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");