acquirewdt.c

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/*
 *  Acquire Single Board Computer Watchdog Timer driver
 *
 *  Based on wdt.c. Original copyright messages:
 *
 *  (c) Copyright 1996 Alan Cox <[email protected]>,
 *                      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 <[email protected]>
 *
 *  14-Dec-2001 Matt Domsch <[email protected]>
 *      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, ...
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

/* 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 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 bool nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, bool, 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 {
        pr_crit("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,
    .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)) {
            pr_err("I/O address 0x%04x already in use\n", wdt_stop);
            ret = -EIO;
            goto out;
        }
    }

    if (!request_region(wdt_start, 1, WATCHDOG_NAME)) {
        pr_err("I/O address 0x%04x already in use\n", wdt_start);
        ret = -EIO;
        goto unreg_stop;
    }
    ret = misc_register(&acq_miscdev);
    if (ret != 0) {
        pr_err("cannot register miscdev on minor=%d (err=%d)\n",
               WATCHDOG_MINOR, ret);
        goto unreg_regions;
    }
    pr_info("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;

    pr_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);
    pr_info("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);