ledtrig-heartbeat.c

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/*
 * LED Heartbeat Trigger
 *
 * Copyright (C) 2006 Atsushi Nemoto <[email protected]>
 *
 * Based on Richard Purdie's ledtrig-timer.c and some arch's
 * CONFIG_HEARTBEAT code.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 */
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/timer.h>
#include <linux/sched.h>
#include <linux/leds.h>
#include <linux/reboot.h>
#include "leds.h"

static int panic_heartbeats;

struct heartbeat_trig_data {
    unsigned int phase;
    unsigned int period;
    struct timer_list timer;
};

static void led_heartbeat_function(unsigned long data)
{
    struct led_classdev *led_cdev = (struct led_classdev *) data;
    struct heartbeat_trig_data *heartbeat_data = led_cdev->trigger_data;
    unsigned long brightness = LED_OFF;
    unsigned long delay = 0;

    if (unlikely(panic_heartbeats)) {
        led_set_brightness(led_cdev, LED_OFF);
        return;
    }

    /* acts like an actual heart beat -- ie thump-thump-pause... */
    switch (heartbeat_data->phase) {
    case 0:
        /*
         * The hyperbolic function below modifies the
         * heartbeat period length in dependency of the
         * current (1min) load. It goes through the points
         * f(0)=1260, f(1)=860, f(5)=510, f(inf)->300.
         */
        heartbeat_data->period = 300 +
            (6720 << FSHIFT) / (5 * avenrun[0] + (7 << FSHIFT));
        heartbeat_data->period =
            msecs_to_jiffies(heartbeat_data->period);
        delay = msecs_to_jiffies(70);
        heartbeat_data->phase++;
        brightness = led_cdev->max_brightness;
        break;
    case 1:
        delay = heartbeat_data->period / 4 - msecs_to_jiffies(70);
        heartbeat_data->phase++;
        break;
    case 2:
        delay = msecs_to_jiffies(70);
        heartbeat_data->phase++;
        brightness = led_cdev->max_brightness;
        break;
    default:
        delay = heartbeat_data->period - heartbeat_data->period / 4 -
            msecs_to_jiffies(70);
        heartbeat_data->phase = 0;
        break;
    }

    __led_set_brightness(led_cdev, brightness);
    mod_timer(&heartbeat_data->timer, jiffies + delay);
}

static void heartbeat_trig_activate(struct led_classdev *led_cdev)
{
    struct heartbeat_trig_data *heartbeat_data;

    heartbeat_data = kzalloc(sizeof(*heartbeat_data), GFP_KERNEL);
    if (!heartbeat_data)
        return;

    led_cdev->trigger_data = heartbeat_data;
    setup_timer(&heartbeat_data->timer,
            led_heartbeat_function, (unsigned long) led_cdev);
    heartbeat_data->phase = 0;
    led_heartbeat_function(heartbeat_data->timer.data);
    led_cdev->activated = true;
}

static void heartbeat_trig_deactivate(struct led_classdev *led_cdev)
{
    struct heartbeat_trig_data *heartbeat_data = led_cdev->trigger_data;

    if (led_cdev->activated) {
        del_timer_sync(&heartbeat_data->timer);
        kfree(heartbeat_data);
        led_cdev->activated = false;
    }
}

static struct led_trigger heartbeat_led_trigger = {
    .name     = "heartbeat",
    .activate = heartbeat_trig_activate,
    .deactivate = heartbeat_trig_deactivate,
};

static int heartbeat_reboot_notifier(struct notifier_block *nb,
                     unsigned long code, void *unused)
{
    led_trigger_unregister(&heartbeat_led_trigger);
    return NOTIFY_DONE;
}

static int heartbeat_panic_notifier(struct notifier_block *nb,
                     unsigned long code, void *unused)
{
    panic_heartbeats = 1;
    return NOTIFY_DONE;
}

static struct notifier_block heartbeat_reboot_nb = {
    .notifier_call = heartbeat_reboot_notifier,
};

static struct notifier_block heartbeat_panic_nb = {
    .notifier_call = heartbeat_panic_notifier,
};

static int __init heartbeat_trig_init(void)
{
    int rc = led_trigger_register(&heartbeat_led_trigger);

    if (!rc) {
        atomic_notifier_chain_register(&panic_notifier_list,
                           &heartbeat_panic_nb);
        register_reboot_notifier(&heartbeat_reboot_nb);
    }
    return rc;
}

static void __exit heartbeat_trig_exit(void)
{
    unregister_reboot_notifier(&heartbeat_reboot_nb);
    atomic_notifier_chain_unregister(&panic_notifier_list,
                     &heartbeat_panic_nb);
    led_trigger_unregister(&heartbeat_led_trigger);
}

module_init(heartbeat_trig_init);
module_exit(heartbeat_trig_exit);

MODULE_AUTHOR("Atsushi Nemoto <[email protected]>");
MODULE_DESCRIPTION("Heartbeat LED trigger");
MODULE_LICENSE("GPL");