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[linux-2.6.git] / drivers / power / bq27x00_battery.c

/*
 * BQ27x00 battery driver
 *
 * Copyright (C) 2008 Rodolfo Giometti <giometti@linux.it>
 * Copyright (C) 2008 Eurotech S.p.A. <info@eurotech.it>
 * Copyright (C) 2010-2011 Lars-Peter Clausen <lars@metafoo.de>
 * Copyright (C) 2011 Pali Rohár <pali.rohar@gmail.com>
 *
 * Based on a previous work by Copyright (C) 2008 Texas Instruments, Inc.
 *
 * This package 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.
 *
 * THIS PACKAGE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 */

/*
 * Datasheets:
 * http://focus.ti.com/docs/prod/folders/print/bq27000.html
 * http://focus.ti.com/docs/prod/folders/print/bq27500.html
 */

#include <linux/module.h>
#include <linux/param.h>
#include <linux/jiffies.h>
#include <linux/workqueue.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/power_supply.h>
#include <linux/idr.h>
#include <linux/i2c.h>
#include <linux/slab.h>
#include <asm/unaligned.h>

#include <linux/power/bq27x00_battery.h>

#define DRIVER_VERSION                  "1.2.0"

#define BQ27x00_REG_TEMP                0x06
#define BQ27x00_REG_VOLT                0x08
#define BQ27x00_REG_AI                  0x14
#define BQ27x00_REG_FLAGS               0x0A
#define BQ27x00_REG_TTE                 0x16
#define BQ27x00_REG_TTF                 0x18
#define BQ27x00_REG_TTECP               0x26
#define BQ27x00_REG_NAC                 0x0C /* Nominal available capacity */
#define BQ27x00_REG_LMD                 0x12 /* Last measured discharge */
#define BQ27x00_REG_CYCT                0x2A /* Cycle count total */
#define BQ27x00_REG_AE                  0x22 /* Available energy */

#define BQ27000_REG_RSOC                0x0B /* Relative State-of-Charge */
#define BQ27000_REG_ILMD                0x76 /* Initial last measured discharge */
#define BQ27000_FLAG_EDVF               BIT(0) /* Final End-of-Discharge-Voltage flag */
#define BQ27000_FLAG_EDV1               BIT(1) /* First End-of-Discharge-Voltage flag */
#define BQ27000_FLAG_CI                 BIT(4) /* Capacity Inaccurate flag */
#define BQ27000_FLAG_FC                 BIT(5)
#define BQ27000_FLAG_CHGS               BIT(7) /* Charge state flag */

#define BQ27500_REG_SOC                 0x2C
#define BQ27500_REG_DCAP                0x3C /* Design capacity */
#define BQ27500_FLAG_DSC                BIT(0)
#define BQ27500_FLAG_SOCF               BIT(1) /* State-of-Charge threshold final */
#define BQ27500_FLAG_SOC1               BIT(2) /* State-of-Charge threshold 1 */
#define BQ27500_FLAG_FC                 BIT(9)

#define BQ27000_RS                      20 /* Resistor sense */

struct bq27x00_device_info;
struct bq27x00_access_methods {
        int (*read)(struct bq27x00_device_info *di, u8 reg, bool single);
};

enum bq27x00_chip { BQ27000, BQ27500 };

struct bq27x00_reg_cache {
        int temperature;
        int time_to_empty;
        int time_to_empty_avg;
        int time_to_full;
        int charge_full;
        int cycle_count;
        int capacity;
        int energy;
        int flags;
};

struct bq27x00_device_info {
        struct device           *dev;
        int                     id;
        enum bq27x00_chip       chip;

        struct bq27x00_reg_cache cache;
        int charge_design_full;

        unsigned long last_update;
        struct delayed_work work;

        struct power_supply     bat;

        struct bq27x00_access_methods bus;

        struct mutex lock;
};

static enum power_supply_property bq27x00_battery_props[] = {
        POWER_SUPPLY_PROP_STATUS,
        POWER_SUPPLY_PROP_PRESENT,
        POWER_SUPPLY_PROP_VOLTAGE_NOW,
        POWER_SUPPLY_PROP_CURRENT_NOW,
        POWER_SUPPLY_PROP_CAPACITY,
        POWER_SUPPLY_PROP_CAPACITY_LEVEL,
        POWER_SUPPLY_PROP_TEMP,
        POWER_SUPPLY_PROP_TIME_TO_EMPTY_NOW,
        POWER_SUPPLY_PROP_TIME_TO_EMPTY_AVG,
        POWER_SUPPLY_PROP_TIME_TO_FULL_NOW,
        POWER_SUPPLY_PROP_TECHNOLOGY,
        POWER_SUPPLY_PROP_CHARGE_FULL,
        POWER_SUPPLY_PROP_CHARGE_NOW,
        POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN,
        POWER_SUPPLY_PROP_CYCLE_COUNT,
        POWER_SUPPLY_PROP_ENERGY_NOW,
};

static unsigned int poll_interval = 360;
module_param(poll_interval, uint, 0644);
MODULE_PARM_DESC(poll_interval, "battery poll interval in seconds - " \
                                "0 disables polling");

/*
 * Common code for BQ27x00 devices
 */

static inline int bq27x00_read(struct bq27x00_device_info *di, u8 reg,
                bool single)
{
        return di->bus.read(di, reg, single);
}

/*
 * Return the battery Relative State-of-Charge
 * Or < 0 if something fails.
 */
static int bq27x00_battery_read_rsoc(struct bq27x00_device_info *di)
{
        int rsoc;

        if (di->chip == BQ27500)
                rsoc = bq27x00_read(di, BQ27500_REG_SOC, false);
        else
                rsoc = bq27x00_read(di, BQ27000_REG_RSOC, true);

        if (rsoc < 0)
                dev_dbg(di->dev, "error reading relative State-of-Charge\n");

        return rsoc;
}

/*
 * Return a battery charge value in µAh
 * Or < 0 if something fails.
 */
static int bq27x00_battery_read_charge(struct bq27x00_device_info *di, u8 reg)
{
        int charge;

        charge = bq27x00_read(di, reg, false);
        if (charge < 0) {
                dev_dbg(di->dev, "error reading charge register %02x: %d\n",
                        reg, charge);
                return charge;
        }

        if (di->chip == BQ27500)
                charge *= 1000;
        else
                charge = charge * 3570 / BQ27000_RS;

        return charge;
}

/*
 * Return the battery Nominal available capaciy in µAh
 * Or < 0 if something fails.
 */
static inline int bq27x00_battery_read_nac(struct bq27x00_device_info *di)
{
        return bq27x00_battery_read_charge(di, BQ27x00_REG_NAC);
}

/*
 * Return the battery Last measured discharge in µAh
 * Or < 0 if something fails.
 */
static inline int bq27x00_battery_read_lmd(struct bq27x00_device_info *di)
{
        return bq27x00_battery_read_charge(di, BQ27x00_REG_LMD);
}

/*
 * Return the battery Initial last measured discharge in µAh
 * Or < 0 if something fails.
 */
static int bq27x00_battery_read_ilmd(struct bq27x00_device_info *di)
{
        int ilmd;

        if (di->chip == BQ27500)
                ilmd = bq27x00_read(di, BQ27500_REG_DCAP, false);
        else
                ilmd = bq27x00_read(di, BQ27000_REG_ILMD, true);

        if (ilmd < 0) {
                dev_dbg(di->dev, "error reading initial last measured discharge\n");
                return ilmd;
        }

        if (di->chip == BQ27500)
                ilmd *= 1000;
        else
                ilmd = ilmd * 256 * 3570 / BQ27000_RS;

        return ilmd;
}

/*
 * Return the battery Available energy in µWh
 * Or < 0 if something fails.
 */
static int bq27x00_battery_read_energy(struct bq27x00_device_info *di)
{
        int ae;

        ae = bq27x00_read(di, BQ27x00_REG_AE, false);
        if (ae < 0) {
                dev_dbg(di->dev, "error reading available energy\n");
                return ae;
        }

        if (di->chip == BQ27500)
                ae *= 1000;
        else
                ae = ae * 29200 / BQ27000_RS;

        return ae;
}

/*
 * Return the battery temperature in tenths of degree Celsius
 * Or < 0 if something fails.
 */
static int bq27x00_battery_read_temperature(struct bq27x00_device_info *di)
{
        int temp;

        temp = bq27x00_read(di, BQ27x00_REG_TEMP, false);
        if (temp < 0) {
                dev_err(di->dev, "error reading temperature\n");
                return temp;
        }

        if (di->chip == BQ27500)
                temp -= 2731;
        else
                temp = ((temp * 5) - 5463) / 2;

        return temp;
}

/*
 * Return the battery Cycle count total
 * Or < 0 if something fails.
 */
static int bq27x00_battery_read_cyct(struct bq27x00_device_info *di)
{
        int cyct;

        cyct = bq27x00_read(di, BQ27x00_REG_CYCT, false);
        if (cyct < 0)
                dev_err(di->dev, "error reading cycle count total\n");

        return cyct;
}

/*
 * Read a time register.
 * Return < 0 if something fails.
 */
static int bq27x00_battery_read_time(struct bq27x00_device_info *di, u8 reg)
{
        int tval;

        tval = bq27x00_read(di, reg, false);
        if (tval < 0) {
                dev_dbg(di->dev, "error reading time register %02x: %d\n",
                        reg, tval);
                return tval;
        }

        if (tval == 65535)
                return -ENODATA;

        return tval * 60;
}

static void bq27x00_update(struct bq27x00_device_info *di)
{
        struct bq27x00_reg_cache cache = {0, };
        bool is_bq27500 = di->chip == BQ27500;

        cache.flags = bq27x00_read(di, BQ27x00_REG_FLAGS, !is_bq27500);
        if (cache.flags >= 0) {
                if (!is_bq27500 && (cache.flags & BQ27000_FLAG_CI)) {
                        dev_info(di->dev, "battery is not calibrated! ignoring capacity values\n");
                        cache.capacity = -ENODATA;
                        cache.energy = -ENODATA;
                        cache.time_to_empty = -ENODATA;
                        cache.time_to_empty_avg = -ENODATA;
                        cache.time_to_full = -ENODATA;
                        cache.charge_full = -ENODATA;
                } else {
                        cache.capacity = bq27x00_battery_read_rsoc(di);
                        cache.energy = bq27x00_battery_read_energy(di);
                        cache.time_to_empty = bq27x00_battery_read_time(di, BQ27x00_REG_TTE);
                        cache.time_to_empty_avg = bq27x00_battery_read_time(di, BQ27x00_REG_TTECP);
                        cache.time_to_full = bq27x00_battery_read_time(di, BQ27x00_REG_TTF);
                        cache.charge_full = bq27x00_battery_read_lmd(di);
                }
                cache.temperature = bq27x00_battery_read_temperature(di);
                cache.cycle_count = bq27x00_battery_read_cyct(di);

                /* We only have to read charge design full once */
                if (di->charge_design_full <= 0)
                        di->charge_design_full = bq27x00_battery_read_ilmd(di);
        }

        if (memcmp(&di->cache, &cache, sizeof(cache)) != 0) {
                di->cache = cache;
                power_supply_changed(&di->bat);
        }

        di->last_update = jiffies;
}

static void bq27x00_battery_poll(struct work_struct *work)
{
        struct bq27x00_device_info *di =
                container_of(work, struct bq27x00_device_info, work.work);

        bq27x00_update(di);

        if (poll_interval > 0) {
                /* The timer does not have to be accurate. */
                set_timer_slack(&di->work.timer, poll_interval * HZ / 4);
                schedule_delayed_work(&di->work, poll_interval * HZ);
        }
}

/*
 * Return the battery average current in µA
 * Note that current can be negative signed as well
 * Or 0 if something fails.
 */
static int bq27x00_battery_current(struct bq27x00_device_info *di,
        union power_supply_propval *val)
{
        int curr;
        int flags;

        curr = bq27x00_read(di, BQ27x00_REG_AI, false);
        if (curr < 0) {
                dev_err(di->dev, "error reading current\n");
                return curr;
        }

        if (di->chip == BQ27500) {
                /* bq27500 returns signed value */
                val->intval = (int)((s16)curr) * 1000;
        } else {
                flags = bq27x00_read(di, BQ27x00_REG_FLAGS, false);
                if (flags & BQ27000_FLAG_CHGS) {
                        dev_dbg(di->dev, "negative current!\n");
                        curr = -curr;
                }

                val->intval = curr * 3570 / BQ27000_RS;
        }

        return 0;
}

static int bq27x00_battery_status(struct bq27x00_device_info *di,
        union power_supply_propval *val)
{
        int status;

        if (di->chip == BQ27500) {
                if (di->cache.flags & BQ27500_FLAG_FC)
                        status = POWER_SUPPLY_STATUS_FULL;
                else if (di->cache.flags & BQ27500_FLAG_DSC)
                        status = POWER_SUPPLY_STATUS_DISCHARGING;
                else
                        status = POWER_SUPPLY_STATUS_CHARGING;
        } else {
                if (di->cache.flags & BQ27000_FLAG_FC)
                        status = POWER_SUPPLY_STATUS_FULL;
                else if (di->cache.flags & BQ27000_FLAG_CHGS)
                        status = POWER_SUPPLY_STATUS_CHARGING;
                else if (power_supply_am_i_supplied(&di->bat))
                        status = POWER_SUPPLY_STATUS_NOT_CHARGING;
                else
                        status = POWER_SUPPLY_STATUS_DISCHARGING;
        }

        val->intval = status;

        return 0;
}

static int bq27x00_battery_capacity_level(struct bq27x00_device_info *di,
        union power_supply_propval *val)
{
        int level;

        if (di->chip == BQ27500) {
                if (di->cache.flags & BQ27500_FLAG_FC)
                        level = POWER_SUPPLY_CAPACITY_LEVEL_FULL;
                else if (di->cache.flags & BQ27500_FLAG_SOC1)
                        level = POWER_SUPPLY_CAPACITY_LEVEL_LOW;
                else if (di->cache.flags & BQ27500_FLAG_SOCF)
                        level = POWER_SUPPLY_CAPACITY_LEVEL_CRITICAL;
                else
                        level = POWER_SUPPLY_CAPACITY_LEVEL_NORMAL;
        } else {
                if (di->cache.flags & BQ27000_FLAG_FC)
                        level = POWER_SUPPLY_CAPACITY_LEVEL_FULL;
                else if (di->cache.flags & BQ27000_FLAG_EDV1)
                        level = POWER_SUPPLY_CAPACITY_LEVEL_LOW;
                else if (di->cache.flags & BQ27000_FLAG_EDVF)
                        level = POWER_SUPPLY_CAPACITY_LEVEL_CRITICAL;
                else
                        level = POWER_SUPPLY_CAPACITY_LEVEL_NORMAL;
        }

        val->intval = level;

        return 0;
}

/*
 * Return the battery Voltage in millivolts
 * Or < 0 if something fails.
 */
static int bq27x00_battery_voltage(struct bq27x00_device_info *di,
        union power_supply_propval *val)
{
        int volt;

        volt = bq27x00_read(di, BQ27x00_REG_VOLT, false);
        if (volt < 0) {
                dev_err(di->dev, "error reading voltage\n");
                return volt;
        }

        val->intval = volt * 1000;

        return 0;
}

static int bq27x00_simple_value(int value,
        union power_supply_propval *val)
{
        if (value < 0)
                return value;

        val->intval = value;

        return 0;
}

#define to_bq27x00_device_info(x) container_of((x), \
                                struct bq27x00_device_info, bat);

static int bq27x00_battery_get_property(struct power_supply *psy,
                                        enum power_supply_property psp,
                                        union power_supply_propval *val)
{
        int ret = 0;
        struct bq27x00_device_info *di = to_bq27x00_device_info(psy);

        mutex_lock(&di->lock);
        if (time_is_before_jiffies(di->last_update + 5 * HZ)) {
                cancel_delayed_work_sync(&di->work);
                bq27x00_battery_poll(&di->work.work);
        }
        mutex_unlock(&di->lock);

        if (psp != POWER_SUPPLY_PROP_PRESENT && di->cache.flags < 0)
                return -ENODEV;

        switch (psp) {
        case POWER_SUPPLY_PROP_STATUS:
                ret = bq27x00_battery_status(di, val);
                break;
        case POWER_SUPPLY_PROP_VOLTAGE_NOW:
                ret = bq27x00_battery_voltage(di, val);
                break;
        case POWER_SUPPLY_PROP_PRESENT:
                val->intval = di->cache.flags < 0 ? 0 : 1;
                break;
        case POWER_SUPPLY_PROP_CURRENT_NOW:
                ret = bq27x00_battery_current(di, val);
                break;
        case POWER_SUPPLY_PROP_CAPACITY:
                ret = bq27x00_simple_value(di->cache.capacity, val);
                break;
        case POWER_SUPPLY_PROP_CAPACITY_LEVEL:
                ret = bq27x00_battery_capacity_level(di, val);
                break;
        case POWER_SUPPLY_PROP_TEMP:
                ret = bq27x00_simple_value(di->cache.temperature, val);
                break;
        case POWER_SUPPLY_PROP_TIME_TO_EMPTY_NOW:
                ret = bq27x00_simple_value(di->cache.time_to_empty, val);
                break;
        case POWER_SUPPLY_PROP_TIME_TO_EMPTY_AVG:
                ret = bq27x00_simple_value(di->cache.time_to_empty_avg, val);
                break;
        case POWER_SUPPLY_PROP_TIME_TO_FULL_NOW:
                ret = bq27x00_simple_value(di->cache.time_to_full, val);
                break;
        case POWER_SUPPLY_PROP_TECHNOLOGY:
                val->intval = POWER_SUPPLY_TECHNOLOGY_LION;
                break;
        case POWER_SUPPLY_PROP_CHARGE_NOW:
                ret = bq27x00_simple_value(bq27x00_battery_read_nac(di), val);
                break;
        case POWER_SUPPLY_PROP_CHARGE_FULL:
                ret = bq27x00_simple_value(di->cache.charge_full, val);
                break;
        case POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN:
                ret = bq27x00_simple_value(di->charge_design_full, val);
                break;
        case POWER_SUPPLY_PROP_CYCLE_COUNT:
                ret = bq27x00_simple_value(di->cache.cycle_count, val);
                break;
        case POWER_SUPPLY_PROP_ENERGY_NOW:
                ret = bq27x00_simple_value(di->cache.energy, val);
                break;
        default:
                return -EINVAL;
        }

        return ret;
}

static void bq27x00_external_power_changed(struct power_supply *psy)
{
        struct bq27x00_device_info *di = to_bq27x00_device_info(psy);

        cancel_delayed_work_sync(&di->work);
        schedule_delayed_work(&di->work, 0);
}

static int bq27x00_powersupply_init(struct bq27x00_device_info *di)
{
        int ret;

        di->bat.type = POWER_SUPPLY_TYPE_BATTERY;
        di->bat.properties = bq27x00_battery_props;
        di->bat.num_properties = ARRAY_SIZE(bq27x00_battery_props);
        di->bat.get_property = bq27x00_battery_get_property;
        di->bat.external_power_changed = bq27x00_external_power_changed;

        INIT_DELAYED_WORK(&di->work, bq27x00_battery_poll);
        mutex_init(&di->lock);

        ret = power_supply_register(di->dev, &di->bat);
        if (ret) {
                dev_err(di->dev, "failed to register battery: %d\n", ret);
                return ret;
        }

        dev_info(di->dev, "support ver. %s enabled\n", DRIVER_VERSION);

        bq27x00_update(di);

        return 0;
}

static void bq27x00_powersupply_unregister(struct bq27x00_device_info *di)
{
        /*
         * power_supply_unregister call bq27x00_battery_get_property which
         * call bq27x00_battery_poll.
         * Make sure that bq27x00_battery_poll will not call
         * schedule_delayed_work again after unregister (which cause OOPS).
         */
        poll_interval = 0;

        cancel_delayed_work_sync(&di->work);

        power_supply_unregister(&di->bat);

        mutex_destroy(&di->lock);
}


/* i2c specific code */
#ifdef CONFIG_BATTERY_BQ27X00_I2C

/* If the system has several batteries we need a different name for each
 * of them...
 */
static DEFINE_IDR(battery_id);
static DEFINE_MUTEX(battery_mutex);

static int bq27x00_read_i2c(struct bq27x00_device_info *di, u8 reg, bool single)
{
        struct i2c_client *client = to_i2c_client(di->dev);
        struct i2c_msg msg[2];
        unsigned char data[2];
        int ret;

        if (!client->adapter)
                return -ENODEV;

        msg[0].addr = client->addr;
        msg[0].flags = 0;
        msg[0].buf = &reg;
        msg[0].len = sizeof(reg);
        msg[1].addr = client->addr;
        msg[1].flags = I2C_M_RD;
        msg[1].buf = data;
        if (single)
                msg[1].len = 1;
        else
                msg[1].len = 2;

        ret = i2c_transfer(client->adapter, msg, ARRAY_SIZE(msg));
        if (ret < 0)
                return ret;

        if (!single)
                ret = get_unaligned_le16(data);
        else
                ret = data[0];

        return ret;
}

static int bq27x00_battery_probe(struct i2c_client *client,
                                 const struct i2c_device_id *id)
{
        char *name;
        struct bq27x00_device_info *di;
        int num;
        int retval = 0;

        /* Get new ID for the new battery device */
        retval = idr_pre_get(&battery_id, GFP_KERNEL);
        if (retval == 0)
                return -ENOMEM;
        mutex_lock(&battery_mutex);
        retval = idr_get_new(&battery_id, client, &num);
        mutex_unlock(&battery_mutex);
        if (retval < 0)
                return retval;

        name = kasprintf(GFP_KERNEL, "%s-%d", id->name, num);
        if (!name) {
                dev_err(&client->dev, "failed to allocate device name\n");
                retval = -ENOMEM;
                goto batt_failed_1;
        }

        di = kzalloc(sizeof(*di), GFP_KERNEL);
        if (!di) {
                dev_err(&client->dev, "failed to allocate device info data\n");
                retval = -ENOMEM;
                goto batt_failed_2;
        }

        di->id = num;
        di->dev = &client->dev;
        di->chip = id->driver_data;
        di->bat.name = name;
        di->bus.read = &bq27x00_read_i2c;

        if (bq27x00_powersupply_init(di))
                goto batt_failed_3;

        i2c_set_clientdata(client, di);

        return 0;

batt_failed_3:
        kfree(di);
batt_failed_2:
        kfree(name);
batt_failed_1:
        mutex_lock(&battery_mutex);
        idr_remove(&battery_id, num);
        mutex_unlock(&battery_mutex);

        return retval;
}

static int bq27x00_battery_remove(struct i2c_client *client)
{
        struct bq27x00_device_info *di = i2c_get_clientdata(client);

        bq27x00_powersupply_unregister(di);

        kfree(di->bat.name);

        mutex_lock(&battery_mutex);
        idr_remove(&battery_id, di->id);
        mutex_unlock(&battery_mutex);

        kfree(di);

        return 0;
}

static const struct i2c_device_id bq27x00_id[] = {
        { "bq27200", BQ27000 }, /* bq27200 is same as bq27000, but with i2c */
        { "bq27500", BQ27500 },
        {},
};
MODULE_DEVICE_TABLE(i2c, bq27x00_id);

static struct i2c_driver bq27x00_battery_driver = {
        .driver = {
                .name = "bq27x00-battery",
        },
        .probe = bq27x00_battery_probe,
        .remove = bq27x00_battery_remove,
        .id_table = bq27x00_id,
};

static inline int bq27x00_battery_i2c_init(void)
{
        int ret = i2c_add_driver(&bq27x00_battery_driver);
        if (ret)
                printk(KERN_ERR "Unable to register BQ27x00 i2c driver\n");

        return ret;
}

static inline void bq27x00_battery_i2c_exit(void)
{
        i2c_del_driver(&bq27x00_battery_driver);
}

#else

static inline int bq27x00_battery_i2c_init(void) { return 0; }
static inline void bq27x00_battery_i2c_exit(void) {};

#endif

/* platform specific code */
#ifdef CONFIG_BATTERY_BQ27X00_PLATFORM

static int bq27000_read_platform(struct bq27x00_device_info *di, u8 reg,
                        bool single)
{
        struct device *dev = di->dev;
        struct bq27000_platform_data *pdata = dev->platform_data;
        unsigned int timeout = 3;
        int upper, lower;
        int temp;

        if (!single) {
                /* Make sure the value has not changed in between reading the
                 * lower and the upper part */
                upper = pdata->read(dev, reg + 1);
                do {
                        temp = upper;
                        if (upper < 0)
                                return upper;

                        lower = pdata->read(dev, reg);
                        if (lower < 0)
                                return lower;

                        upper = pdata->read(dev, reg + 1);
                } while (temp != upper && --timeout);

                if (timeout == 0)
                        return -EIO;

                return (upper << 8) | lower;
        }

        return pdata->read(dev, reg);
}

static int __devinit bq27000_battery_probe(struct platform_device *pdev)
{
        struct bq27x00_device_info *di;
        struct bq27000_platform_data *pdata = pdev->dev.platform_data;
        int ret;

        if (!pdata) {
                dev_err(&pdev->dev, "no platform_data supplied\n");
                return -EINVAL;
        }

        if (!pdata->read) {
                dev_err(&pdev->dev, "no hdq read callback supplied\n");
                return -EINVAL;
        }

        di = kzalloc(sizeof(*di), GFP_KERNEL);
        if (!di) {
                dev_err(&pdev->dev, "failed to allocate device info data\n");
                return -ENOMEM;
        }

        platform_set_drvdata(pdev, di);

        di->dev = &pdev->dev;
        di->chip = BQ27000;

        di->bat.name = pdata->name ?: dev_name(&pdev->dev);
        di->bus.read = &bq27000_read_platform;

        ret = bq27x00_powersupply_init(di);
        if (ret)
                goto err_free;

        return 0;

err_free:
        platform_set_drvdata(pdev, NULL);
        kfree(di);

        return ret;
}

static int __devexit bq27000_battery_remove(struct platform_device *pdev)
{
        struct bq27x00_device_info *di = platform_get_drvdata(pdev);

        bq27x00_powersupply_unregister(di);

        platform_set_drvdata(pdev, NULL);
        kfree(di);

        return 0;
}

static struct platform_driver bq27000_battery_driver = {
        .probe  = bq27000_battery_probe,
        .remove = __devexit_p(bq27000_battery_remove),
        .driver = {
                .name = "bq27000-battery",
                .owner = THIS_MODULE,
        },
};

static inline int bq27x00_battery_platform_init(void)
{
        int ret = platform_driver_register(&bq27000_battery_driver);
        if (ret)
                printk(KERN_ERR "Unable to register BQ27000 platform driver\n");

        return ret;
}

static inline void bq27x00_battery_platform_exit(void)
{
        platform_driver_unregister(&bq27000_battery_driver);
}

#else

static inline int bq27x00_battery_platform_init(void) { return 0; }
static inline void bq27x00_battery_platform_exit(void) {};

#endif

/*
 * Module stuff
 */

static int __init bq27x00_battery_init(void)
{
        int ret;

        ret = bq27x00_battery_i2c_init();
        if (ret)
                return ret;

        ret = bq27x00_battery_platform_init();
        if (ret)
                bq27x00_battery_i2c_exit();

        return ret;
}
module_init(bq27x00_battery_init);

static void __exit bq27x00_battery_exit(void)
{
        bq27x00_battery_platform_exit();
        bq27x00_battery_i2c_exit();
}
module_exit(bq27x00_battery_exit);

MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
MODULE_DESCRIPTION("BQ27x00 battery monitor driver");
MODULE_LICENSE("GPL");