// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * MixCom Watchdog: A Simple Hardware Watchdog Device
 * Based on Softdog driver by Alan Cox and PC Watchdog driver by Ken Hollis
 *
 * Author: Gergely Madarasz <gorgo@itc.hu>
 *
 * Copyright (c) 1999 ITConsult-Pro Co. <info@itc.hu>
 *
 * Version 0.1 (99/04/15):
 *              - first version
 *
 * Version 0.2 (99/06/16):
 *              - added kernel timer watchdog ping after close
 *                since the hardware does not support watchdog shutdown
 *
 * Version 0.3 (99/06/21):
 *              - added WDIOC_GETSTATUS and WDIOC_GETSUPPORT ioctl calls
 *
 * Version 0.3.1 (99/06/22):
 *              - allow module removal while internal timer is active,
 *                print warning about probable reset
 *
 * Version 0.4 (99/11/15):
 *              - support for one more type board
 *
 * Version 0.5 (2001/12/14) Matt Domsch <Matt_Domsch@dell.com>
 *              - added nowayout module option to override
 *                CONFIG_WATCHDOG_NOWAYOUT
 *
 * Version 0.6 (2002/04/12): Rob Radez <rob@osinvestor.com>
 *              - make mixcomwd_opened unsigned,
 *                removed lock_kernel/unlock_kernel from mixcomwd_release,
 *                modified ioctl a bit to conform to API
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#define VERSION "0.6"
#define WATCHDOG_NAME "mixcomwd"

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/miscdevice.h>
#include <linux/ioport.h>
#include <linux/watchdog.h>
#include <linux/fs.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/jiffies.h>
#include <linux/timer.h>
#include <linux/uaccess.h>
#include <linux/io.h>

/*
 * We have two types of cards that can be probed:
 * 1) The Mixcom cards: these cards can be found at addresses
 *    0x180, 0x280, 0x380 with an additional offset of 0xc10.
 *    (Or 0xd90, 0xe90, 0xf90).
 * 2) The FlashCOM cards: these cards can be set up at
 *    0x300 -> 0x378, in 0x8 jumps with an offset of 0x04.
 *    (Or 0x304 -> 0x37c in 0x8 jumps).
 *    Each card has it's own ID.
 */
#define MIXCOM_ID 0x11
#define FLASHCOM_ID 0x18
static struct {
        int ioport;
        int id;
} mixcomwd_io_info[] = {
        /* The Mixcom cards */
        {0x0d90, MIXCOM_ID},
        {0x0e90, MIXCOM_ID},
        {0x0f90, MIXCOM_ID},
        /* The FlashCOM cards */
        {0x0304, FLASHCOM_ID},
        {0x030c, FLASHCOM_ID},
        {0x0314, FLASHCOM_ID},
        {0x031c, FLASHCOM_ID},
        {0x0324, FLASHCOM_ID},
        {0x032c, FLASHCOM_ID},
        {0x0334, FLASHCOM_ID},
        {0x033c, FLASHCOM_ID},
        {0x0344, FLASHCOM_ID},
        {0x034c, FLASHCOM_ID},
        {0x0354, FLASHCOM_ID},
        {0x035c, FLASHCOM_ID},
        {0x0364, FLASHCOM_ID},
        {0x036c, FLASHCOM_ID},
        {0x0374, FLASHCOM_ID},
        {0x037c, FLASHCOM_ID},
        /* The end of the list */
        {0x0000, 0},
};

static void mixcomwd_timerfun(struct timer_list *unused);

static unsigned long mixcomwd_opened; /* long req'd for setbit --RR */

static int watchdog_port;
static int mixcomwd_timer_alive;
static DEFINE_TIMER(mixcomwd_timer, mixcomwd_timerfun);
static char expect_close;

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) ")");

static void mixcomwd_ping(void)
{
        outb_p(55, watchdog_port);
        return;
}

static void mixcomwd_timerfun(struct timer_list *unused)
{
        mixcomwd_ping();
        mod_timer(&mixcomwd_timer, jiffies + 5 * HZ);
}

/*
 *      Allow only one person to hold it open
 */

static int mixcomwd_open(struct inode *inode, struct file *file)
{
        if (test_and_set_bit(0, &mixcomwd_opened))
                return -EBUSY;

        mixcomwd_ping();

        if (nowayout)
                /*
                 * fops_get() code via open() has already done
                 * a try_module_get() so it is safe to do the
                 * __module_get().
                 */
                __module_get(THIS_MODULE);
        else {
                if (mixcomwd_timer_alive) {
                        timer_delete(&mixcomwd_timer);
                        mixcomwd_timer_alive = 0;
                }
        }
        return stream_open(inode, file);
}

static int mixcomwd_release(struct inode *inode, struct file *file)
{
        if (expect_close == 42) {
                if (mixcomwd_timer_alive) {
                        pr_err("release called while internal timer alive\n");
                        return -EBUSY;
                }
                mixcomwd_timer_alive = 1;
                mod_timer(&mixcomwd_timer, jiffies + 5 * HZ);
        } else
                pr_crit("WDT device closed unexpectedly.  WDT will not stop!\n");

        clear_bit(0, &mixcomwd_opened);
        expect_close = 0;
        return 0;
}


static ssize_t mixcomwd_write(struct file *file, const char __user *data,
                                                size_t len, loff_t *ppos)
{
        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;
                        }
                }
                mixcomwd_ping();
        }
        return len;
}

static long mixcomwd_ioctl(struct file *file,
                                unsigned int cmd, unsigned long arg)
{
        void __user *argp = (void __user *)arg;
        int __user *p = argp;
        int status;
        static const struct watchdog_info ident = {
                .options = WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
                .firmware_version = 1,
                .identity = "MixCOM watchdog",
        };

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                if (copy_to_user(argp, &ident, sizeof(ident)))
                        return -EFAULT;
                break;
        case WDIOC_GETSTATUS:
                status = mixcomwd_opened;
                if (!nowayout)
                        status |= mixcomwd_timer_alive;
                return put_user(status, p);
        case WDIOC_GETBOOTSTATUS:
                return put_user(0, p);
        case WDIOC_KEEPALIVE:
                mixcomwd_ping();
                break;
        default:
                return -ENOTTY;
        }
        return 0;
}

static const struct file_operations mixcomwd_fops = {
        .owner          = THIS_MODULE,
        .write          = mixcomwd_write,
        .unlocked_ioctl = mixcomwd_ioctl,
        .compat_ioctl   = compat_ptr_ioctl,
        .open           = mixcomwd_open,
        .release        = mixcomwd_release,
};

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

static int __init checkcard(int port, int card_id)
{
        int id;

        if (!request_region(port, 1, "MixCOM watchdog"))
                return 0;

        id = inb_p(port);
        if (card_id == MIXCOM_ID)
                id &= 0x3f;

        if (id != card_id) {
                release_region(port, 1);
                return 0;
        }
        return 1;
}

static int __init mixcomwd_init(void)
{
        int i, ret, found = 0;

        for (i = 0; !found && mixcomwd_io_info[i].ioport != 0; i++) {
                if (checkcard(mixcomwd_io_info[i].ioport,
                              mixcomwd_io_info[i].id)) {
                        found = 1;
                        watchdog_port = mixcomwd_io_info[i].ioport;
                }
        }

        if (!found) {
                pr_err("No card detected, or port not available\n");
                return -ENODEV;
        }

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

        pr_info("MixCOM watchdog driver v%s, watchdog port at 0x%3x\n",
                VERSION, watchdog_port);

        return 0;

error_misc_register_watchdog:
        release_region(watchdog_port, 1);
        watchdog_port = 0x0000;
        return ret;
}

static void __exit mixcomwd_exit(void)
{
        if (!nowayout) {
                if (mixcomwd_timer_alive) {
                        pr_warn("I quit now, hardware will probably reboot!\n");
                        timer_delete_sync(&mixcomwd_timer);
                        mixcomwd_timer_alive = 0;
                }
        }
        misc_deregister(&mixcomwd_miscdev);
        release_region(watchdog_port, 1);
}

module_init(mixcomwd_init);
module_exit(mixcomwd_exit);

MODULE_AUTHOR("Gergely Madarasz <gorgo@itc.hu>");
MODULE_DESCRIPTION("MixCom Watchdog driver");
MODULE_VERSION(VERSION);
MODULE_LICENSE("GPL");