// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      SBC EPX C3 0.1  A Hardware Watchdog Device for the Winsystems EPX-C3
 *      single board computer
 *
 *      (c) Copyright 2006 Calin A. Culianu <calin@ajvar.org>, All Rights
 *      Reserved.
 *
 *      based on softdog.c by Alan Cox <alan@lxorguk.ukuu.org.uk>
 */

#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 stream_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,
        .write          = epx_c3_write,
        .unlocked_ioctl = epx_c3_ioctl,
        .compat_ioctl   = compat_ptr_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 <calin@ajvar.org>");
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");