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);
74