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 <[email protected]>
   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         struct led_trigger *trig;
  25
  26         list_for_each_entry(trig, &trigger_list, next_trig) {
  27                 if (strcmp("panic", trig->name))
  28                         continue;
  29                 if (led_cdev->trigger)
  30                         list_del(&led_cdev->trig_list);
  31                 list_add_tail(&led_cdev->trig_list, &trig->led_cdevs);
  32
  33                 /* Avoid the delayed blink path */
  34                 led_cdev->blink_delay_on = 0;
  35                 led_cdev->blink_delay_off = 0;
  36
  37                 led_cdev->trigger = trig;
  38                 if (trig->activate)
  39                         trig->activate(led_cdev);
  40                 break;
  41         }
  42 }
  43
  44 static int led_trigger_panic_notifier(struct notifier_block *nb,
  45                                       unsigned long code, void *unused)
  46 {
  47         struct led_classdev *led_cdev;
  48
  49         list_for_each_entry(led_cdev, &leds_list, node)
  50                 if (led_cdev->flags & LED_PANIC_INDICATOR)
  51                         led_trigger_set_panic(led_cdev);
  52         return NOTIFY_DONE;
  53 }
  54
  55 static struct notifier_block led_trigger_panic_nb = {
  56         .notifier_call = led_trigger_panic_notifier,
  57 };
  58
  59 static long led_panic_blink(int state)
  60 {
  61         led_trigger_event(trigger, state ? LED_FULL : LED_OFF);
  62         return 0;
  63 }
  64
  65 static int __init ledtrig_panic_init(void)
  66 {
  67         atomic_notifier_chain_register(&panic_notifier_list,
  68                                        &led_trigger_panic_nb);
  69
  70         led_trigger_register_simple("panic", &trigger);
  71         panic_blink = led_panic_blink;
  72         return 0;
  73 }
  74 device_initcall(ledtrig_panic_init);