GNU Linux-libre 5.13.14-gnu1
[releases.git] / drivers / leds / uleds.c
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
22 enum uleds_state {
23         ULEDS_STATE_UNKNOWN,
24         ULEDS_STATE_REGISTERED,
25 };
26
27 struct 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
37 static struct miscdevice uleds_misc;
38
39 static 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
52 static 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
73 static 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
125 out:
126         mutex_unlock(&udev->mutex);
127
128         return ret;
129 }
130
131 static 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
170 static __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
182 static 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
196 static 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
206 static struct miscdevice uleds_misc = {
207         .fops           = &uleds_fops,
208         .minor          = MISC_DYNAMIC_MINOR,
209         .name           = ULEDS_NAME,
210 };
211
212 static int __init uleds_init(void)
213 {
214         return misc_register(&uleds_misc);
215 }
216 module_init(uleds_init);
217
218 static void __exit uleds_exit(void)
219 {
220         misc_deregister(&uleds_misc);
221 }
222 module_exit(uleds_exit);
223
224 MODULE_AUTHOR("David Lechner <david@lechnology.com>");
225 MODULE_DESCRIPTION("Userspace driver for the LED subsystem");
226 MODULE_LICENSE("GPL");