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(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 | |
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(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 | |
125 | out: |
126 | mutex_unlock(lock: &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(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 | |
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(filp: file, wait_address: &udev->waitq, p: 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(parent: uleds_misc.this_device, |
189 | led_cdev: &udev->led_cdev); |
190 | } |
191 | kfree(objp: 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 | module_misc_device(uleds_misc); |
213 | |
214 | MODULE_AUTHOR("David Lechner <david@lechnology.com>" ); |
215 | MODULE_DESCRIPTION("Userspace driver for the LED subsystem" ); |
216 | MODULE_LICENSE("GPL" ); |
217 | |