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/leds.h>
  12 #include "../leds.h"
  13
  14 static struct led_trigger *trigger;
  15
  16 /*
  17  * This is called in a special context by the atomic panic
  18  * notifier. This means the trigger can be changed without
  19  * worrying about locking.
  20  */
  21 static void led_trigger_set_panic(struct led_classdev *led_cdev)
  22 {
  23         struct led_trigger *trig;
  24
  25         list_for_each_entry(trig, &trigger_list, next_trig) {
  26                 if (strcmp("panic", trig->name))
  27                         continue;
  28                 if (led_cdev->trigger)
  29                         list_del(&led_cdev->trig_list);
  30                 list_add_tail(&led_cdev->trig_list, &trig->led_cdevs);
  31
  32                 /* Avoid the delayed blink path */
  33                 led_cdev->blink_delay_on = 0;
  34                 led_cdev->blink_delay_off = 0;
  35
  36                 led_cdev->trigger = trig;
  37                 if (trig->activate)
  38                         trig->activate(led_cdev);
  39                 break;
  40         }
  41 }
  42
  43 static int led_trigger_panic_notifier(struct notifier_block *nb,
  44                                       unsigned long code, void *unused)
  45 {
  46         struct led_classdev *led_cdev;
  47
  48         list_for_each_entry(led_cdev, &leds_list, node)
  49                 if (led_cdev->flags & LED_PANIC_INDICATOR)
  50                         led_trigger_set_panic(led_cdev);
  51         return NOTIFY_DONE;
  52 }
  53
  54 static struct notifier_block led_trigger_panic_nb = {
  55         .notifier_call = led_trigger_panic_notifier,
  56 };
  57
  58 static long led_panic_blink(int state)
  59 {
  60         led_trigger_event(trigger, state ? LED_FULL : LED_OFF);
  61         return 0;
  62 }
  63
  64 static int __init ledtrig_panic_init(void)
  65 {
  66         atomic_notifier_chain_register(&panic_notifier_list,
  67                                        &led_trigger_panic_nb);
  68
  69         led_trigger_register_simple("panic", &trigger);
  70         panic_blink = led_panic_blink;
  71         return 0;
  72 }
  73 device_initcall(ledtrig_panic_init);