text: /*
   * 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.
   *
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #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		0x00
  #define M41T80_REG_SEC		0x01
  #define M41T80_REG_MIN		0x02
  #define M41T80_REG_HOUR		0x03
  #define M41T80_REG_WDAY		0x04
  #define M41T80_REG_DAY		0x05
  #define M41T80_REG_MON		0x06
  #define M41T80_REG_YEAR		0x07
  #define M41T80_REG_ALARM_MON	0x0a
  #define M41T80_REG_ALARM_DAY	0x0b
  #define M41T80_REG_ALARM_HOUR	0x0c
  #define M41T80_REG_ALARM_MIN	0x0d
  #define M41T80_REG_ALARM_SEC	0x0e
  #define M41T80_REG_FLAGS	0x0f
  #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		BIT(7)	/* ST: Stop Bit */
  #define M41T80_ALMON_AFE	BIT(7)	/* AFE: AF Enable Bit */
  #define M41T80_ALMON_SQWE	BIT(6)	/* SQWE: SQW Enable Bit */
  #define M41T80_ALHOUR_HT	BIT(6)	/* HT: Halt Update Bit */
  #define M41T80_FLAGS_OF		BIT(2)	/* OF: Oscillator Failure Bit */
  #define M41T80_FLAGS_AF		BIT(6)	/* AF: Alarm Flag Bit */
  #define M41T80_FLAGS_BATT_LOW	BIT(4)	/* BL: Battery Low Bit */
  #define M41T80_WATCHDOG_RB2	BIT(7)	/* RB: Watchdog resolution */
  #define M41T80_WATCHDOG_RB1	BIT(1)	/* RB: Watchdog resolution */
  #define M41T80_WATCHDOG_RB0	BIT(0)	/* RB: Watchdog resolution */
  
  #define M41T80_FEATURE_HT	BIT(0)	/* Halt feature */
  #define M41T80_FEATURE_BL	BIT(1)	/* Battery low indicator */
  #define M41T80_FEATURE_SQ	BIT(2)	/* Squarewave feature */
  #define M41T80_FEATURE_WD	BIT(3)	/* Extra watchdog resolution */
  #define M41T80_FEATURE_SQ_ALT	BIT(4)	/* RSx bits are in reg 4 */
  
  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 },
  	{ "rv4162", M41T80_FEATURE_SQ | M41T80_FEATURE_WD | M41T80_FEATURE_SQ_ALT },
  	{ }
  };
  MODULE_DEVICE_TABLE(i2c, m41t80_id);
  
  struct m41t80_data {
  	u8 features;
  	struct rtc_device *rtc;
  };
  
  static irqreturn_t m41t80_handle_irq(int irq, void *dev_id)
  {
  	struct i2c_client *client = dev_id;
  	struct m41t80_data *m41t80 = i2c_get_clientdata(client);
  	struct mutex *lock = &m41t80->rtc->ops_lock;
  	unsigned long events = 0;
  	int flags, flags_afe;
  
  	mutex_lock(lock);
  
  	flags_afe = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);
  	if (flags_afe < 0) {
  		mutex_unlock(lock);
  		return IRQ_NONE;
  	}
  
  	flags = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
  	if (flags <= 0) {
  		mutex_unlock(lock);
  		return IRQ_NONE;
  	}
  
  	if (flags & M41T80_FLAGS_AF) {
  		flags &= ~M41T80_FLAGS_AF;
  		flags_afe &= ~M41T80_ALMON_AFE;
  		events |= RTC_AF;
  	}
  
  	if (events) {
  		rtc_update_irq(m41t80->rtc, 1, events);
  		i2c_smbus_write_byte_data(client, M41T80_REG_FLAGS, flags);
  		i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
  					  flags_afe);
  	}
  
  	mutex_unlock(lock);
  
  	return IRQ_HANDLED;
  }
  
  static int m41t80_get_datetime(struct i2c_client *client,
  			       struct rtc_time *tm)
  {
  	unsigned char buf[8];
  	int err, flags;
  
  	flags = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
  	if (flags < 0)
  		return flags;
  
  	if (flags & M41T80_FLAGS_OF) {
  		dev_err(&client->dev, "Oscillator failure, data is invalid.\n");
  		return -EINVAL;
  	}
  
  	err = i2c_smbus_read_i2c_block_data(client, M41T80_REG_SSEC,
  					    sizeof(buf), buf);
  	if (err < 0) {
  		dev_err(&client->dev, "Unable to read date\n");
  		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)
  {
  	unsigned char buf[8];
  	int err, flags;
  
  	if (tm->tm_year < 100 || tm->tm_year > 199)
  		return -EINVAL;
  
  	buf[M41T80_REG_SSEC] = 0;
  	buf[M41T80_REG_SEC] = bin2bcd(tm->tm_sec);
  	buf[M41T80_REG_MIN] = bin2bcd(tm->tm_min);
  	buf[M41T80_REG_HOUR] = bin2bcd(tm->tm_hour);
  	buf[M41T80_REG_DAY] = bin2bcd(tm->tm_mday);
  	buf[M41T80_REG_MON] = bin2bcd(tm->tm_mon + 1);
  	buf[M41T80_REG_YEAR] = bin2bcd(tm->tm_year - 100);
  	buf[M41T80_REG_WDAY] = tm->tm_wday;
  
  	err = i2c_smbus_write_i2c_block_data(client, M41T80_REG_SSEC,
  					     sizeof(buf), buf);
  	if (err < 0) {
  		dev_err(&client->dev, "Unable to write to date registers\n");
  		return err;
  	}
  
  	/* Clear the OF bit of Flags Register */
  	flags = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
  	if (flags < 0)
  		return flags;
  
  	if (i2c_smbus_write_byte_data(client, M41T80_REG_FLAGS,
  				      flags & ~M41T80_FLAGS_OF)) {
  		dev_err(&client->dev, "Unable to write flags register\n");
  		return -EIO;
  	}
  
  	return err;
  }
  
  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\n",
  			   (reg & M41T80_FLAGS_BATT_LOW) ? "exhausted" : "ok");
  	}
  	return 0;
  }
  
  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_alarm_irq_enable(struct device *dev, unsigned int enabled)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  	int flags, retval;
  
  	flags = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);
  	if (flags < 0)
  		return flags;
  
  	if (enabled)
  		flags |= M41T80_ALMON_AFE;
  	else
  		flags &= ~M41T80_ALMON_AFE;
  
  	retval = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON, flags);
  	if (retval < 0) {
  		dev_info(dev, "Unable to enable alarm IRQ %d\n", retval);
  		return retval;
  	}
  	return 0;
  }
  
  static int m41t80_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  	u8 alarmvals[5];
  	int ret, err;
  
  	alarmvals[0] = bin2bcd(alrm->time.tm_mon + 1);
  	alarmvals[1] = bin2bcd(alrm->time.tm_mday);
  	alarmvals[2] = bin2bcd(alrm->time.tm_hour);
  	alarmvals[3] = bin2bcd(alrm->time.tm_min);
  	alarmvals[4] = bin2bcd(alrm->time.tm_sec);
  
  	/* Clear AF and AFE flags */
  	ret = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);
  	if (ret < 0)
  		return ret;
  	err = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
  					ret & ~(M41T80_ALMON_AFE));
  	if (err < 0) {
  		dev_err(dev, "Unable to clear AFE bit\n");
  		return err;
  	}
  
  	ret = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
  	if (ret < 0)
  		return ret;
  
  	err = i2c_smbus_write_byte_data(client, M41T80_REG_FLAGS,
  					ret & ~(M41T80_FLAGS_AF));
  	if (err < 0) {
  		dev_err(dev, "Unable to clear AF bit\n");
  		return err;
  	}
  
  	/* Write the alarm */
  	err = i2c_smbus_write_i2c_block_data(client, M41T80_REG_ALARM_MON,
  					     5, alarmvals);
  	if (err)
  		return err;
  
  	/* Enable the alarm interrupt */
  	if (alrm->enabled) {
  		alarmvals[0] |= M41T80_ALMON_AFE;
  		err = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
  						alarmvals[0]);
  		if (err)
  			return err;
  	}
  
  	return 0;
  }
  
  static int m41t80_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  	u8 alarmvals[5];
  	int flags, ret;
  
  	ret = i2c_smbus_read_i2c_block_data(client, M41T80_REG_ALARM_MON,
  					    5, alarmvals);
  	if (ret != 5)
  		return ret < 0 ? ret : -EIO;
  
  	flags = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
  	if (flags < 0)
  		return flags;
  
  	alrm->time.tm_sec  = bcd2bin(alarmvals[4] & 0x7f);
  	alrm->time.tm_min  = bcd2bin(alarmvals[3] & 0x7f);
  	alrm->time.tm_hour = bcd2bin(alarmvals[2] & 0x3f);
  	alrm->time.tm_wday = -1;
  	alrm->time.tm_mday = bcd2bin(alarmvals[1] & 0x3f);
  	alrm->time.tm_mon  = bcd2bin(alarmvals[0] & 0x3f);
  	alrm->time.tm_year = -1;
  
  	alrm->enabled = !!(alarmvals[0] & M41T80_ALMON_AFE);
  	alrm->pending = (flags & M41T80_FLAGS_AF) && alrm->enabled;
  
  	return 0;
  }
  
  static struct rtc_class_ops m41t80_rtc_ops = {
  	.read_time = m41t80_rtc_read_time,
  	.set_time = m41t80_rtc_set_time,
  	.proc = m41t80_rtc_proc,
  };
  
  static ssize_t flags_show(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 val;
  	return sprintf(buf, "%#x\n", val);
  }
  static DEVICE_ATTR_RO(flags);
  
  static ssize_t sqwfreq_show(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 val;
  	val = (val >> 4) & 0xf;
  	switch (val) {
  	case 0:
  		break;
  	case 1:
  		val = 32768;
  		break;
  	default:
  		val = 32768 >> val;
  	}
  	return sprintf(buf, "%d\n", val);
  }
  
  static ssize_t sqwfreq_store(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, rc;
  	unsigned long val;
  
  	rc = kstrtoul(buf, 0, &val);
  	if (rc < 0)
  		return rc;
  
  	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 almon;
  	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 sqw;
  	sqw = (sqw & 0x0f) | (val << 4);
  
  	rc = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
  				       almon & ~M41T80_ALMON_SQWE);
  	if (rc < 0)
  		return rc;
  
  	if (val) {
  		rc = i2c_smbus_write_byte_data(client, reg_sqw, sqw);
  		if (rc < 0)
  			return rc;
  
  		rc = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
  					       almon | M41T80_ALMON_SQWE);
  		if (rc < 0)
  			return rc;
  	}
  	return count;
  }
  static DEVICE_ATTR_RW(sqwfreq);
  
  static struct attribute *attrs[] = {
  	&dev_attr_flags.attr,
  	&dev_attr_sqwfreq.attr,
  	NULL,
  };
  
  static struct attribute_group attr_group = {
  	.attrs = attrs,
  };
  
  #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("disable watchdog\n");
  			wdt_disable();
  		}
  
  		if (rv & WDIOS_ENABLECARD) {
  			pr_info("enable watchdog\n");
  			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 void m41t80_remove_sysfs_group(void *_dev)
  {
  	struct device *dev = _dev;
  
  	sysfs_remove_group(&dev->kobj, &attr_group);
  }
  
  static int m41t80_probe(struct i2c_client *client,
  			const struct i2c_device_id *id)
  {
  	struct i2c_adapter *adapter = to_i2c_adapter(client->dev.parent);
  	int rc = 0;
  	struct rtc_device *rtc = NULL;
  	struct rtc_time tm;
  	struct m41t80_data *m41t80_data = NULL;
  
  	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_I2C_BLOCK |
  				     I2C_FUNC_SMBUS_BYTE_DATA)) {
  		dev_err(&adapter->dev, "doesn't support I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_I2C_BLOCK\n");
  		return -ENODEV;
  	}
  
  	m41t80_data = devm_kzalloc(&client->dev, sizeof(*m41t80_data),
  				   GFP_KERNEL);
  	if (!m41t80_data)
  		return -ENOMEM;
  
  	m41t80_data->features = id->driver_data;
  	i2c_set_clientdata(client, m41t80_data);
  
  	if (client->irq > 0) {
  		rc = devm_request_threaded_irq(&client->dev, client->irq,
  					       NULL, m41t80_handle_irq,
  					       IRQF_TRIGGER_LOW | IRQF_ONESHOT,
  					       "m41t80", client);
  		if (rc) {
  			dev_warn(&client->dev, "unable to request IRQ, alarms disabled\n");
  			client->irq = 0;
  		} else {
  			m41t80_rtc_ops.read_alarm = m41t80_read_alarm;
  			m41t80_rtc_ops.set_alarm = m41t80_set_alarm;
  			m41t80_rtc_ops.alarm_irq_enable = m41t80_alarm_irq_enable;
  			/* Enable the wakealarm */
  			device_init_wakeup(&client->dev, true);
  		}
  	}
  
  	rtc = devm_rtc_device_register(&client->dev, client->name,
  				       &m41t80_rtc_ops, THIS_MODULE);
  	if (IS_ERR(rtc))
  		return PTR_ERR(rtc);
  
  	m41t80_data->rtc = rtc;
  
  	/* Make sure HT (Halt Update) bit is cleared */
  	rc = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_HOUR);
  
  	if (rc >= 0 && rc & M41T80_ALHOUR_HT) {
  		if (m41t80_data->features & M41T80_FEATURE_HT) {
  			m41t80_get_datetime(client, &tm);
  			dev_info(&client->dev, "HT bit was set!\n");
  			dev_info(&client->dev,
  				 "Power Down at %04i-%02i-%02i %02i:%02i:%02i\n",
  				 tm.tm_year + 1900,
  				 tm.tm_mon + 1, tm.tm_mday, tm.tm_hour,
  				 tm.tm_min, tm.tm_sec);
  		}
  		rc = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_HOUR,
  					       rc & ~M41T80_ALHOUR_HT);
  	}
  
  	if (rc < 0) {
  		dev_err(&client->dev, "Can't clear HT bit\n");
  		return rc;
  	}
  
  	/* Make sure ST (stop) bit is cleared */
  	rc = i2c_smbus_read_byte_data(client, M41T80_REG_SEC);
  
  	if (rc >= 0 && rc & M41T80_SEC_ST)
  		rc = i2c_smbus_write_byte_data(client, M41T80_REG_SEC,
  					       rc & ~M41T80_SEC_ST);
  	if (rc < 0) {
  		dev_err(&client->dev, "Can't clear ST bit\n");
  		return rc;
  	}
  
  	/* Export sysfs entries */
  	rc = sysfs_create_group(&(&client->dev)->kobj, &attr_group);
  	if (rc) {
  		dev_err(&client->dev, "Failed to create sysfs group: %d\n", rc);
  		return rc;
  	}
  
  	rc = devm_add_action(&client->dev, m41t80_remove_sysfs_group,
  			     &client->dev);
  	if (rc) {
  		m41t80_remove_sysfs_group(&client->dev);
  		dev_err(&client->dev,
  			"Failed to add sysfs cleanup action: %d\n", rc);
  		return rc;
  	}
  
  #ifdef CONFIG_RTC_DRV_M41T80_WDT
  	if (m41t80_data->features & M41T80_FEATURE_HT) {
  		save_client = client;
  		rc = misc_register(&wdt_dev);
  		if (rc)
  			return rc;
  		rc = register_reboot_notifier(&wdt_notifier);
  		if (rc) {
  			misc_deregister(&wdt_dev);
  			return rc;
  		}
  	}
  #endif
  	return 0;
  }
  
  static int m41t80_remove(struct i2c_client *client)
  {
  #ifdef CONFIG_RTC_DRV_M41T80_WDT
  	struct m41t80_data *clientdata = i2c_get_clientdata(client);
  
  	if (clientdata->features & M41T80_FEATURE_HT) {
  		misc_deregister(&wdt_dev);
  		unregister_reboot_notifier(&wdt_notifier);
  	}
  #endif
  
  	return 0;
  }
  
  static struct i2c_driver m41t80_driver = {
  	.driver = {
  		.name = "rtc-m41t80",
  	},
  	.probe = m41t80_probe,
  	.remove = m41t80_remove,
  	.id_table = m41t80_id,
  };
  
  module_i2c_driver(m41t80_driver);
  
  MODULE_AUTHOR("Alexander Bigga <ab@mycable.de>");
  MODULE_DESCRIPTION("ST Microelectronics M41T80 series RTC I2C Client Driver");
  MODULE_LICENSE("GPL");
  