/*
   *	Acquire Single Board Computer Watchdog Timer driver
   *

   *	Based on wdt.c. Original copyright messages:

   *

   *	(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>

   *

   *	14-Dec-2001 Matt Domsch <Matt_Domsch@dell.com>
   *	    Added nowayout module option to override CONFIG_WATCHDOG_NOWAYOUT
   *	    Can't add timeout - driver doesn't allow changing value

   */
  
  /*
   *	Theory of Operation:
   *		The Watch-Dog Timer is provided to ensure that standalone
   *		Systems can always recover from catastrophic conditions that

   *		caused the CPU to crash. This condition may have occurred by

   *		external EMI or a software bug. When the CPU stops working
   *		correctly, hardware on the board will either perform a hardware
   *		reset (cold boot) or a non-maskable interrupt (NMI) to bring the
   *		system back to a known state.
   *
   *		The Watch-Dog Timer is controlled by two I/O Ports.
   *		  443 hex	- Read	- Enable or refresh the Watch-Dog Timer
   *		  043 hex	- Read	- Disable the Watch-Dog Timer
   *
   *		To enable the Watch-Dog Timer, a read from I/O port 443h must
   *		be performed. This will enable and activate the countdown timer
   *		which will eventually time out and either reset the CPU or cause
   *		an NMI depending on the setting of a jumper. To ensure that this
   *		reset condition does not occur, the Watch-Dog Timer must be
   *		periodically refreshed by reading the same I/O port 443h.
   *		The Watch-Dog Timer is disabled by reading I/O port 043h.
   *
   *		The Watch-Dog Timer Time-Out Period is set via jumpers.
   *		It can be 1, 2, 10, 20, 110 or 220 seconds.
   */

  /*
   *	Includes, defines, variables, module parameters, ...
   */

  /* Includes */
  #include <linux/module.h>		/* For module specific items */
  #include <linux/moduleparam.h>		/* For new moduleparam's */
  #include <linux/types.h>		/* For standard types (like size_t) */
  #include <linux/errno.h>		/* For the -ENODEV/... values */
  #include <linux/kernel.h>		/* For printk/panic/... */

  #include <linux/miscdevice.h>		/* For MODULE_ALIAS_MISCDEV
  							(WATCHDOG_MINOR) */

  #include <linux/watchdog.h>		/* For the watchdog specific items */
  #include <linux/fs.h>			/* For file operations */
  #include <linux/ioport.h>		/* For io-port access */

  #include <linux/platform_device.h>	/* For platform_driver framework */

  #include <linux/init.h>			/* For __init/__exit/... */

  #include <linux/uaccess.h>		/* For copy_to_user/put_user/... */
  #include <linux/io.h>			/* For inb/outb/... */

  
  /* Module information */
  #define DRV_NAME "acquirewdt"
  #define PFX DRV_NAME ": "

  #define WATCHDOG_NAME "Acquire WDT"

  /* There is no way to see what the correct time-out period is */
  #define WATCHDOG_HEARTBEAT 0

  /* internal variables */

  /* the watchdog platform device */
  static struct platform_device *acq_platform_device;

  static unsigned long acq_is_open;
  static char expect_close;

  /* module parameters */

  /* You must set this - there is no sane way to probe for this board. */
  static int wdt_stop = 0x43;

  module_param(wdt_stop, int, 0);
  MODULE_PARM_DESC(wdt_stop, "Acquire WDT 'stop' io port (default 0x43)");

  /* You must set this - there is no sane way to probe for this board. */
  static int wdt_start = 0x443;

  module_param(wdt_start, int, 0);
  MODULE_PARM_DESC(wdt_start, "Acquire WDT 'start' io port (default 0x443)");

  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) ")");

  
  /*

   *	Watchdog Operations

   */
  
  static void acq_keepalive(void)
  {
  	/* Write a watchdog value */
  	inb_p(wdt_start);
  }
  
  static void acq_stop(void)
  {
  	/* Turn the card off */
  	inb_p(wdt_stop);
  }
  
  /*

   *	/dev/watchdog handling

   */

  static ssize_t acq_write(struct file *file, const char __user *buf,
  						size_t count, loff_t *ppos)

  {
  	/* See if we got the magic character 'V' and reload the timer */

  	if (count) {

  		if (!nowayout) {
  			size_t i;

  			/* note: just in case someone wrote the magic character

  			   five months ago... */

  			expect_close = 0;

  			/* scan to see whether or not we got the
  			   magic character */

  			for (i = 0; i != count; i++) {
  				char c;
  				if (get_user(c, buf + i))
  					return -EFAULT;
  				if (c == 'V')
  					expect_close = 42;
  			}
  		}

  		/* Well, anyhow someone wrote to us, we should
  				return that favour */

  		acq_keepalive();
  	}
  	return count;
  }

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

  {
  	int options, retval = -EINVAL;
  	void __user *argp = (void __user *)arg;
  	int __user *p = argp;

  	static const struct watchdog_info ident = {

  		.options = WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
  		.firmware_version = 1,

  		.identity = WATCHDOG_NAME,

  	};

  	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_SETOPTIONS:
  	{

  		if (get_user(options, p))
  			return -EFAULT;
  		if (options & WDIOS_DISABLECARD) {
  			acq_stop();
  			retval = 0;
  		}
  		if (options & WDIOS_ENABLECARD) {
  			acq_keepalive();
  			retval = 0;
  		}
  		return retval;

  	}

  	case WDIOC_KEEPALIVE:
  		acq_keepalive();
  		return 0;
  
  	case WDIOC_GETTIMEOUT:
  		return put_user(WATCHDOG_HEARTBEAT, p);

  	default:

  		return -ENOTTY;

  	}
  }
  
  static int acq_open(struct inode *inode, struct file *file)
  {
  	if (test_and_set_bit(0, &acq_is_open))
  		return -EBUSY;
  
  	if (nowayout)
  		__module_get(THIS_MODULE);
  
  	/* Activate */
  	acq_keepalive();
  	return nonseekable_open(inode, file);
  }
  
  static int acq_close(struct inode *inode, struct file *file)
  {
  	if (expect_close == 42) {
  		acq_stop();
  	} else {

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

  		acq_keepalive();
  	}
  	clear_bit(0, &acq_is_open);
  	expect_close = 0;
  	return 0;
  }
  
  /*

   *	Kernel Interfaces
   */

  static const struct file_operations acq_fops = {

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

  	.unlocked_ioctl	= acq_ioctl,

  	.open		= acq_open,
  	.release	= acq_close,
  };

  static struct miscdevice acq_miscdev = {
  	.minor	= WATCHDOG_MINOR,
  	.name	= "watchdog",
  	.fops	= &acq_fops,

  };
  
  /*

   *	Init & exit routines
   */

  static int __devinit acq_probe(struct platform_device *dev)

  {
  	int ret;

  	if (wdt_stop != wdt_start) {
  		if (!request_region(wdt_stop, 1, WATCHDOG_NAME)) {

  			printk(KERN_ERR PFX
  			    "I/O address 0x%04x already in use
  ", wdt_stop);

  			ret = -EIO;
  			goto out;
  		}
  	}
  
  	if (!request_region(wdt_start, 1, WATCHDOG_NAME)) {

  		printk(KERN_ERR PFX "I/O address 0x%04x already in use
  ",

  			wdt_start);
  		ret = -EIO;
  		goto unreg_stop;
  	}

  	ret = misc_register(&acq_miscdev);
  	if (ret != 0) {

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

  		goto unreg_regions;

  	}

  	printk(KERN_INFO PFX "initialized. (nowayout=%d)
  ", nowayout);

  
  	return 0;

  unreg_regions:
  	release_region(wdt_start, 1);
  unreg_stop:
  	if (wdt_stop != wdt_start)
  		release_region(wdt_stop, 1);
  out:
  	return ret;
  }

  static int __devexit acq_remove(struct platform_device *dev)

  {
  	misc_deregister(&acq_miscdev);

  	release_region(wdt_start, 1);
  	if (wdt_stop != wdt_start)
  		release_region(wdt_stop, 1);

  
  	return 0;
  }

  static void acq_shutdown(struct platform_device *dev)
  {
  	/* Turn the WDT off if we have a soft shutdown */
  	acq_stop();
  }

  static struct platform_driver acquirewdt_driver = {
  	.probe		= acq_probe,
  	.remove		= __devexit_p(acq_remove),

  	.shutdown	= acq_shutdown,

  	.driver		= {
  		.owner	= THIS_MODULE,
  		.name	= DRV_NAME,
  	},
  };
  
  static int __init acq_init(void)
  {
  	int err;

  	printk(KERN_INFO
  	      "WDT driver for Acquire single board computer initialising.
  ");

  
  	err = platform_driver_register(&acquirewdt_driver);
  	if (err)
  		return err;

  	acq_platform_device = platform_device_register_simple(DRV_NAME,
  								-1, NULL, 0);

  	if (IS_ERR(acq_platform_device)) {
  		err = PTR_ERR(acq_platform_device);
  		goto unreg_platform_driver;
  	}

  	return 0;
  
  unreg_platform_driver:
  	platform_driver_unregister(&acquirewdt_driver);
  	return err;
  }
  
  static void __exit acq_exit(void)
  {
  	platform_device_unregister(acq_platform_device);
  	platform_driver_unregister(&acquirewdt_driver);
  	printk(KERN_INFO PFX "Watchdog Module Unloaded.
  ");

  }
  
  module_init(acq_init);
  module_exit(acq_exit);
  
  MODULE_AUTHOR("David Woodhouse");
  MODULE_DESCRIPTION("Acquire Inc. Single Board Computer Watchdog Timer driver");
  MODULE_LICENSE("GPL");
  MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);