#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/init.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/uaccess.h>
#include <linux/timer.h>

#define WATCHDOG_NAME		"IT87 WDT"
#define DEVICE_NAME		"watchdog"
#define CLASS_NAME		"watchdog_class"

/* Defaults for Module Parameter */
#define DEFAULT_TIMEOUT		60
#define DEFAULT_TESTMODE	0

/* IO Ports */
#define REG		0x4e
#define VAL		0x4f

/* Logical device Numbers LDN */
#define GPIO		0x07

/* Configuration Registers and Functions */
#define LDNREG		0x07
#define CHIPID		0x20
#define CHIPREV		0x22

/* Chip Id numbers */
#define NO_DEV_ID	0xffff
#define IT8607_ID	0x8607
#define IT8620_ID	0x8620
#define IT8622_ID	0x8622
#define IT8625_ID	0x8625
#define IT8628_ID	0x8628
#define IT8655_ID	0x8655
#define IT8665_ID	0x8665
#define IT8686_ID	0x8686
#define IT8702_ID	0x8702
#define IT8705_ID	0x8705
#define IT8712_ID	0x8712
#define IT8716_ID	0x8716
#define IT8718_ID	0x8718
#define IT8720_ID	0x8720
#define IT8721_ID	0x8721
#define IT8726_ID	0x8726	/* the data sheet suggest wrongly 0x8716 */
#define IT8728_ID	0x8728
#define IT8772_ID	0x8772
#define IT8783_ID	0x8783
#define IT8784_ID	0x8784
#define IT8786_ID	0x8786

/* GPIO Configuration Registers LDN=0x07 */
#define WDTCTRL		0x71
#define WDTCFG		0x72
#define WDTVALLSB	0x73
#define WDTVALMSB	0x74

/* GPIO Bits WDTCFG */
#define WDT_TOV1	0x80
#define WDT_KRST	0x40
#define WDT_TOVE	0x20
#define WDT_PWROK	0x10 /* not in it8721 */
#define WDT_INT_MASK	0x0f

static unsigned int max_units, chip_type;

static unsigned int timeout = DEFAULT_TIMEOUT;
static int testmode = DEFAULT_TESTMODE;

module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds, default="
		__MODULE_STRING(DEFAULT_TIMEOUT));
module_param(testmode, int, 0);
MODULE_PARM_DESC(testmode, "Watchdog test mode (1 = no reboot), default="
		__MODULE_STRING(DEFAULT_TESTMODE));

/* Character device variables */
static int major_number;
static struct class *watchdog_class = NULL;
static struct device *watchdog_device = NULL;

/* Watchdog state: 0 = OFF, 1 = ON */
static int watchdog_state = 0;
static DEFINE_MUTEX(watchdog_mutex);

/* Software timer for servicing watchdog */
static struct timer_list watchdog_timer;

extern struct kobject *vfiec_kobj;

/* Superio Chip */

static inline int superio_enter(void)
{
	/*
	 * Try to reserve REG and REG + 1 for exclusive access.
	 */
	if (!request_muxed_region(REG, 2, WATCHDOG_NAME))
		return -EBUSY;

	outb(0x87, REG);
	outb(0x01, REG);
	outb(0x55, REG);
	outb(0xaa, REG);
	return 0;
}

static inline void superio_exit(void)
{
	outb(0x02, REG);
	outb(0x02, VAL);
	release_region(REG, 2);
}

static inline void superio_select(int ldn)
{
	outb(LDNREG, REG);
	outb(ldn, VAL);
}

static inline int superio_inb(int reg)
{
	outb(reg, REG);
	return inb(VAL);
}

static inline void superio_outb(int val, int reg)
{
	outb(reg, REG);
	outb(val, VAL);
}

static inline int superio_inw(int reg)
{
	int val;
	outb(reg++, REG);
	val = inb(VAL) << 8;
	outb(reg, REG);
	val |= inb(VAL);
	return val;
}

/* Internal function, should be called after superio_select(GPIO) */
static void _wdt_update_timeout(unsigned int t)
{
	unsigned char cfg = WDT_KRST;

	if (testmode)
		cfg = 0;

	if (t <= max_units)
		cfg |= WDT_TOV1;
	else
		t /= 60;

	if (chip_type != IT8721_ID)
		cfg |= WDT_PWROK;

	superio_outb(cfg, WDTCFG);
	superio_outb(t, WDTVALLSB);
	if (max_units > 255)
		superio_outb(t >> 8, WDTVALMSB);
	else
		superio_outb(0, WDTVALMSB);
}

static int wdt_update_timeout(unsigned int t)
{
	int ret;

	ret = superio_enter();
	if (ret)
		return ret;

	superio_select(GPIO);
	_wdt_update_timeout(t);
	superio_exit();

	return 0;
}

static int wdt_round_time(int t)
{
	t += 59;
	t -= t % 60;
	return t;
}

/* Software timer callback - service the watchdog */
static void watchdog_timer_callback(struct timer_list *t)
{
	/* Re-trigger the hardware watchdog by writing timeout again */
	wdt_update_timeout(timeout);
	
	/* Restart timer (periodic servicing, e.g., every half timeout) */
	mod_timer(&watchdog_timer, jiffies + (timeout * HZ / 2));
}

/* Enable watchdog - start hardware and software timer */
static int watchdog_enable(void)
{
	int ret;
	
	pr_info("Enabling watchdog timer\n");
	
	ret = wdt_update_timeout(timeout);
	if (ret) {
		pr_err("Failed to set watchdog timeout\n");
		return ret;
	}
	
	/* Start periodic software timer to service watchdog */
	timer_setup(&watchdog_timer, watchdog_timer_callback, 0);
	mod_timer(&watchdog_timer, jiffies + (timeout * HZ / 2));
	
	return 0;
}

/* Disable watchdog - stop hardware and software timer */
static int watchdog_disable(void)
{
	pr_info("Disabling watchdog timer\n");
	
	/* Stop and delete software timer */
	del_timer_sync(&watchdog_timer);
	
	/* Disable hardware watchdog by setting timeout to 0 */
	return wdt_update_timeout(0);
}

/* Parse user command: supports "ON", "OFF", "1", "0" */
static int parse_watchdog_command(const char *buf, size_t count)
{	
	/* Skip whitespace */
	while (count > 0 && (*buf == ' ' || *buf == '\t' || *buf == '\n' || *buf == '\r')) {
		buf++;
		count--;
	}
	
	if (count == 0)
		return -1;
	
	/* Check for numeric value */
	if (count == 1 && (buf[0] == '0' || buf[0] == '1')) {
		return buf[0] - '0';
	}
	
	/* Check for "ON" or "OFF" (case insensitive) */
	if (count >= 2) {
		if ((buf[0] == 'O' || buf[0] == 'o') &&
		    (buf[1] == 'N' || buf[1] == 'n')) {
			return 1;
		}
		if (count >= 3 &&
		    (buf[0] == 'O' || buf[0] == 'o') &&
		    (buf[1] == 'F' || buf[1] == 'f') &&
		    (buf[2] == 'F' || buf[2] == 'f')) {
			return 0;
		}
	}
	
	return -1;
}

/* Character device file operations */
static ssize_t watchdog_read(struct file *file, char __user *user_buf,
			      size_t count, loff_t *ppos)
{	
	char status_buf[64];
	int len;
	
	if (*ppos > 0)
		return 0;
	
	mutex_lock(&watchdog_mutex);
	if (watchdog_state)
		len = snprintf(status_buf, sizeof(status_buf),
			       "The watchdog is on\nThe args value is 1\n");
	else
		len = snprintf(status_buf, sizeof(status_buf),
			       "The watchdog is off\nThe args value is 0\n");
	mutex_unlock(&watchdog_mutex);
	
	if (copy_to_user(user_buf, status_buf, len))
		return -EFAULT;
	
	*ppos += len;
	return len;
}

static ssize_t watchdog_write(struct file *file, const char __user *user_buf,
			       size_t count, loff_t *ppos)
{
	char buf[16];
	int cmd;
	int ret = count;
	
	if (count == 0 || count >= sizeof(buf))
		return -EINVAL;
	
	if (copy_from_user(buf, user_buf, count))
		return -EFAULT;
	
	buf[count] = '\0';
	
	cmd = parse_watchdog_command(buf, count);
	if (cmd < 0)
		return -EINVAL;
	
	mutex_lock(&watchdog_mutex);
	
	if (cmd == watchdog_state) {
		/* No state change */
		if (cmd)
			pr_info("Watchdog is already on\n");
		else
			pr_info("Watchdog is already off\n");
	} else {
		if (cmd) {
			/* Turn ON */
			if (watchdog_enable() == 0) {
				watchdog_state = 1;
				pr_info("Watchdog turned on successfully\n");
			} else {
				ret = -EIO;
			}
		} else {
			/* Turn OFF */
			if (watchdog_disable() == 0) {
				watchdog_state = 0;
				pr_info("Watchdog turned off successfully\n");
			} else {
				ret = -EIO;
			}
		}
	}
	
	mutex_unlock(&watchdog_mutex);
	return ret;
}

static int watchdog_open(struct inode *inode, struct file *file)
{	
	return 0;
}

static int watchdog_release(struct inode *inode, struct file *file)
{	
	return 0;
}

static const struct file_operations watchdog_fops = {
	.owner = THIS_MODULE,
	.read = watchdog_read,
	.write = watchdog_write,
	.open = watchdog_open,
	.release = watchdog_release,
};
static char *my_devnode(struct device *dev, umode_t *mode) {
    if (mode) {
        *mode = 0666;
    }
    return NULL;
}

static ssize_t watchdog_show(struct kobject *kobj, struct kobj_attribute *attr,
                         char *buf)
{
    return 0;
}

static ssize_t watchdog_store(struct kobject *kobj, struct kobj_attribute *attr,
                          const char *buf, size_t count)
{
	int cmd;
	int ret = count;
	
	// if (count == 0 || count >= sizeof(buf))
	// 	return -EINVAL;
	
	// if (strscpy(buf, user_buf, count) < 0)
	// 	return -EFAULT;
	
	// buf[count] = '\0';
	
	cmd = parse_watchdog_command(buf, count);
	if (cmd < 0)
		return -EINVAL;
	
	mutex_lock(&watchdog_mutex);
	
	if (cmd == watchdog_state) {
		/* No state change */
		if (cmd)
			pr_info("Watchdog is already on\n");
		else
			pr_info("Watchdog is already off\n");
	} else {
		if (cmd) {
			/* Turn ON */
			if (watchdog_enable() == 0) {
				watchdog_state = 1;
				pr_info("Watchdog turned on successfully\n");
			} else {
				ret = -EIO;
			}
		} else {
			/* Turn OFF */
			if (watchdog_disable() == 0) {
				watchdog_state = 0;
				pr_info("Watchdog turned off successfully\n");
			} else {
				ret = -EIO;
			}
		}
	}
	
	mutex_unlock(&watchdog_mutex);
	return ret;
}

static struct kobj_attribute watchdog_attr =
    __ATTR(watchdog, 0644, watchdog_show, watchdog_store);

static struct attribute *watchdog_attrs[] = {
    &watchdog_attr.attr,
    NULL,
};

static struct attribute_group watchdog_attr_group = {
    .attrs = watchdog_attrs,
};

int watchdog_init(void)
{	
	u8  chip_rev;
	int rc;

	rc = sysfs_create_group(vfiec_kobj, &watchdog_attr_group);
    if (rc)
    {
        pr_err("Faiec_version to create sysfs group: %d\n", rc);
		return -1;
    }

	rc = superio_enter();
	if (rc)
		return rc;

	chip_type = superio_inw(CHIPID);
	chip_rev  = superio_inb(CHIPREV) & 0x0f;
	superio_exit();

	switch (chip_type) {
	case IT8702_ID:
		max_units = 255;
		break;
	case IT8712_ID:
		max_units = (chip_rev < 8) ? 255 : 65535;
		break;
	case IT8716_ID:
	case IT8726_ID:
		max_units = 65535;
		break;
	case IT8607_ID:
	case IT8620_ID:
	case IT8622_ID:
	case IT8625_ID:
	case IT8628_ID:
	case IT8655_ID:
	case IT8665_ID:
	case IT8686_ID:
	case IT8718_ID:
	case IT8720_ID:
	case IT8721_ID:
	case IT8728_ID:
	case IT8772_ID:
	case IT8783_ID:
	case IT8784_ID:
	case IT8786_ID:
		max_units = 65535;
		break;
	case IT8705_ID:
		pr_err("Unsupported Chip found, Chip %04x Revision %02x\n",
		       chip_type, chip_rev);
		return -ENODEV;
	case NO_DEV_ID:
		pr_err("no device\n");
		return -ENODEV;
	default:
		pr_err("Unknown Chip found, Chip %04x Revision %04x\n",
		       chip_type, chip_rev);
		return -ENODEV;
	}

	rc = superio_enter();
	if (rc)
		return rc;

	superio_select(GPIO);
	superio_outb(WDT_TOV1, WDTCFG);
	superio_outb(0x00, WDTCTRL);
	superio_exit();

	if (timeout < 1 || timeout > max_units * 60) {
		timeout = DEFAULT_TIMEOUT;
		pr_warn("Timeout value out of range, use default %d sec\n",
			DEFAULT_TIMEOUT);
	}

	if (timeout > max_units)
		timeout = wdt_round_time(timeout);

	/* Register character device */
	major_number = register_chrdev(0, DEVICE_NAME, &watchdog_fops);
	if (major_number < 0) {
		pr_err("Failed to register character device\n");
		return major_number;
	}

	/* Create device class */
	watchdog_class = class_create(THIS_MODULE, CLASS_NAME);
	if (IS_ERR(watchdog_class)) {
		unregister_chrdev(major_number, DEVICE_NAME);
		pr_err("Failed to create device class\n");
		return PTR_ERR(watchdog_class);
	}

	watchdog_class->devnode = my_devnode;

	/* Create device node /dev/watchdog */
	watchdog_device = device_create(watchdog_class, NULL,
					MKDEV(major_number, 0),
					NULL, DEVICE_NAME);
	if (IS_ERR(watchdog_device)) {
		class_destroy(watchdog_class);
		unregister_chrdev(major_number, DEVICE_NAME);
		pr_err("Failed to create device node\n");
		return PTR_ERR(watchdog_device);
	}

	/* Initialize state */
	watchdog_state = 0;
	
	/* Initialize timer */
	timer_setup(&watchdog_timer, watchdog_timer_callback, 0);

	pr_info("Chip IT%04x revision %d initialized. timeout=%d sec (testmode=%d)\n",
		chip_type, chip_rev, timeout, testmode);
	pr_info("Device /dev/watchdog created. Default state: OFF\n");

	return 0;
}

void watchdog_exit(void)
{	
	/* Ensure watchdog is disabled before exit */
	if (watchdog_state) {
		watchdog_disable();
		watchdog_state = 0;
	}
	
	/* Delete timer */
	del_timer_sync(&watchdog_timer);
	sysfs_remove_group(vfiec_kobj, &watchdog_attr_group);

	/* Remove device */
	device_destroy(watchdog_class, MKDEV(major_number, 0));
	class_destroy(watchdog_class);
	unregister_chrdev(major_number, DEVICE_NAME);
	
	pr_info("Watchdog driver exited\n");
}