// SPDX-License-Identifier: GPL-2.0-only
/*
 * Kernel Panic LED Trigger
 *
 * Copyright 2016 Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/notifier.h>
#include <linux/panic_notifier.h>
#include <linux/leds.h>
#include "../leds.h"

static struct led_trigger *trigger;

/*
 * This is called in a special context by the atomic panic
 * notifier. This means the trigger can be changed without
 * worrying about locking.
 */
static void led_trigger_set_panic(struct led_classdev *led_cdev)
{
        if (led_cdev->trigger)
                list_del(&led_cdev->trig_list);
        list_add_tail(&led_cdev->trig_list, &trigger->led_cdevs);

        /* Avoid the delayed blink path */
        led_cdev->blink_delay_on = 0;
        led_cdev->blink_delay_off = 0;

        led_cdev->trigger = trigger;
}

static int led_trigger_panic_notifier(struct notifier_block *nb,
                                      unsigned long code, void *unused)
{
        struct led_classdev *led_cdev;

        list_for_each_entry(led_cdev, &leds_list, node)
                if (led_cdev->flags & LED_PANIC_INDICATOR)
                        led_trigger_set_panic(led_cdev);
        return NOTIFY_DONE;
}

static struct notifier_block led_trigger_panic_nb = {
        .notifier_call = led_trigger_panic_notifier,
};

static long led_panic_blink(int state)
{
        led_trigger_event(trigger, state ? LED_FULL : LED_OFF);
        return 0;
}

static int __init ledtrig_panic_init(void)
{
        led_trigger_register_simple("panic", &trigger);
        if (!trigger)
                return -ENOMEM;

        atomic_notifier_chain_register(&panic_notifier_list,
                                       &led_trigger_panic_nb);

        panic_blink = led_panic_blink;
        return 0;
}
device_initcall(ledtrig_panic_init);