1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * Userspace driver for the LED subsystem
  4 *
  5 * Copyright (C) 2016 David Lechner <david@lechnology.com>
  6 *
  7 * Based on uinput.c: Aristeu Sergio Rozanski Filho <aris@cathedrallabs.org>
  8 */
  9#include <linux/fs.h>
 10#include <linux/init.h>
 11#include <linux/leds.h>
 12#include <linux/miscdevice.h>
 13#include <linux/module.h>
 14#include <linux/poll.h>
 15#include <linux/sched.h>
 16#include <linux/slab.h>
 17
 18#include <uapi/linux/uleds.h>
 19
 20#define ULEDS_NAME	"uleds"
 21
 22enum uleds_state {
 23	ULEDS_STATE_UNKNOWN,
 24	ULEDS_STATE_REGISTERED,
 25};
 26
 27struct uleds_device {
 28	struct uleds_user_dev	user_dev;
 29	struct led_classdev	led_cdev;
 30	struct mutex		mutex;
 31	enum uleds_state	state;
 32	wait_queue_head_t	waitq;
 33	int			brightness;
 34	bool			new_data;
 35};
 36
 37static struct miscdevice uleds_misc;
 38
 39static void uleds_brightness_set(struct led_classdev *led_cdev,
 40				 enum led_brightness brightness)
 41{
 42	struct uleds_device *udev = container_of(led_cdev, struct uleds_device,
 43						 led_cdev);
 44
 45	if (udev->brightness != brightness) {
 46		udev->brightness = brightness;
 47		udev->new_data = true;
 48		wake_up_interruptible(&udev->waitq);
 49	}
 50}
 51
 52static int uleds_open(struct inode *inode, struct file *file)
 53{
 54	struct uleds_device *udev;
 55
 56	udev = kzalloc(sizeof(*udev), GFP_KERNEL);
 57	if (!udev)
 58		return -ENOMEM;
 59
 60	udev->led_cdev.name = udev->user_dev.name;
 61	udev->led_cdev.brightness_set = uleds_brightness_set;
 62
 63	mutex_init(&udev->mutex);
 64	init_waitqueue_head(&udev->waitq);
 65	udev->state = ULEDS_STATE_UNKNOWN;
 66
 67	file->private_data = udev;
 68	stream_open(inode, file);
 69
 70	return 0;
 71}
 72
 73static ssize_t uleds_write(struct file *file, const char __user *buffer,
 74			   size_t count, loff_t *ppos)
 75{
 76	struct uleds_device *udev = file->private_data;
 77	const char *name;
 78	int ret;
 79
 80	if (count == 0)
 81		return 0;
 82
 83	ret = mutex_lock_interruptible(&udev->mutex);
 84	if (ret)
 85		return ret;
 86
 87	if (udev->state == ULEDS_STATE_REGISTERED) {
 88		ret = -EBUSY;
 89		goto out;
 90	}
 91
 92	if (count != sizeof(struct uleds_user_dev)) {
 93		ret = -EINVAL;
 94		goto out;
 95	}
 96
 97	if (copy_from_user(&udev->user_dev, buffer,
 98			   sizeof(struct uleds_user_dev))) {
 99		ret = -EFAULT;
100		goto out;
101	}
102
103	name = udev->user_dev.name;
104	if (!name[0] || !strcmp(name, ".") || !strcmp(name, "..") ||
105	    strchr(name, '/')) {
106		ret = -EINVAL;
107		goto out;
108	}
109
110	if (udev->user_dev.max_brightness <= 0) {
111		ret = -EINVAL;
112		goto out;
113	}
114	udev->led_cdev.max_brightness = udev->user_dev.max_brightness;
115
116	ret = devm_led_classdev_register(uleds_misc.this_device,
117					 &udev->led_cdev);
118	if (ret < 0)
119		goto out;
120
121	udev->new_data = true;
122	udev->state = ULEDS_STATE_REGISTERED;
123	ret = count;
124
125out:
126	mutex_unlock(&udev->mutex);
127
128	return ret;
129}
130
131static ssize_t uleds_read(struct file *file, char __user *buffer, size_t count,
132			  loff_t *ppos)
133{
134	struct uleds_device *udev = file->private_data;
135	ssize_t retval;
136
137	if (count < sizeof(udev->brightness))
138		return 0;
139
140	do {
141		retval = mutex_lock_interruptible(&udev->mutex);
142		if (retval)
143			return retval;
144
145		if (udev->state != ULEDS_STATE_REGISTERED) {
146			retval = -ENODEV;
147		} else if (!udev->new_data && (file->f_flags & O_NONBLOCK)) {
148			retval = -EAGAIN;
149		} else if (udev->new_data) {
150			retval = copy_to_user(buffer, &udev->brightness,
151					      sizeof(udev->brightness));
152			udev->new_data = false;
153			retval = sizeof(udev->brightness);
154		}
155
156		mutex_unlock(&udev->mutex);
157
158		if (retval)
159			break;
160
161		if (!(file->f_flags & O_NONBLOCK))
162			retval = wait_event_interruptible(udev->waitq,
163					udev->new_data ||
164					udev->state != ULEDS_STATE_REGISTERED);
165	} while (retval == 0);
166
167	return retval;
168}
169
170static __poll_t uleds_poll(struct file *file, poll_table *wait)
171{
172	struct uleds_device *udev = file->private_data;
173
174	poll_wait(file, &udev->waitq, wait);
175
176	if (udev->new_data)
177		return EPOLLIN | EPOLLRDNORM;
178
179	return 0;
180}
181
182static int uleds_release(struct inode *inode, struct file *file)
183{
184	struct uleds_device *udev = file->private_data;
185
186	if (udev->state == ULEDS_STATE_REGISTERED) {
187		udev->state = ULEDS_STATE_UNKNOWN;
188		devm_led_classdev_unregister(uleds_misc.this_device,
189					     &udev->led_cdev);
190	}
191	kfree(udev);
192
193	return 0;
194}
195
196static const struct file_operations uleds_fops = {
197	.owner		= THIS_MODULE,
198	.open		= uleds_open,
199	.release	= uleds_release,
200	.read		= uleds_read,
201	.write		= uleds_write,
202	.poll		= uleds_poll,
203	.llseek		= no_llseek,
204};
205
206static struct miscdevice uleds_misc = {
207	.fops		= &uleds_fops,
208	.minor		= MISC_DYNAMIC_MINOR,
209	.name		= ULEDS_NAME,
210};
211
212static int __init uleds_init(void)
213{
214	return misc_register(&uleds_misc);
215}
216module_init(uleds_init);
217
218static void __exit uleds_exit(void)
219{
220	misc_deregister(&uleds_misc);
221}
222module_exit(uleds_exit);
223
224MODULE_AUTHOR("David Lechner <david@lechnology.com>");
225MODULE_DESCRIPTION("Userspace driver for the LED subsystem");
226MODULE_LICENSE("GPL");