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
15static 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 */
22static void led_trigger_set_panic(struct led_classdev *led_cdev)
23{
24 if (led_cdev->trigger)
25 list_del(entry: &led_cdev->trig_list);
26 list_add_tail(new: &led_cdev->trig_list, head: &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
35static 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
46static struct notifier_block led_trigger_panic_nb = {
47 .notifier_call = led_trigger_panic_notifier,
48};
49
50static long led_panic_blink(int state)
51{
52 led_trigger_event(trigger, event: state ? LED_FULL : LED_OFF);
53 return 0;
54}
55
56static int __init ledtrig_panic_init(void)
57{
58 led_trigger_register_simple(name: "panic", trigger: &trigger);
59 if (!trigger)
60 return -ENOMEM;
61
62 atomic_notifier_chain_register(nh: &panic_notifier_list,
63 nb: &led_trigger_panic_nb);
64
65 panic_blink = led_panic_blink;
66 return 0;
67}
68device_initcall(ledtrig_panic_init);
69

source code of linux/drivers/leds/trigger/ledtrig-panic.c