/*
   * Driver for batteries with DS2760 chips inside.
   *
   * Copyright © 2007 Anton Vorontsov
   *	       2004-2007 Matt Reimer
   *	       2004 Szabolcs Gyurko
   *
   * Use consistent with the GNU GPL is permitted,
   * provided that this copyright notice is
   * preserved in its entirety in all copies and derived works.
   *
   * Author:  Anton Vorontsov <cbou@mail.ru>
   *	    February 2007
   *
   *	    Matt Reimer <mreimer@vpop.net>
   *	    April 2004, 2005, 2007
   *
   *	    Szabolcs Gyurko <szabolcs.gyurko@tlt.hu>
   *	    September 2004
   */
  
  #include <linux/module.h>
  #include <linux/param.h>
  #include <linux/jiffies.h>
  #include <linux/workqueue.h>
  #include <linux/pm.h>
  #include <linux/slab.h>
  #include <linux/platform_device.h>
  #include <linux/power_supply.h>
  
  #include "../w1/w1.h"
  #include "../w1/slaves/w1_ds2760.h"
  
  struct ds2760_device_info {
  	struct device *dev;
  
  	/* DS2760 data, valid after calling ds2760_battery_read_status() */
  	unsigned long update_time;	/* jiffies when data read */
  	char raw[DS2760_DATA_SIZE];	/* raw DS2760 data */
  	int voltage_raw;		/* units of 4.88 mV */
  	int voltage_uV;			/* units of µV */
  	int current_raw;		/* units of 0.625 mA */
  	int current_uA;			/* units of µA */
  	int accum_current_raw;		/* units of 0.25 mAh */
  	int accum_current_uAh;		/* units of µAh */
  	int temp_raw;			/* units of 0.125 °C */
  	int temp_C;			/* units of 0.1 °C */
  	int rated_capacity;		/* units of µAh */
  	int rem_capacity;		/* percentage */
  	int full_active_uAh;		/* units of µAh */
  	int empty_uAh;			/* units of µAh */
  	int life_sec;			/* units of seconds */
  	int charge_status;		/* POWER_SUPPLY_STATUS_* */
  
  	int full_counter;
  	struct power_supply bat;
  	struct device *w1_dev;
  	struct workqueue_struct *monitor_wqueue;
  	struct delayed_work monitor_work;
  	struct delayed_work set_charged_work;
  };
  
  static unsigned int cache_time = 1000;
  module_param(cache_time, uint, 0644);
  MODULE_PARM_DESC(cache_time, "cache time in milliseconds");
  
  static bool pmod_enabled;
  module_param(pmod_enabled, bool, 0644);
  MODULE_PARM_DESC(pmod_enabled, "PMOD enable bit");
  
  static unsigned int rated_capacity;
  module_param(rated_capacity, uint, 0644);
  MODULE_PARM_DESC(rated_capacity, "rated battery capacity, 10*mAh or index");
  
  static unsigned int current_accum;
  module_param(current_accum, uint, 0644);
  MODULE_PARM_DESC(current_accum, "current accumulator value");
  
  /* Some batteries have their rated capacity stored a N * 10 mAh, while
   * others use an index into this table. */
  static int rated_capacities[] = {
  	0,
  	920,	/* Samsung */
  	920,	/* BYD */
  	920,	/* Lishen */
  	920,	/* NEC */
  	1440,	/* Samsung */
  	1440,	/* BYD */
  #ifdef CONFIG_MACH_H4700
  	1800,	/* HP iPAQ hx4700 3.7V 1800mAh (359113-001) */
  #else
  	1440,	/* Lishen */
  #endif
  	1440,	/* NEC */
  	2880,	/* Samsung */
  	2880,	/* BYD */
  	2880,	/* Lishen */
  	2880,	/* NEC */
  #ifdef CONFIG_MACH_H4700
  	0,
  	3600,	/* HP iPAQ hx4700 3.7V 3600mAh (359114-001) */
  #endif
  };
  
  /* array is level at temps 0°C, 10°C, 20°C, 30°C, 40°C
   * temp is in Celsius */
  static int battery_interpolate(int array[], int temp)
  {
  	int index, dt;
  
  	if (temp <= 0)
  		return array[0];
  	if (temp >= 40)
  		return array[4];
  
  	index = temp / 10;
  	dt    = temp % 10;
  
  	return array[index] + (((array[index + 1] - array[index]) * dt) / 10);
  }
  
  static int ds2760_battery_read_status(struct ds2760_device_info *di)
  {
  	int ret, i, start, count, scale[5];
  
  	if (di->update_time && time_before(jiffies, di->update_time +
  					   msecs_to_jiffies(cache_time)))
  		return 0;
  
  	/* The first time we read the entire contents of SRAM/EEPROM,
  	 * but after that we just read the interesting bits that change. */
  	if (di->update_time == 0) {
  		start = 0;
  		count = DS2760_DATA_SIZE;
  	} else {
  		start = DS2760_VOLTAGE_MSB;
  		count = DS2760_TEMP_LSB - start + 1;
  	}
  
  	ret = w1_ds2760_read(di->w1_dev, di->raw + start, start, count);
  	if (ret != count) {
  		dev_warn(di->dev, "call to w1_ds2760_read failed (0x%p)
  ",
  			 di->w1_dev);
  		return 1;
  	}
  
  	di->update_time = jiffies;
  
  	/* DS2760 reports voltage in units of 4.88mV, but the battery class
  	 * reports in units of uV, so convert by multiplying by 4880. */
  	di->voltage_raw = (di->raw[DS2760_VOLTAGE_MSB] << 3) |
  			  (di->raw[DS2760_VOLTAGE_LSB] >> 5);
  	di->voltage_uV = di->voltage_raw * 4880;
  
  	/* DS2760 reports current in signed units of 0.625mA, but the battery
  	 * class reports in units of µA, so convert by multiplying by 625. */
  	di->current_raw =
  	    (((signed char)di->raw[DS2760_CURRENT_MSB]) << 5) |
  			  (di->raw[DS2760_CURRENT_LSB] >> 3);
  	di->current_uA = di->current_raw * 625;
  
  	/* DS2760 reports accumulated current in signed units of 0.25mAh. */
  	di->accum_current_raw =
  	    (((signed char)di->raw[DS2760_CURRENT_ACCUM_MSB]) << 8) |
  			   di->raw[DS2760_CURRENT_ACCUM_LSB];
  	di->accum_current_uAh = di->accum_current_raw * 250;
  
  	/* DS2760 reports temperature in signed units of 0.125°C, but the
  	 * battery class reports in units of 1/10 °C, so we convert by
  	 * multiplying by .125 * 10 = 1.25. */
  	di->temp_raw = (((signed char)di->raw[DS2760_TEMP_MSB]) << 3) |
  				     (di->raw[DS2760_TEMP_LSB] >> 5);
  	di->temp_C = di->temp_raw + (di->temp_raw / 4);
  
  	/* At least some battery monitors (e.g. HP iPAQ) store the battery's
  	 * maximum rated capacity. */
  	if (di->raw[DS2760_RATED_CAPACITY] < ARRAY_SIZE(rated_capacities))
  		di->rated_capacity = rated_capacities[
  			(unsigned int)di->raw[DS2760_RATED_CAPACITY]];
  	else
  		di->rated_capacity = di->raw[DS2760_RATED_CAPACITY] * 10;
  
  	di->rated_capacity *= 1000; /* convert to µAh */
  
  	/* Calculate the full level at the present temperature. */
  	di->full_active_uAh = di->raw[DS2760_ACTIVE_FULL] << 8 |
  			      di->raw[DS2760_ACTIVE_FULL + 1];
  
  	/* If the full_active_uAh value is not given, fall back to the rated
  	 * capacity. This is likely to happen when chips are not part of the
  	 * battery pack and is therefore not bootstrapped. */
  	if (di->full_active_uAh == 0)
  		di->full_active_uAh = di->rated_capacity / 1000L;
  
  	scale[0] = di->full_active_uAh;
  	for (i = 1; i < 5; i++)
  		scale[i] = scale[i - 1] + di->raw[DS2760_ACTIVE_FULL + 1 + i];
  
  	di->full_active_uAh = battery_interpolate(scale, di->temp_C / 10);
  	di->full_active_uAh *= 1000; /* convert to µAh */
  
  	/* Calculate the empty level at the present temperature. */
  	scale[4] = di->raw[DS2760_ACTIVE_EMPTY + 4];
  	for (i = 3; i >= 0; i--)
  		scale[i] = scale[i + 1] + di->raw[DS2760_ACTIVE_EMPTY + i];
  
  	di->empty_uAh = battery_interpolate(scale, di->temp_C / 10);
  	di->empty_uAh *= 1000; /* convert to µAh */
  
  	if (di->full_active_uAh == di->empty_uAh)
  		di->rem_capacity = 0;
  	else
  		/* From Maxim Application Note 131: remaining capacity =
  		 * ((ICA - Empty Value) / (Full Value - Empty Value)) x 100% */
  		di->rem_capacity = ((di->accum_current_uAh - di->empty_uAh) * 100L) /
  				    (di->full_active_uAh - di->empty_uAh);
  
  	if (di->rem_capacity < 0)
  		di->rem_capacity = 0;
  	if (di->rem_capacity > 100)
  		di->rem_capacity = 100;
  
  	if (di->current_uA < -100L)
  		di->life_sec = -((di->accum_current_uAh - di->empty_uAh) * 36L)
  					/ (di->current_uA / 100L);
  	else
  		di->life_sec = 0;
  
  	return 0;
  }
  
  static void ds2760_battery_set_current_accum(struct ds2760_device_info *di,
  					     unsigned int acr_val)
  {
  	unsigned char acr[2];
  
  	/* acr is in units of 0.25 mAh */
  	acr_val *= 4L;
  	acr_val /= 1000;
  
  	acr[0] = acr_val >> 8;
  	acr[1] = acr_val & 0xff;
  
  	if (w1_ds2760_write(di->w1_dev, acr, DS2760_CURRENT_ACCUM_MSB, 2) < 2)
  		dev_warn(di->dev, "ACR write failed
  ");
  }
  
  static void ds2760_battery_update_status(struct ds2760_device_info *di)
  {
  	int old_charge_status = di->charge_status;
  
  	ds2760_battery_read_status(di);
  
  	if (di->charge_status == POWER_SUPPLY_STATUS_UNKNOWN)
  		di->full_counter = 0;
  
  	if (power_supply_am_i_supplied(&di->bat)) {
  		if (di->current_uA > 10000) {
  			di->charge_status = POWER_SUPPLY_STATUS_CHARGING;
  			di->full_counter = 0;
  		} else if (di->current_uA < -5000) {
  			if (di->charge_status != POWER_SUPPLY_STATUS_NOT_CHARGING)
  				dev_notice(di->dev, "not enough power to "
  					   "charge
  ");
  			di->charge_status = POWER_SUPPLY_STATUS_NOT_CHARGING;
  			di->full_counter = 0;
  		} else if (di->current_uA < 10000 &&
  			    di->charge_status != POWER_SUPPLY_STATUS_FULL) {
  
  			/* Don't consider the battery to be full unless
  			 * we've seen the current < 10 mA at least two
  			 * consecutive times. */
  
  			di->full_counter++;
  
  			if (di->full_counter < 2) {
  				di->charge_status = POWER_SUPPLY_STATUS_CHARGING;
  			} else {
  				di->charge_status = POWER_SUPPLY_STATUS_FULL;
  				ds2760_battery_set_current_accum(di,
  						di->full_active_uAh);
  			}
  		}
  	} else {
  		di->charge_status = POWER_SUPPLY_STATUS_DISCHARGING;
  		di->full_counter = 0;
  	}
  
  	if (di->charge_status != old_charge_status)
  		power_supply_changed(&di->bat);
  }
  
  static void ds2760_battery_write_status(struct ds2760_device_info *di,
  					char status)
  {
  	if (status == di->raw[DS2760_STATUS_REG])
  		return;
  
  	w1_ds2760_write(di->w1_dev, &status, DS2760_STATUS_WRITE_REG, 1);
  	w1_ds2760_store_eeprom(di->w1_dev, DS2760_EEPROM_BLOCK1);
  	w1_ds2760_recall_eeprom(di->w1_dev, DS2760_EEPROM_BLOCK1);
  }
  
  static void ds2760_battery_write_rated_capacity(struct ds2760_device_info *di,
  						unsigned char rated_capacity)
  {
  	if (rated_capacity == di->raw[DS2760_RATED_CAPACITY])
  		return;
  
  	w1_ds2760_write(di->w1_dev, &rated_capacity, DS2760_RATED_CAPACITY, 1);
  	w1_ds2760_store_eeprom(di->w1_dev, DS2760_EEPROM_BLOCK1);
  	w1_ds2760_recall_eeprom(di->w1_dev, DS2760_EEPROM_BLOCK1);
  }
  
  static void ds2760_battery_write_active_full(struct ds2760_device_info *di,
  					     int active_full)
  {
  	unsigned char tmp[2] = {
  		active_full >> 8,
  		active_full & 0xff
  	};
  
  	if (tmp[0] == di->raw[DS2760_ACTIVE_FULL] &&
  	    tmp[1] == di->raw[DS2760_ACTIVE_FULL + 1])
  		return;
  
  	w1_ds2760_write(di->w1_dev, tmp, DS2760_ACTIVE_FULL, sizeof(tmp));
  	w1_ds2760_store_eeprom(di->w1_dev, DS2760_EEPROM_BLOCK0);
  	w1_ds2760_recall_eeprom(di->w1_dev, DS2760_EEPROM_BLOCK0);
  
  	/* Write to the di->raw[] buffer directly - the DS2760_ACTIVE_FULL
  	 * values won't be read back by ds2760_battery_read_status() */
  	di->raw[DS2760_ACTIVE_FULL] = tmp[0];
  	di->raw[DS2760_ACTIVE_FULL + 1] = tmp[1];
  }
  
  static void ds2760_battery_work(struct work_struct *work)
  {
  	struct ds2760_device_info *di = container_of(work,
  		struct ds2760_device_info, monitor_work.work);
  	const int interval = HZ * 60;
  
  	dev_dbg(di->dev, "%s
  ", __func__);
  
  	ds2760_battery_update_status(di);
  	queue_delayed_work(di->monitor_wqueue, &di->monitor_work, interval);
  }
  
  #define to_ds2760_device_info(x) container_of((x), struct ds2760_device_info, \
  					      bat);
  
  static void ds2760_battery_external_power_changed(struct power_supply *psy)
  {
  	struct ds2760_device_info *di = to_ds2760_device_info(psy);
  
  	dev_dbg(di->dev, "%s
  ", __func__);
  
  	mod_delayed_work(di->monitor_wqueue, &di->monitor_work, HZ/10);
  }
  
  
  static void ds2760_battery_set_charged_work(struct work_struct *work)
  {
  	char bias;
  	struct ds2760_device_info *di = container_of(work,
  		struct ds2760_device_info, set_charged_work.work);
  
  	dev_dbg(di->dev, "%s
  ", __func__);
  
  	ds2760_battery_read_status(di);
  
  	/* When we get notified by external circuitry that the battery is
  	 * considered fully charged now, we know that there is no current
  	 * flow any more. However, the ds2760's internal current meter is
  	 * too inaccurate to rely on - spec say something ~15% failure.
  	 * Hence, we use the current offset bias register to compensate
  	 * that error.
  	 */
  
  	if (!power_supply_am_i_supplied(&di->bat))
  		return;
  
  	bias = (signed char) di->current_raw +
  		(signed char) di->raw[DS2760_CURRENT_OFFSET_BIAS];
  
  	dev_dbg(di->dev, "%s: bias = %d
  ", __func__, bias);
  
  	w1_ds2760_write(di->w1_dev, &bias, DS2760_CURRENT_OFFSET_BIAS, 1);
  	w1_ds2760_store_eeprom(di->w1_dev, DS2760_EEPROM_BLOCK1);
  	w1_ds2760_recall_eeprom(di->w1_dev, DS2760_EEPROM_BLOCK1);
  
  	/* Write to the di->raw[] buffer directly - the CURRENT_OFFSET_BIAS
  	 * value won't be read back by ds2760_battery_read_status() */
  	di->raw[DS2760_CURRENT_OFFSET_BIAS] = bias;
  }
  
  static void ds2760_battery_set_charged(struct power_supply *psy)
  {
  	struct ds2760_device_info *di = to_ds2760_device_info(psy);
  
  	/* postpone the actual work by 20 secs. This is for debouncing GPIO
  	 * signals and to let the current value settle. See AN4188. */
  	mod_delayed_work(di->monitor_wqueue, &di->set_charged_work, HZ * 20);
  }
  
  static int ds2760_battery_get_property(struct power_supply *psy,
  				       enum power_supply_property psp,
  				       union power_supply_propval *val)
  {
  	struct ds2760_device_info *di = to_ds2760_device_info(psy);
  
  	switch (psp) {
  	case POWER_SUPPLY_PROP_STATUS:
  		val->intval = di->charge_status;
  		return 0;
  	default:
  		break;
  	}
  
  	ds2760_battery_read_status(di);
  
  	switch (psp) {
  	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
  		val->intval = di->voltage_uV;
  		break;
  	case POWER_SUPPLY_PROP_CURRENT_NOW:
  		val->intval = di->current_uA;
  		break;
  	case POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN:
  		val->intval = di->rated_capacity;
  		break;
  	case POWER_SUPPLY_PROP_CHARGE_FULL:
  		val->intval = di->full_active_uAh;
  		break;
  	case POWER_SUPPLY_PROP_CHARGE_EMPTY:
  		val->intval = di->empty_uAh;
  		break;
  	case POWER_SUPPLY_PROP_CHARGE_NOW:
  		val->intval = di->accum_current_uAh;
  		break;
  	case POWER_SUPPLY_PROP_TEMP:
  		val->intval = di->temp_C;
  		break;
  	case POWER_SUPPLY_PROP_TIME_TO_EMPTY_NOW:
  		val->intval = di->life_sec;
  		break;
  	case POWER_SUPPLY_PROP_CAPACITY:
  		val->intval = di->rem_capacity;
  		break;
  	default:
  		return -EINVAL;
  	}
  
  	return 0;
  }
  
  static int ds2760_battery_set_property(struct power_supply *psy,
  				       enum power_supply_property psp,
  				       const union power_supply_propval *val)
  {
  	struct ds2760_device_info *di = to_ds2760_device_info(psy);
  
  	switch (psp) {
  	case POWER_SUPPLY_PROP_CHARGE_FULL:
  		/* the interface counts in uAh, convert the value */
  		ds2760_battery_write_active_full(di, val->intval / 1000L);
  		break;
  
  	case POWER_SUPPLY_PROP_CHARGE_NOW:
  		/* ds2760_battery_set_current_accum() does the conversion */
  		ds2760_battery_set_current_accum(di, val->intval);
  		break;
  
  	default:
  		return -EPERM;
  	}
  
  	return 0;
  }
  
  static int ds2760_battery_property_is_writeable(struct power_supply *psy,
  						enum power_supply_property psp)
  {
  	switch (psp) {
  	case POWER_SUPPLY_PROP_CHARGE_FULL:
  	case POWER_SUPPLY_PROP_CHARGE_NOW:
  		return 1;
  
  	default:
  		break;
  	}
  
  	return 0;
  }
  
  static enum power_supply_property ds2760_battery_props[] = {
  	POWER_SUPPLY_PROP_STATUS,
  	POWER_SUPPLY_PROP_VOLTAGE_NOW,
  	POWER_SUPPLY_PROP_CURRENT_NOW,
  	POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN,
  	POWER_SUPPLY_PROP_CHARGE_FULL,
  	POWER_SUPPLY_PROP_CHARGE_EMPTY,
  	POWER_SUPPLY_PROP_CHARGE_NOW,
  	POWER_SUPPLY_PROP_TEMP,
  	POWER_SUPPLY_PROP_TIME_TO_EMPTY_NOW,
  	POWER_SUPPLY_PROP_CAPACITY,
  };
  
  static int ds2760_battery_probe(struct platform_device *pdev)
  {
  	char status;
  	int retval = 0;
  	struct ds2760_device_info *di;
  
  	di = devm_kzalloc(&pdev->dev, sizeof(*di), GFP_KERNEL);
  	if (!di) {
  		retval = -ENOMEM;
  		goto di_alloc_failed;
  	}
  
  	platform_set_drvdata(pdev, di);
  
  	di->dev			= &pdev->dev;
  	di->w1_dev		= pdev->dev.parent;
  	di->bat.name		= dev_name(&pdev->dev);
  	di->bat.type		= POWER_SUPPLY_TYPE_BATTERY;
  	di->bat.properties	= ds2760_battery_props;
  	di->bat.num_properties	= ARRAY_SIZE(ds2760_battery_props);
  	di->bat.get_property	= ds2760_battery_get_property;
  	di->bat.set_property	= ds2760_battery_set_property;
  	di->bat.property_is_writeable =
  				  ds2760_battery_property_is_writeable;
  	di->bat.set_charged	= ds2760_battery_set_charged;
  	di->bat.external_power_changed =
  				  ds2760_battery_external_power_changed;
  
  	di->charge_status = POWER_SUPPLY_STATUS_UNKNOWN;
  
  	/* enable sleep mode feature */
  	ds2760_battery_read_status(di);
  	status = di->raw[DS2760_STATUS_REG];
  	if (pmod_enabled)
  		status |= DS2760_STATUS_PMOD;
  	else
  		status &= ~DS2760_STATUS_PMOD;
  
  	ds2760_battery_write_status(di, status);
  
  	/* set rated capacity from module param */
  	if (rated_capacity)
  		ds2760_battery_write_rated_capacity(di, rated_capacity);
  
  	/* set current accumulator if given as parameter.
  	 * this should only be done for bootstrapping the value */
  	if (current_accum)
  		ds2760_battery_set_current_accum(di, current_accum);
  
  	retval = power_supply_register(&pdev->dev, &di->bat);
  	if (retval) {
  		dev_err(di->dev, "failed to register battery
  ");
  		goto batt_failed;
  	}
  
  	INIT_DELAYED_WORK(&di->monitor_work, ds2760_battery_work);
  	INIT_DELAYED_WORK(&di->set_charged_work,
  			  ds2760_battery_set_charged_work);
  	di->monitor_wqueue = create_singlethread_workqueue(dev_name(&pdev->dev));
  	if (!di->monitor_wqueue) {
  		retval = -ESRCH;
  		goto workqueue_failed;
  	}
  	queue_delayed_work(di->monitor_wqueue, &di->monitor_work, HZ * 1);
  
  	goto success;
  
  workqueue_failed:
  	power_supply_unregister(&di->bat);
  batt_failed:
  di_alloc_failed:
  success:
  	return retval;
  }
  
  static int ds2760_battery_remove(struct platform_device *pdev)
  {
  	struct ds2760_device_info *di = platform_get_drvdata(pdev);
  
  	cancel_delayed_work_sync(&di->monitor_work);
  	cancel_delayed_work_sync(&di->set_charged_work);
  	destroy_workqueue(di->monitor_wqueue);
  	power_supply_unregister(&di->bat);
  
  	return 0;
  }
  
  #ifdef CONFIG_PM
  
  static int ds2760_battery_suspend(struct platform_device *pdev,
  				  pm_message_t state)
  {
  	struct ds2760_device_info *di = platform_get_drvdata(pdev);
  
  	di->charge_status = POWER_SUPPLY_STATUS_UNKNOWN;
  
  	return 0;
  }
  
  static int ds2760_battery_resume(struct platform_device *pdev)
  {
  	struct ds2760_device_info *di = platform_get_drvdata(pdev);
  
  	di->charge_status = POWER_SUPPLY_STATUS_UNKNOWN;
  	power_supply_changed(&di->bat);
  
  	mod_delayed_work(di->monitor_wqueue, &di->monitor_work, HZ);
  
  	return 0;
  }
  
  #else
  
  #define ds2760_battery_suspend NULL
  #define ds2760_battery_resume NULL
  
  #endif /* CONFIG_PM */
  
  MODULE_ALIAS("platform:ds2760-battery");
  
  static struct platform_driver ds2760_battery_driver = {
  	.driver = {
  		.name = "ds2760-battery",
  	},
  	.probe	  = ds2760_battery_probe,
  	.remove   = ds2760_battery_remove,
  	.suspend  = ds2760_battery_suspend,
  	.resume	  = ds2760_battery_resume,
  };
  
  module_platform_driver(ds2760_battery_driver);
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Szabolcs Gyurko <szabolcs.gyurko@tlt.hu>, "
  	      "Matt Reimer <mreimer@vpop.net>, "
  	      "Anton Vorontsov <cbou@mail.ru>");
  MODULE_DESCRIPTION("ds2760 battery driver");