/*
   * 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>
  #include <linux/module.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[] = {
  		{/* setup read ptr */
  			.addr = client->addr,
  			.len = 1,
  			.buf = &addr
  		},
  		{/* read date */
  			.addr = client->addr,
  			.flags = I2C_M_RD,
  			.len = 4,
  			.buf = buf
  		},
  	};
  
  	/* 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[] = {
  		{/* setup read ptr */
  			.addr = client->addr,
  			.len = 1,
  			.buf = &addr
  		},
  		{/* read control */
  			.addr = client->addr,
  			.flags = I2C_M_RD,
  			.len = 1,
  			.buf = status
  		},
  	};
  
  	/* 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_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 = devm_rtc_device_register(&client->dev, ds1672_driver.driver.name,
  				  &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:
  	return err;
  }
  
  static struct i2c_device_id ds1672_id[] = {
  	{ "ds1672", 0 },
  	{ }
  };
  
  static struct i2c_driver ds1672_driver = {
  	.driver = {
  		   .name = "rtc-ds1672",
  		   },
  	.probe = &ds1672_probe,
  	.id_table = ds1672_id,
  };
  
  module_i2c_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);