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 unsigned int 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 POLLIN | POLLRDNORM;
 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");