1/*
  2 * Userspace driver for the LED subsystem
  3 *
  4 * Copyright (C) 2016 David Lechner <david@lechnology.com>
  5 *
  6 * Based on uinput.c: Aristeu Sergio Rozanski Filho <aris@cathedrallabs.org>
  7 *
  8 * This program is free software; you can redistribute it and/or modify
  9 * it under the terms of the GNU General Public License as published by
 10 * the Free Software Foundation; either version 2 of the License, or
 11 * (at your option) any later version.
 12 *
 13 * This program is distributed in the hope that it will be useful,
 14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 16 * GNU General Public License for more details.
 17 */
 18#include <linux/fs.h>
 19#include <linux/init.h>
 20#include <linux/leds.h>
 21#include <linux/miscdevice.h>
 22#include <linux/module.h>
 23#include <linux/poll.h>
 24#include <linux/sched.h>
 25#include <linux/slab.h>
 26
 27#include <uapi/linux/uleds.h>
 28
 29#define ULEDS_NAME	"uleds"
 30
 31enum uleds_state {
 32	ULEDS_STATE_UNKNOWN,
 33	ULEDS_STATE_REGISTERED,
 34};
 35
 36struct uleds_device {
 37	struct uleds_user_dev	user_dev;
 38	struct led_classdev	led_cdev;
 39	struct mutex		mutex;
 40	enum uleds_state	state;
 41	wait_queue_head_t	waitq;
 42	int			brightness;
 43	bool			new_data;
 44};
 45
 46static struct miscdevice uleds_misc;
 47
 48static void uleds_brightness_set(struct led_classdev *led_cdev,
 49				 enum led_brightness brightness)
 50{
 51	struct uleds_device *udev = container_of(led_cdev, struct uleds_device,
 52						 led_cdev);
 53
 54	if (udev->brightness != brightness) {
 55		udev->brightness = brightness;
 56		udev->new_data = true;
 57		wake_up_interruptible(&udev->waitq);
 58	}
 59}
 60
 61static int uleds_open(struct inode *inode, struct file *file)
 62{
 63	struct uleds_device *udev;
 64
 65	udev = kzalloc(sizeof(*udev), GFP_KERNEL);
 66	if (!udev)
 67		return -ENOMEM;
 68
 69	udev->led_cdev.name = udev->user_dev.name;
 70	udev->led_cdev.brightness_set = uleds_brightness_set;
 71
 72	mutex_init(&udev->mutex);
 73	init_waitqueue_head(&udev->waitq);
 74	udev->state = ULEDS_STATE_UNKNOWN;
 75
 76	file->private_data = udev;
 77	nonseekable_open(inode, file);
 78
 79	return 0;
 80}
 81
 82static ssize_t uleds_write(struct file *file, const char __user *buffer,
 83			   size_t count, loff_t *ppos)
 84{
 85	struct uleds_device *udev = file->private_data;
 86	const char *name;
 87	int ret;
 88
 89	if (count == 0)
 90		return 0;
 91
 92	ret = mutex_lock_interruptible(&udev->mutex);
 93	if (ret)
 94		return ret;
 95
 96	if (udev->state == ULEDS_STATE_REGISTERED) {
 97		ret = -EBUSY;
 98		goto out;
 99	}
100
101	if (count != sizeof(struct uleds_user_dev)) {
102		ret = -EINVAL;
103		goto out;
104	}
105
106	if (copy_from_user(&udev->user_dev, buffer,
107			   sizeof(struct uleds_user_dev))) {
108		ret = -EFAULT;
109		goto out;
110	}
111
112	name = udev->user_dev.name;
113	if (!name[0] || !strcmp(name, ".") || !strcmp(name, "..") ||
114	    strchr(name, '/')) {
115		ret = -EINVAL;
116		goto out;
117	}
118
119	if (udev->user_dev.max_brightness <= 0) {
120		ret = -EINVAL;
121		goto out;
122	}
123	udev->led_cdev.max_brightness = udev->user_dev.max_brightness;
124
125	ret = devm_led_classdev_register(uleds_misc.this_device,
126					 &udev->led_cdev);
127	if (ret < 0)
128		goto out;
129
130	udev->new_data = true;
131	udev->state = ULEDS_STATE_REGISTERED;
132	ret = count;
133
134out:
135	mutex_unlock(&udev->mutex);
136
137	return ret;
138}
139
140static ssize_t uleds_read(struct file *file, char __user *buffer, size_t count,
141			  loff_t *ppos)
142{
143	struct uleds_device *udev = file->private_data;
144	ssize_t retval;
145
146	if (count < sizeof(udev->brightness))
147		return 0;
148
149	do {
150		retval = mutex_lock_interruptible(&udev->mutex);
151		if (retval)
152			return retval;
153
154		if (udev->state != ULEDS_STATE_REGISTERED) {
155			retval = -ENODEV;
156		} else if (!udev->new_data && (file->f_flags & O_NONBLOCK)) {
157			retval = -EAGAIN;
158		} else if (udev->new_data) {
159			retval = copy_to_user(buffer, &udev->brightness,
160					      sizeof(udev->brightness));
161			udev->new_data = false;
162			retval = sizeof(udev->brightness);
163		}
164
165		mutex_unlock(&udev->mutex);
166
167		if (retval)
168			break;
169
170		if (!(file->f_flags & O_NONBLOCK))
171			retval = wait_event_interruptible(udev->waitq,
172					udev->new_data ||
173					udev->state != ULEDS_STATE_REGISTERED);
174	} while (retval == 0);
175
176	return retval;
177}
178
179static unsigned int uleds_poll(struct file *file, poll_table *wait)
180{
181	struct uleds_device *udev = file->private_data;
182
183	poll_wait(file, &udev->waitq, wait);
184
185	if (udev->new_data)
186		return POLLIN | POLLRDNORM;
187
188	return 0;
189}
190
191static int uleds_release(struct inode *inode, struct file *file)
192{
193	struct uleds_device *udev = file->private_data;
194
195	if (udev->state == ULEDS_STATE_REGISTERED) {
196		udev->state = ULEDS_STATE_UNKNOWN;
197		devm_led_classdev_unregister(uleds_misc.this_device,
198					     &udev->led_cdev);
199	}
200	kfree(udev);
201
202	return 0;
203}
204
205static const struct file_operations uleds_fops = {
206	.owner		= THIS_MODULE,
207	.open		= uleds_open,
208	.release	= uleds_release,
209	.read		= uleds_read,
210	.write		= uleds_write,
211	.poll		= uleds_poll,
212	.llseek		= no_llseek,
213};
214
215static struct miscdevice uleds_misc = {
216	.fops		= &uleds_fops,
217	.minor		= MISC_DYNAMIC_MINOR,
218	.name		= ULEDS_NAME,
219};
220
221static int __init uleds_init(void)
222{
223	return misc_register(&uleds_misc);
224}
225module_init(uleds_init);
226
227static void __exit uleds_exit(void)
228{
229	misc_deregister(&uleds_misc);
230}
231module_exit(uleds_exit);
232
233MODULE_AUTHOR("David Lechner <david@lechnology.com>");
234MODULE_DESCRIPTION("Userspace driver for the LED subsystem");
235MODULE_LICENSE("GPL");