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 
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);
75