/*
 *  battery.c - ACPI Battery Driver (Revision: 2.0)
 *
 *  Copyright (C) 2007 Alexey Starikovskiy <astarikovskiy@suse.de>
 *  Copyright (C) 2004-2007 Vladimir Lebedev <vladimir.p.lebedev@intel.com>
 *  Copyright (C) 2001, 2002 Andy Grover <andrew.grover@intel.com>
 *  Copyright (C) 2001, 2002 Paul Diefenbaugh <paul.s.diefenbaugh@intel.com>
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or (at
 *  your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful, but
 *  WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/jiffies.h>
#include <linux/async.h>
#include <linux/dmi.h>
#include <linux/slab.h>
#include <linux/suspend.h>
#include <asm/unaligned.h>

#include <acpi/acpi_bus.h>
#include <acpi/acpi_drivers.h>
#include <linux/power_supply.h>

#define PREFIX "ACPI: "

#define ACPI_BATTERY_VALUE_UNKNOWN 0xFFFFFFFF

#define ACPI_BATTERY_CLASS		"battery"
#define ACPI_BATTERY_DEVICE_NAME	"Battery"
#define ACPI_BATTERY_NOTIFY_STATUS	0x80
#define ACPI_BATTERY_NOTIFY_INFO	0x81
#define ACPI_BATTERY_NOTIFY_THRESHOLD   0x82

/* Battery power unit: 0 means mW, 1 means mA */
#define ACPI_BATTERY_POWER_UNIT_MA	1

#define _COMPONENT		ACPI_BATTERY_COMPONENT

ACPI_MODULE_NAME("battery");

MODULE_AUTHOR("Paul Diefenbaugh");
MODULE_AUTHOR("Alexey Starikovskiy <astarikovskiy@suse.de>");
MODULE_DESCRIPTION("ACPI Battery Driver");
MODULE_LICENSE("GPL");

static unsigned int cache_time = 1000;
module_param(cache_time, uint, 0644);
MODULE_PARM_DESC(cache_time, "cache time in milliseconds");

static const struct acpi_device_id battery_device_ids[] = {
	{"PNP0C0A", 0},
	{"", 0},
};

MODULE_DEVICE_TABLE(acpi, battery_device_ids);

enum {
	ACPI_BATTERY_ALARM_PRESENT,
	ACPI_BATTERY_XINFO_PRESENT,
	ACPI_BATTERY_QUIRK_PERCENTAGE_CAPACITY,
	/* On Lenovo Thinkpad models from 2010 and 2011, the power unit
	   switches between mWh and mAh depending on whether the system
	   is running on battery or not.  When mAh is the unit, most
	   reported values are incorrect and need to be adjusted by
	   10000/design_voltage.  Verified on x201, t410, t410s, and x220.
	   Pre-2010 and 2012 models appear to always report in mWh and
	   are thus unaffected (tested with t42, t61, t500, x200, x300,
	   and x230).  Also, in mid-2012 Lenovo issued a BIOS update for
	   the 2011 models that fixes the issue (tested on x220 with a
	   post-1.29 BIOS), but as of Nov. 2012, no such update is
	   available for the 2010 models.  */
	ACPI_BATTERY_QUIRK_THINKPAD_MAH,
};

struct acpi_battery {
	struct mutex lock;
	struct mutex sysfs_lock;
	struct power_supply bat;
	struct acpi_device *device;
	struct notifier_block pm_nb;
	unsigned long update_time;
	int revision;
	int rate_now;
	int capacity_now;
	int voltage_now;
	int design_capacity;
	int full_charge_capacity;
	int technology;
	int design_voltage;
	int design_capacity_warning;
	int design_capacity_low;
	int cycle_count;
	int measurement_accuracy;
	int max_sampling_time;
	int min_sampling_time;
	int max_averaging_interval;
	int min_averaging_interval;
	int capacity_granularity_1;
	int capacity_granularity_2;
	int alarm;
	char model_number[32];
	char serial_number[32];
	char type[32];
	char oem_info[32];
	int state;
	int power_unit;
	unsigned long flags;
};

#define to_acpi_battery(x) container_of(x, struct acpi_battery, bat)

static inline int acpi_battery_present(struct acpi_battery *battery)
{
	return battery->device->status.battery_present;
}

static int acpi_battery_technology(struct acpi_battery *battery)
{
	if (!strcasecmp("NiCd", battery->type))
		return POWER_SUPPLY_TECHNOLOGY_NiCd;
	if (!strcasecmp("NiMH", battery->type))
		return POWER_SUPPLY_TECHNOLOGY_NiMH;
	if (!strcasecmp("LION", battery->type))
		return POWER_SUPPLY_TECHNOLOGY_LION;
	if (!strncasecmp("LI-ION", battery->type, 6))
		return POWER_SUPPLY_TECHNOLOGY_LION;
	if (!strcasecmp("LiP", battery->type))
		return POWER_SUPPLY_TECHNOLOGY_LIPO;
	return POWER_SUPPLY_TECHNOLOGY_UNKNOWN;
}

static int acpi_battery_get_state(struct acpi_battery *battery);

static int acpi_battery_is_charged(struct acpi_battery *battery)
{
	/* either charging or discharging */
	if (battery->state != 0)
		return 0;

	/* battery not reporting charge */
	if (battery->capacity_now == ACPI_BATTERY_VALUE_UNKNOWN ||
	    battery->capacity_now == 0)
		return 0;

	/* good batteries update full_charge as the batteries degrade */
	if (battery->full_charge_capacity == battery->capacity_now)
		return 1;

	/* fallback to using design values for broken batteries */
	if (battery->design_capacity == battery->capacity_now)
		return 1;

	/* we don't do any sort of metric based on percentages */
	return 0;
}

static int acpi_battery_get_property(struct power_supply *psy,
				     enum power_supply_property psp,
				     union power_supply_propval *val)
{
	int ret = 0;
	struct acpi_battery *battery = to_acpi_battery(psy);

	if (acpi_battery_present(battery)) {
		/* run battery update only if it is present */
		acpi_battery_get_state(battery);
	} else if (psp != POWER_SUPPLY_PROP_PRESENT)
		return -ENODEV;
	switch (psp) {
	case POWER_SUPPLY_PROP_STATUS:
		if (battery->state & 0x01)
			val->intval = POWER_SUPPLY_STATUS_DISCHARGING;
		else if (battery->state & 0x02)
			val->intval = POWER_SUPPLY_STATUS_CHARGING;
		else if (acpi_battery_is_charged(battery))
			val->intval = POWER_SUPPLY_STATUS_FULL;
		else
			val->intval = POWER_SUPPLY_STATUS_UNKNOWN;
		break;
	case POWER_SUPPLY_PROP_PRESENT:
		val->intval = acpi_battery_present(battery);
		break;
	case POWER_SUPPLY_PROP_TECHNOLOGY:
		val->intval = acpi_battery_technology(battery);
		break;
	case POWER_SUPPLY_PROP_CYCLE_COUNT:
		val->intval = battery->cycle_count;
		break;
	case POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN:
		if (battery->design_voltage == ACPI_BATTERY_VALUE_UNKNOWN)
			ret = -ENODEV;
		else
			val->intval = battery->design_voltage * 1000;
		break;
	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
		if (battery->voltage_now == ACPI_BATTERY_VALUE_UNKNOWN)
			ret = -ENODEV;
		else
			val->intval = battery->voltage_now * 1000;
		break;
	case POWER_SUPPLY_PROP_CURRENT_NOW:
	case POWER_SUPPLY_PROP_POWER_NOW:
		if (battery->rate_now == ACPI_BATTERY_VALUE_UNKNOWN)
			ret = -ENODEV;
		else
			val->intval = battery->rate_now * 1000;
		break;
	case POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN:
	case POWER_SUPPLY_PROP_ENERGY_FULL_DESIGN:
		if (battery->design_capacity == ACPI_BATTERY_VALUE_UNKNOWN)
			ret = -ENODEV;
		else
			val->intval = battery->design_capacity * 1000;
		break;
	case POWER_SUPPLY_PROP_CHARGE_FULL:
	case POWER_SUPPLY_PROP_ENERGY_FULL:
		if (battery->full_charge_capacity == ACPI_BATTERY_VALUE_UNKNOWN)
			ret = -ENODEV;
		else
			val->intval = battery->full_charge_capacity * 1000;
		break;
	case POWER_SUPPLY_PROP_CHARGE_NOW:
	case POWER_SUPPLY_PROP_ENERGY_NOW:
		if (battery->capacity_now == ACPI_BATTERY_VALUE_UNKNOWN)
			ret = -ENODEV;
		else
			val->intval = battery->capacity_now * 1000;
		break;
	case POWER_SUPPLY_PROP_CAPACITY:
		if (battery->capacity_now && battery->full_charge_capacity)
			val->intval = battery->capacity_now * 100/
					battery->full_charge_capacity;
		else
			val->intval = 0;
		break;
	case POWER_SUPPLY_PROP_MODEL_NAME:
		val->strval = battery->model_number;
		break;
	case POWER_SUPPLY_PROP_MANUFACTURER:
		val->strval = battery->oem_info;
		break;
	case POWER_SUPPLY_PROP_SERIAL_NUMBER:
		val->strval = battery->serial_number;
		break;
	default:
		ret = -EINVAL;
	}
	return ret;
}

static enum power_supply_property charge_battery_props[] = {
	POWER_SUPPLY_PROP_STATUS,
	POWER_SUPPLY_PROP_PRESENT,
	POWER_SUPPLY_PROP_TECHNOLOGY,
	POWER_SUPPLY_PROP_CYCLE_COUNT,
	POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN,
	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_NOW,
	POWER_SUPPLY_PROP_CAPACITY,
	POWER_SUPPLY_PROP_MODEL_NAME,
	POWER_SUPPLY_PROP_MANUFACTURER,
	POWER_SUPPLY_PROP_SERIAL_NUMBER,
};

static enum power_supply_property energy_battery_props[] = {
	POWER_SUPPLY_PROP_STATUS,
	POWER_SUPPLY_PROP_PRESENT,
	POWER_SUPPLY_PROP_TECHNOLOGY,
	POWER_SUPPLY_PROP_CYCLE_COUNT,
	POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN,
	POWER_SUPPLY_PROP_VOLTAGE_NOW,
	POWER_SUPPLY_PROP_POWER_NOW,
	POWER_SUPPLY_PROP_ENERGY_FULL_DESIGN,
	POWER_SUPPLY_PROP_ENERGY_FULL,
	POWER_SUPPLY_PROP_ENERGY_NOW,
	POWER_SUPPLY_PROP_CAPACITY,
	POWER_SUPPLY_PROP_MODEL_NAME,
	POWER_SUPPLY_PROP_MANUFACTURER,
	POWER_SUPPLY_PROP_SERIAL_NUMBER,
};

/* --------------------------------------------------------------------------
                               Battery Management
   -------------------------------------------------------------------------- */
struct acpi_offsets {
	size_t offset;		/* offset inside struct acpi_sbs_battery */
	u8 mode;		/* int or string? */
};

static struct acpi_offsets state_offsets[] = {
	{offsetof(struct acpi_battery, state), 0},
	{offsetof(struct acpi_battery, rate_now), 0},
	{offsetof(struct acpi_battery, capacity_now), 0},
	{offsetof(struct acpi_battery, voltage_now), 0},
};

static struct acpi_offsets info_offsets[] = {
	{offsetof(struct acpi_battery, power_unit), 0},
	{offsetof(struct acpi_battery, design_capacity), 0},
	{offsetof(struct acpi_battery, full_charge_capacity), 0},
	{offsetof(struct acpi_battery, technology), 0},
	{offsetof(struct acpi_battery, design_voltage), 0},
	{offsetof(struct acpi_battery, design_capacity_warning), 0},
	{offsetof(struct acpi_battery, design_capacity_low), 0},
	{offsetof(struct acpi_battery, capacity_granularity_1), 0},
	{offsetof(struct acpi_battery, capacity_granularity_2), 0},
	{offsetof(struct acpi_battery, model_number), 1},
	{offsetof(struct acpi_battery, serial_number), 1},
	{offsetof(struct acpi_battery, type), 1},
	{offsetof(struct acpi_battery, oem_info), 1},
};

static struct acpi_offsets extended_info_offsets[] = {
	{offsetof(struct acpi_battery, revision), 0},
	{offsetof(struct acpi_battery, power_unit), 0},
	{offsetof(struct acpi_battery, design_capacity), 0},
	{offsetof(struct acpi_battery, full_charge_capacity), 0},
	{offsetof(struct acpi_battery, technology), 0},
	{offsetof(struct acpi_battery, design_voltage), 0},
	{offsetof(struct acpi_battery, design_capacity_warning), 0},
	{offsetof(struct acpi_battery, design_capacity_low), 0},
	{offsetof(struct acpi_battery, cycle_count), 0},
	{offsetof(struct acpi_battery, measurement_accuracy), 0},
	{offsetof(struct acpi_battery, max_sampling_time), 0},
	{offsetof(struct acpi_battery, min_sampling_time), 0},
	{offsetof(struct acpi_battery, max_averaging_interval), 0},
	{offsetof(struct acpi_battery, min_averaging_interval), 0},
	{offsetof(struct acpi_battery, capacity_granularity_1), 0},
	{offsetof(struct acpi_battery, capacity_granularity_2), 0},
	{offsetof(struct acpi_battery, model_number), 1},
	{offsetof(struct acpi_battery, serial_number), 1},
	{offsetof(struct acpi_battery, type), 1},
	{offsetof(struct acpi_battery, oem_info), 1},
};

static int extract_package(struct acpi_battery *battery,
			   union acpi_object *package,
			   struct acpi_offsets *offsets, int num)
{
	int i;
	union acpi_object *element;
	if (package->type != ACPI_TYPE_PACKAGE)
		return -EFAULT;
	for (i = 0; i < num; ++i) {
		if (package->package.count <= i)
			return -EFAULT;
		element = &package->package.elements[i];
		if (offsets[i].mode) {
			u8 *ptr = (u8 *)battery + offsets[i].offset;
			if (element->type == ACPI_TYPE_STRING ||
			    element->type == ACPI_TYPE_BUFFER)
				strncpy(ptr, element->string.pointer, 32);
			else if (element->type == ACPI_TYPE_INTEGER) {
				strncpy(ptr, (u8 *)&element->integer.value,
					sizeof(u64));
				ptr[sizeof(u64)] = 0;
			} else
				*ptr = 0; /* don't have value */
		} else {
			int *x = (int *)((u8 *)battery + offsets[i].offset);
			*x = (element->type == ACPI_TYPE_INTEGER) ?
				element->integer.value : -1;
		}
	}
	return 0;
}

static int acpi_battery_get_status(struct acpi_battery *battery)
{
	if (acpi_bus_get_status(battery->device)) {
		ACPI_EXCEPTION((AE_INFO, AE_ERROR, "Evaluating _STA"));
		return -ENODEV;
	}
	return 0;
}

static int acpi_battery_get_info(struct acpi_battery *battery)
{
	int result = -EFAULT;
	acpi_status status = 0;
	char *name = test_bit(ACPI_BATTERY_XINFO_PRESENT, &battery->flags) ?
			"_BIX" : "_BIF";

	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };

	if (!acpi_battery_present(battery))
		return 0;
	mutex_lock(&battery->lock);
	status = acpi_evaluate_object(battery->device->handle, name,
						NULL, &buffer);
	mutex_unlock(&battery->lock);

	if (ACPI_FAILURE(status)) {
		ACPI_EXCEPTION((AE_INFO, status, "Evaluating %s", name));
		return -ENODEV;
	}
	if (test_bit(ACPI_BATTERY_XINFO_PRESENT, &battery->flags))
		result = extract_package(battery, buffer.pointer,
				extended_info_offsets,
				ARRAY_SIZE(extended_info_offsets));
	else
		result = extract_package(battery, buffer.pointer,
				info_offsets, ARRAY_SIZE(info_offsets));
	kfree(buffer.pointer);
	if (test_bit(ACPI_BATTERY_QUIRK_PERCENTAGE_CAPACITY, &battery->flags))
		battery->full_charge_capacity = battery->design_capacity;
	if (test_bit(ACPI_BATTERY_QUIRK_THINKPAD_MAH, &battery->flags) &&
	    battery->power_unit && battery->design_voltage) {
		battery->design_capacity = battery->design_capacity *
		    10000 / battery->design_voltage;
		battery->full_charge_capacity = battery->full_charge_capacity *
		    10000 / battery->design_voltage;
		battery->design_capacity_warning =
		    battery->design_capacity_warning *
		    10000 / battery->design_voltage;
		/* Curiously, design_capacity_low, unlike the rest of them,
		   is correct.  */
		/* capacity_granularity_* equal 1 on the systems tested, so
		   it's impossible to tell if they would need an adjustment
		   or not if their values were higher.  */
	}
	return result;
}

static int acpi_battery_get_state(struct acpi_battery *battery)
{
	int result = 0;
	acpi_status status = 0;
	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };

	if (!acpi_battery_present(battery))
		return 0;

	if (battery->update_time &&
	    time_before(jiffies, battery->update_time +
			msecs_to_jiffies(cache_time)))
		return 0;

	mutex_lock(&battery->lock);
	status = acpi_evaluate_object(battery->device->handle, "_BST",
				      NULL, &buffer);
	mutex_unlock(&battery->lock);

	if (ACPI_FAILURE(status)) {
		ACPI_EXCEPTION((AE_INFO, status, "Evaluating _BST"));
		return -ENODEV;
	}

	result = extract_package(battery, buffer.pointer,
				 state_offsets, ARRAY_SIZE(state_offsets));
	battery->update_time = jiffies;
	kfree(buffer.pointer);

	/* For buggy DSDTs that report negative 16-bit values for either
	 * charging or discharging current and/or report 0 as 65536
	 * due to bad math.
	 */
	if (battery->power_unit == ACPI_BATTERY_POWER_UNIT_MA &&
		battery->rate_now != ACPI_BATTERY_VALUE_UNKNOWN &&
		(s16)(battery->rate_now) < 0) {
		battery->rate_now = abs((s16)battery->rate_now);
		printk_once(KERN_WARNING FW_BUG "battery: (dis)charge rate"
			" invalid.\n");
	}

	if (test_bit(ACPI_BATTERY_QUIRK_PERCENTAGE_CAPACITY, &battery->flags)
	    && battery->capacity_now >= 0 && battery->capacity_now <= 100)
		battery->capacity_now = (battery->capacity_now *
				battery->full_charge_capacity) / 100;
	if (test_bit(ACPI_BATTERY_QUIRK_THINKPAD_MAH, &battery->flags) &&
	    battery->power_unit && battery->design_voltage) {
		battery->capacity_now = battery->capacity_now *
		    10000 / battery->design_voltage;
	}
	return result;
}

static int acpi_battery_set_alarm(struct acpi_battery *battery)
{
	acpi_status status = 0;

	if (!acpi_battery_present(battery) ||
	    !test_bit(ACPI_BATTERY_ALARM_PRESENT, &battery->flags))
		return -ENODEV;

	mutex_lock(&battery->lock);
	status = acpi_execute_simple_method(battery->device->handle, "_BTP",
					    battery->alarm);
	mutex_unlock(&battery->lock);

	if (ACPI_FAILURE(status))
		return -ENODEV;

	ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Alarm set to %d\n", battery->alarm));
	return 0;
}

static int acpi_battery_init_alarm(struct acpi_battery *battery)
{
	/* See if alarms are supported, and if so, set default */
	if (!acpi_has_method(battery->device->handle, "_BTP")) {
		clear_bit(ACPI_BATTERY_ALARM_PRESENT, &battery->flags);
		return 0;
	}
	set_bit(ACPI_BATTERY_ALARM_PRESENT, &battery->flags);
	if (!battery->alarm)
		battery->alarm = battery->design_capacity_warning;
	return acpi_battery_set_alarm(battery);
}

static ssize_t acpi_battery_alarm_show(struct device *dev,
					struct device_attribute *attr,
					char *buf)
{
	struct acpi_battery *battery = to_acpi_battery(dev_get_drvdata(dev));
	return sprintf(buf, "%d\n", battery->alarm * 1000);
}

static ssize_t acpi_battery_alarm_store(struct device *dev,
					struct device_attribute *attr,
					const char *buf, size_t count)
{
	unsigned long x;
	struct acpi_battery *battery = to_acpi_battery(dev_get_drvdata(dev));
	if (sscanf(buf, "%ld\n", &x) == 1)
		battery->alarm = x/1000;
	if (acpi_battery_present(battery))
		acpi_battery_set_alarm(battery);
	return count;
}

static struct device_attribute alarm_attr = {
	.attr = {.name = "alarm", .mode = 0644},
	.show = acpi_battery_alarm_show,
	.store = acpi_battery_alarm_store,
};

static int sysfs_add_battery(struct acpi_battery *battery)
{
	int result;

	if (battery->power_unit == ACPI_BATTERY_POWER_UNIT_MA) {
		battery->bat.properties = charge_battery_props;
		battery->bat.num_properties =
			ARRAY_SIZE(charge_battery_props);
	} else {
		battery->bat.properties = energy_battery_props;
		battery->bat.num_properties =
			ARRAY_SIZE(energy_battery_props);
	}

	battery->bat.name = acpi_device_bid(battery->device);
	battery->bat.type = POWER_SUPPLY_TYPE_BATTERY;
	battery->bat.get_property = acpi_battery_get_property;

	result = power_supply_register(&battery->device->dev, &battery->bat);
	if (result)
		return result;
	return device_create_file(battery->bat.dev, &alarm_attr);
}

static void sysfs_remove_battery(struct acpi_battery *battery)
{
	mutex_lock(&battery->sysfs_lock);
	if (!battery->bat.dev) {
		mutex_unlock(&battery->sysfs_lock);
		return;
	}

	device_remove_file(battery->bat.dev, &alarm_attr);
	power_supply_unregister(&battery->bat);
	battery->bat.dev = NULL;
	mutex_unlock(&battery->sysfs_lock);
}

static void find_battery(const struct dmi_header *dm, void *private)
{
	struct acpi_battery *battery = (struct acpi_battery *)private;
	/* Note: the hardcoded offsets below have been extracted from
	   the source code of dmidecode.  */
	if (dm->type == DMI_ENTRY_PORTABLE_BATTERY && dm->length >= 8) {
		const u8 *dmi_data = (const u8 *)(dm + 1);
		int dmi_capacity = get_unaligned((const u16 *)(dmi_data + 6));
		if (dm->length >= 18)
			dmi_capacity *= dmi_data[17];
		if (battery->design_capacity * battery->design_voltage / 1000
		    != dmi_capacity &&
		    battery->design_capacity * 10 == dmi_capacity)
			set_bit(ACPI_BATTERY_QUIRK_THINKPAD_MAH,
				&battery->flags);
	}
}

/*
 * According to the ACPI spec, some kinds of primary batteries can
 * report percentage battery remaining capacity directly to OS.
 * In this case, it reports the Last Full Charged Capacity == 100
 * and BatteryPresentRate == 0xFFFFFFFF.
 *
 * Now we found some battery reports percentage remaining capacity
 * even if it's rechargeable.
 * https://bugzilla.kernel.org/show_bug.cgi?id=15979
 *
 * Handle this correctly so that they won't break userspace.
 */
static void acpi_battery_quirks(struct acpi_battery *battery)
{
	if (test_bit(ACPI_BATTERY_QUIRK_PERCENTAGE_CAPACITY, &battery->flags))
		return;

	if (battery->full_charge_capacity == 100 &&
		battery->rate_now == ACPI_BATTERY_VALUE_UNKNOWN &&
		battery->capacity_now >= 0 && battery->capacity_now <= 100) {
		set_bit(ACPI_BATTERY_QUIRK_PERCENTAGE_CAPACITY, &battery->flags);
		battery->full_charge_capacity = battery->design_capacity;
		battery->capacity_now = (battery->capacity_now *
				battery->full_charge_capacity) / 100;
	}

	if (test_bit(ACPI_BATTERY_QUIRK_THINKPAD_MAH, &battery->flags))
		return;

	if (battery->power_unit && dmi_name_in_vendors("LENOVO")) {
		const char *s;
		s = dmi_get_system_info(DMI_PRODUCT_VERSION);
		if (s && !strnicmp(s, "ThinkPad", 8)) {
			dmi_walk(find_battery, battery);
			if (test_bit(ACPI_BATTERY_QUIRK_THINKPAD_MAH,
				     &battery->flags) &&
			    battery->design_voltage) {
				battery->design_capacity =
				    battery->design_capacity *
				    10000 / battery->design_voltage;
				battery->full_charge_capacity =
				    battery->full_charge_capacity *
				    10000 / battery->design_voltage;
				battery->design_capacity_warning =
				    battery->design_capacity_warning *
				    10000 / battery->design_voltage;
				battery->capacity_now = battery->capacity_now *
				    10000 / battery->design_voltage;
			}
		}
	}
}

static int acpi_battery_update(struct acpi_battery *battery)
{
	int result, old_present = acpi_battery_present(battery);
	result = acpi_battery_get_status(battery);
	if (result)
		return result;
	if (!acpi_battery_present(battery)) {
		sysfs_remove_battery(battery);
		battery->update_time = 0;
		return 0;
	}
	if (!battery->update_time ||
	    old_present != acpi_battery_present(battery)) {
		result = acpi_battery_get_info(battery);
		if (result)
			return result;
		acpi_battery_init_alarm(battery);
	}
	if (!battery->bat.dev) {
		result = sysfs_add_battery(battery);
		if (result)
			return result;
	}
	result = acpi_battery_get_state(battery);
	acpi_battery_quirks(battery);
	return result;
}

static void acpi_battery_refresh(struct acpi_battery *battery)
{
	int power_unit;

	if (!battery->bat.dev)
		return;

	power_unit = battery->power_unit;

	acpi_battery_get_info(battery);

	if (power_unit == battery->power_unit)
		return;

	/* The battery has changed its reporting units. */
	sysfs_remove_battery(battery);
	sysfs_add_battery(battery);
}

/* --------------------------------------------------------------------------
                                 Driver Interface
   -------------------------------------------------------------------------- */

static void acpi_battery_notify(struct acpi_device *device, u32 event)
{
	struct acpi_battery *battery = acpi_driver_data(device);
	struct device *old;

	if (!battery)
		return;
	old = battery->bat.dev;
	if (event == ACPI_BATTERY_NOTIFY_INFO)
		acpi_battery_refresh(battery);
	acpi_battery_update(battery);
	acpi_bus_generate_netlink_event(device->pnp.device_class,
					dev_name(&device->dev), event,
					acpi_battery_present(battery));
	/* acpi_battery_update could remove power_supply object */
	if (old && battery->bat.dev)
		power_supply_changed(&battery->bat);
}

static int battery_notify(struct notifier_block *nb,
			       unsigned long mode, void *_unused)
{
	struct acpi_battery *battery = container_of(nb, struct acpi_battery,
						    pm_nb);
	switch (mode) {
	case PM_POST_HIBERNATION:
	case PM_POST_SUSPEND:
		if (battery->bat.dev) {
			sysfs_remove_battery(battery);
			sysfs_add_battery(battery);
		}
		break;
	}

	return 0;
}

static int acpi_battery_add(struct acpi_device *device)
{
	int result = 0;
	struct acpi_battery *battery = NULL;

	if (!device)
		return -EINVAL;
	battery = kzalloc(sizeof(struct acpi_battery), GFP_KERNEL);
	if (!battery)
		return -ENOMEM;
	battery->device = device;
	strcpy(acpi_device_name(device), ACPI_BATTERY_DEVICE_NAME);
	strcpy(acpi_device_class(device), ACPI_BATTERY_CLASS);
	device->driver_data = battery;
	mutex_init(&battery->lock);
	mutex_init(&battery->sysfs_lock);
	if (acpi_has_method(battery->device->handle, "_BIX"))
		set_bit(ACPI_BATTERY_XINFO_PRESENT, &battery->flags);
	result = acpi_battery_update(battery);
	if (result)
		goto fail;

	printk(KERN_INFO PREFIX "%s Slot [%s] (battery %s)\n",
		ACPI_BATTERY_DEVICE_NAME, acpi_device_bid(device),
		device->status.battery_present ? "present" : "absent");

	battery->pm_nb.notifier_call = battery_notify;
	register_pm_notifier(&battery->pm_nb);

	return result;

fail:
	sysfs_remove_battery(battery);
	mutex_destroy(&battery->lock);
	mutex_destroy(&battery->sysfs_lock);
	kfree(battery);
	return result;
}

static int acpi_battery_remove(struct acpi_device *device)
{
	struct acpi_battery *battery = NULL;

	if (!device || !acpi_driver_data(device))
		return -EINVAL;
	battery = acpi_driver_data(device);
	unregister_pm_notifier(&battery->pm_nb);
	sysfs_remove_battery(battery);
	mutex_destroy(&battery->lock);
	mutex_destroy(&battery->sysfs_lock);
	kfree(battery);
	return 0;
}

#ifdef CONFIG_PM_SLEEP
/* this is needed to learn about changes made in suspended state */
static int acpi_battery_resume(struct device *dev)
{
	struct acpi_battery *battery;

	if (!dev)
		return -EINVAL;

	battery = acpi_driver_data(to_acpi_device(dev));
	if (!battery)
		return -EINVAL;

	battery->update_time = 0;
	acpi_battery_update(battery);
	return 0;
}
#endif

static SIMPLE_DEV_PM_OPS(acpi_battery_pm, NULL, acpi_battery_resume);

static struct acpi_driver acpi_battery_driver = {
	.name = "battery",
	.class = ACPI_BATTERY_CLASS,
	.ids = battery_device_ids,
	.flags = ACPI_DRIVER_ALL_NOTIFY_EVENTS,
	.ops = {
		.add = acpi_battery_add,
		.remove = acpi_battery_remove,
		.notify = acpi_battery_notify,
		},
	.drv.pm = &acpi_battery_pm,
};

static void __init acpi_battery_init_async(void *unused, async_cookie_t cookie)
{
	if (acpi_disabled)
		return;
	acpi_bus_register_driver(&acpi_battery_driver);
}

static int __init acpi_battery_init(void)
{
	async_schedule(acpi_battery_init_async, NULL);
	return 0;
}

static void __exit acpi_battery_exit(void)
{
	acpi_bus_unregister_driver(&acpi_battery_driver);
}

module_init(acpi_battery_init);
module_exit(acpi_battery_exit);