aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/leds/uleds.c
blob: 7320337b22d2cf6bd6324c713c6ef032e77c6cb3 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Userspace driver for the LED subsystem
 *
 * Copyright (C) 2016 David Lechner <david@lechnology.com>
 *
 * Based on uinput.c: Aristeu Sergio Rozanski Filho <aris@cathedrallabs.org>
 */
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/leds.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/poll.h>
#include <linux/sched.h>
#include <linux/slab.h>

#include <uapi/linux/uleds.h>

#define ULEDS_NAME	"uleds"

enum uleds_state {
	ULEDS_STATE_UNKNOWN,
	ULEDS_STATE_REGISTERED,
};

struct uleds_device {
	struct uleds_user_dev	user_dev;
	struct led_classdev	led_cdev;
	struct mutex		mutex;
	enum uleds_state	state;
	wait_queue_head_t	waitq;
	int			brightness;
	bool			new_data;
};

static struct miscdevice uleds_misc;

static void uleds_brightness_set(struct led_classdev *led_cdev,
				 enum led_brightness brightness)
{
	struct uleds_device *udev = container_of(led_cdev, struct uleds_device,
						 led_cdev);

	if (udev->brightness != brightness) {
		udev->brightness = brightness;
		udev->new_data = true;
		wake_up_interruptible(&udev->waitq);
	}
}

static int uleds_open(struct inode *inode, struct file *file)
{
	struct uleds_device *udev;

	udev = kzalloc(sizeof(*udev), GFP_KERNEL);
	if (!udev)
		return -ENOMEM;

	udev->led_cdev.name = udev->user_dev.name;
	udev->led_cdev.brightness_set = uleds_brightness_set;

	mutex_init(&udev->mutex);
	init_waitqueue_head(&udev->waitq);
	udev->state = ULEDS_STATE_UNKNOWN;

	file->private_data = udev;
	stream_open(inode, file);

	return 0;
}

static ssize_t uleds_write(struct file *file, const char __user *buffer,
			   size_t count, loff_t *ppos)
{
	struct uleds_device *udev = file->private_data;
	const char *name;
	int ret;

	if (count == 0)
		return 0;

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

	if (udev->state == ULEDS_STATE_REGISTERED) {
		ret = -EBUSY;
		goto out;
	}

	if (count != sizeof(struct uleds_user_dev)) {
		ret = -EINVAL;
		goto out;
	}

	if (copy_from_user(&udev->user_dev, buffer,
			   sizeof(struct uleds_user_dev))) {
		ret = -EFAULT;
		goto out;
	}

	name = udev->user_dev.name;
	if (!name[0] || !strcmp(name, ".") || !strcmp(name, "..") ||
	    strchr(name, '/')) {
		ret = -EINVAL;
		goto out;
	}

	if (udev->user_dev.max_brightness <= 0) {
		ret = -EINVAL;
		goto out;
	}
	udev->led_cdev.max_brightness = udev->user_dev.max_brightness;

	ret = devm_led_classdev_register(uleds_misc.this_device,
					 &udev->led_cdev);
	if (ret < 0)
		goto out;

	udev->new_data = true;
	udev->state = ULEDS_STATE_REGISTERED;
	ret = count;

out:
	mutex_unlock(&udev->mutex);

	return ret;
}

static ssize_t uleds_read(struct file *file, char __user *buffer, size_t count,
			  loff_t *ppos)
{
	struct uleds_device *udev = file->private_data;
	ssize_t retval;

	if (count < sizeof(udev->brightness))
		return 0;

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

		if (udev->state != ULEDS_STATE_REGISTERED) {
			retval = -ENODEV;
		} else if (!udev->new_data && (file->f_flags & O_NONBLOCK)) {
			retval = -EAGAIN;
		} else if (udev->new_data) {
			retval = copy_to_user(buffer, &udev->brightness,
					      sizeof(udev->brightness));
			udev->new_data = false;
			retval = sizeof(udev->brightness);
		}

		mutex_unlock(&udev->mutex);

		if (retval)
			break;

		if (!(file->f_flags & O_NONBLOCK))
			retval = wait_event_interruptible(udev->waitq,
					udev->new_data ||
					udev->state != ULEDS_STATE_REGISTERED);
	} while (retval == 0);

	return retval;
}

static __poll_t uleds_poll(struct file *file, poll_table *wait)
{
	struct uleds_device *udev = file->private_data;

	poll_wait(file, &udev->waitq, wait);

	if (udev->new_data)
		return EPOLLIN | EPOLLRDNORM;

	return 0;
}

static int uleds_release(struct inode *inode, struct file *file)
{
	struct uleds_device *udev = file->private_data;

	if (udev->state == ULEDS_STATE_REGISTERED) {
		udev->state = ULEDS_STATE_UNKNOWN;
		devm_led_classdev_unregister(uleds_misc.this_device,
					     &udev->led_cdev);
	}
	kfree(udev);

	return 0;
}

static const struct file_operations uleds_fops = {
	.owner		= THIS_MODULE,
	.open		= uleds_open,
	.release	= uleds_release,
	.read		= uleds_read,
	.write		= uleds_write,
	.poll		= uleds_poll,
	.llseek		= no_llseek,
};

static struct miscdevice uleds_misc = {
	.fops		= &uleds_fops,
	.minor		= MISC_DYNAMIC_MINOR,
	.name		= ULEDS_NAME,
};

static int __init uleds_init(void)
{
	return misc_register(&uleds_misc);
}
module_init(uleds_init);

static void __exit uleds_exit(void)
{
	misc_deregister(&uleds_misc);
}
module_exit(uleds_exit);

MODULE_AUTHOR("David Lechner <david@lechnology.com>");
MODULE_DESCRIPTION("Userspace driver for the LED subsystem");
MODULE_LICENSE("GPL");