1 /*
2  * Kernel Panic LED Trigger
3  *
4  * Copyright 2016 Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
5  *
6  * This program is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License version 2 as
8  * published by the Free Software Foundation.
9  *
10  */
11 
12 #include <linux/kernel.h>
13 #include <linux/init.h>
14 #include <linux/notifier.h>
15 #include <linux/leds.h>
16 #include "../leds.h"
17 
18 static struct led_trigger *trigger;
19 
20 /*
21  * This is called in a special context by the atomic panic
22  * notifier. This means the trigger can be changed without
23  * worrying about locking.
24  */
25 static void led_trigger_set_panic(struct led_classdev *led_cdev)
26 {
27 	struct led_trigger *trig;
28 
29 	list_for_each_entry(trig, &trigger_list, next_trig) {
30 		if (strcmp("panic", trig->name))
31 			continue;
32 		if (led_cdev->trigger)
33 			list_del(&led_cdev->trig_list);
34 		list_add_tail(&led_cdev->trig_list, &trig->led_cdevs);
35 
36 		/* Avoid the delayed blink path */
37 		led_cdev->blink_delay_on = 0;
38 		led_cdev->blink_delay_off = 0;
39 
40 		led_cdev->trigger = trig;
41 		if (trig->activate)
42 			trig->activate(led_cdev);
43 		break;
44 	}
45 }
46 
47 static int led_trigger_panic_notifier(struct notifier_block *nb,
48 				      unsigned long code, void *unused)
49 {
50 	struct led_classdev *led_cdev;
51 
52 	list_for_each_entry(led_cdev, &leds_list, node)
53 		if (led_cdev->flags & LED_PANIC_INDICATOR)
54 			led_trigger_set_panic(led_cdev);
55 	return NOTIFY_DONE;
56 }
57 
58 static struct notifier_block led_trigger_panic_nb = {
59 	.notifier_call = led_trigger_panic_notifier,
60 };
61 
62 static long led_panic_blink(int state)
63 {
64 	led_trigger_event(trigger, state ? LED_FULL : LED_OFF);
65 	return 0;
66 }
67 
68 static int __init ledtrig_panic_init(void)
69 {
70 	atomic_notifier_chain_register(&panic_notifier_list,
71 				       &led_trigger_panic_nb);
72 
73 	led_trigger_register_simple("panic", &trigger);
74 	panic_blink = led_panic_blink;
75 	return 0;
76 }
77 device_initcall(ledtrig_panic_init);
78