/*
   * max6650.c - Part of lm_sensors, Linux kernel modules for hardware
   *             monitoring.
   *
   * (C) 2007 by Hans J. Koch <hjk@hansjkoch.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>
  
  /*
   * 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);
  
  /*
   * 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_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", 1 },
  	{ "max6651", 4 },
  	{ }
  };
  MODULE_DEVICE_TABLE(i2c, max6650_id);
  
  static struct i2c_driver max6650_driver = {
  	.driver = {
  		.name	= "max6650",
  	},
  	.probe		= max6650_probe,
  	.remove		= max6650_remove,
  	.id_table	= max6650_id,
  };
  
  /*
   * Client data (each client gets its own)
   */
  
  struct max6650_data {
  	struct device *hwmon_dev;
  	struct mutex update_lock;
  	int nr_fans;
  	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
  ", 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
  ", 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 kscale, ktach;
  	unsigned long rpm;
  	int err;
  
  	err = kstrtoul(buf, 10, &rpm);
  	if (err)
  		return err;
  
  	rpm = clamp_val(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
  ", 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);
  	unsigned long pwm;
  	int err;
  
  	err = kstrtoul(buf, 10, &pwm);
  	if (err)
  		return err;
  
  	pwm = clamp_val(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
  ", 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 max6650_modes[3] = {0, 3, 2};
  	unsigned long mode;
  	int err;
  
  	err = kstrtoul(buf, 10, &mode);
  	if (err)
  		return err;
  
  	if (mode > 2)
  		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
  ", 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);
  	unsigned long div;
  	int err;
  
  	err = kstrtoul(buf, 10, &div);
  	if (err)
  		return err;
  
  	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);
  		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
  ", 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 umode_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,
  	&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,
  };
  
  static struct attribute *max6651_attrs[] = {
  	&sensor_dev_attr_fan2_input.dev_attr.attr,
  	&sensor_dev_attr_fan3_input.dev_attr.attr,
  	&sensor_dev_attr_fan4_input.dev_attr.attr,
  	NULL
  };
  
  static const struct attribute_group max6651_attr_grp = {
  	.attrs = max6651_attrs,
  };
  
  /*
   * Real code
   */
  
  static int max6650_probe(struct i2c_client *client,
  			 const struct i2c_device_id *id)
  {
  	struct max6650_data *data;
  	int err;
  
  	data = devm_kzalloc(&client->dev, sizeof(struct max6650_data),
  			    GFP_KERNEL);
  	if (!data) {
  		dev_err(&client->dev, "out of memory.
  ");
  		return -ENOMEM;
  	}
  
  	i2c_set_clientdata(client, data);
  	mutex_init(&data->update_lock);
  	data->nr_fans = id->driver_data;
  
  	/*
  	 * Initialize the max6650 chip
  	 */
  	err = max6650_init_client(client);
  	if (err)
  		return err;
  
  	err = sysfs_create_group(&client->dev.kobj, &max6650_attr_grp);
  	if (err)
  		return err;
  	/* 3 additional fan inputs for the MAX6651 */
  	if (data->nr_fans == 4) {
  		err = sysfs_create_group(&client->dev.kobj, &max6651_attr_grp);
  		if (err)
  			goto err_remove;
  	}
  
  	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.
  ");
  	if (data->nr_fans == 4)
  		sysfs_remove_group(&client->dev.kobj, &max6651_attr_grp);
  err_remove:
  	sysfs_remove_group(&client->dev.kobj, &max6650_attr_grp);
  	return err;
  }
  
  static int max6650_remove(struct i2c_client *client)
  {
  	struct max6650_data *data = i2c_get_clientdata(client);
  
  	hwmon_device_unregister(data->hwmon_dev);
  	if (data->nr_fans == 4)
  		sysfs_remove_group(&client->dev.kobj, &max6651_attr_grp);
  	sysfs_remove_group(&client->dev.kobj, &max6650_attr_grp);
  	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.
  ");
  		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)
  ",
  			fan_voltage);
  	}
  
  	dev_info(&client->dev, "Fan voltage is set to %dV.
  ",
  		 (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)
  ",
  			prescaler);
  	}
  
  	dev_info(&client->dev, "Prescaler is set to %d.
  ",
  		 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 specifications.
  	 */
  
  	if ((config & MAX6650_CFG_MODE_MASK) == MAX6650_CFG_MODE_OFF) {
  		dev_dbg(&client->dev, "Change mode to open loop, full off.
  ");
  		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.
  ");
  			return err;
  		}
  	}
  
  	if (i2c_smbus_write_byte_data(client, MAX6650_REG_CONFIG, config)) {
  		dev_err(&client->dev, "Config write error, aborting.
  ");
  		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 < data->nr_fans; 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;
  }
  
  module_i2c_driver(max6650_driver);
  
  MODULE_AUTHOR("Hans J. Koch");
  MODULE_DESCRIPTION("MAX6650 sensor driver");
  MODULE_LICENSE("GPL");