/*
   * An rtc/i2c driver for the Dallas DS1672

   * Copyright 2005-06 Tower Technologies
   *
   * Author: Alessandro Zummo <a.zummo@towertech.it>

   *
   * 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/i2c.h>
  #include <linux/rtc.h>

  #define DRV_VERSION "0.4"

  
  /* Registers */
  
  #define DS1672_REG_CNT_BASE	0
  #define DS1672_REG_CONTROL	4
  #define DS1672_REG_TRICKLE	5

  #define DS1672_REG_CONTROL_EOSC	0x80

  static struct i2c_driver ds1672_driver;

  
  /*
   * In the routines that deal directly with the ds1672 hardware, we use
   * rtc_time -- month 0-11, hour 0-23, yr = calendar year-epoch
   * Epoch is initialized as 2000. Time is set to UTC.
   */
  static int ds1672_get_datetime(struct i2c_client *client, struct rtc_time *tm)
  {
  	unsigned long time;
  	unsigned char addr = DS1672_REG_CNT_BASE;
  	unsigned char buf[4];
  
  	struct i2c_msg msgs[] = {

  		{client->addr, 0, 1, &addr},	/* setup read ptr */
  		{client->addr, I2C_M_RD, 4, buf},	/* read date */

  	};
  
  	/* read date registers */
  	if ((i2c_transfer(client->adapter, &msgs[0], 2)) != 2) {

  		dev_err(&client->dev, "%s: read error
  ", __func__);

  		return -EIO;
  	}
  
  	dev_dbg(&client->dev,

  		"%s: raw read data - counters=%02x,%02x,%02x,%02x
  ",

  		__func__, buf[0], buf[1], buf[2], buf[3]);

  
  	time = (buf[3] << 24) | (buf[2] << 16) | (buf[1] << 8) | buf[0];
  
  	rtc_time_to_tm(time, tm);
  
  	dev_dbg(&client->dev, "%s: tm is secs=%d, mins=%d, hours=%d, "
  		"mday=%d, mon=%d, year=%d, wday=%d
  ",

  		__func__, tm->tm_sec, tm->tm_min, tm->tm_hour,

  		tm->tm_mday, tm->tm_mon, tm->tm_year, tm->tm_wday);
  
  	return 0;
  }
  
  static int ds1672_set_mmss(struct i2c_client *client, unsigned long secs)
  {
  	int xfer;

  	unsigned char buf[6];

  
  	buf[0] = DS1672_REG_CNT_BASE;
  	buf[1] = secs & 0x000000FF;
  	buf[2] = (secs & 0x0000FF00) >> 8;
  	buf[3] = (secs & 0x00FF0000) >> 16;
  	buf[4] = (secs & 0xFF000000) >> 24;

  	buf[5] = 0;		/* set control reg to enable counting */

  	xfer = i2c_master_send(client, buf, 6);
  	if (xfer != 6) {

  		dev_err(&client->dev, "%s: send: %d
  ", __func__, xfer);

  		return -EIO;
  	}
  
  	return 0;
  }

  static int ds1672_rtc_read_time(struct device *dev, struct rtc_time *tm)
  {
  	return ds1672_get_datetime(to_i2c_client(dev), tm);
  }

  static int ds1672_rtc_set_mmss(struct device *dev, unsigned long secs)
  {
  	return ds1672_set_mmss(to_i2c_client(dev), secs);
  }

  static int ds1672_get_control(struct i2c_client *client, u8 *status)
  {
  	unsigned char addr = DS1672_REG_CONTROL;
  
  	struct i2c_msg msgs[] = {

  		{client->addr, 0, 1, &addr},	/* setup read ptr */
  		{client->addr, I2C_M_RD, 1, status},	/* read control */

  	};
  
  	/* read control register */
  	if ((i2c_transfer(client->adapter, &msgs[0], 2)) != 2) {

  		dev_err(&client->dev, "%s: read error
  ", __func__);

  		return -EIO;
  	}
  
  	return 0;
  }
  
  /* following are the sysfs callback functions */

  static ssize_t show_control(struct device *dev, struct device_attribute *attr,
  			    char *buf)

  {
  	struct i2c_client *client = to_i2c_client(dev);

  	u8 control;
  	int err;
  
  	err = ds1672_get_control(client, &control);
  	if (err)
  		return err;

  	return sprintf(buf, "%s
  ", (control & DS1672_REG_CONTROL_EOSC)

  		       ? "disabled" : "enabled");

  }

  static DEVICE_ATTR(control, S_IRUGO, show_control, NULL);

  static const struct rtc_class_ops ds1672_rtc_ops = {

  	.read_time = ds1672_rtc_read_time,

  	.set_mmss = ds1672_rtc_set_mmss,

  };

  static int ds1672_remove(struct i2c_client *client)

  {

  	struct rtc_device *rtc = i2c_get_clientdata(client);

  	if (rtc)

  		rtc_device_unregister(rtc);

  	return 0;
  }

  static int ds1672_probe(struct i2c_client *client,
  			const struct i2c_device_id *id)

  {
  	int err = 0;

  	u8 control;

  	struct rtc_device *rtc;

  	dev_dbg(&client->dev, "%s
  ", __func__);

  	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
  		return -ENODEV;

  
  	dev_info(&client->dev, "chip found, driver version " DRV_VERSION "
  ");
  
  	rtc = rtc_device_register(ds1672_driver.driver.name, &client->dev,

  				  &ds1672_rtc_ops, THIS_MODULE);

  	if (IS_ERR(rtc))
  		return PTR_ERR(rtc);

  
  	i2c_set_clientdata(client, rtc);

  	/* read control register */
  	err = ds1672_get_control(client, &control);

  	if (err)

  		goto exit_devreg;

  
  	if (control & DS1672_REG_CONTROL_EOSC)
  		dev_warn(&client->dev, "Oscillator not enabled. "

  			 "Set time to enable.
  ");

  
  	/* Register sysfs hooks */

  	err = device_create_file(&client->dev, &dev_attr_control);
  	if (err)
  		goto exit_devreg;

  	return 0;

   exit_devreg:

  	rtc_device_unregister(rtc);

  	return err;
  }

  static struct i2c_device_id ds1672_id[] = {
  	{ "ds1672", 0 },
  	{ }
  };

  static struct i2c_driver ds1672_driver = {
  	.driver = {
  		   .name = "rtc-ds1672",
  		   },
  	.probe = &ds1672_probe,
  	.remove = &ds1672_remove,

  	.id_table = ds1672_id,

  };

  static int __init ds1672_init(void)
  {
  	return i2c_add_driver(&ds1672_driver);
  }
  
  static void __exit ds1672_exit(void)
  {
  	i2c_del_driver(&ds1672_driver);
  }
  
  MODULE_AUTHOR("Alessandro Zummo <a.zummo@towertech.it>");
  MODULE_DESCRIPTION("Dallas/Maxim DS1672 timekeeper driver");
  MODULE_LICENSE("GPL");
  MODULE_VERSION(DRV_VERSION);
  
  module_init(ds1672_init);
  module_exit(ds1672_exit);