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(size: 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, filp: 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(to: &udev->user_dev, from: buffer,
98 n: 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(parent: uleds_misc.this_device,
117 led_cdev: &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(lock: &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(to: buffer, from: &udev->brightness,
151 n: sizeof(udev->brightness));
152 udev->new_data = false;
153 retval = sizeof(udev->brightness);
154 }
155
156 mutex_unlock(lock: &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(filp: file, wait_address: &udev->waitq, p: 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(parent: uleds_misc.this_device,
189 led_cdev: &udev->led_cdev);
190 }
191 kfree(objp: 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
212module_misc_device(uleds_misc);
213
214MODULE_AUTHOR("David Lechner <david@lechnology.com>");
215MODULE_DESCRIPTION("Userspace driver for the LED subsystem");
216MODULE_LICENSE("GPL");
217

source code of linux/drivers/leds/uleds.c