Driver for MAX6620 Fan sensor

From: Cumulus Networks <support@cumulusnetworks.com>


---
 drivers/hwmon/Kconfig   |   10 +
 drivers/hwmon/Makefile  |    1 
 drivers/hwmon/max6620.c |  702 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 713 insertions(+)
 create mode 100644 drivers/hwmon/max6620.c

diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 02d3d85..ca38e05 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -784,6 +784,16 @@ config SENSORS_MAX6650
 	  This driver can also be built as a module.  If so, the module
 	  will be called max6650.
 
+config SENSORS_MAX6620
+	tristate "Maxim MAX6620 sensor chip"
+	depends on I2C
+	help
+	  If you say yes here you get support for the MAX6620
+	  sensor chips.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called max6620.
+
 config SENSORS_MAX6697
 	tristate "Maxim MAX6697 and compatibles"
 	depends on I2C
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index 3dc0f02..8837a7b 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -111,6 +111,7 @@ obj-$(CONFIG_SENSORS_MAX197)	+= max197.o
 obj-$(CONFIG_SENSORS_MAX6639)	+= max6639.o
 obj-$(CONFIG_SENSORS_MAX6642)	+= max6642.o
 obj-$(CONFIG_SENSORS_MAX6650)	+= max6650.o
+obj-$(CONFIG_SENSORS_MAX6620)	+= max6620.o
 obj-$(CONFIG_SENSORS_MAX6697)	+= max6697.o
 obj-$(CONFIG_SENSORS_MC13783_ADC)+= mc13783-adc.o
 obj-$(CONFIG_SENSORS_MCP3021)	+= mcp3021.o
diff --git a/drivers/hwmon/max6620.c b/drivers/hwmon/max6620.c
new file mode 100644
index 0000000..3c337c7
--- /dev/null
+++ b/drivers/hwmon/max6620.c
@@ -0,0 +1,702 @@
+/*
+ * max6620.c - Linux Kernel module for hardware monitoring.
+ *
+ * (C) 2012 by L. Grunenberg <contact@lgrunenberg.de>
+ *
+ * based on code written by :
+ * 2007 by Hans J. Koch <hjk@hansjkoch.de>
+ * 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 MAX6620 chip.
+ *
+ * The datasheet was last seen at:
+ *
+ *        http://pdfserv.maxim-ic.com/en/ds/MAX6620.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
+ */
+
+
+/* clock: The clock frequency of the chip the driver should assume */
+static int clock = 8192;
+
+module_param(clock, int, S_IRUGO);
+
+static const unsigned short normal_i2c[] = {0x0a, 0x1a, 0x2a, I2C_CLIENT_END};
+
+/*
+ * MAX 6620 registers
+ */
+
+#define MAX6620_REG_CONFIG	0x00
+#define MAX6620_REG_FAULT	0x01
+#define MAX6620_REG_CONF_FAN0	0x02
+#define MAX6620_REG_CONF_FAN1	0x03
+#define MAX6620_REG_CONF_FAN2	0x04
+#define MAX6620_REG_CONF_FAN3	0x05
+#define MAX6620_REG_DYN_FAN0	0x06
+#define MAX6620_REG_DYN_FAN1	0x07
+#define MAX6620_REG_DYN_FAN2	0x08
+#define MAX6620_REG_DYN_FAN3	0x09
+#define MAX6620_REG_TACH0	0x10
+#define MAX6620_REG_TACH1	0x12
+#define MAX6620_REG_TACH2	0x14
+#define MAX6620_REG_TACH3	0x16
+#define MAX6620_REG_VOLT0	0x18
+#define MAX6620_REG_VOLT1	0x1A
+#define MAX6620_REG_VOLT2	0x1C
+#define MAX6620_REG_VOLT3	0x1E
+#define MAX6620_REG_TAR0	0x20
+#define MAX6620_REG_TAR1	0x22
+#define MAX6620_REG_TAR2	0x24
+#define MAX6620_REG_TAR3	0x26
+#define MAX6620_REG_DAC0	0x28
+#define MAX6620_REG_DAC1	0x2A
+#define MAX6620_REG_DAC2	0x2C
+#define MAX6620_REG_DAC3	0x2E
+
+/*
+ * Config register bits
+ */
+
+#define MAX6620_CFG_RUN			0x80
+#define MAX6620_CFG_POR			0x40
+#define MAX6620_CFG_TIMEOUT		0x20
+#define MAX6620_CFG_FULLFAN		0x10
+#define MAX6620_CFG_OSC			0x08
+#define MAX6620_CFG_WD_MASK		0x06
+#define MAX6620_CFG_WD_2		0x02
+#define MAX6620_CFG_WD_6		0x04
+#define MAX6620_CFG_WD10		0x06
+#define MAX6620_CFG_WD			0x01
+
+
+/*
+ * Failure status register bits
+ */
+
+#define MAX6620_FAIL_TACH0	0x10
+#define MAX6620_FAIL_TACH1	0x20
+#define MAX6620_FAIL_TACH2	0x40
+#define MAX6620_FAIL_TACH3	0x80
+#define MAX6620_FAIL_MASK0	0x01
+#define MAX6620_FAIL_MASK1	0x02
+#define MAX6620_FAIL_MASK2	0x04
+#define MAX6620_FAIL_MASK3	0x08
+
+
+/* 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 & 0xE0) >> 5))
+
+static int max6620_probe(struct i2c_client *client, const struct i2c_device_id *id);
+static int max6620_init_client(struct i2c_client *client);
+static int max6620_remove(struct i2c_client *client);
+static struct max6620_data *max6620_update_device(struct device *dev);
+
+static const u8 config_reg[] = {
+	MAX6620_REG_CONF_FAN0,
+	MAX6620_REG_CONF_FAN1,
+	MAX6620_REG_CONF_FAN2,
+	MAX6620_REG_CONF_FAN3,
+};
+
+static const u8 dyn_reg[] = {
+	MAX6620_REG_DYN_FAN0,
+	MAX6620_REG_DYN_FAN1,
+	MAX6620_REG_DYN_FAN2,
+	MAX6620_REG_DYN_FAN3,
+};
+
+static const u8 tach_reg[] = {
+	MAX6620_REG_TACH0,
+	MAX6620_REG_TACH1,
+	MAX6620_REG_TACH2,
+	MAX6620_REG_TACH3,
+};
+
+static const u8 volt_reg[] = {
+	MAX6620_REG_VOLT0,
+	MAX6620_REG_VOLT1,
+	MAX6620_REG_VOLT2,
+	MAX6620_REG_VOLT3,
+};
+
+static const u8 target_reg[] = {
+	MAX6620_REG_TAR0,
+	MAX6620_REG_TAR1,
+	MAX6620_REG_TAR2,
+	MAX6620_REG_TAR3,
+};
+
+static const u8 dac_reg[] = {
+	MAX6620_REG_DAC0,
+	MAX6620_REG_DAC1,
+	MAX6620_REG_DAC2,
+	MAX6620_REG_DAC3,
+};
+
+/*
+ * Driver data (common to all clients)
+ */
+
+static const struct i2c_device_id max6620_id[] = {
+	{ "max6620", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, max6620_id);
+
+static struct i2c_driver max6620_driver = {
+	.class		= I2C_CLASS_HWMON,
+	.driver = {
+		.name	= "max6620",
+	},
+	.probe		= max6620_probe,
+	.remove		= __devexit_p(max6620_remove),
+	.id_table	= max6620_id,
+	.address_list	= normal_i2c,
+};
+
+/*
+ * Client data (each client gets its own)
+ */
+
+struct max6620_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[4];
+	u8 config;
+	u8 fancfg[4];
+	u8 fandyn[4];
+	u8 tach[4];
+	u8 volt[4];
+	u8 target[4];
+	u8 dac[4];
+	u8 fault;
+};
+
+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 max6620_data *data = max6620_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).
+	 */
+	if(data->tach[attr->index] == 0 || data->tach[attr->index] == 255) {
+		rpm = 0;
+	} else {
+		rpm = ((clock / (data->tach[attr->index] << 3)) * 30 * DIV_FROM_REG(data->fandyn[attr->index]));
+	}
+
+	return sprintf(buf, "%d\n", rpm);
+}
+
+static ssize_t get_target(struct device *dev, struct device_attribute *devattr, char *buf) {
+
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
+	struct max6620_data *data = max6620_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->fandyn[attr->index]);
+	ktach = data->target[attr->index];
+	if(ktach == 0) {
+		rpm = 0;
+	} else {
+		rpm = ((60 * kscale * clock) / (ktach << 3));
+	}
+	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 sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
+	struct max6620_data *data = i2c_get_clientdata(client);
+	int kscale, ktach;
+	unsigned long rpm;
+	int err;
+
+	err = kstrtoul(buf, 10, &rpm);
+	if (err)
+		return err;
+
+	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->fandyn[attr->index]);
+	ktach = ((60 * kscale * clock) / rpm);
+	if (ktach < 0)
+		ktach = 0;
+	if (ktach > 255)
+		ktach = 255;
+	data->target[attr->index] = ktach;
+
+	i2c_smbus_write_byte_data(client, target_reg[attr->index], data->target[attr->index]);
+	i2c_smbus_write_byte_data(client, target_reg[attr->index]+0x01, 0x00);
+
+	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 sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
+	struct max6620_data *data = max6620_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.
+	 */
+	pwm = ((int)data->volt[attr->index]);
+
+	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 sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
+	struct max6620_data *data = i2c_get_clientdata(client);
+	unsigned long pwm;
+	int err;
+
+	err = kstrtoul(buf, 10, &pwm);
+	if (err)
+		return err;
+
+	pwm = SENSORS_LIMIT(pwm, 0, 255);
+
+	mutex_lock(&data->update_lock);
+
+		data->dac[attr->index] = pwm;
+
+
+	i2c_smbus_write_byte_data(client, dac_reg[attr->index], data->dac[attr->index]);
+	i2c_smbus_write_byte_data(client, dac_reg[attr->index]+1, 0x00);
+
+	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 max6620_data *data = max6620_update_device(dev);
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
+	int mode = (data->fancfg[attr->index] & 0x80 ) >> 7;
+	int sysfs_modes[2] = {1, 2};
+
+	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 max6620_data *data = i2c_get_clientdata(client);
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
+	int max6620_modes[3] = {0, 1, 0};
+	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->fancfg[attr->index] = i2c_smbus_read_byte_data(client, config_reg[attr->index]);
+	data->fancfg[attr->index] = (data->fancfg[attr->index] & ~0x80)
+		       | (max6620_modes[mode] << 7);
+
+	i2c_smbus_write_byte_data(client, config_reg[attr->index], data->fancfg[attr->index]);
+
+	mutex_unlock(&data->update_lock);
+
+	return count;
+}
+
+/*
+ * Read/write functions for fan1_div sysfs file. The MAX6620 has no such
+ * divider. We handle this by converting between divider and counttime:
+ *
+ * (counttime == k) <==> (divider == 2^k), k = 0, 1, 2, 3, 4 or 5
+ *
+ * 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 max6620_data *data = max6620_update_device(dev);
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
+
+	return sprintf(buf, "%d\n", DIV_FROM_REG(data->fandyn[attr->index]));
+}
+
+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 max6620_data *data = i2c_get_clientdata(client);
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
+	unsigned long div;
+	int err;
+	u8 div_bin;
+
+	err = kstrtoul(buf, 10, &div);
+	if (err)
+		return err;
+
+	mutex_lock(&data->update_lock);
+	switch (div) {
+	case 1:
+		div_bin = 0;
+		break;
+	case 2:
+		div_bin = 1;
+		break;
+	case 4:
+		div_bin = 2;
+		break;
+	case 8:
+		div_bin = 3;
+		break;
+	case 16:
+		div_bin = 4;
+		break;
+	case 32:
+		div_bin = 5;
+		break;
+	default:
+		mutex_unlock(&data->update_lock);
+		return -EINVAL;
+	}
+	data->fandyn[attr->index] &= 0x1F;
+	data->fandyn[attr->index] |= div_bin << 5;
+	i2c_smbus_write_byte_data(client, dyn_reg[attr->index], data->fandyn[attr->index]);
+	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 max6620_data *data = max6620_update_device(dev);
+	struct i2c_client *client = to_i2c_client(dev);
+	int alarm = 0;
+
+	if (data->fault & (1 << attr->index)) {
+		mutex_lock(&data->update_lock);
+		alarm = 1;
+		data->fault &= ~(1 << attr->index);
+		data->fault |= i2c_smbus_read_byte_data(client,
+							MAX6620_REG_FAULT);
+		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 SENSOR_DEVICE_ATTR(fan1_target, S_IWUSR | S_IRUGO, get_target, set_target, 0);
+static SENSOR_DEVICE_ATTR(fan1_div, S_IWUSR | S_IRUGO, get_div, set_div, 0);
+// static SENSOR_DEVICE_ATTR(pwm1_enable, S_IWUSR | S_IRUGO, get_enable, set_enable, 0);
+static SENSOR_DEVICE_ATTR(pwm1, S_IWUSR | S_IRUGO, get_pwm, set_pwm, 0);
+static SENSOR_DEVICE_ATTR(fan2_target, S_IWUSR | S_IRUGO, get_target, set_target, 1);
+static SENSOR_DEVICE_ATTR(fan2_div, S_IWUSR | S_IRUGO, get_div, set_div, 1);
+// static SENSOR_DEVICE_ATTR(pwm2_enable, S_IWUSR | S_IRUGO, get_enable, set_enable, 1);
+static SENSOR_DEVICE_ATTR(pwm2, S_IWUSR | S_IRUGO, get_pwm, set_pwm, 1);
+static SENSOR_DEVICE_ATTR(fan3_target, S_IWUSR | S_IRUGO, get_target, set_target, 2);
+static SENSOR_DEVICE_ATTR(fan3_div, S_IWUSR | S_IRUGO, get_div, set_div, 2);
+// static SENSOR_DEVICE_ATTR(pwm3_enable, S_IWUSR | S_IRUGO, get_enable, set_enable, 2);
+static SENSOR_DEVICE_ATTR(pwm3, S_IWUSR | S_IRUGO, get_pwm, set_pwm, 2);
+static SENSOR_DEVICE_ATTR(fan4_target, S_IWUSR | S_IRUGO, get_target, set_target, 3);
+static SENSOR_DEVICE_ATTR(fan4_div, S_IWUSR | S_IRUGO, get_div, set_div, 3);
+// static SENSOR_DEVICE_ATTR(pwm4_enable, S_IWUSR | S_IRUGO, get_enable, set_enable, 3);
+static SENSOR_DEVICE_ATTR(pwm4, S_IWUSR | S_IRUGO, get_pwm, set_pwm, 3);
+
+static struct attribute *max6620_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,
+	&sensor_dev_attr_fan1_target.dev_attr.attr,
+	&sensor_dev_attr_fan1_div.dev_attr.attr,
+//	&sensor_dev_attr_pwm1_enable.dev_attr.attr,
+	&sensor_dev_attr_pwm1.dev_attr.attr,
+	&sensor_dev_attr_fan2_target.dev_attr.attr,
+	&sensor_dev_attr_fan2_div.dev_attr.attr,
+//	&sensor_dev_attr_pwm2_enable.dev_attr.attr,
+	&sensor_dev_attr_pwm2.dev_attr.attr,
+	&sensor_dev_attr_fan3_target.dev_attr.attr,
+	&sensor_dev_attr_fan3_div.dev_attr.attr,
+//	&sensor_dev_attr_pwm3_enable.dev_attr.attr,
+	&sensor_dev_attr_pwm3.dev_attr.attr,
+	&sensor_dev_attr_fan4_target.dev_attr.attr,
+	&sensor_dev_attr_fan4_div.dev_attr.attr,
+//	&sensor_dev_attr_pwm4_enable.dev_attr.attr,
+	&sensor_dev_attr_pwm4.dev_attr.attr,
+	NULL
+};
+
+static struct attribute_group max6620_attr_grp = {
+	.attrs = max6620_attrs,
+};
+
+
+/*
+ * Real code
+ */
+
+static int __devinit max6620_probe(struct i2c_client *client, const struct i2c_device_id *id) {
+
+	struct max6620_data *data;
+	int err;
+
+	data = devm_kzalloc(&client->dev, sizeof(struct max6620_data), GFP_KERNEL);
+	if (!data) {
+		dev_err(&client->dev, "out of memory.\n");
+		return -ENOMEM;
+	}
+
+	i2c_set_clientdata(client, data);
+	mutex_init(&data->update_lock);
+	data->nr_fans = id->driver_data;
+
+	/*
+	 * Initialize the max6620 chip
+	 */
+	dev_info(&client->dev, "About to initialize module\n");
+
+	err = max6620_init_client(client);
+	if (err)
+		return err;
+	dev_info(&client->dev, "Module initialized\n");
+
+	err = sysfs_create_group(&client->dev.kobj, &max6620_attr_grp);
+	if (err)
+		return err;
+dev_info(&client->dev, "Sysfs entries created\n");
+
+	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, &max6620_attr_grp);
+	return err;
+}
+
+static int __devexit max6620_remove(struct i2c_client *client) {
+
+	struct max6620_data *data = i2c_get_clientdata(client);
+
+	hwmon_device_unregister(data->hwmon_dev);
+
+	sysfs_remove_group(&client->dev.kobj, &max6620_attr_grp);
+	return 0;
+}
+
+static int max6620_init_client(struct i2c_client *client) {
+
+	struct max6620_data *data = i2c_get_clientdata(client);
+	int config;
+	int err = -EIO;
+	int i;
+
+	config = i2c_smbus_read_byte_data(client, MAX6620_REG_CONFIG);
+
+	if (config < 0) {
+		dev_err(&client->dev, "Error reading config, aborting.\n");
+		return err;
+	}
+
+
+
+	if (i2c_smbus_write_byte_data(client, MAX6620_REG_CONFIG, config)) {
+		dev_err(&client->dev, "Config write error, aborting.\n");
+		return err;
+	}
+
+	data->config = config;
+	for (i = 0; i < 4; i++) {
+		data->fancfg[i] = i2c_smbus_read_byte_data(client, config_reg[i]);
+		data->fancfg[i] |= 0x80;		// enable TACH monitoring
+		i2c_smbus_write_byte_data(client, config_reg[i], data->fancfg[i]);
+		data->fandyn[i] = i2c_smbus_read_byte_data(client, dyn_reg[i]);
+		data-> fandyn[i] |= 0x1C;
+		i2c_smbus_write_byte_data(client, dyn_reg[i], data->fandyn[i]);
+		data->tach[i] = i2c_smbus_read_byte_data(client, tach_reg[i]);
+		data->volt[i] = i2c_smbus_read_byte_data(client, volt_reg[i]);
+		data->target[i] = i2c_smbus_read_byte_data(client, target_reg[i]);
+		data->dac[i] = i2c_smbus_read_byte_data(client, dac_reg[i]);
+
+
+
+	}
+
+
+
+	return 0;
+}
+
+
+
+
+static struct max6620_data *max6620_update_device(struct device *dev)
+{
+	int i;
+	struct i2c_client *client = to_i2c_client(dev);
+	struct max6620_data *data = i2c_get_clientdata(client);
+
+	mutex_lock(&data->update_lock);
+
+	if (time_after(jiffies, data->last_updated + HZ) || !data->valid) {
+
+		for (i = 0; i < 4; i++) {
+			data->fancfg[i] = i2c_smbus_read_byte_data(client, config_reg[i]);
+			data->fandyn[i] = i2c_smbus_read_byte_data(client, dyn_reg[i]);
+			data->tach[i] = i2c_smbus_read_byte_data(client, tach_reg[i]);
+			data->volt[i] = i2c_smbus_read_byte_data(client, volt_reg[i]);
+			data->target[i] = i2c_smbus_read_byte_data(client, target_reg[i]);
+			data->dac[i] = i2c_smbus_read_byte_data(client, dac_reg[i]);
+		}
+
+
+		/*
+		 * 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.
+		 */
+		u8 fault_reg;
+		fault_reg = i2c_smbus_read_byte_data(client, MAX6620_REG_FAULT);
+		data->fault |= (fault_reg >> 4) & (fault_reg & 0x0F);
+
+		data->last_updated = jiffies;
+		data->valid = 1;
+	}
+
+	mutex_unlock(&data->update_lock);
+
+	return data;
+}
+
+module_i2c_driver(max6620_driver);
+
+static int __init max6620_init(void)
+{
+	return i2c_add_driver(&max6620_driver);
+}
+module_init(max6620_init);
+
+/**
+ * sht21_init() - clean up driver
+ *
+ * Called when module is removed.
+ */
+static void __exit max6620_exit(void)
+{
+	i2c_del_driver(&max6620_driver);
+}
+module_exit(max6620_exit);
+
+MODULE_AUTHOR("Lucas Grunenberg");
+MODULE_DESCRIPTION("MAX6620 sensor driver");
+MODULE_LICENSE("GPL");
