
			udev->requests[id] = request;
			reserved = true;
			break;
		}
	}

	spin_unlock(&udev->requests_lock);
	return reserved;
}

static struct uinput_request *uinput_request_find(struct uinput_device *udev,
						  unsigned int id)
{
	/* Find an input request, by ID. Returns NULL if the ID isn't valid. */
	if (id >= UINPUT_NUM_REQUESTS)
		return NULL;

	return udev->requests[id];
}

static int uinput_request_reserve_slot(struct uinput_device *udev,
				       struct uinput_request *request)
{
	/* Allocate slot. If none are available right away, wait. */
	return wait_event_interruptible(udev->requests_waitq,
					uinput_request_alloc_id(udev, request));
}

static void uinput_request_release_slot(struct uinput_device *udev,
					unsigned int id)
{
	/* Mark slot as available */
	spin_lock(&udev->requests_lock);
	udev->requests[id] = NULL;
	spin_unlock(&udev->requests_lock);

	wake_up(&udev->requests_waitq);
}

static int uinput_request_send(struct uinput_device *udev,
			       struct uinput_request *request)
{
	int retval;

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

	if (udev->state != UIST_CREATED) {
		retval = -ENODEV;
		goto out;
	}

	init_completion(&request->done);

	/*
	 * Tell our userspace application about this new request
	 * by queueing an input event.
	 */
	uinput_dev_event(udev->dev, EV_UINPUT, request->code, request->id);

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

static int uinput_request_submit(struct uinput_device *udev,
				 struct uinput_request *request)
{
	int retval;

	retval = uinput_request_reserve_slot(udev, request);
	if (retval)
		return retval;

	retval = uinput_request_send(udev,