drivers/leds/trigger/ledtrig-panic.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Kernel Panic LED Trigger
   4  *
   5  * Copyright 2016 Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
   6  */
   7
   8 #include <linux/kernel.h>
   9 #include <linux/init.h>
  10 #include <linux/notifier.h>
  11 #include <linux/panic_notifier.h>
  12 #include <linux/leds.h>
  13 #include "../leds.h"
  14
  15 static struct led_trigger *trigger;
  16
  17 /*
  18  * This is called in a special context by the atomic panic
  19  * notifier. This means the trigger can be changed without
  20  * worrying about locking.
  21  */
  22 static void led_trigger_set_panic(struct led_classdev *led_cdev)
  23 {
  24         if (led_cdev->trigger)
  25                 list_del(&led_cdev->trig_list);
  26         list_add_tail(&led_cdev->trig_list, &trigger->led_cdevs);
  27
  28         /* Avoid the delayed blink path */
  29         led_cdev->blink_delay_on = 0;
  30         led_cdev->blink_delay_off = 0;
  31
  32         led_cdev->trigger = trigger;
  33 }
  34
  35 static int led_trigger_panic_notifier(struct notifier_block *nb,
  36                                       unsigned long code, void *unused)
  37 {
  38         struct led_classdev *led_cdev;
  39
  40         list_for_each_entry(led_cdev, &leds_list, node)
  41                 if (led_cdev->flags & LED_PANIC_INDICATOR)
  42                         led_trigger_set_panic(led_cdev);
  43         return NOTIFY_DONE;
  44 }
  45
  46 static struct notifier_block led_trigger_panic_nb = {
  47         .notifier_call = led_trigger_panic_notifier,
  48 };
  49
  50 static long led_panic_blink(int state)
  51 {
  52         led_trigger_event(trigger, state ? LED_FULL : LED_OFF);
  53         return 0;
  54 }
  55
  56 static int __init ledtrig_panic_init(void)
  57 {
  58         led_trigger_register_simple("panic", &trigger);
  59         if (!trigger)
  60                 return -ENOMEM;
  61
  62         atomic_notifier_chain_register(&panic_notifier_list,
  63                                        &led_trigger_panic_nb);
  64
  65         panic_blink = led_panic_blink;
  66         return 0;
  67 }
  68 device_initcall(ledtrig_panic_init);