drivers/leds/trigger/ledtrig-panic.c

   1 /*
   2  * Kernel Panic LED Trigger
   3  *
   4  * Copyright 2016 Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  */
  11
  12 #include <linux/kernel.h>
  13 #include <linux/init.h>
  14 #include <linux/notifier.h>
  15 #include <linux/leds.h>
  16 #include "../leds.h"
  17
  18 static struct led_trigger *trigger;
  19
  20 /*
  21  * This is called in a special context by the atomic panic
  22  * notifier. This means the trigger can be changed without
  23  * worrying about locking.
  24  */
  25 static void led_trigger_set_panic(struct led_classdev *led_cdev)
  26 {
  27         struct led_trigger *trig;
  28
  29         list_for_each_entry(trig, &trigger_list, next_trig) {
  30                 if (strcmp("panic", trig->name))
  31                         continue;
  32                 if (led_cdev->trigger)
  33                         list_del(&led_cdev->trig_list);
  34                 list_add_tail(&led_cdev->trig_list, &trig->led_cdevs);
  35
  36                 /* Avoid the delayed blink path */
  37                 led_cdev->blink_delay_on = 0;
  38                 led_cdev->blink_delay_off = 0;
  39
  40                 led_cdev->trigger = trig;
  41                 if (trig->activate)
  42                         trig->activate(led_cdev);
  43                 break;
  44         }
  45 }
  46
  47 static int led_trigger_panic_notifier(struct notifier_block *nb,
  48                                       unsigned long code, void *unused)
  49 {
  50         struct led_classdev *led_cdev;
  51
  52         list_for_each_entry(led_cdev, &leds_list, node)
  53                 if (led_cdev->flags & LED_PANIC_INDICATOR)
  54                         led_trigger_set_panic(led_cdev);
  55         return NOTIFY_DONE;
  56 }
  57
  58 static struct notifier_block led_trigger_panic_nb = {
  59         .notifier_call = led_trigger_panic_notifier,
  60 };
  61
  62 static long led_panic_blink(int state)
  63 {
  64         led_trigger_event(trigger, state ? LED_FULL : LED_OFF);
  65         return 0;
  66 }
  67
  68 static int __init ledtrig_panic_init(void)
  69 {
  70         atomic_notifier_chain_register(&panic_notifier_list,
  71                                        &led_trigger_panic_nb);
  72
  73         led_trigger_register_simple("panic", &trigger);
  74         panic_blink = led_panic_blink;
  75         return 0;
  76 }
  77 device_initcall(ledtrig_panic_init);