text: /*
   *	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/hrtimer.h>
  #include <linux/init.h>
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/moduleparam.h>
  #include <linux/reboot.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 struct hrtimer softdog_ticktock;
  static struct hrtimer softdog_preticktock;
  
  static enum hrtimer_restart softdog_fire(struct hrtimer *timer)
  {
  	module_put(THIS_MODULE);
  	if (soft_noboot) {
  		pr_crit("Triggered - Reboot ignored\n");
  	} else if (soft_panic) {
  		pr_crit("Initiating panic\n");
  		panic("Software Watchdog Timer expired");
  	} else {
  		pr_crit("Initiating system reboot\n");
  		emergency_restart();
  		pr_crit("Reboot didn't ?????\n");
  	}
  
  	return HRTIMER_NORESTART;
  }
  
  static struct watchdog_device softdog_dev;
  
  static enum hrtimer_restart softdog_pretimeout(struct hrtimer *timer)
  {
  	watchdog_notify_pretimeout(&softdog_dev);
  
  	return HRTIMER_NORESTART;
  }
  
  static int softdog_ping(struct watchdog_device *w)
  {
  	if (!hrtimer_active(&softdog_ticktock))
  		__module_get(THIS_MODULE);
  	hrtimer_start(&softdog_ticktock, ktime_set(w->timeout, 0),
  		      HRTIMER_MODE_REL);
  
  	if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT)) {
  		if (w->pretimeout)
  			hrtimer_start(&softdog_preticktock,
  				      ktime_set(w->timeout - w->pretimeout, 0),
  				      HRTIMER_MODE_REL);
  		else
  			hrtimer_cancel(&softdog_preticktock);
  	}
  
  	return 0;
  }
  
  static int softdog_stop(struct watchdog_device *w)
  {
  	if (hrtimer_cancel(&softdog_ticktock))
  		module_put(THIS_MODULE);
  
  	if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT))
  		hrtimer_cancel(&softdog_preticktock);
  
  	return 0;
  }
  
  static struct watchdog_info softdog_info = {
  	.identity = "Software Watchdog",
  	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
  };
  
  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);
  
  	hrtimer_init(&softdog_ticktock, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
  	softdog_ticktock.function = softdog_fire;
  
  	if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT)) {
  		softdog_info.options |= WDIOF_PRETIMEOUT;
  		hrtimer_init(&softdog_preticktock, CLOCK_MONOTONIC,
  			     HRTIMER_MODE_REL);
  		softdog_preticktock.function = softdog_pretimeout;
  	}
  
  	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)\n",
  		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");
  