/*
   * Dallas Semiconductor DS1682 Elapsed Time Recorder device driver
   *
   * Written by: Grant Likely <grant.likely@secretlab.ca>
   *
   * Copyright (C) 2007 Secret Lab Technologies Ltd.
   *
   * 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.
   */
  
  /*
   * The DS1682 elapsed timer recorder is a simple device that implements
   * one elapsed time counter, one event counter, an alarm signal and 10
   * bytes of general purpose EEPROM.
   *
   * This driver provides access to the DS1682 counters and user data via
   * the sysfs.  The following attributes are added to the device node:
   *     elapsed_time (u32): Total elapsed event time in ms resolution
   *     alarm_time (u32): When elapsed time exceeds the value in alarm_time,
   *                       then the alarm pin is asserted.
   *     event_count (u16): number of times the event pin has gone low.
   *     eeprom (u8[10]): general purpose EEPROM
   *
   * Counter registers and user data are both read/write unless the device
   * has been write protected.  This driver does not support turning off write
   * protection.  Once write protection is turned on, it is impossible to
   * turn it off again, so I have left the feature out of this driver to avoid
   * accidental enabling, but it is trivial to add write protect support.
   *
   */
  
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/i2c.h>
  #include <linux/string.h>
  #include <linux/list.h>
  #include <linux/sysfs.h>
  #include <linux/ctype.h>
  #include <linux/hwmon-sysfs.h>
  
  /* Device registers */
  #define DS1682_REG_CONFIG		0x00
  #define DS1682_REG_ALARM		0x01
  #define DS1682_REG_ELAPSED		0x05
  #define DS1682_REG_EVT_CNTR		0x09
  #define DS1682_REG_EEPROM		0x0b
  #define DS1682_REG_RESET		0x1d
  #define DS1682_REG_WRITE_DISABLE	0x1e
  #define DS1682_REG_WRITE_MEM_DISABLE	0x1f
  
  #define DS1682_EEPROM_SIZE		10
  
  /*
   * Generic counter attributes
   */
  static ssize_t ds1682_show(struct device *dev, struct device_attribute *attr,
  			   char *buf)
  {
  	struct sensor_device_attribute_2 *sattr = to_sensor_dev_attr_2(attr);
  	struct i2c_client *client = to_i2c_client(dev);
  	__le32 val = 0;
  	int rc;
  
  	dev_dbg(dev, "ds1682_show() called on %s
  ", attr->attr.name);
  
  	/* Read the register */
  	rc = i2c_smbus_read_i2c_block_data(client, sattr->index, sattr->nr,
  					   (u8 *) & val);
  	if (rc < 0)
  		return -EIO;
  
  	/* Special case: the 32 bit regs are time values with 1/4s
  	 * resolution, scale them up to milliseconds */
  	if (sattr->nr == 4)
  		return sprintf(buf, "%llu
  ",
  			((unsigned long long)le32_to_cpu(val)) * 250);
  
  	/* Format the output string and return # of bytes */
  	return sprintf(buf, "%li
  ", (long)le32_to_cpu(val));
  }
  
  static ssize_t ds1682_store(struct device *dev, struct device_attribute *attr,
  			    const char *buf, size_t count)
  {
  	struct sensor_device_attribute_2 *sattr = to_sensor_dev_attr_2(attr);
  	struct i2c_client *client = to_i2c_client(dev);
  	char *endp;
  	u64 val;
  	__le32 val_le;
  	int rc;
  
  	dev_dbg(dev, "ds1682_store() called on %s
  ", attr->attr.name);
  
  	/* Decode input */
  	val = simple_strtoull(buf, &endp, 0);
  	if (buf == endp) {
  		dev_dbg(dev, "input string not a number
  ");
  		return -EINVAL;
  	}
  
  	/* Special case: the 32 bit regs are time values with 1/4s
  	 * resolution, scale input down to quarter-seconds */
  	if (sattr->nr == 4)
  		do_div(val, 250);
  
  	/* write out the value */
  	val_le = cpu_to_le32(val);
  	rc = i2c_smbus_write_i2c_block_data(client, sattr->index, sattr->nr,
  					    (u8 *) & val_le);
  	if (rc < 0) {
  		dev_err(dev, "register write failed; reg=0x%x, size=%i
  ",
  			sattr->index, sattr->nr);
  		return -EIO;
  	}
  
  	return count;
  }
  
  /*
   * Simple register attributes
   */
  static SENSOR_DEVICE_ATTR_2(elapsed_time, S_IRUGO | S_IWUSR, ds1682_show,
  			    ds1682_store, 4, DS1682_REG_ELAPSED);
  static SENSOR_DEVICE_ATTR_2(alarm_time, S_IRUGO | S_IWUSR, ds1682_show,
  			    ds1682_store, 4, DS1682_REG_ALARM);
  static SENSOR_DEVICE_ATTR_2(event_count, S_IRUGO | S_IWUSR, ds1682_show,
  			    ds1682_store, 2, DS1682_REG_EVT_CNTR);
  
  static const struct attribute_group ds1682_group = {
  	.attrs = (struct attribute *[]) {
  		&sensor_dev_attr_elapsed_time.dev_attr.attr,
  		&sensor_dev_attr_alarm_time.dev_attr.attr,
  		&sensor_dev_attr_event_count.dev_attr.attr,
  		NULL,
  	},
  };
  
  /*
   * User data attribute
   */
  static ssize_t ds1682_eeprom_read(struct file *filp, struct kobject *kobj,
  				  struct bin_attribute *attr,
  				  char *buf, loff_t off, size_t count)
  {
  	struct i2c_client *client = kobj_to_i2c_client(kobj);
  	int rc;
  
  	dev_dbg(&client->dev, "ds1682_eeprom_read(p=%p, off=%lli, c=%zi)
  ",
  		buf, off, count);
  
  	if (off >= DS1682_EEPROM_SIZE)
  		return 0;
  
  	if (off + count > DS1682_EEPROM_SIZE)
  		count = DS1682_EEPROM_SIZE - off;
  
  	rc = i2c_smbus_read_i2c_block_data(client, DS1682_REG_EEPROM + off,
  					   count, buf);
  	if (rc < 0)
  		return -EIO;
  
  	return count;
  }
  
  static ssize_t ds1682_eeprom_write(struct file *filp, struct kobject *kobj,
  				   struct bin_attribute *attr,
  				   char *buf, loff_t off, size_t count)
  {
  	struct i2c_client *client = kobj_to_i2c_client(kobj);
  
  	dev_dbg(&client->dev, "ds1682_eeprom_write(p=%p, off=%lli, c=%zi)
  ",
  		buf, off, count);
  
  	if (off >= DS1682_EEPROM_SIZE)
  		return -ENOSPC;
  
  	if (off + count > DS1682_EEPROM_SIZE)
  		count = DS1682_EEPROM_SIZE - off;
  
  	/* Write out to the device */
  	if (i2c_smbus_write_i2c_block_data(client, DS1682_REG_EEPROM + off,
  					   count, buf) < 0)
  		return -EIO;
  
  	return count;
  }
  
  static struct bin_attribute ds1682_eeprom_attr = {
  	.attr = {
  		.name = "eeprom",
  		.mode = S_IRUGO | S_IWUSR,
  	},
  	.size = DS1682_EEPROM_SIZE,
  	.read = ds1682_eeprom_read,
  	.write = ds1682_eeprom_write,
  };
  
  /*
   * Called when a ds1682 device is matched with this driver
   */
  static int ds1682_probe(struct i2c_client *client,
  			const struct i2c_device_id *id)
  {
  	int rc;
  
  	if (!i2c_check_functionality(client->adapter,
  				     I2C_FUNC_SMBUS_I2C_BLOCK)) {
  		dev_err(&client->dev, "i2c bus does not support the ds1682
  ");
  		rc = -ENODEV;
  		goto exit;
  	}
  
  	rc = sysfs_create_group(&client->dev.kobj, &ds1682_group);
  	if (rc)
  		goto exit;
  
  	rc = sysfs_create_bin_file(&client->dev.kobj, &ds1682_eeprom_attr);
  	if (rc)
  		goto exit_bin_attr;
  
  	return 0;
  
   exit_bin_attr:
  	sysfs_remove_group(&client->dev.kobj, &ds1682_group);
   exit:
  	return rc;
  }
  
  static int ds1682_remove(struct i2c_client *client)
  {
  	sysfs_remove_bin_file(&client->dev.kobj, &ds1682_eeprom_attr);
  	sysfs_remove_group(&client->dev.kobj, &ds1682_group);
  	return 0;
  }
  
  static const struct i2c_device_id ds1682_id[] = {
  	{ "ds1682", 0 },
  	{ }
  };
  MODULE_DEVICE_TABLE(i2c, ds1682_id);
  
  static struct i2c_driver ds1682_driver = {
  	.driver = {
  		.name = "ds1682",
  	},
  	.probe = ds1682_probe,
  	.remove = ds1682_remove,
  	.id_table = ds1682_id,
  };
  
  module_i2c_driver(ds1682_driver);
  
  MODULE_AUTHOR("Grant Likely <grant.likely@secretlab.ca>");
  MODULE_DESCRIPTION("DS1682 Elapsed Time Indicator driver");
  MODULE_LICENSE("GPL");