// SPDX-License-Identifier: GPL-2.0-only

  /*
   * Dallas Semiconductor DS1682 Elapsed Time Recorder device driver
   *
   * Written by: Grant Likely <grant.likely@secretlab.ca>
   *
   * Copyright (C) 2007 Secret Lab Technologies Ltd.

   */
  
  /*
   * 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/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);

  	unsigned long long val, check;

  	__le32 val_le = 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_le);

  	if (rc < 0)
  		return -EIO;

  	val = le32_to_cpu(val_le);

  	if (sattr->index == DS1682_REG_ELAPSED) {
  		int retries = 5;
  
  		/* Detect and retry when a tick occurs mid-read */
  		do {
  			rc = i2c_smbus_read_i2c_block_data(client, sattr->index,
  							   sattr->nr,
  							   (u8 *)&val_le);
  			if (rc < 0 || retries <= 0)
  				return -EIO;
  
  			check = val;
  			val = le32_to_cpu(val_le);
  			retries--;
  		} while (val != check && val != (check + 1));
  	}

  	/* Format the output string and return # of bytes
  	 * Special case: the 32 bit regs are time values with 1/4s
  	 * resolution, scale them up to milliseconds
  	 */
  	return sprintf(buf, "%llu
  ", (sattr->nr == 4) ? (val * 250) : 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);

  	u64 val;
  	__le32 val_le;
  	int rc;
  
  	dev_dbg(dev, "ds1682_store() called on %s
  ", attr->attr.name);
  
  	/* Decode input */

  	rc = kstrtoull(buf, 0, &val);
  	if (rc < 0) {

  		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);

  	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);

  	/* 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 const 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 const struct of_device_id ds1682_of_match[] = {
  	{ .compatible = "dallas,ds1682", },
  	{}
  };
  MODULE_DEVICE_TABLE(of, ds1682_of_match);

  static struct i2c_driver ds1682_driver = {
  	.driver = {
  		.name = "ds1682",

  		.of_match_table = ds1682_of_match,

  	},
  	.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");