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	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
44static 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
55static struct notifier_block led_trigger_panic_nb = {
56	.notifier_call = led_trigger_panic_notifier,
57};
58
59static long led_panic_blink(int state)
60{
61	led_trigger_event(trigger, state ? LED_FULL : LED_OFF);
62	return 0;
63}
64
65static 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}
74device_initcall(ledtrig_panic_init);