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ledtrig-heartbeat.c

/*
 * LED Heartbeat Trigger
 *
 * Copyright (C) 2006 Atsushi Nemoto <anemo@mba.ocn.ne.jp>
 *
 * 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/timer.h>
#include <linux/sched.h>
#include <linux/leds.h>
#include "leds.h"

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;

      /* 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_FULL;
            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_FULL;
            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);
}

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

      if (heartbeat_data) {
            del_timer_sync(&heartbeat_data->timer);
            kfree(heartbeat_data);
      }
}

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

static int __init heartbeat_trig_init(void)
{
      return led_trigger_register(&heartbeat_led_trigger);
}

static void __exit heartbeat_trig_exit(void)
{
      led_trigger_unregister(&heartbeat_led_trigger);
}

module_init(heartbeat_trig_init);
module_exit(heartbeat_trig_exit);

MODULE_AUTHOR("Atsushi Nemoto <anemo@mba.ocn.ne.jp>");
MODULE_DESCRIPTION("Heartbeat LED trigger");
MODULE_LICENSE("GPL");

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