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 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 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 50 static long led_panic_blink(int state) 51 { 52 led_trigger_event(trigger, state ? LED_FULL : LED_OFF); 53 return 0; 54 } 55 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