/*
   * rtc-ds1307.c - RTC driver for some mostly-compatible I2C chips.
   *
   *  Copyright (C) 2005 James Chapman (ds1337 core)
   *  Copyright (C) 2006 David Brownell
   *
   * 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/module.h>
  #include <linux/init.h>
  #include <linux/slab.h>
  #include <linux/i2c.h>
  #include <linux/string.h>
  #include <linux/rtc.h>
  #include <linux/bcd.h>
  
  
  
  /* We can't determine type by probing, but if we expect pre-Linux code
   * to have set the chip up as a clock (turning on the oscillator and
   * setting the date and time), Linux can ignore the non-clock features.
   * That's a natural job for a factory or repair bench.

   */
  enum ds_type {

  	ds_1307,
  	ds_1337,
  	ds_1338,
  	ds_1339,
  	ds_1340,
  	m41t00,

  	// rs5c372 too?  different address...
  };

  
  /* RTC registers don't differ much, except for the century flag */
  #define DS1307_REG_SECS		0x00	/* 00-59 */
  #	define DS1307_BIT_CH		0x80

  #	define DS1340_BIT_nEOSC		0x80

  #define DS1307_REG_MIN		0x01	/* 00-59 */
  #define DS1307_REG_HOUR		0x02	/* 00-23, or 1-12{am,pm} */

  #	define DS1307_BIT_12HR		0x40	/* in REG_HOUR */
  #	define DS1307_BIT_PM		0x20	/* in REG_HOUR */

  #	define DS1340_BIT_CENTURY_EN	0x80	/* in REG_HOUR */
  #	define DS1340_BIT_CENTURY	0x40	/* in REG_HOUR */
  #define DS1307_REG_WDAY		0x03	/* 01-07 */
  #define DS1307_REG_MDAY		0x04	/* 01-31 */
  #define DS1307_REG_MONTH	0x05	/* 01-12 */
  #	define DS1337_BIT_CENTURY	0x80	/* in REG_MONTH */
  #define DS1307_REG_YEAR		0x06	/* 00-99 */
  
  /* Other registers (control, status, alarms, trickle charge, NVRAM, etc)

   * start at 7, and they differ a LOT. Only control and status matter for
   * basic RTC date and time functionality; be careful using them.

   */

  #define DS1307_REG_CONTROL	0x07		/* or ds1338 */

  #	define DS1307_BIT_OUT		0x80

  #	define DS1338_BIT_OSF		0x20

  #	define DS1307_BIT_SQWE		0x10
  #	define DS1307_BIT_RS1		0x02
  #	define DS1307_BIT_RS0		0x01
  #define DS1337_REG_CONTROL	0x0e
  #	define DS1337_BIT_nEOSC		0x80

  #	define DS1339_BIT_BBSQI		0x20

  #	define DS1337_BIT_RS2		0x10
  #	define DS1337_BIT_RS1		0x08
  #	define DS1337_BIT_INTCN		0x04
  #	define DS1337_BIT_A2IE		0x02
  #	define DS1337_BIT_A1IE		0x01

  #define DS1340_REG_CONTROL	0x07
  #	define DS1340_BIT_OUT		0x80
  #	define DS1340_BIT_FT		0x40
  #	define DS1340_BIT_CALIB_SIGN	0x20
  #	define DS1340_M_CALIBRATION	0x1f

  #define DS1340_REG_FLAG		0x09
  #	define DS1340_BIT_OSF		0x80

  #define DS1337_REG_STATUS	0x0f
  #	define DS1337_BIT_OSF		0x80
  #	define DS1337_BIT_A2I		0x02
  #	define DS1337_BIT_A1I		0x01

  #define DS1339_REG_ALARM1_SECS	0x07

  #define DS1339_REG_TRICKLE	0x10
  
  
  
  struct ds1307 {

  	u8			regs[11];

  	enum ds_type		type;

  	unsigned long		flags;
  #define HAS_NVRAM	0		/* bit 0 == sysfs file active */
  #define HAS_ALARM	1		/* bit 1 == irq claimed */

  	struct i2c_client	*client;

  	struct rtc_device	*rtc;

  	struct work_struct	work;

  };

  struct chip_desc {

  	unsigned		nvram56:1;
  	unsigned		alarm:1;

  };

  static const struct chip_desc chips[] = {
  [ds_1307] = {

  	.nvram56	= 1,

  },
  [ds_1337] = {

  	.alarm		= 1,

  },
  [ds_1338] = {

  	.nvram56	= 1,

  },
  [ds_1339] = {

  	.alarm		= 1,

  },
  [ds_1340] = {
  },
  [m41t00] = {

  }, };

  static const struct i2c_device_id ds1307_id[] = {
  	{ "ds1307", ds_1307 },
  	{ "ds1337", ds_1337 },
  	{ "ds1338", ds_1338 },
  	{ "ds1339", ds_1339 },
  	{ "ds1340", ds_1340 },
  	{ "m41t00", m41t00 },
  	{ }
  };
  MODULE_DEVICE_TABLE(i2c, ds1307_id);

  /*----------------------------------------------------------------------*/
  
  /*
   * The IRQ logic includes a "real" handler running in IRQ context just
   * long enough to schedule this workqueue entry.   We need a task context
   * to talk to the RTC, since I2C I/O calls require that; and disable the
   * IRQ until we clear its status on the chip, so that this handler can
   * work with any type of triggering (not just falling edge).
   *
   * The ds1337 and ds1339 both have two alarms, but we only use the first
   * one (with a "seconds" field).  For ds1337 we expect nINTA is our alarm
   * signal; ds1339 chips have only one alarm signal.
   */
  static void ds1307_work(struct work_struct *work)
  {
  	struct ds1307		*ds1307;
  	struct i2c_client	*client;
  	struct mutex		*lock;
  	int			stat, control;
  
  	ds1307 = container_of(work, struct ds1307, work);
  	client = ds1307->client;
  	lock = &ds1307->rtc->ops_lock;
  
  	mutex_lock(lock);
  	stat = i2c_smbus_read_byte_data(client, DS1337_REG_STATUS);
  	if (stat < 0)
  		goto out;
  
  	if (stat & DS1337_BIT_A1I) {
  		stat &= ~DS1337_BIT_A1I;
  		i2c_smbus_write_byte_data(client, DS1337_REG_STATUS, stat);
  
  		control = i2c_smbus_read_byte_data(client, DS1337_REG_CONTROL);
  		if (control < 0)
  			goto out;
  
  		control &= ~DS1337_BIT_A1IE;
  		i2c_smbus_write_byte_data(client, DS1337_REG_CONTROL, control);
  
  		/* rtc_update_irq() assumes that it is called
  		 * from IRQ-disabled context.
  		 */
  		local_irq_disable();
  		rtc_update_irq(ds1307->rtc, 1, RTC_AF | RTC_IRQF);
  		local_irq_enable();
  	}
  
  out:
  	if (test_bit(HAS_ALARM, &ds1307->flags))
  		enable_irq(client->irq);
  	mutex_unlock(lock);
  }
  
  static irqreturn_t ds1307_irq(int irq, void *dev_id)
  {
  	struct i2c_client	*client = dev_id;
  	struct ds1307		*ds1307 = i2c_get_clientdata(client);
  
  	disable_irq_nosync(irq);
  	schedule_work(&ds1307->work);
  	return IRQ_HANDLED;
  }
  
  /*----------------------------------------------------------------------*/

  static int ds1307_get_time(struct device *dev, struct rtc_time *t)
  {
  	struct ds1307	*ds1307 = dev_get_drvdata(dev);
  	int		tmp;

  	/* read the RTC date and time registers all at once */

  	tmp = i2c_smbus_read_i2c_block_data(ds1307->client,
  		DS1307_REG_SECS, 7, ds1307->regs);
  	if (tmp != 7) {

  		dev_err(dev, "%s error %d
  ", "read", tmp);
  		return -EIO;
  	}
  
  	dev_dbg(dev, "%s: %02x %02x %02x %02x %02x %02x %02x
  ",
  			"read",
  			ds1307->regs[0], ds1307->regs[1],
  			ds1307->regs[2], ds1307->regs[3],
  			ds1307->regs[4], ds1307->regs[5],
  			ds1307->regs[6]);

  	t->tm_sec = bcd2bin(ds1307->regs[DS1307_REG_SECS] & 0x7f);
  	t->tm_min = bcd2bin(ds1307->regs[DS1307_REG_MIN] & 0x7f);

  	tmp = ds1307->regs[DS1307_REG_HOUR] & 0x3f;

  	t->tm_hour = bcd2bin(tmp);
  	t->tm_wday = bcd2bin(ds1307->regs[DS1307_REG_WDAY] & 0x07) - 1;
  	t->tm_mday = bcd2bin(ds1307->regs[DS1307_REG_MDAY] & 0x3f);

  	tmp = ds1307->regs[DS1307_REG_MONTH] & 0x1f;

  	t->tm_mon = bcd2bin(tmp) - 1;

  
  	/* assume 20YY not 19YY, and ignore DS1337_BIT_CENTURY */

  	t->tm_year = bcd2bin(ds1307->regs[DS1307_REG_YEAR]) + 100;

  
  	dev_dbg(dev, "%s secs=%d, mins=%d, "
  		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d
  ",
  		"read", t->tm_sec, t->tm_min,
  		t->tm_hour, t->tm_mday,
  		t->tm_mon, t->tm_year, t->tm_wday);

  	/* initial clock setting can be undefined */
  	return rtc_valid_tm(t);

  }
  
  static int ds1307_set_time(struct device *dev, struct rtc_time *t)
  {
  	struct ds1307	*ds1307 = dev_get_drvdata(dev);
  	int		result;
  	int		tmp;
  	u8		*buf = ds1307->regs;
  
  	dev_dbg(dev, "%s secs=%d, mins=%d, "
  		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d
  ",

  		"write", t->tm_sec, t->tm_min,
  		t->tm_hour, t->tm_mday,
  		t->tm_mon, t->tm_year, t->tm_wday);

  	buf[DS1307_REG_SECS] = bin2bcd(t->tm_sec);
  	buf[DS1307_REG_MIN] = bin2bcd(t->tm_min);
  	buf[DS1307_REG_HOUR] = bin2bcd(t->tm_hour);
  	buf[DS1307_REG_WDAY] = bin2bcd(t->tm_wday + 1);
  	buf[DS1307_REG_MDAY] = bin2bcd(t->tm_mday);
  	buf[DS1307_REG_MONTH] = bin2bcd(t->tm_mon + 1);

  
  	/* assume 20YY not 19YY */
  	tmp = t->tm_year - 100;

  	buf[DS1307_REG_YEAR] = bin2bcd(tmp);

  	switch (ds1307->type) {
  	case ds_1337:
  	case ds_1339:

  		buf[DS1307_REG_MONTH] |= DS1337_BIT_CENTURY;

  		break;
  	case ds_1340:

  		buf[DS1307_REG_HOUR] |= DS1340_BIT_CENTURY_EN
  				| DS1340_BIT_CENTURY;

  		break;
  	default:
  		break;
  	}

  	dev_dbg(dev, "%s: %02x %02x %02x %02x %02x %02x %02x
  ",
  		"write", buf[0], buf[1], buf[2], buf[3],
  		buf[4], buf[5], buf[6]);

  	result = i2c_smbus_write_i2c_block_data(ds1307->client, 0, 7, buf);
  	if (result < 0) {
  		dev_err(dev, "%s error %d
  ", "write", result);
  		return result;

  	}
  	return 0;
  }

  static int ds1337_read_alarm(struct device *dev, struct rtc_wkalrm *t)

  {
  	struct i2c_client       *client = to_i2c_client(dev);
  	struct ds1307		*ds1307 = i2c_get_clientdata(client);
  	int			ret;
  
  	if (!test_bit(HAS_ALARM, &ds1307->flags))
  		return -EINVAL;
  
  	/* read all ALARM1, ALARM2, and status registers at once */

  	ret = i2c_smbus_read_i2c_block_data(client,
  			DS1339_REG_ALARM1_SECS, 9, ds1307->regs);
  	if (ret != 9) {

  		dev_err(dev, "%s error %d
  ", "alarm read", ret);
  		return -EIO;
  	}
  
  	dev_dbg(dev, "%s: %02x %02x %02x %02x, %02x %02x %02x, %02x %02x
  ",
  			"alarm read",
  			ds1307->regs[0], ds1307->regs[1],
  			ds1307->regs[2], ds1307->regs[3],
  			ds1307->regs[4], ds1307->regs[5],
  			ds1307->regs[6], ds1307->regs[7],
  			ds1307->regs[8]);
  
  	/* report alarm time (ALARM1); assume 24 hour and day-of-month modes,
  	 * and that all four fields are checked matches
  	 */
  	t->time.tm_sec = bcd2bin(ds1307->regs[0] & 0x7f);
  	t->time.tm_min = bcd2bin(ds1307->regs[1] & 0x7f);
  	t->time.tm_hour = bcd2bin(ds1307->regs[2] & 0x3f);
  	t->time.tm_mday = bcd2bin(ds1307->regs[3] & 0x3f);
  	t->time.tm_mon = -1;
  	t->time.tm_year = -1;
  	t->time.tm_wday = -1;
  	t->time.tm_yday = -1;
  	t->time.tm_isdst = -1;
  
  	/* ... and status */
  	t->enabled = !!(ds1307->regs[7] & DS1337_BIT_A1IE);
  	t->pending = !!(ds1307->regs[8] & DS1337_BIT_A1I);
  
  	dev_dbg(dev, "%s secs=%d, mins=%d, "
  		"hours=%d, mday=%d, enabled=%d, pending=%d
  ",
  		"alarm read", t->time.tm_sec, t->time.tm_min,
  		t->time.tm_hour, t->time.tm_mday,
  		t->enabled, t->pending);
  
  	return 0;
  }

  static int ds1337_set_alarm(struct device *dev, struct rtc_wkalrm *t)

  {
  	struct i2c_client       *client = to_i2c_client(dev);
  	struct ds1307		*ds1307 = i2c_get_clientdata(client);
  	unsigned char		*buf = ds1307->regs;
  	u8			control, status;
  	int			ret;
  
  	if (!test_bit(HAS_ALARM, &ds1307->flags))
  		return -EINVAL;
  
  	dev_dbg(dev, "%s secs=%d, mins=%d, "
  		"hours=%d, mday=%d, enabled=%d, pending=%d
  ",
  		"alarm set", t->time.tm_sec, t->time.tm_min,
  		t->time.tm_hour, t->time.tm_mday,
  		t->enabled, t->pending);
  
  	/* read current status of both alarms and the chip */

  	ret = i2c_smbus_read_i2c_block_data(client,
  			DS1339_REG_ALARM1_SECS, 9, buf);
  	if (ret != 9) {

  		dev_err(dev, "%s error %d
  ", "alarm write", ret);
  		return -EIO;
  	}
  	control = ds1307->regs[7];
  	status = ds1307->regs[8];
  
  	dev_dbg(dev, "%s: %02x %02x %02x %02x, %02x %02x %02x, %02x %02x
  ",
  			"alarm set (old status)",
  			ds1307->regs[0], ds1307->regs[1],
  			ds1307->regs[2], ds1307->regs[3],
  			ds1307->regs[4], ds1307->regs[5],
  			ds1307->regs[6], control, status);
  
  	/* set ALARM1, using 24 hour and day-of-month modes */

  	buf[0] = bin2bcd(t->time.tm_sec);
  	buf[1] = bin2bcd(t->time.tm_min);
  	buf[2] = bin2bcd(t->time.tm_hour);
  	buf[3] = bin2bcd(t->time.tm_mday);
  
  	/* set ALARM2 to non-garbage */
  	buf[4] = 0;
  	buf[5] = 0;
  	buf[6] = 0;
  
  	/* optionally enable ALARM1 */
  	buf[7] = control & ~(DS1337_BIT_A1IE | DS1337_BIT_A2IE);
  	if (t->enabled) {
  		dev_dbg(dev, "alarm IRQ armed
  ");
  		buf[7] |= DS1337_BIT_A1IE;	/* only ALARM1 is used */
  	}
  	buf[8] = status & ~(DS1337_BIT_A1I | DS1337_BIT_A2I);

  	ret = i2c_smbus_write_i2c_block_data(client,
  			DS1339_REG_ALARM1_SECS, 9, buf);
  	if (ret < 0) {

  		dev_err(dev, "can't set alarm time
  ");

  		return ret;

  	}
  
  	return 0;
  }
  
  static int ds1307_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
  {
  	struct i2c_client	*client = to_i2c_client(dev);
  	struct ds1307		*ds1307 = i2c_get_clientdata(client);
  	int			ret;
  
  	switch (cmd) {
  	case RTC_AIE_OFF:
  		if (!test_bit(HAS_ALARM, &ds1307->flags))
  			return -ENOTTY;
  
  		ret = i2c_smbus_read_byte_data(client, DS1337_REG_CONTROL);
  		if (ret < 0)
  			return ret;
  
  		ret &= ~DS1337_BIT_A1IE;
  
  		ret = i2c_smbus_write_byte_data(client,
  						DS1337_REG_CONTROL, ret);
  		if (ret < 0)
  			return ret;
  
  		break;
  
  	case RTC_AIE_ON:
  		if (!test_bit(HAS_ALARM, &ds1307->flags))
  			return -ENOTTY;
  
  		ret = i2c_smbus_read_byte_data(client, DS1337_REG_CONTROL);
  		if (ret < 0)
  			return ret;
  
  		ret |= DS1337_BIT_A1IE;
  
  		ret = i2c_smbus_write_byte_data(client,
  						DS1337_REG_CONTROL, ret);
  		if (ret < 0)
  			return ret;
  
  		break;
  
  	default:
  		return -ENOIOCTLCMD;
  	}
  
  	return 0;
  }

  static const struct rtc_class_ops ds13xx_rtc_ops = {

  	.read_time	= ds1307_get_time,
  	.set_time	= ds1307_set_time,

  	.read_alarm	= ds1337_read_alarm,
  	.set_alarm	= ds1337_set_alarm,

  	.ioctl		= ds1307_ioctl,

  };

  /*----------------------------------------------------------------------*/
  
  #define NVRAM_SIZE	56
  
  static ssize_t
  ds1307_nvram_read(struct kobject *kobj, struct bin_attribute *attr,
  		char *buf, loff_t off, size_t count)
  {
  	struct i2c_client	*client;
  	struct ds1307		*ds1307;

  	int			result;

  	client = kobj_to_i2c_client(kobj);

  	ds1307 = i2c_get_clientdata(client);
  
  	if (unlikely(off >= NVRAM_SIZE))
  		return 0;
  	if ((off + count) > NVRAM_SIZE)
  		count = NVRAM_SIZE - off;
  	if (unlikely(!count))
  		return count;

  	result = i2c_smbus_read_i2c_block_data(client, 8 + off, count, buf);
  	if (result < 0)

  		dev_err(&client->dev, "%s error %d
  ", "nvram read", result);

  	return result;

  }
  
  static ssize_t
  ds1307_nvram_write(struct kobject *kobj, struct bin_attribute *attr,
  		char *buf, loff_t off, size_t count)
  {
  	struct i2c_client	*client;

  	int			result;

  	client = kobj_to_i2c_client(kobj);

  
  	if (unlikely(off >= NVRAM_SIZE))
  		return -EFBIG;
  	if ((off + count) > NVRAM_SIZE)
  		count = NVRAM_SIZE - off;
  	if (unlikely(!count))
  		return count;

  	result = i2c_smbus_write_i2c_block_data(client, 8 + off, count, buf);
  	if (result < 0) {
  		dev_err(&client->dev, "%s error %d
  ", "nvram write", result);
  		return result;
  	}
  	return count;

  }
  
  static struct bin_attribute nvram = {
  	.attr = {
  		.name	= "nvram",
  		.mode	= S_IRUGO | S_IWUSR,

  	},
  
  	.read	= ds1307_nvram_read,
  	.write	= ds1307_nvram_write,
  	.size	= NVRAM_SIZE,
  };
  
  /*----------------------------------------------------------------------*/

  static struct i2c_driver ds1307_driver;

  static int __devinit ds1307_probe(struct i2c_client *client,
  				  const struct i2c_device_id *id)

  {
  	struct ds1307		*ds1307;
  	int			err = -ENODEV;

  	int			tmp;

  	const struct chip_desc	*chip = &chips[id->driver_data];

  	struct i2c_adapter	*adapter = to_i2c_adapter(client->dev.parent);

  	int			want_irq = false;

  	unsigned char		*buf;

  	if (!i2c_check_functionality(adapter,

  			I2C_FUNC_SMBUS_WRITE_BYTE_DATA |
  			I2C_FUNC_SMBUS_I2C_BLOCK))

  		return -EIO;
  
  	if (!(ds1307 = kzalloc(sizeof(struct ds1307), GFP_KERNEL)))
  		return -ENOMEM;

  
  	ds1307->client = client;

  	i2c_set_clientdata(client, ds1307);

  	ds1307->type = id->driver_data;

  	buf = ds1307->regs;

  
  	switch (ds1307->type) {
  	case ds_1337:
  	case ds_1339:

  		/* has IRQ? */
  		if (ds1307->client->irq > 0 && chip->alarm) {
  			INIT_WORK(&ds1307->work, ds1307_work);
  			want_irq = true;
  		}

  		/* get registers that the "rtc" read below won't read... */

  		tmp = i2c_smbus_read_i2c_block_data(ds1307->client,
  				DS1337_REG_CONTROL, 2, buf);

  		if (tmp != 2) {
  			pr_debug("read error %d
  ", tmp);
  			err = -EIO;
  			goto exit_free;
  		}

  		/* oscillator off?  turn it on, so clock can tick. */
  		if (ds1307->regs[0] & DS1337_BIT_nEOSC)

  			ds1307->regs[0] &= ~DS1337_BIT_nEOSC;
  
  		/* Using IRQ?  Disable the square wave and both alarms.
  		 * For ds1339, be sure alarms can trigger when we're
  		 * running on Vbackup (BBSQI); we assume ds1337 will
  		 * ignore that bit
  		 */
  		if (want_irq) {
  			ds1307->regs[0] |= DS1337_BIT_INTCN | DS1339_BIT_BBSQI;
  			ds1307->regs[0] &= ~(DS1337_BIT_A2IE | DS1337_BIT_A1IE);
  		}
  
  		i2c_smbus_write_byte_data(client, DS1337_REG_CONTROL,
  							ds1307->regs[0]);

  
  		/* oscillator fault?  clear flag, and warn */
  		if (ds1307->regs[1] & DS1337_BIT_OSF) {
  			i2c_smbus_write_byte_data(client, DS1337_REG_STATUS,
  				ds1307->regs[1] & ~DS1337_BIT_OSF);
  			dev_warn(&client->dev, "SET TIME!
  ");

  		}

  		break;
  	default:
  		break;
  	}

  
  read_rtc:
  	/* read RTC registers */

  	tmp = i2c_smbus_read_i2c_block_data(ds1307->client, 0, 8, buf);
  	if (tmp != 8) {

  		pr_debug("read error %d
  ", tmp);
  		err = -EIO;
  		goto exit_free;
  	}
  
  	/* minimal sanity checking; some chips (like DS1340) don't
  	 * specify the extra bits as must-be-zero, but there are
  	 * still a few values that are clearly out-of-range.
  	 */
  	tmp = ds1307->regs[DS1307_REG_SECS];

  	switch (ds1307->type) {
  	case ds_1307:

  	case m41t00:

  		/* clock halted?  turn it on, so clock can tick. */

  		if (tmp & DS1307_BIT_CH) {

  			i2c_smbus_write_byte_data(client, DS1307_REG_SECS, 0);
  			dev_warn(&client->dev, "SET TIME!
  ");

  			goto read_rtc;

  		}

  		break;

  	case ds_1338:
  		/* clock halted?  turn it on, so clock can tick. */

  		if (tmp & DS1307_BIT_CH)

  			i2c_smbus_write_byte_data(client, DS1307_REG_SECS, 0);
  
  		/* oscillator fault?  clear flag, and warn */
  		if (ds1307->regs[DS1307_REG_CONTROL] & DS1338_BIT_OSF) {
  			i2c_smbus_write_byte_data(client, DS1307_REG_CONTROL,

  					ds1307->regs[DS1307_REG_CONTROL]

  					& ~DS1338_BIT_OSF);
  			dev_warn(&client->dev, "SET TIME!
  ");
  			goto read_rtc;
  		}

  		break;

  	case ds_1340:
  		/* clock halted?  turn it on, so clock can tick. */
  		if (tmp & DS1340_BIT_nEOSC)
  			i2c_smbus_write_byte_data(client, DS1307_REG_SECS, 0);
  
  		tmp = i2c_smbus_read_byte_data(client, DS1340_REG_FLAG);
  		if (tmp < 0) {
  			pr_debug("read error %d
  ", tmp);
  			err = -EIO;
  			goto exit_free;
  		}
  
  		/* oscillator fault?  clear flag, and warn */
  		if (tmp & DS1340_BIT_OSF) {
  			i2c_smbus_write_byte_data(client, DS1340_REG_FLAG, 0);
  			dev_warn(&client->dev, "SET TIME!
  ");
  		}
  		break;

  	case ds_1337:
  	case ds_1339:

  		break;

  	}

  	tmp = ds1307->regs[DS1307_REG_HOUR];

  	switch (ds1307->type) {
  	case ds_1340:
  	case m41t00:
  		/* NOTE: ignores century bits; fix before deploying
  		 * systems that will run through year 2100.
  		 */
  		break;
  	default:
  		if (!(tmp & DS1307_BIT_12HR))
  			break;
  
  		/* Be sure we're in 24 hour mode.  Multi-master systems
  		 * take note...
  		 */

  		tmp = bcd2bin(tmp & 0x1f);

  		if (tmp == 12)
  			tmp = 0;
  		if (ds1307->regs[DS1307_REG_HOUR] & DS1307_BIT_PM)
  			tmp += 12;

  		i2c_smbus_write_byte_data(client,
  				DS1307_REG_HOUR,

  				bin2bcd(tmp));

  	}

  	ds1307->rtc = rtc_device_register(client->name, &client->dev,
  				&ds13xx_rtc_ops, THIS_MODULE);
  	if (IS_ERR(ds1307->rtc)) {
  		err = PTR_ERR(ds1307->rtc);
  		dev_err(&client->dev,
  			"unable to register the class device
  ");

  		goto exit_free;

  	}

  	if (want_irq) {
  		err = request_irq(client->irq, ds1307_irq, 0,
  			  ds1307->rtc->name, client);
  		if (err) {
  			dev_err(&client->dev,
  				"unable to request IRQ!
  ");
  			goto exit_irq;
  		}
  		set_bit(HAS_ALARM, &ds1307->flags);
  		dev_dbg(&client->dev, "got IRQ %d
  ", client->irq);
  	}

  	if (chip->nvram56) {
  		err = sysfs_create_bin_file(&client->dev.kobj, &nvram);
  		if (err == 0) {

  			set_bit(HAS_NVRAM, &ds1307->flags);

  			dev_info(&client->dev, "56 bytes nvram
  ");
  		}
  	}

  	return 0;

  exit_irq:
  	if (ds1307->rtc)
  		rtc_device_unregister(ds1307->rtc);

  exit_free:
  	kfree(ds1307);

  	return err;
  }

  static int __devexit ds1307_remove(struct i2c_client *client)

  {

  	struct ds1307		*ds1307 = i2c_get_clientdata(client);
  
  	if (test_and_clear_bit(HAS_ALARM, &ds1307->flags)) {
  		free_irq(client->irq, client);
  		cancel_work_sync(&ds1307->work);
  	}

  	if (test_and_clear_bit(HAS_NVRAM, &ds1307->flags))

  		sysfs_remove_bin_file(&client->dev.kobj, &nvram);

  	rtc_device_unregister(ds1307->rtc);

  	kfree(ds1307);
  	return 0;
  }
  
  static struct i2c_driver ds1307_driver = {
  	.driver = {

  		.name	= "rtc-ds1307",

  		.owner	= THIS_MODULE,
  	},

  	.probe		= ds1307_probe,
  	.remove		= __devexit_p(ds1307_remove),

  	.id_table	= ds1307_id,

  };
  
  static int __init ds1307_init(void)
  {
  	return i2c_add_driver(&ds1307_driver);
  }
  module_init(ds1307_init);
  
  static void __exit ds1307_exit(void)
  {
  	i2c_del_driver(&ds1307_driver);
  }
  module_exit(ds1307_exit);
  
  MODULE_DESCRIPTION("RTC driver for DS1307 and similar chips");
  MODULE_LICENSE("GPL");