/*
 *      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>

#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)");

/*
 *      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.\n");
        else {
                printk(KERN_CRIT PFX "Initiating system reboot.\n");
                emergency_restart();
                printk(KERN_CRIT PFX "Reboot didn't ?????\n");
        }
}

/*
 *      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!\n");
                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 (nowayout= %d)\n";

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\n",
                        TIMER_MARGIN);
        }

        ret = register_reboot_notifier(&softdog_notifier);
        if (ret) {
                printk(KERN_ERR PFX
                        "cannot register reboot notifier (err=%d)\n", ret);
                return ret;
        }

        ret = misc_register(&softdog_miscdev);
        if (ret) {
                printk(KERN_ERR PFX
                        "cannot register miscdev on minor=%d (err=%d)\n",
                                                WATCHDOG_MINOR, ret);
                unregister_reboot_notifier(&softdog_notifier);
                return ret;
        }

        printk(banner, soft_noboot, soft_margin, 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);