/*

   *	SoftDog:	A Software Watchdog Device

   *

   *	(c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>,
   *							All Rights Reserved.

   *
   *	This program is free software; you can redistribute it and/or
   *	modify it under the terms of the GNU General Public License
   *	as published by the Free Software Foundation; either version
   *	2 of the License, or (at your option) any later version.
   *
   *	Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
   *	warranty for any of this software. This material is provided
   *	"AS-IS" and at no charge.
   *
   *	(c) Copyright 1995    Alan Cox <alan@lxorguk.ukuu.org.uk>
   *
   *	Software only watchdog driver. Unlike its big brother the WDT501P
   *	driver this won't always recover a failed machine.

   */

  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

  #include <linux/init.h>
  #include <linux/jiffies.h>
  #include <linux/kernel.h>

  #include <linux/module.h>
  #include <linux/moduleparam.h>

  #include <linux/reboot.h>

  #include <linux/timer.h>

  #include <linux/types.h>

  #include <linux/watchdog.h>

  #define TIMER_MARGIN	60		/* Default is 60 seconds */

  static unsigned int soft_margin = TIMER_MARGIN;	/* in seconds */
  module_param(soft_margin, uint, 0);

  MODULE_PARM_DESC(soft_margin,
  	"Watchdog soft_margin in seconds. (0 < soft_margin < 65536, default="
  					__MODULE_STRING(TIMER_MARGIN) ")");

  static bool nowayout = WATCHDOG_NOWAYOUT;
  module_param(nowayout, bool, 0);

  MODULE_PARM_DESC(nowayout,
  		"Watchdog cannot be stopped once started (default="
  				__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

  static int soft_noboot;

  module_param(soft_noboot, int, 0);

  MODULE_PARM_DESC(soft_noboot,

  	"Softdog action, set to 1 to ignore reboots, 0 to reboot (default=0)");

  static int soft_panic;
  module_param(soft_panic, int, 0);
  MODULE_PARM_DESC(soft_panic,
  	"Softdog action, set to 1 to panic, 0 to reboot (default=0)");

  static void softdog_fire(unsigned long data)

  {

  	module_put(THIS_MODULE);

  	if (soft_noboot) {

  		pr_crit("Triggered - Reboot ignored
  ");

  	} else if (soft_panic) {

  		pr_crit("Initiating panic
  ");
  		panic("Software Watchdog Timer expired");

  	} else {

  		pr_crit("Initiating system reboot
  ");

  		emergency_restart();

  		pr_crit("Reboot didn't ?????
  ");

  	}
  }

  static struct timer_list softdog_ticktock =
  		TIMER_INITIALIZER(softdog_fire, 0, 0);

  static struct watchdog_device softdog_dev;
  
  static void softdog_pretimeout(unsigned long data)
  {
  	watchdog_notify_pretimeout(&softdog_dev);
  }
  
  static struct timer_list softdog_preticktock =
  		TIMER_INITIALIZER(softdog_pretimeout, 0, 0);

  static int softdog_ping(struct watchdog_device *w)

  {

  	if (!mod_timer(&softdog_ticktock, jiffies + (w->timeout * HZ)))

  		__module_get(THIS_MODULE);

  
  	if (w->pretimeout)
  		mod_timer(&softdog_preticktock, jiffies +
  			  (w->timeout - w->pretimeout) * HZ);
  	else
  		del_timer(&softdog_preticktock);

  	return 0;
  }

  static int softdog_stop(struct watchdog_device *w)

  {

  	if (del_timer(&softdog_ticktock))

  		module_put(THIS_MODULE);

  	del_timer(&softdog_preticktock);

  	return 0;
  }

  static struct watchdog_info softdog_info = {
  	.identity = "Software Watchdog",

  	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE |
  		   WDIOF_PRETIMEOUT,

  };

  static const struct watchdog_ops softdog_ops = {

  	.owner = THIS_MODULE,
  	.start = softdog_ping,
  	.stop = softdog_stop,

  };
  
  static struct watchdog_device softdog_dev = {
  	.info = &softdog_info,
  	.ops = &softdog_ops,
  	.min_timeout = 1,

  	.max_timeout = 65535,
  	.timeout = TIMER_MARGIN,

  };

  static int __init softdog_init(void)

  {
  	int ret;

  	watchdog_init_timeout(&softdog_dev, soft_margin, NULL);

  	watchdog_set_nowayout(&softdog_dev, nowayout);

  	watchdog_stop_on_reboot(&softdog_dev);

  	ret = watchdog_register_device(&softdog_dev);

  	if (ret)

  		return ret;

  	pr_info("initialized. soft_noboot=%d soft_margin=%d sec soft_panic=%d (nowayout=%d)
  ",
  		soft_noboot, softdog_dev.timeout, soft_panic, nowayout);

  
  	return 0;
  }

  module_init(softdog_init);

  static void __exit softdog_exit(void)

  {

  	watchdog_unregister_device(&softdog_dev);

  }

  module_exit(softdog_exit);

  
  MODULE_AUTHOR("Alan Cox");
  MODULE_DESCRIPTION("Software Watchdog Device Driver");
  MODULE_LICENSE("GPL");