0c43bfac9598e32788f39118ab8902c57d05a775
[sfrench/cifs-2.6.git] / drivers / leds / uleds.c
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
31 enum uleds_state {
32         ULEDS_STATE_UNKNOWN,
33         ULEDS_STATE_REGISTERED,
34 };
35
36 struct 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
46 static struct miscdevice uleds_misc;
47
48 static 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
61 static 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
82 static 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
134 out:
135         mutex_unlock(&udev->mutex);
136
137         return ret;
138 }
139
140 static 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
179 static __poll_t 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 EPOLLIN | EPOLLRDNORM;
187
188         return 0;
189 }
190
191 static 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
205 static 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
215 static struct miscdevice uleds_misc = {
216         .fops           = &uleds_fops,
217         .minor          = MISC_DYNAMIC_MINOR,
218         .name           = ULEDS_NAME,
219 };
220
221 static int __init uleds_init(void)
222 {
223         return misc_register(&uleds_misc);
224 }
225 module_init(uleds_init);
226
227 static void __exit uleds_exit(void)
228 {
229         misc_deregister(&uleds_misc);
230 }
231 module_exit(uleds_exit);
232
233 MODULE_AUTHOR("David Lechner <david@lechnology.com>");
234 MODULE_DESCRIPTION("Userspace driver for the LED subsystem");
235 MODULE_LICENSE("GPL");