leds/trigger/ledtrig-panic.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  * Kernel Panic LED Trigger
0004  *
0005  * Copyright 2016 Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
0006  */
0007
0008 #include <linux/kernel.h>
0009 #include <linux/init.h>
0010 #include <linux/notifier.h>
0011 #include <linux/panic_notifier.h>
0012 #include <linux/leds.h>
0013 #include "../leds.h"
0014
0015 static struct led_trigger *trigger;
0016
0017 /*
0018  * This is called in a special context by the atomic panic
0019  * notifier. This means the trigger can be changed without
0020  * worrying about locking.
0021  */
0022 static void led_trigger_set_panic(struct led_classdev *led_cdev)
0023 {
0024     struct led_trigger *trig;
0025
0026     list_for_each_entry(trig, &trigger_list, next_trig) {
0027         if (strcmp("panic", trig->name))
0028             continue;
0029         if (led_cdev->trigger)
0030             list_del(&led_cdev->trig_list);
0031         list_add_tail(&led_cdev->trig_list, &trig->led_cdevs);
0032
0033         /* Avoid the delayed blink path */
0034         led_cdev->blink_delay_on = 0;
0035         led_cdev->blink_delay_off = 0;
0036
0037         led_cdev->trigger = trig;
0038         if (trig->activate)
0039             trig->activate(led_cdev);
0040         break;
0041     }
0042 }
0043
0044 static int led_trigger_panic_notifier(struct notifier_block *nb,
0045                       unsigned long code, void *unused)
0046 {
0047     struct led_classdev *led_cdev;
0048
0049     list_for_each_entry(led_cdev, &leds_list, node)
0050         if (led_cdev->flags & LED_PANIC_INDICATOR)
0051             led_trigger_set_panic(led_cdev);
0052     return NOTIFY_DONE;
0053 }
0054
0055 static struct notifier_block led_trigger_panic_nb = {
0056     .notifier_call = led_trigger_panic_notifier,
0057 };
0058
0059 static long led_panic_blink(int state)
0060 {
0061     led_trigger_event(trigger, state ? LED_FULL : LED_OFF);
0062     return 0;
0063 }
0064
0065 static int __init ledtrig_panic_init(void)
0066 {
0067     atomic_notifier_chain_register(&panic_notifier_list,
0068                        &led_trigger_panic_nb);
0069
0070     led_trigger_register_simple("panic", &trigger);
0071     panic_blink = led_panic_blink;
0072     return 0;
0073 }
0074 device_initcall(ledtrig_panic_init);