xref: /linux/drivers/leds/trigger/ledtrig-panic.c (revision 79790b6818e96c58fe2bffee1b418c16e64e7b80)
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  */
led_trigger_set_panic(struct led_classdev * led_cdev)22 static void led_trigger_set_panic(struct led_classdev *led_cdev)
23 {
24 	if (led_cdev->trigger)
25 		list_del(&led_cdev->trig_list);
26 	list_add_tail(&led_cdev->trig_list, &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 
led_trigger_panic_notifier(struct notifier_block * nb,unsigned long code,void * unused)35 static 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 
46 static struct notifier_block led_trigger_panic_nb = {
47 	.notifier_call = led_trigger_panic_notifier,
48 };
49 
led_panic_blink(int state)50 static long led_panic_blink(int state)
51 {
52 	led_trigger_event(trigger, state ? LED_FULL : LED_OFF);
53 	return 0;
54 }
55 
ledtrig_panic_init(void)56 static int __init ledtrig_panic_init(void)
57 {
58 	led_trigger_register_simple("panic", &trigger);
59 	if (!trigger)
60 		return -ENOMEM;
61 
62 	atomic_notifier_chain_register(&panic_notifier_list,
63 				       &led_trigger_panic_nb);
64 
65 	panic_blink = led_panic_blink;
66 	return 0;
67 }
68 device_initcall(ledtrig_panic_init);
69