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         unsigned char           brightness;
  43         unsigned char           new_data;
  44 };
  45
  46 static void uleds_brightness_set(struct led_classdev *led_cdev,
  47                                  enum led_brightness brightness)
  48 {
  49         struct uleds_device *udev = container_of(led_cdev, struct uleds_device,
  50                                                  led_cdev);
  51
  52         if (udev->brightness != brightness) {
  53                 udev->brightness = brightness;
  54                 udev->new_data = 1;
  55                 wake_up_interruptible(&udev->waitq);
  56         }
  57 }
  58
  59 static int uleds_open(struct inode *inode, struct file *file)
  60 {
  61         struct uleds_device *udev;
  62
  63         udev = kzalloc(sizeof(*udev), GFP_KERNEL);
  64         if (!udev)
  65                 return -ENOMEM;
  66
  67         udev->led_cdev.name = udev->user_dev.name;
  68         udev->led_cdev.max_brightness = LED_FULL;
  69         udev->led_cdev.brightness_set = uleds_brightness_set;
  70
  71         mutex_init(&udev->mutex);
  72         init_waitqueue_head(&udev->waitq);
  73         udev->state = ULEDS_STATE_UNKNOWN;
  74
  75         file->private_data = udev;
  76         nonseekable_open(inode, file);
  77
  78         return 0;
  79 }
  80
  81 static ssize_t uleds_write(struct file *file, const char __user *buffer,
  82                            size_t count, loff_t *ppos)
  83 {
  84         struct uleds_device *udev = file->private_data;
  85         int ret;
  86
  87         if (count == 0)
  88                 return 0;
  89
  90         ret = mutex_lock_interruptible(&udev->mutex);
  91         if (ret)
  92                 return ret;
  93
  94         if (udev->state == ULEDS_STATE_REGISTERED) {
  95                 ret = -EBUSY;
  96                 goto out;
  97         }
  98
  99         if (count != sizeof(struct uleds_user_dev)) {
 100                 ret = -EINVAL;
 101                 goto out;
 102         }
 103
 104         if (copy_from_user(&udev->user_dev, buffer,
 105                            sizeof(struct uleds_user_dev))) {
 106                 ret = -EFAULT;
 107                 goto out;
 108         }
 109
 110         if (!udev->user_dev.name[0]) {
 111                 ret = -EINVAL;
 112                 goto out;
 113         }
 114
 115         ret = led_classdev_register(NULL, &udev->led_cdev);
 116         if (ret < 0)
 117                 goto out;
 118
 119         udev->state = ULEDS_STATE_REGISTERED;
 120         ret = count;
 121
 122 out:
 123         mutex_unlock(&udev->mutex);
 124
 125         return ret;
 126 }
 127
 128 static ssize_t uleds_read(struct file *file, char __user *buffer, size_t count,
 129                           loff_t *ppos)
 130 {
 131         struct uleds_device *udev = file->private_data;
 132         ssize_t retval;
 133
 134         if (count == 0)
 135                 return 0;
 136
 137         if (count != 1)
 138                 return -EINVAL;
 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 {
 150                         retval = copy_to_user(buffer, &udev->brightness, 1);
 151                         udev->new_data = 0;
 152                         retval = 1;
 153                 }
 154
 155                 mutex_unlock(&udev->mutex);
 156
 157                 if (retval || count == 0)
 158                         break;
 159
 160                 if (!(file->f_flags & O_NONBLOCK))
 161                         retval = wait_event_interruptible(udev->waitq,
 162                                         udev->new_data ||
 163                                         udev->state != ULEDS_STATE_REGISTERED);
 164         } while (retval == 0);
 165
 166         return retval;
 167 }
 168
 169 static unsigned int uleds_poll(struct file *file, poll_table *wait)
 170 {
 171         struct uleds_device *udev = file->private_data;
 172
 173         poll_wait(file, &udev->waitq, wait);
 174
 175         if (udev->new_data)
 176                 return POLLIN | POLLRDNORM;
 177
 178         return 0;
 179 }
 180
 181 static int uleds_release(struct inode *inode, struct file *file)
 182 {
 183         struct uleds_device *udev = file->private_data;
 184
 185         if (udev->state == ULEDS_STATE_REGISTERED) {
 186                 udev->state = ULEDS_STATE_UNKNOWN;
 187                 led_classdev_unregister(&udev->led_cdev);
 188         }
 189         kfree(udev);
 190
 191         return 0;
 192 }
 193
 194 static const struct file_operations uleds_fops = {
 195         .owner          = THIS_MODULE,
 196         .open           = uleds_open,
 197         .release        = uleds_release,
 198         .read           = uleds_read,
 199         .write          = uleds_write,
 200         .poll           = uleds_poll,
 201         .llseek         = no_llseek,
 202 };
 203
 204 static struct miscdevice uleds_misc = {
 205         .fops           = &uleds_fops,
 206         .minor          = MISC_DYNAMIC_MINOR,
 207         .name           = ULEDS_NAME,
 208 };
 209
 210 static int __init uleds_init(void)
 211 {
 212         return misc_register(&uleds_misc);
 213 }
 214 module_init(uleds_init);
 215
 216 static void __exit uleds_exit(void)
 217 {
 218         misc_deregister(&uleds_misc);
 219 }
 220 module_exit(uleds_exit);
 221
 222 MODULE_AUTHOR("David Lechner <david@lechnology.com>");
 223 MODULE_DESCRIPTION("Userspace driver for the LED subsystem");
 224 MODULE_LICENSE("GPL");