/*
 * max6650.c - Part of lm_sensors, Linux kernel modules for hardware
 *             monitoring.
 *
 * (C) 2007 by Hans J. Koch <hjk@linutronix.de>
 *
 * based on code written by John Morris <john.morris@spirentcom.com>
 * Copyright (c) 2003 Spirent Communications
 * and Claus Gindhart <claus.gindhart@kontron.com>
 *
 * This module has only been tested with the MAX6650 chip. It should
 * also work with the MAX6651. It does not distinguish max6650 and max6651
 * chips.
 *
 * The datasheet was last seen at:
 *
 *        http://pdfserv.maxim-ic.com/en/ds/MAX6650-MAX6651.pdf
 *
 * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/jiffies.h>
#include <linux/i2c.h>
#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>
#include <linux/err.h>

/*
 * Addresses to scan. There are four disjoint possibilities, by pin config.
 */

static const unsigned short normal_i2c[] = {0x1b, 0x1f, 0x48, 0x4b,
                                                I2C_CLIENT_END};

/*
 * Insmod parameters
 */

/* fan_voltage: 5=5V fan, 12=12V fan, 0=don't change */
static int fan_voltage;
/* prescaler: Possible values are 1, 2, 4, 8, 16 or 0 for don't change */
static int prescaler;
/* clock: The clock frequency of the chip the driver should assume */
static int clock = 254000;

module_param(fan_voltage, int, S_IRUGO);
module_param(prescaler, int, S_IRUGO);
module_param(clock, int, S_IRUGO);

I2C_CLIENT_INSMOD_1(max6650);

/*
 * MAX 6650/6651 registers
 */

#define MAX6650_REG_SPEED       0x00
#define MAX6650_REG_CONFIG      0x02
#define MAX6650_REG_GPIO_DEF    0x04
#define MAX6650_REG_DAC         0x06
#define MAX6650_REG_ALARM_EN    0x08
#define MAX6650_REG_ALARM       0x0A
#define MAX6650_REG_TACH0       0x0C
#define MAX6650_REG_TACH1       0x0E
#define MAX6650_REG_TACH2       0x10
#define MAX6650_REG_TACH3       0x12
#define MAX6650_REG_GPIO_STAT   0x14
#define MAX6650_REG_COUNT       0x16

/*
 * Config register bits
 */

#define MAX6650_CFG_V12                 0x08
#define MAX6650_CFG_PRESCALER_MASK      0x07
#define MAX6650_CFG_PRESCALER_2         0x01
#define MAX6650_CFG_PRESCALER_4         0x02
#define MAX6650_CFG_PRESCALER_8         0x03
#define MAX6650_CFG_PRESCALER_16        0x04
#define MAX6650_CFG_MODE_MASK           0x30
#define MAX6650_CFG_MODE_ON             0x00
#define MAX6650_CFG_MODE_OFF            0x10
#define MAX6650_CFG_MODE_CLOSED_LOOP    0x20
#define MAX6650_CFG_MODE_OPEN_LOOP      0x30
#define MAX6650_COUNT_MASK              0x03

/*
 * Alarm status register bits
 */

#define MAX6650_ALRM_MAX        0x01
#define MAX6650_ALRM_MIN        0x02
#define MAX6650_ALRM_TACH       0x04
#define MAX6650_ALRM_GPIO1      0x08
#define MAX6650_ALRM_GPIO2      0x10

/* Minimum and maximum values of the FAN-RPM */
#define FAN_RPM_MIN 240
#define FAN_RPM_MAX 30000

#define DIV_FROM_REG(reg) (1 << (reg & 7))

static int max6650_probe(struct i2c_client *client,
                         const struct i2c_device_id *id);
static int max6650_detect(struct i2c_client *client, int kind,
                          struct i2c_board_info *info);
static int max6650_init_client(struct i2c_client *client);
static int max6650_remove(struct i2c_client *client);
static struct max6650_data *max6650_update_device(struct device *dev);

/*
 * Driver data (common to all clients)
 */

static const struct i2c_device_id max6650_id[] = {
        { "max6650", max6650 },
        { }
};
MODULE_DEVICE_TABLE(i2c, max6650_id);

static struct i2c_driver max6650_driver = {
        .class          = I2C_CLASS_HWMON,
        .driver = {
                .name   = "max6650",
        },
        .probe          = max6650_probe,
        .remove         = max6650_remove,
        .id_table       = max6650_id,
        .detect         = max6650_detect,
        .address_data   = &addr_data,
};

/*
 * Client data (each client gets its own)
 */

struct max6650_data
{
        struct device *hwmon_dev;
        struct mutex update_lock;
        char valid; /* zero until following fields are valid */
        unsigned long last_updated; /* in jiffies */

        /* register values */
        u8 speed;
        u8 config;
        u8 tach[4];
        u8 count;
        u8 dac;
        u8 alarm;
};

static ssize_t get_fan(struct device *dev, struct device_attribute *devattr,
                       char *buf)
{
        struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
        struct max6650_data *data = max6650_update_device(dev);
        int rpm;

        /*
        * Calculation details:
        *
        * Each tachometer counts over an interval given by the "count"
        * register (0.25, 0.5, 1 or 2 seconds). This module assumes
        * that the fans produce two pulses per revolution (this seems
        * to be the most common).
        */

        rpm = ((data->tach[attr->index] * 120) / DIV_FROM_REG(data->count));
        return sprintf(buf, "%d\n", rpm);
}

/*
 * Set the fan speed to the specified RPM (or read back the RPM setting).
 * This works in closed loop mode only. Use pwm1 for open loop speed setting.
 *
 * The MAX6650/1 will automatically control fan speed when in closed loop
 * mode.
 *
 * Assumptions:
 *
 * 1) The MAX6650/1 internal 254kHz clock frequency is set correctly. Use
 *    the clock module parameter if you need to fine tune this.
 *
 * 2) The prescaler (low three bits of the config register) has already
 *    been set to an appropriate value. Use the prescaler module parameter
 *    if your BIOS doesn't initialize the chip properly.
 *
 * The relevant equations are given on pages 21 and 22 of the datasheet.
 *
 * From the datasheet, the relevant equation when in regulation is:
 *
 *    [fCLK / (128 x (KTACH + 1))] = 2 x FanSpeed / KSCALE
 *
 * where:
 *
 *    fCLK is the oscillator frequency (either the 254kHz internal
 *         oscillator or the externally applied clock)
 *
 *    KTACH is the value in the speed register
 *
 *    FanSpeed is the speed of the fan in rps
 *
 *    KSCALE is the prescaler value (1, 2, 4, 8, or 16)
 *
 * When reading, we need to solve for FanSpeed. When writing, we need to
 * solve for KTACH.
 *
 * Note: this tachometer is completely separate from the tachometers
 * used to measure the fan speeds. Only one fan's speed (fan1) is
 * controlled.
 */

static ssize_t get_target(struct device *dev, struct device_attribute *devattr,
                         char *buf)
{
        struct max6650_data *data = max6650_update_device(dev);
        int kscale, ktach, rpm;

        /*
        * Use the datasheet equation:
        *
        *    FanSpeed = KSCALE x fCLK / [256 x (KTACH + 1)]
        *
        * then multiply by 60 to give rpm.
        */

        kscale = DIV_FROM_REG(data->config);
        ktach = data->speed;
        rpm = 60 * kscale * clock / (256 * (ktach + 1));
        return sprintf(buf, "%d\n", rpm);
}

static ssize_t set_target(struct device *dev, struct device_attribute *devattr,
                         const char *buf, size_t count)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct max6650_data *data = i2c_get_clientdata(client);
        int rpm = simple_strtoul(buf, NULL, 10);
        int kscale, ktach;

        rpm = SENSORS_LIMIT(rpm, FAN_RPM_MIN, FAN_RPM_MAX);

        /*
        * Divide the required speed by 60 to get from rpm to rps, then
        * use the datasheet equation:
        *
        *     KTACH = [(fCLK x KSCALE) / (256 x FanSpeed)] - 1
        */

        mutex_lock(&data->update_lock);

        kscale = DIV_FROM_REG(data->config);
        ktach = ((clock * kscale) / (256 * rpm / 60)) - 1;
        if (ktach < 0)
                ktach = 0;
        if (ktach > 255)
                ktach = 255;
        data->speed = ktach;

        i2c_smbus_write_byte_data(client, MAX6650_REG_SPEED, data->speed);

        mutex_unlock(&data->update_lock);

        return count;
}

/*
 * Get/set the fan speed in open loop mode using pwm1 sysfs file.
 * Speed is given as a relative value from 0 to 255, where 255 is maximum
 * speed. Note that this is done by writing directly to the chip's DAC,
 * it won't change the closed loop speed set by fan1_target.
 * Also note that due to rounding errors it is possible that you don't read
 * back exactly the value you have set.
 */

static ssize_t get_pwm(struct device *dev, struct device_attribute *devattr,
                       char *buf)
{
        int pwm;
        struct max6650_data *data = max6650_update_device(dev);

        /* Useful range for dac is 0-180 for 12V fans and 0-76 for 5V fans.
           Lower DAC values mean higher speeds. */
        if (data->config & MAX6650_CFG_V12)
                pwm = 255 - (255 * (int)data->dac)/180;
        else
                pwm = 255 - (255 * (int)data->dac)/76;

        if (pwm < 0)
                pwm = 0;

        return sprintf(buf, "%d\n", pwm);
}

static ssize_t set_pwm(struct device *dev, struct device_attribute *devattr,
                        const char *buf, size_t count)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct max6650_data *data = i2c_get_clientdata(client);
        int pwm = simple_strtoul(buf, NULL, 10);

        pwm = SENSORS_LIMIT(pwm, 0, 255);

        mutex_lock(&data->update_lock);

        if (data->config & MAX6650_CFG_V12)
                data->dac = 180 - (180 * pwm)/255;
        else
                data->dac = 76 - (76 * pwm)/255;

        i2c_smbus_write_byte_data(client, MAX6650_REG_DAC, data->dac);

        mutex_unlock(&data->update_lock);

        return count;
}

/*
 * Get/Set controller mode:
 * Possible values:
 * 0 = Fan always on
 * 1 = Open loop, Voltage is set according to speed, not regulated.
 * 2 = Closed loop, RPM for all fans regulated by fan1 tachometer
 */

static ssize_t get_enable(struct device *dev, struct device_attribute *devattr,
                          char *buf)
{
        struct max6650_data *data = max6650_update_device(dev);
        int mode = (data->config & MAX6650_CFG_MODE_MASK) >> 4;
        int sysfs_modes[4] = {0, 1, 2, 1};

        return sprintf(buf, "%d\n", sysfs_modes[mode]);
}

static ssize_t set_enable(struct device *dev, struct device_attribute *devattr,
                          const char *buf, size_t count)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct max6650_data *data = i2c_get_clientdata(client);
        int mode = simple_strtoul(buf, NULL, 10);
        int max6650_modes[3] = {0, 3, 2};

        if ((mode < 0)||(mode > 2)) {
                dev_err(&client->dev,
                        "illegal value for pwm1_enable (%d)\n", mode);
                return -EINVAL;
        }

        mutex_lock(&data->update_lock);

        data->config = i2c_smbus_read_byte_data(client, MAX6650_REG_CONFIG);
        data->config = (data->config & ~MAX6650_CFG_MODE_MASK)
                       | (max6650_modes[mode] << 4);

        i2c_smbus_write_byte_data(client, MAX6650_REG_CONFIG, data->config);

        mutex_unlock(&data->update_lock);

        return count;
}

/*
 * Read/write functions for fan1_div sysfs file. The MAX6650 has no such
 * divider. We handle this by converting between divider and counttime:
 *
 * (counttime == k) <==> (divider == 2^k), k = 0, 1, 2, or 3
 *
 * Lower values of k allow to connect a faster fan without the risk of
 * counter overflow. The price is lower resolution. You can also set counttime
 * using the module parameter. Note that the module parameter "prescaler" also
 * influences the behaviour. Unfortunately, there's no sysfs attribute
 * defined for that. See the data sheet for details.
 */

static ssize_t get_div(struct device *dev, struct device_attribute *devattr,
                       char *buf)
{
        struct max6650_data *data = max6650_update_device(dev);

        return sprintf(buf, "%d\n", DIV_FROM_REG(data->count));
}

static ssize_t set_div(struct device *dev, struct device_attribute *devattr,
                       const char *buf, size_t count)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct max6650_data *data = i2c_get_clientdata(client);
        int div = simple_strtoul(buf, NULL, 10);

        mutex_lock(&data->update_lock);
        switch (div) {
        case 1:
                data->count = 0;
                break;
        case 2:
                data->count = 1;
                break;
        case 4:
                data->count = 2;
                break;
        case 8:
                data->count = 3;
                break;
        default:
                mutex_unlock(&data->update_lock);
                dev_err(&client->dev,
                        "illegal value for fan divider (%d)\n", div);
                return -EINVAL;
        }

        i2c_smbus_write_byte_data(client, MAX6650_REG_COUNT, data->count);
        mutex_unlock(&data->update_lock);

        return count;
}

/*
 * Get alarm stati:
 * Possible values:
 * 0 = no alarm
 * 1 = alarm
 */

static ssize_t get_alarm(struct device *dev, struct device_attribute *devattr,
                         char *buf)
{
        struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
        struct max6650_data *data = max6650_update_device(dev);
        struct i2c_client *client = to_i2c_client(dev);
        int alarm = 0;

        if (data->alarm & attr->index) {
                mutex_lock(&data->update_lock);
                alarm = 1;
                data->alarm &= ~attr->index;
                data->alarm |= i2c_smbus_read_byte_data(client,
                                                        MAX6650_REG_ALARM);
                mutex_unlock(&data->update_lock);
        }

        return sprintf(buf, "%d\n", alarm);
}

static SENSOR_DEVICE_ATTR(fan1_input, S_IRUGO, get_fan, NULL, 0);
static SENSOR_DEVICE_ATTR(fan2_input, S_IRUGO, get_fan, NULL, 1);
static SENSOR_DEVICE_ATTR(fan3_input, S_IRUGO, get_fan, NULL, 2);
static SENSOR_DEVICE_ATTR(fan4_input, S_IRUGO, get_fan, NULL, 3);
static DEVICE_ATTR(fan1_target, S_IWUSR | S_IRUGO, get_target, set_target);
static DEVICE_ATTR(fan1_div, S_IWUSR | S_IRUGO, get_div, set_div);
static DEVICE_ATTR(pwm1_enable, S_IWUSR | S_IRUGO, get_enable, set_enable);
static DEVICE_ATTR(pwm1, S_IWUSR | S_IRUGO, get_pwm, set_pwm);
static SENSOR_DEVICE_ATTR(fan1_max_alarm, S_IRUGO, get_alarm, NULL,
                          MAX6650_ALRM_MAX);
static SENSOR_DEVICE_ATTR(fan1_min_alarm, S_IRUGO, get_alarm, NULL,
                          MAX6650_ALRM_MIN);
static SENSOR_DEVICE_ATTR(fan1_fault, S_IRUGO, get_alarm, NULL,
                          MAX6650_ALRM_TACH);
static SENSOR_DEVICE_ATTR(gpio1_alarm, S_IRUGO, get_alarm, NULL,
                          MAX6650_ALRM_GPIO1);
static SENSOR_DEVICE_ATTR(gpio2_alarm, S_IRUGO, get_alarm, NULL,
                          MAX6650_ALRM_GPIO2);

static mode_t max6650_attrs_visible(struct kobject *kobj, struct attribute *a,
                                    int n)
{
        struct device *dev = container_of(kobj, struct device, kobj);
        struct i2c_client *client = to_i2c_client(dev);
        u8 alarm_en = i2c_smbus_read_byte_data(client, MAX6650_REG_ALARM_EN);
        struct device_attribute *devattr;

        /*
         * Hide the alarms that have not been enabled by the firmware
         */

        devattr = container_of(a, struct device_attribute, attr);
        if (devattr == &sensor_dev_attr_fan1_max_alarm.dev_attr
         || devattr == &sensor_dev_attr_fan1_min_alarm.dev_attr
         || devattr == &sensor_dev_attr_fan1_fault.dev_attr
         || devattr == &sensor_dev_attr_gpio1_alarm.dev_attr
         || devattr == &sensor_dev_attr_gpio2_alarm.dev_attr) {
                if (!(alarm_en & to_sensor_dev_attr(devattr)->index))
                        return 0;
        }

        return a->mode;
}

static struct attribute *max6650_attrs[] = {
        &sensor_dev_attr_fan1_input.dev_attr.attr,
        &sensor_dev_attr_fan2_input.dev_attr.attr,
        &sensor_dev_attr_fan3_input.dev_attr.attr,
        &sensor_dev_attr_fan4_input.dev_attr.attr,
        &dev_attr_fan1_target.attr,
        &dev_attr_fan1_div.attr,
        &dev_attr_pwm1_enable.attr,
        &dev_attr_pwm1.attr,
        &sensor_dev_attr_fan1_max_alarm.dev_attr.attr,
        &sensor_dev_attr_fan1_min_alarm.dev_attr.attr,
        &sensor_dev_attr_fan1_fault.dev_attr.attr,
        &sensor_dev_attr_gpio1_alarm.dev_attr.attr,
        &sensor_dev_attr_gpio2_alarm.dev_attr.attr,
        NULL
};

static struct attribute_group max6650_attr_grp = {
        .attrs = max6650_attrs,
        .is_visible = max6650_attrs_visible,
};

/*
 * Real code
 */

/* Return 0 if detection is successful, -ENODEV otherwise */
static int max6650_detect(struct i2c_client *client, int kind,
                          struct i2c_board_info *info)
{
        struct i2c_adapter *adapter = client->adapter;
        int address = client->addr;

        dev_dbg(&adapter->dev, "max6650_detect called, kind = %d\n", kind);

        if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA)) {
                dev_dbg(&adapter->dev, "max6650: I2C bus doesn't support "
                                        "byte read mode, skipping.\n");
                return -ENODEV;
        }

        /*
         * Now we do the remaining detection. A negative kind means that
         * the driver was loaded with no force parameter (default), so we
         * must both detect and identify the chip (actually there is only
         * one possible kind of chip for now, max6650). A zero kind means that
         * the driver was loaded with the force parameter, the detection
         * step shall be skipped. A positive kind means that the driver
         * was loaded with the force parameter and a given kind of chip is
         * requested, so both the detection and the identification steps
         * are skipped.
         *
         * Currently I can find no way to distinguish between a MAX6650 and
         * a MAX6651. This driver has only been tried on the former.
         */

        if ((kind < 0) &&
           (  (i2c_smbus_read_byte_data(client, MAX6650_REG_CONFIG) & 0xC0)
            ||(i2c_smbus_read_byte_data(client, MAX6650_REG_GPIO_STAT) & 0xE0)
            ||(i2c_smbus_read_byte_data(client, MAX6650_REG_ALARM_EN) & 0xE0)
            ||(i2c_smbus_read_byte_data(client, MAX6650_REG_ALARM) & 0xE0)
            ||(i2c_smbus_read_byte_data(client, MAX6650_REG_COUNT) & 0xFC))) {
                dev_dbg(&adapter->dev,
                        "max6650: detection failed at 0x%02x.\n", address);
                return -ENODEV;
        }

        dev_info(&adapter->dev, "max6650: chip found at 0x%02x.\n", address);

        strlcpy(info->type, "max6650", I2C_NAME_SIZE);

        return 0;
}

static int max6650_probe(struct i2c_client *client,
                         const struct i2c_device_id *id)
{
        struct max6650_data *data;
        int err;

        if (!(data = kzalloc(sizeof(struct max6650_data), GFP_KERNEL))) {
                dev_err(&client->dev, "out of memory.\n");
                return -ENOMEM;
        }

        i2c_set_clientdata(client, data);
        mutex_init(&data->update_lock);

        /*
         * Initialize the max6650 chip
         */
        err = max6650_init_client(client);
        if (err)
                goto err_free;

        err = sysfs_create_group(&client->dev.kobj, &max6650_attr_grp);
        if (err)
                goto err_free;

        data->hwmon_dev = hwmon_device_register(&client->dev);
        if (!IS_ERR(data->hwmon_dev))
                return 0;

        err = PTR_ERR(data->hwmon_dev);
        dev_err(&client->dev, "error registering hwmon device.\n");
        sysfs_remove_group(&client->dev.kobj, &max6650_attr_grp);
err_free:
        kfree(data);
        return err;
}

static int max6650_remove(struct i2c_client *client)
{
        struct max6650_data *data = i2c_get_clientdata(client);

        sysfs_remove_group(&client->dev.kobj, &max6650_attr_grp);
        hwmon_device_unregister(data->hwmon_dev);
        kfree(data);
        return 0;
}

static int max6650_init_client(struct i2c_client *client)
{
        struct max6650_data *data = i2c_get_clientdata(client);
        int config;
        int err = -EIO;

        config = i2c_smbus_read_byte_data(client, MAX6650_REG_CONFIG);

        if (config < 0) {
                dev_err(&client->dev, "Error reading config, aborting.\n");
                return err;
        }

        switch (fan_voltage) {
                case 0:
                        break;
                case 5:
                        config &= ~MAX6650_CFG_V12;
                        break;
                case 12:
                        config |= MAX6650_CFG_V12;
                        break;
                default:
                        dev_err(&client->dev,
                                "illegal value for fan_voltage (%d)\n",
                                fan_voltage);
        }

        dev_info(&client->dev, "Fan voltage is set to %dV.\n",
                 (config & MAX6650_CFG_V12) ? 12 : 5);

        switch (prescaler) {
                case 0:
                        break;
                case 1:
                        config &= ~MAX6650_CFG_PRESCALER_MASK;
                        break;
                case 2:
                        config = (config & ~MAX6650_CFG_PRESCALER_MASK)
                                 | MAX6650_CFG_PRESCALER_2;
                        break;
                case  4:
                        config = (config & ~MAX6650_CFG_PRESCALER_MASK)
                                 | MAX6650_CFG_PRESCALER_4;
                        break;
                case  8:
                        config = (config & ~MAX6650_CFG_PRESCALER_MASK)
                                 | MAX6650_CFG_PRESCALER_8;
                        break;
                case 16:
                        config = (config & ~MAX6650_CFG_PRESCALER_MASK)
                                 | MAX6650_CFG_PRESCALER_16;
                        break;
                default:
                        dev_err(&client->dev,
                                "illegal value for prescaler (%d)\n",
                                prescaler);
        }

        dev_info(&client->dev, "Prescaler is set to %d.\n",
                 1 << (config & MAX6650_CFG_PRESCALER_MASK));

        /* If mode is set to "full off", we change it to "open loop" and
         * set DAC to 255, which has the same effect. We do this because
         * there's no "full off" mode defined in hwmon specifcations.
         */

        if ((config & MAX6650_CFG_MODE_MASK) == MAX6650_CFG_MODE_OFF) {
                dev_dbg(&client->dev, "Change mode to open loop, full off.\n");
                config = (config & ~MAX6650_CFG_MODE_MASK)
                         | MAX6650_CFG_MODE_OPEN_LOOP;
                if (i2c_smbus_write_byte_data(client, MAX6650_REG_DAC, 255)) {
                        dev_err(&client->dev, "DAC write error, aborting.\n");
                        return err;
                }
        }

        if (i2c_smbus_write_byte_data(client, MAX6650_REG_CONFIG, config)) {
                dev_err(&client->dev, "Config write error, aborting.\n");
                return err;
        }

        data->config = config;
        data->count = i2c_smbus_read_byte_data(client, MAX6650_REG_COUNT);

        return 0;
}

static const u8 tach_reg[] = {
        MAX6650_REG_TACH0,
        MAX6650_REG_TACH1,
        MAX6650_REG_TACH2,
        MAX6650_REG_TACH3,
};

static struct max6650_data *max6650_update_device(struct device *dev)
{
        int i;
        struct i2c_client *client = to_i2c_client(dev);
        struct max6650_data *data = i2c_get_clientdata(client);

        mutex_lock(&data->update_lock);

        if (time_after(jiffies, data->last_updated + HZ) || !data->valid) {
                data->speed = i2c_smbus_read_byte_data(client,
                                                       MAX6650_REG_SPEED);
                data->config = i2c_smbus_read_byte_data(client,
                                                        MAX6650_REG_CONFIG);
                for (i = 0; i < 4; i++) {
                        data->tach[i] = i2c_smbus_read_byte_data(client,
                                                                 tach_reg[i]);
                }
                data->count = i2c_smbus_read_byte_data(client,
                                                        MAX6650_REG_COUNT);
                data->dac = i2c_smbus_read_byte_data(client, MAX6650_REG_DAC);

                /* Alarms are cleared on read in case the condition that
                 * caused the alarm is removed. Keep the value latched here
                 * for providing the register through different alarm files. */
                data->alarm |= i2c_smbus_read_byte_data(client,
                                                        MAX6650_REG_ALARM);

                data->last_updated = jiffies;
                data->valid = 1;
        }

        mutex_unlock(&data->update_lock);

        return data;
}

static int __init sensors_max6650_init(void)
{
        return i2c_add_driver(&max6650_driver);
}

static void __exit sensors_max6650_exit(void)
{
        i2c_del_driver(&max6650_driver);
}

MODULE_AUTHOR("Hans J. Koch");
MODULE_DESCRIPTION("MAX6650 sensor driver");
MODULE_LICENSE("GPL");

module_init(sensors_max6650_init);
module_exit(sensors_max6650_exit);