/*
   * I2C client/driver for the ST M41T80 family of i2c rtc chips.
   *
   * Author: Alexander Bigga <ab@mycable.de>
   *
   * Based on m41t00.c by Mark A. Greer <mgreer@mvista.com>
   *
   * 2006 (c) mycable GmbH
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   *
   */

  #include <linux/bcd.h>
  #include <linux/i2c.h>

  #include <linux/init.h>

  #include <linux/kernel.h>

  #include <linux/module.h>
  #include <linux/rtc.h>

  #include <linux/slab.h>

  #include <linux/mutex.h>

  #include <linux/string.h>

  #ifdef CONFIG_RTC_DRV_M41T80_WDT

  #include <linux/fs.h>
  #include <linux/ioctl.h>

  #include <linux/miscdevice.h>
  #include <linux/reboot.h>
  #include <linux/watchdog.h>

  #endif

  
  #define M41T80_REG_SSEC	0
  #define M41T80_REG_SEC	1
  #define M41T80_REG_MIN	2
  #define M41T80_REG_HOUR	3
  #define M41T80_REG_WDAY	4
  #define M41T80_REG_DAY	5
  #define M41T80_REG_MON	6
  #define M41T80_REG_YEAR	7
  #define M41T80_REG_ALARM_MON	0xa
  #define M41T80_REG_ALARM_DAY	0xb
  #define M41T80_REG_ALARM_HOUR	0xc
  #define M41T80_REG_ALARM_MIN	0xd
  #define M41T80_REG_ALARM_SEC	0xe
  #define M41T80_REG_FLAGS	0xf
  #define M41T80_REG_SQW	0x13
  
  #define M41T80_DATETIME_REG_SIZE	(M41T80_REG_YEAR + 1)
  #define M41T80_ALARM_REG_SIZE	\
  	(M41T80_REG_ALARM_SEC + 1 - M41T80_REG_ALARM_MON)
  
  #define M41T80_SEC_ST		(1 << 7)	/* ST: Stop Bit */
  #define M41T80_ALMON_AFE	(1 << 7)	/* AFE: AF Enable Bit */
  #define M41T80_ALMON_SQWE	(1 << 6)	/* SQWE: SQW Enable Bit */
  #define M41T80_ALHOUR_HT	(1 << 6)	/* HT: Halt Update Bit */
  #define M41T80_FLAGS_AF		(1 << 6)	/* AF: Alarm Flag Bit */
  #define M41T80_FLAGS_BATT_LOW	(1 << 4)	/* BL: Battery Low Bit */

  #define M41T80_WATCHDOG_RB2	(1 << 7)	/* RB: Watchdog resolution */
  #define M41T80_WATCHDOG_RB1	(1 << 1)	/* RB: Watchdog resolution */
  #define M41T80_WATCHDOG_RB0	(1 << 0)	/* RB: Watchdog resolution */

  #define M41T80_FEATURE_HT	(1 << 0)	/* Halt feature */
  #define M41T80_FEATURE_BL	(1 << 1)	/* Battery low indicator */
  #define M41T80_FEATURE_SQ	(1 << 2)	/* Squarewave feature */
  #define M41T80_FEATURE_WD	(1 << 3)	/* Extra watchdog resolution */

  #define M41T80_FEATURE_SQ_ALT	(1 << 4)	/* RSx bits are in reg 4 */

  
  #define DRV_VERSION "0.05"

  static DEFINE_MUTEX(m41t80_rtc_mutex);

  static const struct i2c_device_id m41t80_id[] = {

  	{ "m41t62", M41T80_FEATURE_SQ | M41T80_FEATURE_SQ_ALT },

  	{ "m41t65", M41T80_FEATURE_HT | M41T80_FEATURE_WD },
  	{ "m41t80", M41T80_FEATURE_SQ },
  	{ "m41t81", M41T80_FEATURE_HT | M41T80_FEATURE_SQ},
  	{ "m41t81s", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
  	{ "m41t82", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
  	{ "m41t83", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
  	{ "m41st84", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
  	{ "m41st85", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
  	{ "m41st87", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },

  	{ }

  };

  MODULE_DEVICE_TABLE(i2c, m41t80_id);

  
  struct m41t80_data {

  	u8 features;

  	struct rtc_device *rtc;
  };
  
  static int m41t80_get_datetime(struct i2c_client *client,
  			       struct rtc_time *tm)
  {
  	u8 buf[M41T80_DATETIME_REG_SIZE], dt_addr[1] = { M41T80_REG_SEC };
  	struct i2c_msg msgs[] = {
  		{
  			.addr	= client->addr,
  			.flags	= 0,
  			.len	= 1,
  			.buf	= dt_addr,
  		},
  		{
  			.addr	= client->addr,
  			.flags	= I2C_M_RD,
  			.len	= M41T80_DATETIME_REG_SIZE - M41T80_REG_SEC,
  			.buf	= buf + M41T80_REG_SEC,
  		},
  	};
  
  	if (i2c_transfer(client->adapter, msgs, 2) < 0) {
  		dev_err(&client->dev, "read error
  ");
  		return -EIO;
  	}

  	tm->tm_sec = bcd2bin(buf[M41T80_REG_SEC] & 0x7f);
  	tm->tm_min = bcd2bin(buf[M41T80_REG_MIN] & 0x7f);
  	tm->tm_hour = bcd2bin(buf[M41T80_REG_HOUR] & 0x3f);
  	tm->tm_mday = bcd2bin(buf[M41T80_REG_DAY] & 0x3f);

  	tm->tm_wday = buf[M41T80_REG_WDAY] & 0x07;

  	tm->tm_mon = bcd2bin(buf[M41T80_REG_MON] & 0x1f) - 1;

  
  	/* assume 20YY not 19YY, and ignore the Century Bit */

  	tm->tm_year = bcd2bin(buf[M41T80_REG_YEAR]) + 100;

  	return rtc_valid_tm(tm);

  }
  
  /* Sets the given date and time to the real time clock. */
  static int m41t80_set_datetime(struct i2c_client *client, struct rtc_time *tm)
  {
  	u8 wbuf[1 + M41T80_DATETIME_REG_SIZE];
  	u8 *buf = &wbuf[1];
  	u8 dt_addr[1] = { M41T80_REG_SEC };
  	struct i2c_msg msgs_in[] = {
  		{
  			.addr	= client->addr,
  			.flags	= 0,
  			.len	= 1,
  			.buf	= dt_addr,
  		},
  		{
  			.addr	= client->addr,
  			.flags	= I2C_M_RD,
  			.len	= M41T80_DATETIME_REG_SIZE - M41T80_REG_SEC,
  			.buf	= buf + M41T80_REG_SEC,
  		},
  	};
  	struct i2c_msg msgs[] = {
  		{
  			.addr	= client->addr,
  			.flags	= 0,
  			.len	= 1 + M41T80_DATETIME_REG_SIZE,
  			.buf	= wbuf,
  		 },
  	};
  
  	/* Read current reg values into buf[1..7] */
  	if (i2c_transfer(client->adapter, msgs_in, 2) < 0) {
  		dev_err(&client->dev, "read error
  ");
  		return -EIO;
  	}
  
  	wbuf[0] = 0; /* offset into rtc's regs */
  	/* Merge time-data and register flags into buf[0..7] */
  	buf[M41T80_REG_SSEC] = 0;
  	buf[M41T80_REG_SEC] =

  		bin2bcd(tm->tm_sec) | (buf[M41T80_REG_SEC] & ~0x7f);

  	buf[M41T80_REG_MIN] =

  		bin2bcd(tm->tm_min) | (buf[M41T80_REG_MIN] & ~0x7f);

  	buf[M41T80_REG_HOUR] =

  		bin2bcd(tm->tm_hour) | (buf[M41T80_REG_HOUR] & ~0x3f) ;

  	buf[M41T80_REG_WDAY] =
  		(tm->tm_wday & 0x07) | (buf[M41T80_REG_WDAY] & ~0x07);
  	buf[M41T80_REG_DAY] =

  		bin2bcd(tm->tm_mday) | (buf[M41T80_REG_DAY] & ~0x3f);

  	buf[M41T80_REG_MON] =

  		bin2bcd(tm->tm_mon + 1) | (buf[M41T80_REG_MON] & ~0x1f);

  	/* assume 20YY not 19YY */

  	buf[M41T80_REG_YEAR] = bin2bcd(tm->tm_year % 100);

  
  	if (i2c_transfer(client->adapter, msgs, 1) != 1) {
  		dev_err(&client->dev, "write error
  ");
  		return -EIO;
  	}
  	return 0;
  }
  
  #if defined(CONFIG_RTC_INTF_PROC) || defined(CONFIG_RTC_INTF_PROC_MODULE)
  static int m41t80_rtc_proc(struct device *dev, struct seq_file *seq)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  	struct m41t80_data *clientdata = i2c_get_clientdata(client);
  	u8 reg;

  	if (clientdata->features & M41T80_FEATURE_BL) {

  		reg = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
  		seq_printf(seq, "battery\t\t: %s
  ",
  			   (reg & M41T80_FLAGS_BATT_LOW) ? "exhausted" : "ok");
  	}
  	return 0;
  }
  #else
  #define m41t80_rtc_proc NULL
  #endif
  
  static int m41t80_rtc_read_time(struct device *dev, struct rtc_time *tm)
  {
  	return m41t80_get_datetime(to_i2c_client(dev), tm);
  }
  
  static int m41t80_rtc_set_time(struct device *dev, struct rtc_time *tm)
  {
  	return m41t80_set_datetime(to_i2c_client(dev), tm);
  }

  static int m41t80_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)

  {
  	struct i2c_client *client = to_i2c_client(dev);
  	int rc;

  	rc = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);
  	if (rc < 0)
  		goto err;

  
  	if (enabled)

  		rc |= M41T80_ALMON_AFE;

  	else
  		rc &= ~M41T80_ALMON_AFE;

  	if (i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON, rc) < 0)
  		goto err;

  	return 0;
  err:
  	return -EIO;
  }

  
  static int m41t80_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *t)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  	u8 wbuf[1 + M41T80_ALARM_REG_SIZE];
  	u8 *buf = &wbuf[1];
  	u8 *reg = buf - M41T80_REG_ALARM_MON;
  	u8 dt_addr[1] = { M41T80_REG_ALARM_MON };
  	struct i2c_msg msgs_in[] = {
  		{
  			.addr	= client->addr,
  			.flags	= 0,
  			.len	= 1,
  			.buf	= dt_addr,
  		},
  		{
  			.addr	= client->addr,
  			.flags	= I2C_M_RD,
  			.len	= M41T80_ALARM_REG_SIZE,
  			.buf	= buf,
  		},
  	};
  	struct i2c_msg msgs[] = {
  		{
  			.addr	= client->addr,
  			.flags	= 0,
  			.len	= 1 + M41T80_ALARM_REG_SIZE,
  			.buf	= wbuf,
  		 },
  	};
  
  	if (i2c_transfer(client->adapter, msgs_in, 2) < 0) {
  		dev_err(&client->dev, "read error
  ");
  		return -EIO;
  	}
  	reg[M41T80_REG_ALARM_MON] &= ~(0x1f | M41T80_ALMON_AFE);
  	reg[M41T80_REG_ALARM_DAY] = 0;
  	reg[M41T80_REG_ALARM_HOUR] &= ~(0x3f | 0x80);
  	reg[M41T80_REG_ALARM_MIN] = 0;
  	reg[M41T80_REG_ALARM_SEC] = 0;
  
  	wbuf[0] = M41T80_REG_ALARM_MON; /* offset into rtc's regs */
  	reg[M41T80_REG_ALARM_SEC] |= t->time.tm_sec >= 0 ?

  		bin2bcd(t->time.tm_sec) : 0x80;

  	reg[M41T80_REG_ALARM_MIN] |= t->time.tm_min >= 0 ?

  		bin2bcd(t->time.tm_min) : 0x80;

  	reg[M41T80_REG_ALARM_HOUR] |= t->time.tm_hour >= 0 ?

  		bin2bcd(t->time.tm_hour) : 0x80;

  	reg[M41T80_REG_ALARM_DAY] |= t->time.tm_mday >= 0 ?

  		bin2bcd(t->time.tm_mday) : 0x80;

  	if (t->time.tm_mon >= 0)

  		reg[M41T80_REG_ALARM_MON] |= bin2bcd(t->time.tm_mon + 1);

  	else
  		reg[M41T80_REG_ALARM_DAY] |= 0x40;
  
  	if (i2c_transfer(client->adapter, msgs, 1) != 1) {
  		dev_err(&client->dev, "write error
  ");
  		return -EIO;
  	}
  
  	if (t->enabled) {
  		reg[M41T80_REG_ALARM_MON] |= M41T80_ALMON_AFE;
  		if (i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
  					      reg[M41T80_REG_ALARM_MON]) < 0) {
  			dev_err(&client->dev, "write error
  ");
  			return -EIO;
  		}
  	}
  	return 0;
  }
  
  static int m41t80_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *t)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  	u8 buf[M41T80_ALARM_REG_SIZE + 1]; /* all alarm regs and flags */
  	u8 dt_addr[1] = { M41T80_REG_ALARM_MON };
  	u8 *reg = buf - M41T80_REG_ALARM_MON;
  	struct i2c_msg msgs[] = {
  		{
  			.addr	= client->addr,
  			.flags	= 0,
  			.len	= 1,
  			.buf	= dt_addr,
  		},
  		{
  			.addr	= client->addr,
  			.flags	= I2C_M_RD,
  			.len	= M41T80_ALARM_REG_SIZE + 1,
  			.buf	= buf,
  		},
  	};
  
  	if (i2c_transfer(client->adapter, msgs, 2) < 0) {
  		dev_err(&client->dev, "read error
  ");
  		return -EIO;
  	}
  	t->time.tm_sec = -1;
  	t->time.tm_min = -1;
  	t->time.tm_hour = -1;
  	t->time.tm_mday = -1;
  	t->time.tm_mon = -1;
  	if (!(reg[M41T80_REG_ALARM_SEC] & 0x80))

  		t->time.tm_sec = bcd2bin(reg[M41T80_REG_ALARM_SEC] & 0x7f);

  	if (!(reg[M41T80_REG_ALARM_MIN] & 0x80))

  		t->time.tm_min = bcd2bin(reg[M41T80_REG_ALARM_MIN] & 0x7f);

  	if (!(reg[M41T80_REG_ALARM_HOUR] & 0x80))

  		t->time.tm_hour = bcd2bin(reg[M41T80_REG_ALARM_HOUR] & 0x3f);

  	if (!(reg[M41T80_REG_ALARM_DAY] & 0x80))

  		t->time.tm_mday = bcd2bin(reg[M41T80_REG_ALARM_DAY] & 0x3f);

  	if (!(reg[M41T80_REG_ALARM_DAY] & 0x40))

  		t->time.tm_mon = bcd2bin(reg[M41T80_REG_ALARM_MON] & 0x1f) - 1;

  	t->time.tm_year = -1;
  	t->time.tm_wday = -1;
  	t->time.tm_yday = -1;
  	t->time.tm_isdst = -1;
  	t->enabled = !!(reg[M41T80_REG_ALARM_MON] & M41T80_ALMON_AFE);
  	t->pending = !!(reg[M41T80_REG_FLAGS] & M41T80_FLAGS_AF);

  	return 0;

  }
  
  static struct rtc_class_ops m41t80_rtc_ops = {
  	.read_time = m41t80_rtc_read_time,
  	.set_time = m41t80_rtc_set_time,

  	/*
  	 * XXX - m41t80 alarm functionality is reported broken.
  	 * until it is fixed, don't register alarm functions.
  	 *

  	.read_alarm = m41t80_rtc_read_alarm,
  	.set_alarm = m41t80_rtc_set_alarm,

  	*/

  	.proc = m41t80_rtc_proc,

  	/*
  	 * See above comment on broken alarm
  	 *

  	.alarm_irq_enable = m41t80_rtc_alarm_irq_enable,

  	*/

  };
  
  #if defined(CONFIG_RTC_INTF_SYSFS) || defined(CONFIG_RTC_INTF_SYSFS_MODULE)
  static ssize_t m41t80_sysfs_show_flags(struct device *dev,
  				struct device_attribute *attr, char *buf)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  	int val;
  
  	val = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
  	if (val < 0)
  		return -EIO;
  	return sprintf(buf, "%#x
  ", val);
  }
  static DEVICE_ATTR(flags, S_IRUGO, m41t80_sysfs_show_flags, NULL);
  
  static ssize_t m41t80_sysfs_show_sqwfreq(struct device *dev,
  				struct device_attribute *attr, char *buf)
  {
  	struct i2c_client *client = to_i2c_client(dev);

  	struct m41t80_data *clientdata = i2c_get_clientdata(client);

  	int val, reg_sqw;

  	if (!(clientdata->features & M41T80_FEATURE_SQ))
  		return -EINVAL;

  	reg_sqw = M41T80_REG_SQW;
  	if (clientdata->features & M41T80_FEATURE_SQ_ALT)
  		reg_sqw = M41T80_REG_WDAY;
  	val = i2c_smbus_read_byte_data(client, reg_sqw);

  	if (val < 0)
  		return -EIO;
  	val = (val >> 4) & 0xf;
  	switch (val) {
  	case 0:
  		break;
  	case 1:
  		val = 32768;
  		break;
  	default:
  		val = 32768 >> val;
  	}
  	return sprintf(buf, "%d
  ", val);
  }
  static ssize_t m41t80_sysfs_set_sqwfreq(struct device *dev,
  				struct device_attribute *attr,
  				const char *buf, size_t count)
  {
  	struct i2c_client *client = to_i2c_client(dev);

  	struct m41t80_data *clientdata = i2c_get_clientdata(client);

  	int almon, sqw, reg_sqw;

  	int val = simple_strtoul(buf, NULL, 0);

  	if (!(clientdata->features & M41T80_FEATURE_SQ))
  		return -EINVAL;

  	if (val) {
  		if (!is_power_of_2(val))
  			return -EINVAL;
  		val = ilog2(val);
  		if (val == 15)
  			val = 1;
  		else if (val < 14)
  			val = 15 - val;
  		else
  			return -EINVAL;
  	}
  	/* disable SQW, set SQW frequency & re-enable */
  	almon = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);
  	if (almon < 0)
  		return -EIO;

  	reg_sqw = M41T80_REG_SQW;
  	if (clientdata->features & M41T80_FEATURE_SQ_ALT)
  		reg_sqw = M41T80_REG_WDAY;
  	sqw = i2c_smbus_read_byte_data(client, reg_sqw);

  	if (sqw < 0)
  		return -EIO;
  	sqw = (sqw & 0x0f) | (val << 4);
  	if (i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
  				      almon & ~M41T80_ALMON_SQWE) < 0 ||

  	    i2c_smbus_write_byte_data(client, reg_sqw, sqw) < 0)

  		return -EIO;
  	if (val && i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
  					     almon | M41T80_ALMON_SQWE) < 0)
  		return -EIO;
  	return count;
  }
  static DEVICE_ATTR(sqwfreq, S_IRUGO | S_IWUSR,
  		   m41t80_sysfs_show_sqwfreq, m41t80_sysfs_set_sqwfreq);
  
  static struct attribute *attrs[] = {
  	&dev_attr_flags.attr,
  	&dev_attr_sqwfreq.attr,
  	NULL,
  };
  static struct attribute_group attr_group = {
  	.attrs = attrs,
  };
  
  static int m41t80_sysfs_register(struct device *dev)
  {
  	return sysfs_create_group(&dev->kobj, &attr_group);
  }
  #else
  static int m41t80_sysfs_register(struct device *dev)
  {
  	return 0;
  }
  #endif

  #ifdef CONFIG_RTC_DRV_M41T80_WDT
  /*
   *****************************************************************************
   *
   * Watchdog Driver
   *
   *****************************************************************************
   */
  static struct i2c_client *save_client;
  
  /* Default margin */
  #define WD_TIMO 60		/* 1..31 seconds */
  
  static int wdt_margin = WD_TIMO;
  module_param(wdt_margin, int, 0);
  MODULE_PARM_DESC(wdt_margin, "Watchdog timeout in seconds (default 60s)");
  
  static unsigned long wdt_is_open;
  static int boot_flag;
  
  /**
   *	wdt_ping:
   *
   *	Reload counter one with the watchdog timeout. We don't bother reloading
   *	the cascade counter.
   */
  static void wdt_ping(void)
  {
  	unsigned char i2c_data[2];
  	struct i2c_msg msgs1[1] = {
  		{
  			.addr	= save_client->addr,
  			.flags	= 0,
  			.len	= 2,
  			.buf	= i2c_data,
  		},
  	};

  	struct m41t80_data *clientdata = i2c_get_clientdata(save_client);

  	i2c_data[0] = 0x09;		/* watchdog register */
  
  	if (wdt_margin > 31)
  		i2c_data[1] = (wdt_margin & 0xFC) | 0x83; /* resolution = 4s */
  	else
  		/*
  		 * WDS = 1 (0x80), mulitplier = WD_TIMO, resolution = 1s (0x02)
  		 */
  		i2c_data[1] = wdt_margin<<2 | 0x82;

  	/*
  	 * M41T65 has three bits for watchdog resolution.  Don't set bit 7, as
  	 * that would be an invalid resolution.
  	 */
  	if (clientdata->features & M41T80_FEATURE_WD)
  		i2c_data[1] &= ~M41T80_WATCHDOG_RB2;

  	i2c_transfer(save_client->adapter, msgs1, 1);
  }
  
  /**
   *	wdt_disable:
   *
   *	disables watchdog.
   */
  static void wdt_disable(void)
  {
  	unsigned char i2c_data[2], i2c_buf[0x10];
  	struct i2c_msg msgs0[2] = {
  		{
  			.addr	= save_client->addr,
  			.flags	= 0,
  			.len	= 1,
  			.buf	= i2c_data,
  		},
  		{
  			.addr	= save_client->addr,
  			.flags	= I2C_M_RD,
  			.len	= 1,
  			.buf	= i2c_buf,
  		},
  	};
  	struct i2c_msg msgs1[1] = {
  		{
  			.addr	= save_client->addr,
  			.flags	= 0,
  			.len	= 2,
  			.buf	= i2c_data,
  		},
  	};
  
  	i2c_data[0] = 0x09;
  	i2c_transfer(save_client->adapter, msgs0, 2);
  
  	i2c_data[0] = 0x09;
  	i2c_data[1] = 0x00;
  	i2c_transfer(save_client->adapter, msgs1, 1);
  }
  
  /**
   *	wdt_write:
   *	@file: file handle to the watchdog
   *	@buf: buffer to write (unused as data does not matter here
   *	@count: count of bytes
   *	@ppos: pointer to the position to write. No seeks allowed
   *
   *	A write to a watchdog device is defined as a keepalive signal. Any
   *	write of data will do, as we we don't define content meaning.
   */
  static ssize_t wdt_write(struct file *file, const char __user *buf,
  			 size_t count, loff_t *ppos)
  {

  	if (count) {
  		wdt_ping();
  		return 1;
  	}
  	return 0;
  }
  
  static ssize_t wdt_read(struct file *file, char __user *buf,
  			size_t count, loff_t *ppos)
  {
  	return 0;
  }
  
  /**
   *	wdt_ioctl:
   *	@inode: inode of the device
   *	@file: file handle to the device
   *	@cmd: watchdog command
   *	@arg: argument pointer
   *
   *	The watchdog API defines a common set of functions for all watchdogs
   *	according to their available features. We only actually usefully support
   *	querying capabilities and current status.
   */

  static int wdt_ioctl(struct file *file, unsigned int cmd,

  		     unsigned long arg)
  {
  	int new_margin, rv;
  	static struct watchdog_info ident = {
  		.options = WDIOF_POWERUNDER | WDIOF_KEEPALIVEPING |
  			WDIOF_SETTIMEOUT,
  		.firmware_version = 1,
  		.identity = "M41T80 WTD"
  	};
  
  	switch (cmd) {
  	case WDIOC_GETSUPPORT:
  		return copy_to_user((struct watchdog_info __user *)arg, &ident,
  				    sizeof(ident)) ? -EFAULT : 0;
  
  	case WDIOC_GETSTATUS:
  	case WDIOC_GETBOOTSTATUS:
  		return put_user(boot_flag, (int __user *)arg);
  	case WDIOC_KEEPALIVE:
  		wdt_ping();
  		return 0;
  	case WDIOC_SETTIMEOUT:
  		if (get_user(new_margin, (int __user *)arg))
  			return -EFAULT;
  		/* Arbitrary, can't find the card's limits */
  		if (new_margin < 1 || new_margin > 124)
  			return -EINVAL;
  		wdt_margin = new_margin;
  		wdt_ping();
  		/* Fall */
  	case WDIOC_GETTIMEOUT:
  		return put_user(wdt_margin, (int __user *)arg);
  
  	case WDIOC_SETOPTIONS:
  		if (copy_from_user(&rv, (int __user *)arg, sizeof(int)))
  			return -EFAULT;
  
  		if (rv & WDIOS_DISABLECARD) {

  			pr_info("rtc-m41t80: disable watchdog
  ");

  			wdt_disable();
  		}
  
  		if (rv & WDIOS_ENABLECARD) {

  			pr_info("rtc-m41t80: enable watchdog
  ");

  			wdt_ping();
  		}
  
  		return -EINVAL;
  	}
  	return -ENOTTY;
  }

  static long wdt_unlocked_ioctl(struct file *file, unsigned int cmd,
  			       unsigned long arg)
  {
  	int ret;

  	mutex_lock(&m41t80_rtc_mutex);

  	ret = wdt_ioctl(file, cmd, arg);

  	mutex_unlock(&m41t80_rtc_mutex);

  
  	return ret;
  }

  /**
   *	wdt_open:
   *	@inode: inode of device
   *	@file: file handle to device
   *
   */
  static int wdt_open(struct inode *inode, struct file *file)
  {
  	if (MINOR(inode->i_rdev) == WATCHDOG_MINOR) {

  		mutex_lock(&m41t80_rtc_mutex);

  		if (test_and_set_bit(0, &wdt_is_open)) {

  			mutex_unlock(&m41t80_rtc_mutex);

  			return -EBUSY;

  		}

  		/*
  		 *	Activate
  		 */
  		wdt_is_open = 1;

  		mutex_unlock(&m41t80_rtc_mutex);

  		return nonseekable_open(inode, file);

  	}
  	return -ENODEV;
  }
  
  /**
   *	wdt_close:
   *	@inode: inode to board
   *	@file: file handle to board
   *
   */
  static int wdt_release(struct inode *inode, struct file *file)
  {
  	if (MINOR(inode->i_rdev) == WATCHDOG_MINOR)
  		clear_bit(0, &wdt_is_open);
  	return 0;
  }
  
  /**
   *	notify_sys:
   *	@this: our notifier block
   *	@code: the event being reported
   *	@unused: unused
   *
   *	Our notifier is called on system shutdowns. We want to turn the card
   *	off at reboot otherwise the machine will reboot again during memory
   *	test or worse yet during the following fsck. This would suck, in fact
   *	trust me - if it happens it does suck.
   */
  static int wdt_notify_sys(struct notifier_block *this, unsigned long code,
  			  void *unused)
  {
  	if (code == SYS_DOWN || code == SYS_HALT)
  		/* Disable Watchdog */
  		wdt_disable();
  	return NOTIFY_DONE;
  }
  
  static const struct file_operations wdt_fops = {
  	.owner	= THIS_MODULE,
  	.read	= wdt_read,

  	.unlocked_ioctl = wdt_unlocked_ioctl,

  	.write	= wdt_write,
  	.open	= wdt_open,
  	.release = wdt_release,

  	.llseek = no_llseek,

  };
  
  static struct miscdevice wdt_dev = {
  	.minor = WATCHDOG_MINOR,
  	.name = "watchdog",
  	.fops = &wdt_fops,
  };
  
  /*
   *	The WDT card needs to learn about soft shutdowns in order to
   *	turn the timebomb registers off.
   */
  static struct notifier_block wdt_notifier = {
  	.notifier_call = wdt_notify_sys,
  };
  #endif /* CONFIG_RTC_DRV_M41T80_WDT */

  /*
   *****************************************************************************
   *
   *	Driver Interface
   *
   *****************************************************************************
   */

  static int m41t80_probe(struct i2c_client *client,
  			const struct i2c_device_id *id)

  {

  	int rc = 0;

  	struct rtc_device *rtc = NULL;
  	struct rtc_time tm;

  	struct m41t80_data *clientdata = NULL;
  
  	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C
  				     | I2C_FUNC_SMBUS_BYTE_DATA)) {
  		rc = -ENODEV;
  		goto exit;
  	}
  
  	dev_info(&client->dev,
  		 "chip found, driver version " DRV_VERSION "
  ");

  	clientdata = kzalloc(sizeof(*clientdata), GFP_KERNEL);
  	if (!clientdata) {
  		rc = -ENOMEM;
  		goto exit;
  	}

  	clientdata->features = id->driver_data;
  	i2c_set_clientdata(client, clientdata);

  	rtc = rtc_device_register(client->name, &client->dev,
  				  &m41t80_rtc_ops, THIS_MODULE);
  	if (IS_ERR(rtc)) {
  		rc = PTR_ERR(rtc);
  		rtc = NULL;
  		goto exit;
  	}
  
  	clientdata->rtc = rtc;

  
  	/* Make sure HT (Halt Update) bit is cleared */
  	rc = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_HOUR);
  	if (rc < 0)
  		goto ht_err;
  
  	if (rc & M41T80_ALHOUR_HT) {

  		if (clientdata->features & M41T80_FEATURE_HT) {

  			m41t80_get_datetime(client, &tm);
  			dev_info(&client->dev, "HT bit was set!
  ");
  			dev_info(&client->dev,
  				 "Power Down at "
  				 "%04i-%02i-%02i %02i:%02i:%02i
  ",
  				 tm.tm_year + 1900,
  				 tm.tm_mon + 1, tm.tm_mday, tm.tm_hour,
  				 tm.tm_min, tm.tm_sec);
  		}
  		if (i2c_smbus_write_byte_data(client,
  					      M41T80_REG_ALARM_HOUR,
  					      rc & ~M41T80_ALHOUR_HT) < 0)
  			goto ht_err;
  	}
  
  	/* Make sure ST (stop) bit is cleared */
  	rc = i2c_smbus_read_byte_data(client, M41T80_REG_SEC);
  	if (rc < 0)
  		goto st_err;
  
  	if (rc & M41T80_SEC_ST) {
  		if (i2c_smbus_write_byte_data(client, M41T80_REG_SEC,
  					      rc & ~M41T80_SEC_ST) < 0)
  			goto st_err;
  	}
  
  	rc = m41t80_sysfs_register(&client->dev);
  	if (rc)
  		goto exit;

  #ifdef CONFIG_RTC_DRV_M41T80_WDT

  	if (clientdata->features & M41T80_FEATURE_HT) {

  		save_client = client;

  		rc = misc_register(&wdt_dev);
  		if (rc)
  			goto exit;
  		rc = register_reboot_notifier(&wdt_notifier);
  		if (rc) {
  			misc_deregister(&wdt_dev);
  			goto exit;
  		}

  	}
  #endif

  	return 0;
  
  st_err:
  	rc = -EIO;
  	dev_err(&client->dev, "Can't clear ST bit
  ");
  	goto exit;
  ht_err:
  	rc = -EIO;
  	dev_err(&client->dev, "Can't clear HT bit
  ");
  	goto exit;
  
  exit:
  	if (rtc)
  		rtc_device_unregister(rtc);
  	kfree(clientdata);
  	return rc;
  }
  
  static int m41t80_remove(struct i2c_client *client)
  {
  	struct m41t80_data *clientdata = i2c_get_clientdata(client);
  	struct rtc_device *rtc = clientdata->rtc;

  #ifdef CONFIG_RTC_DRV_M41T80_WDT

  	if (clientdata->features & M41T80_FEATURE_HT) {

  		misc_deregister(&wdt_dev);
  		unregister_reboot_notifier(&wdt_notifier);
  	}
  #endif

  	if (rtc)
  		rtc_device_unregister(rtc);
  	kfree(clientdata);
  
  	return 0;
  }
  
  static struct i2c_driver m41t80_driver = {
  	.driver = {

  		.name = "rtc-m41t80",

  	},
  	.probe = m41t80_probe,
  	.remove = m41t80_remove,

  	.id_table = m41t80_id,

  };
  
  static int __init m41t80_rtc_init(void)
  {
  	return i2c_add_driver(&m41t80_driver);
  }
  
  static void __exit m41t80_rtc_exit(void)
  {
  	i2c_del_driver(&m41t80_driver);
  }
  
  MODULE_AUTHOR("Alexander Bigga <ab@mycable.de>");
  MODULE_DESCRIPTION("ST Microelectronics M41T80 series RTC I2C Client Driver");
  MODULE_LICENSE("GPL");
  MODULE_VERSION(DRV_VERSION);
  
  module_init(m41t80_rtc_init);
  module_exit(m41t80_rtc_exit);