sbc_epx_c3.c

Go to the documentation of this file.

/*
 *  SBC EPX C3 0.1  A Hardware Watchdog Device for the Winsystems EPX-C3
 *  single board computer
 *
 *  (c) Copyright 2006 Calin A. Culianu <[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.
 *
 *  based on softdog.c by Alan Cox <[email protected]>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/ioport.h>
#include <linux/uaccess.h>
#include <linux/io.h>

static int epx_c3_alive;

#define WATCHDOG_TIMEOUT 1      /* 1 sec default timeout */

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) ")");

#define EPXC3_WATCHDOG_CTL_REG 0x1ee /* write 1 to enable, 0 to disable */
#define EPXC3_WATCHDOG_PET_REG 0x1ef /* write anything to pet once enabled */

static void epx_c3_start(void)
{
    outb(1, EPXC3_WATCHDOG_CTL_REG);
}

static void epx_c3_stop(void)
{

    outb(0, EPXC3_WATCHDOG_CTL_REG);

    pr_info("Stopped watchdog timer\n");
}

static void epx_c3_pet(void)
{
    outb(1, EPXC3_WATCHDOG_PET_REG);
}

/*
 *  Allow only one person to hold it open
 */
static int epx_c3_open(struct inode *inode, struct file *file)
{
    if (epx_c3_alive)
        return -EBUSY;

    if (nowayout)
        __module_get(THIS_MODULE);

    /* Activate timer */
    epx_c3_start();
    epx_c3_pet();

    epx_c3_alive = 1;
    pr_info("Started watchdog timer\n");

    return nonseekable_open(inode, file);
}

static int epx_c3_release(struct inode *inode, struct file *file)
{
    /* Shut off the timer.
     * Lock it in if it's a module and we defined ...NOWAYOUT */
    if (!nowayout)
        epx_c3_stop();      /* Turn the WDT off */

    epx_c3_alive = 0;

    return 0;
}

static ssize_t epx_c3_write(struct file *file, const char __user *data,
            size_t len, loff_t *ppos)
{
    /* Refresh the timer. */
    if (len)
        epx_c3_pet();
    return len;
}

static long epx_c3_ioctl(struct file *file, unsigned int cmd,
                        unsigned long arg)
{
    int options, retval = -EINVAL;
    int __user *argp = (void __user *)arg;
    static const struct watchdog_info ident = {
        .options        = WDIOF_KEEPALIVEPING,
        .firmware_version   = 0,
        .identity       = "Winsystems EPX-C3 H/W Watchdog",
    };

    switch (cmd) {
    case WDIOC_GETSUPPORT:
        if (copy_to_user(argp, &ident, sizeof(ident)))
            return -EFAULT;
        return 0;
    case WDIOC_GETSTATUS:
    case WDIOC_GETBOOTSTATUS:
        return put_user(0, argp);
    case WDIOC_SETOPTIONS:
        if (get_user(options, argp))
            return -EFAULT;

        if (options & WDIOS_DISABLECARD) {
            epx_c3_stop();
            retval = 0;
        }

        if (options & WDIOS_ENABLECARD) {
            epx_c3_start();
            retval = 0;
        }

        return retval;
    case WDIOC_KEEPALIVE:
        epx_c3_pet();
        return 0;
    case WDIOC_GETTIMEOUT:
        return put_user(WATCHDOG_TIMEOUT, argp);
    default:
        return -ENOTTY;
    }
}

static int epx_c3_notify_sys(struct notifier_block *this, unsigned long code,
                void *unused)
{
    if (code == SYS_DOWN || code == SYS_HALT)
        epx_c3_stop();      /* Turn the WDT off */

    return NOTIFY_DONE;
}

static const struct file_operations epx_c3_fops = {
    .owner      = THIS_MODULE,
    .llseek     = no_llseek,
    .write      = epx_c3_write,
    .unlocked_ioctl = epx_c3_ioctl,
    .open       = epx_c3_open,
    .release    = epx_c3_release,
};

static struct miscdevice epx_c3_miscdev = {
    .minor      = WATCHDOG_MINOR,
    .name       = "watchdog",
    .fops       = &epx_c3_fops,
};

static struct notifier_block epx_c3_notifier = {
    .notifier_call = epx_c3_notify_sys,
};

static int __init watchdog_init(void)
{
    int ret;

    if (!request_region(EPXC3_WATCHDOG_CTL_REG, 2, "epxc3_watchdog"))
        return -EBUSY;

    ret = register_reboot_notifier(&epx_c3_notifier);
    if (ret) {
        pr_err("cannot register reboot notifier (err=%d)\n", ret);
        goto out;
    }

    ret = misc_register(&epx_c3_miscdev);
    if (ret) {
        pr_err("cannot register miscdev on minor=%d (err=%d)\n",
               WATCHDOG_MINOR, ret);
        unregister_reboot_notifier(&epx_c3_notifier);
        goto out;
    }

    pr_info("Hardware Watchdog Timer for Winsystems EPX-C3 SBC: 0.1\n");

    return 0;

out:
    release_region(EPXC3_WATCHDOG_CTL_REG, 2);
    return ret;
}

static void __exit watchdog_exit(void)
{
    misc_deregister(&epx_c3_miscdev);
    unregister_reboot_notifier(&epx_c3_notifier);
    release_region(EPXC3_WATCHDOG_CTL_REG, 2);
}

module_init(watchdog_init);
module_exit(watchdog_exit);

MODULE_AUTHOR("Calin A. Culianu <[email protected]>");
MODULE_DESCRIPTION("Hardware Watchdog Device for Winsystems EPX-C3 SBC.  "
    "Note that there is no way to probe for this device -- "
    "so only use it if you are *sure* you are running on this specific "
    "SBC system from Winsystems!  It writes to IO ports 0x1ee and 0x1ef!");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);