/*
   *	SoftDog	0.07:	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.
   *
   *  03/96: Angelo Haritsis <ah@doc.ic.ac.uk> :
   *	Modularised.
   *	Added soft_margin; use upon insmod to change the timer delay.
   *	NB: uses same minor as wdt (WATCHDOG_MINOR); we could use separate
   *	    minors.
   *
   *  19980911 Alan Cox
   *	Made SMP safe for 2.3.x
   *
   *  20011127 Joel Becker (jlbec@evilplan.org>
   *	Added soft_noboot; Allows testing the softdog trigger without
   *	requiring a recompile.
   *	Added WDIOC_GETTIMEOUT and WDIOC_SETTIMOUT.
   *
   *  20020530 Joel Becker <joel.becker@oracle.com>

   *	Added Matt Domsch's nowayout module option.

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

  #include <linux/types.h>
  #include <linux/timer.h>
  #include <linux/miscdevice.h>
  #include <linux/watchdog.h>
  #include <linux/fs.h>
  #include <linux/notifier.h>
  #include <linux/reboot.h>
  #include <linux/init.h>

  #include <linux/jiffies.h>

  #include <linux/uaccess.h>

  #include <linux/kernel.h>

  
  #define PFX "SoftDog: "
  
  #define TIMER_MARGIN	60		/* Default is 60 seconds */
  static int soft_margin = TIMER_MARGIN;	/* in seconds */
  module_param(soft_margin, int, 0);

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

  static int nowayout = WATCHDOG_NOWAYOUT;

  module_param(nowayout, int, 0);

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

  
  #ifdef ONLY_TESTING
  static int soft_noboot = 1;
  #else
  static int soft_noboot = 0;
  #endif  /* ONLY_TESTING */
  
  module_param(soft_noboot, int, 0);

  MODULE_PARM_DESC(soft_noboot,
  	"Softdog action, set to 1 to ignore reboots, 0 to reboot "
  					"(default depends on ONLY_TESTING)");

  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)");

  /*
   *	Our timer
   */
  
  static void watchdog_fire(unsigned long);
  
  static struct timer_list watchdog_ticktock =
  		TIMER_INITIALIZER(watchdog_fire, 0, 0);

  static unsigned long driver_open, orphan_timer;

  static char expect_close;
  
  
  /*
   *	If the timer expires..
   */
  
  static void watchdog_fire(unsigned long data)
  {

  	if (test_and_clear_bit(0, &orphan_timer))
  		module_put(THIS_MODULE);

  	if (soft_noboot)
  		printk(KERN_CRIT PFX "Triggered - Reboot ignored.
  ");

  	else if (soft_panic) {
  		printk(KERN_CRIT PFX "Initiating panic.
  ");
  		panic("Software Watchdog Timer expired.");
  	} else {

  		printk(KERN_CRIT PFX "Initiating system reboot.
  ");

  		emergency_restart();

  		printk(KERN_CRIT PFX "Reboot didn't ?????
  ");
  	}
  }
  
  /*
   *	Softdog operations
   */
  
  static int softdog_keepalive(void)
  {
  	mod_timer(&watchdog_ticktock, jiffies+(soft_margin*HZ));
  	return 0;
  }
  
  static int softdog_stop(void)
  {
  	del_timer(&watchdog_ticktock);
  	return 0;
  }
  
  static int softdog_set_heartbeat(int t)
  {
  	if ((t < 0x0001) || (t > 0xFFFF))
  		return -EINVAL;
  
  	soft_margin = t;
  	return 0;
  }
  
  /*
   *	/dev/watchdog handling
   */
  
  static int softdog_open(struct inode *inode, struct file *file)
  {

  	if (test_and_set_bit(0, &driver_open))

  		return -EBUSY;

  	if (!test_and_clear_bit(0, &orphan_timer))

  		__module_get(THIS_MODULE);
  	/*
  	 *	Activate timer
  	 */
  	softdog_keepalive();
  	return nonseekable_open(inode, file);
  }
  
  static int softdog_release(struct inode *inode, struct file *file)
  {
  	/*
  	 *	Shut off the timer.

  	 *	Lock it in if it's a module and we set nowayout

  	 */
  	if (expect_close == 42) {
  		softdog_stop();

  		module_put(THIS_MODULE);

  	} else {

  		printk(KERN_CRIT PFX
  			"Unexpected close, not stopping watchdog!
  ");

  		set_bit(0, &orphan_timer);

  		softdog_keepalive();
  	}

  	clear_bit(0, &driver_open);

  	expect_close = 0;
  	return 0;
  }

  static ssize_t softdog_write(struct file *file, const char __user *data,
  						size_t len, loff_t *ppos)

  {
  	/*
  	 *	Refresh the timer.
  	 */

  	if (len) {

  		if (!nowayout) {
  			size_t i;
  
  			/* In case it was set long ago */
  			expect_close = 0;
  
  			for (i = 0; i != len; i++) {
  				char c;
  
  				if (get_user(c, data + i))
  					return -EFAULT;
  				if (c == 'V')
  					expect_close = 42;
  			}
  		}
  		softdog_keepalive();
  	}
  	return len;
  }

  static long softdog_ioctl(struct file *file, unsigned int cmd,
  							unsigned long arg)

  {
  	void __user *argp = (void __user *)arg;
  	int __user *p = argp;
  	int new_margin;

  	static const struct watchdog_info ident = {

  		.options =		WDIOF_SETTIMEOUT |
  					WDIOF_KEEPALIVEPING |
  					WDIOF_MAGICCLOSE,
  		.firmware_version =	0,
  		.identity =		"Software Watchdog",
  	};
  	switch (cmd) {

  	case WDIOC_GETSUPPORT:
  		return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
  	case WDIOC_GETSTATUS:
  	case WDIOC_GETBOOTSTATUS:
  		return put_user(0, p);
  	case WDIOC_KEEPALIVE:
  		softdog_keepalive();
  		return 0;
  	case WDIOC_SETTIMEOUT:
  		if (get_user(new_margin, p))
  			return -EFAULT;
  		if (softdog_set_heartbeat(new_margin))
  			return -EINVAL;
  		softdog_keepalive();
  		/* Fall */
  	case WDIOC_GETTIMEOUT:
  		return put_user(soft_margin, p);

  	default:
  		return -ENOTTY;

  	}
  }
  
  /*
   *	Notifier for system down
   */
  
  static int softdog_notify_sys(struct notifier_block *this, unsigned long code,
  	void *unused)
  {

  	if (code == SYS_DOWN || code == SYS_HALT)

  		/* Turn the WDT off */
  		softdog_stop();

  	return NOTIFY_DONE;
  }
  
  /*
   *	Kernel Interfaces
   */

  static const struct file_operations softdog_fops = {

  	.owner		= THIS_MODULE,
  	.llseek		= no_llseek,
  	.write		= softdog_write,

  	.unlocked_ioctl	= softdog_ioctl,

  	.open		= softdog_open,
  	.release	= softdog_release,
  };
  
  static struct miscdevice softdog_miscdev = {
  	.minor		= WATCHDOG_MINOR,
  	.name		= "watchdog",
  	.fops		= &softdog_fops,
  };
  
  static struct notifier_block softdog_notifier = {
  	.notifier_call	= softdog_notify_sys,
  };

  static char banner[] __initdata = KERN_INFO "Software Watchdog Timer: 0.07 "

  	"initialized. soft_noboot=%d soft_margin=%d sec soft_panic=%d "
  	"(nowayout= %d)
  ";

  
  static int __init watchdog_init(void)
  {
  	int ret;

  	/* Check that the soft_margin value is within it's range;
  	   if not reset to the default */

  	if (softdog_set_heartbeat(soft_margin)) {
  		softdog_set_heartbeat(TIMER_MARGIN);

  		printk(KERN_INFO PFX
  		    "soft_margin must be 0 < soft_margin < 65536, using %d
  ",

  			TIMER_MARGIN);
  	}
  
  	ret = register_reboot_notifier(&softdog_notifier);
  	if (ret) {

  		printk(KERN_ERR PFX
  			"cannot register reboot notifier (err=%d)
  ", ret);

  		return ret;
  	}
  
  	ret = misc_register(&softdog_miscdev);
  	if (ret) {

  		printk(KERN_ERR PFX
  			"cannot register miscdev on minor=%d (err=%d)
  ",
  						WATCHDOG_MINOR, ret);

  		unregister_reboot_notifier(&softdog_notifier);
  		return ret;
  	}

  	printk(banner, soft_noboot, soft_margin, soft_panic, nowayout);

  
  	return 0;
  }
  
  static void __exit watchdog_exit(void)
  {
  	misc_deregister(&softdog_miscdev);
  	unregister_reboot_notifier(&softdog_notifier);
  }
  
  module_init(watchdog_init);
  module_exit(watchdog_exit);
  
  MODULE_AUTHOR("Alan Cox");
  MODULE_DESCRIPTION("Software Watchdog Device Driver");
  MODULE_LICENSE("GPL");
  MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);