drivers/rtc/rtc-ds1307.c - kernel/msm-4.9 - Gitiles

 /*
  * 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.
  *
  * This is currently a simple no-alarms driver.  If your board has the
  * alarm irq wired up on a ds1337 or ds1339, and you want to use that,
  * then look at the rtc-rs5c372 driver for code to steal...
  */
 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 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_TRICKLE	0x10


 struct ds1307 {
 	u8			reg_addr;
 	u8			regs[8];
 	enum ds_type		type;
 	struct i2c_msg		msg[2];
 	struct i2c_client	*client;
 	struct i2c_client	dev;
 	struct rtc_device	*rtc;
 };

 struct chip_desc {
 	char			name[9];
 	unsigned		nvram56:1;
 	unsigned		alarm:1;
 	enum ds_type		type;
 };

 static const struct chip_desc chips[] = { {
 	.name		= "ds1307",
 	.type		= ds_1307,
 	.nvram56	= 1,
 }, {
 	.name		= "ds1337",
 	.type		= ds_1337,
 	.alarm		= 1,
 }, {
 	.name		= "ds1338",
 	.type		= ds_1338,
 	.nvram56	= 1,
 }, {
 	.name		= "ds1339",
 	.type		= ds_1339,
 	.alarm		= 1,
 }, {
 	.name		= "ds1340",
 	.type		= ds_1340,
 }, {
 	.name		= "m41t00",
 	.type		= m41t00,
 }, };

 static inline const struct chip_desc *find_chip(const char *s)
 {
 	unsigned i;

 	for (i = 0; i < ARRAY_SIZE(chips); i++)
 		if (strnicmp(s, chips[i].name, sizeof chips[i].name) == 0)
 			return &chips[i];
 	return NULL;
 }

 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 */
 	ds1307->msg[1].flags = I2C_M_RD;
 	ds1307->msg[1].len = 7;

 	tmp = i2c_transfer(to_i2c_adapter(ds1307->client->dev.parent),
 			ds1307->msg, 2);
 	if (tmp != 2) {
 		dev_err(dev, "%s error %d\n", "read", tmp);
 		return -EIO;
 	}

 	dev_dbg(dev, "%s: %02x %02x %02x %02x %02x %02x %02x\n",
 			"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\n",
 		"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\n",
 		"write", t->tm_sec, t->tm_min,
 		t->tm_hour, t->tm_mday,
 		t->tm_mon, t->tm_year, t->tm_wday);

 	*buf++ = 0;		/* first register addr */
 	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;
 	}

 	ds1307->msg[1].flags = 0;
 	ds1307->msg[1].len = 8;

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

 	result = i2c_transfer(to_i2c_adapter(ds1307->client->dev.parent),
 			&ds1307->msg[1], 1);
 	if (result != 1) {
 		dev_err(dev, "%s error %d\n", "write", tmp);
 		return -EIO;
 	}
 	return 0;
 }

 static const struct rtc_class_ops ds13xx_rtc_ops = {
 	.read_time	= ds1307_get_time,
 	.set_time	= ds1307_set_time,
 };

 static struct i2c_driver ds1307_driver;

 static int __devinit ds1307_probe(struct i2c_client *client)
 {
 	struct ds1307		*ds1307;
 	int			err = -ENODEV;
 	int			tmp;
 	const struct chip_desc	*chip;
 	struct i2c_adapter	*adapter = to_i2c_adapter(client->dev.parent);

 	chip = find_chip(client->name);
 	if (!chip) {
 		dev_err(&client->dev, "unknown chip type '%s'\n",
 				client->name);
 		return -ENODEV;
 	}

 	if (!i2c_check_functionality(adapter,
 			I2C_FUNC_I2C | I2C_FUNC_SMBUS_WRITE_BYTE_DATA))
 		return -EIO;

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

 	ds1307->client = client;
 	i2c_set_clientdata(client, ds1307);

 	ds1307->msg[0].addr = client->addr;
 	ds1307->msg[0].flags = 0;
 	ds1307->msg[0].len = 1;
 	ds1307->msg[0].buf = &ds1307->reg_addr;

 	ds1307->msg[1].addr = client->addr;
 	ds1307->msg[1].flags = I2C_M_RD;
 	ds1307->msg[1].len = sizeof(ds1307->regs);
 	ds1307->msg[1].buf = ds1307->regs;

 	ds1307->type = chip->type;

 	switch (ds1307->type) {
 	case ds_1337:
 	case ds_1339:
 		ds1307->reg_addr = DS1337_REG_CONTROL;
 		ds1307->msg[1].len = 2;

 		/* get registers that the "rtc" read below won't read... */
 		tmp = i2c_transfer(adapter, ds1307->msg, 2);
 		if (tmp != 2) {
 			pr_debug("read error %d\n", tmp);
 			err = -EIO;
 			goto exit_free;
 		}

 		ds1307->reg_addr = 0;
 		ds1307->msg[1].len = sizeof(ds1307->regs);

 		/* oscillator off?  turn it on, so clock can tick. */
 		if (ds1307->regs[0] & DS1337_BIT_nEOSC)
 			i2c_smbus_write_byte_data(client, DS1337_REG_CONTROL,
 				ds1307->regs[0] & ~DS1337_BIT_nEOSC);

 		/* 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!\n");
 		}
 		break;
 	default:
 		break;
 	}

 read_rtc:
 	/* read RTC registers */

 	tmp = i2c_transfer(adapter, ds1307->msg, 2);
 	if (tmp != 2) {
 		pr_debug("read error %d\n", 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_1340:
 		/* FIXME read register with DS1340_BIT_OSF, use that to
 		 * trigger the "set time" warning (*after* restarting the
 		 * oscillator!) instead of this weaker ds1307/m41t00 test.
 		 */
 	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!\n");
 			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!\n");
 			goto read_rtc;
 		}
 		break;
 	case ds_1337:
 	case ds_1339:
 		break;
 	}

 	tmp = ds1307->regs[DS1307_REG_SECS];
 	tmp = BCD2BIN(tmp & 0x7f);
 	if (tmp > 60)
 		goto exit_bad;
 	tmp = BCD2BIN(ds1307->regs[DS1307_REG_MIN] & 0x7f);
 	if (tmp > 60)
 		goto exit_bad;

 	tmp = BCD2BIN(ds1307->regs[DS1307_REG_MDAY] & 0x3f);
 	if (tmp == 0 || tmp > 31)
 		goto exit_bad;

 	tmp = BCD2BIN(ds1307->regs[DS1307_REG_MONTH] & 0x1f);
 	if (tmp == 0 || tmp > 12)
 		goto exit_bad;

 	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\n");
 		goto exit_free;
 	}

 	return 0;

 exit_bad:
 	dev_dbg(&client->dev, "%s: %02x %02x %02x %02x %02x %02x %02x\n",
 			"bogus register",
 			ds1307->regs[0], ds1307->regs[1],
 			ds1307->regs[2], ds1307->regs[3],
 			ds1307->regs[4], ds1307->regs[5],
 			ds1307->regs[6]);

 exit_free:
 	kfree(ds1307);
 	return err;
 }

 static int __devexit ds1307_remove(struct i2c_client *client)
 {
 	struct ds1307	*ds1307 = i2c_get_clientdata(client);

 	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),
 };

 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");
	/*
	* 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.
	*
	* This is currently a simple no-alarms driver. If your board has the
	* alarm irq wired up on a ds1337 or ds1339, and you want to use that,
	* then look at the rtc-rs5c372 driver for code to steal...
	*/
	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 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_TRICKLE 0x10



	struct ds1307 {
	u8 reg_addr;
	u8 regs[8];
	enum ds_type type;
	struct i2c_msg msg[2];
	struct i2c_client *client;
	struct i2c_client dev;
	struct rtc_device *rtc;
	};

	struct chip_desc {
	char name[9];
	unsigned nvram56:1;
	unsigned alarm:1;
	enum ds_type type;
	};

	static const struct chip_desc chips[] = { {
	.name = "ds1307",
	.type = ds_1307,
	.nvram56 = 1,
	}, {
	.name = "ds1337",
	.type = ds_1337,
	.alarm = 1,
	}, {
	.name = "ds1338",
	.type = ds_1338,
	.nvram56 = 1,
	}, {
	.name = "ds1339",
	.type = ds_1339,
	.alarm = 1,
	}, {
	.name = "ds1340",
	.type = ds_1340,
	}, {
	.name = "m41t00",
	.type = m41t00,
	}, };

	static inline const struct chip_desc find_chip(const char s)
	{
	unsigned i;

	for (i = 0; i < ARRAY_SIZE(chips); i++)
	if (strnicmp(s, chips[i].name, sizeof chips[i].name) == 0)
	return &chips[i];
	return NULL;
	}

	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 */
	ds1307->msg[1].flags = I2C_M_RD;
	ds1307->msg[1].len = 7;

	tmp = i2c_transfer(to_i2c_adapter(ds1307->client->dev.parent),
	ds1307->msg, 2);
	if (tmp != 2) {
	dev_err(dev, "%s error %d\n", "read", tmp);
	return -EIO;
	}

	dev_dbg(dev, "%s: %02x %02x %02x %02x %02x %02x %02x\n",
	"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\n",
	"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\n",
	"write", t->tm_sec, t->tm_min,
	t->tm_hour, t->tm_mday,
	t->tm_mon, t->tm_year, t->tm_wday);

	buf++ = 0; / first register addr */
	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;
	}

	ds1307->msg[1].flags = 0;
	ds1307->msg[1].len = 8;

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

	result = i2c_transfer(to_i2c_adapter(ds1307->client->dev.parent),
	&ds1307->msg[1], 1);
	if (result != 1) {
	dev_err(dev, "%s error %d\n", "write", tmp);
	return -EIO;
	}
	return 0;
	}

	static const struct rtc_class_ops ds13xx_rtc_ops = {
	.read_time = ds1307_get_time,
	.set_time = ds1307_set_time,
	};

	static struct i2c_driver ds1307_driver;

	static int __devinit ds1307_probe(struct i2c_client *client)
	{
	struct ds1307 *ds1307;
	int err = -ENODEV;
	int tmp;
	const struct chip_desc *chip;
	struct i2c_adapter *adapter = to_i2c_adapter(client->dev.parent);

	chip = find_chip(client->name);
	if (!chip) {
	dev_err(&client->dev, "unknown chip type '%s'\n",
	client->name);
	return -ENODEV;
	}

	if (!i2c_check_functionality(adapter,
	I2C_FUNC_I2C \| I2C_FUNC_SMBUS_WRITE_BYTE_DATA))
	return -EIO;

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

	ds1307->client = client;
	i2c_set_clientdata(client, ds1307);

	ds1307->msg[0].addr = client->addr;
	ds1307->msg[0].flags = 0;
	ds1307->msg[0].len = 1;
	ds1307->msg[0].buf = &ds1307->reg_addr;

	ds1307->msg[1].addr = client->addr;
	ds1307->msg[1].flags = I2C_M_RD;
	ds1307->msg[1].len = sizeof(ds1307->regs);
	ds1307->msg[1].buf = ds1307->regs;

	ds1307->type = chip->type;

	switch (ds1307->type) {
	case ds_1337:
	case ds_1339:
	ds1307->reg_addr = DS1337_REG_CONTROL;
	ds1307->msg[1].len = 2;

	/* get registers that the "rtc" read below won't read... */
	tmp = i2c_transfer(adapter, ds1307->msg, 2);
	if (tmp != 2) {
	pr_debug("read error %d\n", tmp);
	err = -EIO;
	goto exit_free;
	}

	ds1307->reg_addr = 0;
	ds1307->msg[1].len = sizeof(ds1307->regs);

	/* oscillator off? turn it on, so clock can tick. */
	if (ds1307->regs[0] & DS1337_BIT_nEOSC)
	i2c_smbus_write_byte_data(client, DS1337_REG_CONTROL,
	ds1307->regs[0] & ~DS1337_BIT_nEOSC);

	/* 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!\n");
	}
	break;
	default:
	break;
	}

	read_rtc:
	/* read RTC registers */

	tmp = i2c_transfer(adapter, ds1307->msg, 2);
	if (tmp != 2) {
	pr_debug("read error %d\n", 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_1340:
	/* FIXME read register with DS1340_BIT_OSF, use that to
	* trigger the "set time" warning (after restarting the
	* oscillator!) instead of this weaker ds1307/m41t00 test.
	*/
	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!\n");
	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!\n");
	goto read_rtc;
	}
	break;
	case ds_1337:
	case ds_1339:
	break;
	}

	tmp = ds1307->regs[DS1307_REG_SECS];
	tmp = BCD2BIN(tmp & 0x7f);
	if (tmp > 60)
	goto exit_bad;
	tmp = BCD2BIN(ds1307->regs[DS1307_REG_MIN] & 0x7f);
	if (tmp > 60)
	goto exit_bad;

	tmp = BCD2BIN(ds1307->regs[DS1307_REG_MDAY] & 0x3f);
	if (tmp == 0 \|\| tmp > 31)
	goto exit_bad;

	tmp = BCD2BIN(ds1307->regs[DS1307_REG_MONTH] & 0x1f);
	if (tmp == 0 \|\| tmp > 12)
	goto exit_bad;

	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\n");
	goto exit_free;
	}

	return 0;

	exit_bad:
	dev_dbg(&client->dev, "%s: %02x %02x %02x %02x %02x %02x %02x\n",
	"bogus register",
	ds1307->regs[0], ds1307->regs[1],
	ds1307->regs[2], ds1307->regs[3],
	ds1307->regs[4], ds1307->regs[5],
	ds1307->regs[6]);

	exit_free:
	kfree(ds1307);
	return err;
	}

	static int __devexit ds1307_remove(struct i2c_client *client)
	{
	struct ds1307 *ds1307 = i2c_get_clientdata(client);

	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),
	};

	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");