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/*

 *      Acquire Single Board Computer Watchdog Timer driver

 *

 *      Based on wdt.c. Original copyright messages:

 *

 *      (c) Copyright 1996 Alan Cox <alan@redhat.com>, All Rights Reserved.

 *                              http://www.redhat.com

 *

 *      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@redhat.com>

 *

 *      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 occured 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 <asm/uaccess.h>                /* For copy_to_user/put_user/... */

#include <asm/io.h>                     /* For inb/outb/... */

/* Module information */

#define DRV_NAME "acquirewdt"

#define PFX DRV_NAME ": "

#define WATCHDOG_NAME "Acquire WDT"

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

/* internal variables */

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

static unsigned long acq_is_open;

static char expect_close;

/* module parameters */

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

module_param(wdt_stop, int, 0);

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

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

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 int acq_ioctl(struct inode *inode, struct file *file, unsigned int cmd,

        unsigned long arg)

{

        int options, retval = -EINVAL;

        void __user *argp = (void __user *)arg;

        int __user *p = argp;

        static 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_KEEPALIVE:

          acq_keepalive();

          return 0;

        case WDIOC_GETTIMEOUT:

          return put_user(WATCHDOG_HEARTBEAT, 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;

        }

        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!\n");

                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,

        .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\n",

                                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\n",

                        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)\n",

                        WATCHDOG_MINOR, ret);

                goto unreg_regions;

        }

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

                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.\n");

        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.\n");

}

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);