hwmon: Driver for Maxim MAX31790

The driver supports the Maxim MAX31790.

Signed-off-by: Il Han <corone.il.han@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

3 files changed, 614 insertions, 0 deletions

diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index e13c902e8966..796569eeaf1d 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -840,6 +840,16 @@ config SENSORS_MAX6697
 	  This driver can also be built as a module.  If so, the module
 	  will be called max6697.
 
+config SENSORS_MAX31790
+	tristate "Maxim MAX31790 sensor chip"
+	depends on I2C
+	help
+	  If you say yes here you get support for 6-Channel PWM-Output
+	  Fan RPM Controller.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called max31790.
+
 config SENSORS_HTU21
 	tristate "Measurement Specialties HTU21D humidity/temperature sensors"
 	depends on I2C
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index 9e0f3dd2841d..01855ee641d1 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -115,6 +115,7 @@ obj-$(CONFIG_SENSORS_MAX6639)	+= max6639.o
 obj-$(CONFIG_SENSORS_MAX6642)	+= max6642.o
 obj-$(CONFIG_SENSORS_MAX6650)	+= max6650.o
 obj-$(CONFIG_SENSORS_MAX6697)	+= max6697.o
+obj-$(CONFIG_SENSORS_MAX31790)	+= max31790.o
 obj-$(CONFIG_SENSORS_MC13783_ADC)+= mc13783-adc.o
 obj-$(CONFIG_SENSORS_MCP3021)	+= mcp3021.o
 obj-$(CONFIG_SENSORS_MENF21BMC_HWMON) += menf21bmc_hwmon.o
diff --git a/drivers/hwmon/max31790.c b/drivers/hwmon/max31790.c
new file mode 100644
index 000000000000..f1296680833a
--- /dev/null
+++ b/drivers/hwmon/max31790.c
@@ -0,0 +1,603 @@
+/*
+ * max31790.c - Part of lm_sensors, Linux kernel modules for hardware
+ *             monitoring.
+ *
+ * (C) 2015 by Il Han <corone.il.han@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/err.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/jiffies.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+
+/* MAX31790 registers */
+#define MAX31790_REG_GLOBAL_CONFIG	0x00
+#define MAX31790_REG_FAN_CONFIG(ch)	(0x02 + (ch))
+#define MAX31790_REG_FAN_DYNAMICS(ch)	(0x08 + (ch))
+#define MAX31790_REG_FAN_FAULT_STATUS2	0x10
+#define MAX31790_REG_FAN_FAULT_STATUS1	0x11
+#define MAX31790_REG_TACH_COUNT(ch)	(0x18 + (ch) * 2)
+#define MAX31790_REG_PWM_DUTY_CYCLE(ch)	(0x30 + (ch) * 2)
+#define MAX31790_REG_PWMOUT(ch)		(0x40 + (ch) * 2)
+#define MAX31790_REG_TARGET_COUNT(ch)	(0x50 + (ch) * 2)
+
+/* Fan Config register bits */
+#define MAX31790_FAN_CFG_RPM_MODE	0x80
+#define MAX31790_FAN_CFG_TACH_INPUT_EN	0x08
+#define MAX31790_FAN_CFG_TACH_INPUT	0x01
+
+/* Fan Dynamics register bits */
+#define MAX31790_FAN_DYN_SR_SHIFT	5
+#define MAX31790_FAN_DYN_SR_MASK	0xE0
+#define SR_FROM_REG(reg)		(((reg) & MAX31790_FAN_DYN_SR_MASK) \
+					 >> MAX31790_FAN_DYN_SR_SHIFT)
+
+#define FAN_RPM_MIN			120
+#define FAN_RPM_MAX			7864320
+
+#define RPM_FROM_REG(reg, sr)		(((reg) >> 4) ? \
+					 ((60 * (sr) * 8192) / ((reg) >> 4)) : \
+					 FAN_RPM_MAX)
+#define RPM_TO_REG(rpm, sr)		((60 * (sr) * 8192) / ((rpm) * 2))
+
+#define NR_CHANNEL			6
+
+/*
+ * Client data (each client gets its own)
+ */
+struct max31790_data {
+	struct i2c_client *client;
+	struct mutex update_lock;
+	bool valid; /* zero until following fields are valid */
+	unsigned long last_updated; /* in jiffies */
+
+	/* register values */
+	u8 fan_config[NR_CHANNEL];
+	u8 fan_dynamics[NR_CHANNEL];
+	u16 fault_status;
+	u16 tach[NR_CHANNEL * 2];
+	u16 pwm[NR_CHANNEL];
+	u16 target_count[NR_CHANNEL];
+};
+
+static struct max31790_data *max31790_update_device(struct device *dev)
+{
+	struct max31790_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+	struct max31790_data *ret = data;
+	int i;
+	int rv;
+
+	mutex_lock(&data->update_lock);
+
+	if (time_after(jiffies, data->last_updated + HZ) || !data->valid) {
+		rv = i2c_smbus_read_byte_data(client,
+				MAX31790_REG_FAN_FAULT_STATUS1);
+		if (rv < 0)
+			goto abort;
+		data->fault_status = rv & 0x3F;
+
+		rv = i2c_smbus_read_byte_data(client,
+				MAX31790_REG_FAN_FAULT_STATUS2);
+		if (rv < 0)
+			goto abort;
+		data->fault_status |= (rv & 0x3F) << 6;
+
+		for (i = 0; i < NR_CHANNEL; i++) {
+			rv = i2c_smbus_read_word_swapped(client,
+					MAX31790_REG_TACH_COUNT(i));
+			if (rv < 0)
+				goto abort;
+			data->tach[i] = rv;
+
+			if (data->fan_config[i]
+			    & MAX31790_FAN_CFG_TACH_INPUT) {
+				rv = i2c_smbus_read_word_swapped(client,
+					MAX31790_REG_TACH_COUNT(NR_CHANNEL
+								+ i));
+				if (rv < 0)
+					goto abort;
+				data->tach[NR_CHANNEL + i] = rv;
+			} else {
+				rv = i2c_smbus_read_word_swapped(client,
+						MAX31790_REG_PWMOUT(i));
+				if (rv < 0)
+					goto abort;
+				data->pwm[i] = rv;
+
+				rv = i2c_smbus_read_word_swapped(client,
+						MAX31790_REG_TARGET_COUNT(i));
+				if (rv < 0)
+					goto abort;
+				data->target_count[i] = rv;
+			}
+		}
+
+		data->last_updated = jiffies;
+		data->valid = true;
+	}
+	goto done;
+
+abort:
+	data->valid = false;
+	ret = ERR_PTR(rv);
+
+done:
+	mutex_unlock(&data->update_lock);
+
+	return ret;
+}
+
+static const u8 tach_period[8] = { 1, 2, 4, 8, 16, 32, 32, 32 };
+
+static u8 get_tach_period(u8 fan_dynamics)
+{
+	return tach_period[SR_FROM_REG(fan_dynamics)];
+}
+
+static u8 bits_for_tach_period(int rpm)
+{
+	u8 bits;
+
+	if (rpm < 500)
+		bits = 0x0;
+	else if (rpm < 1000)
+		bits = 0x1;
+	else if (rpm < 2000)
+		bits = 0x2;
+	else if (rpm < 4000)
+		bits = 0x3;
+	else if (rpm < 8000)
+		bits = 0x4;
+	else
+		bits = 0x5;
+
+	return bits;
+}
+
+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 max31790_data *data = max31790_update_device(dev);
+	int sr = get_tach_period(data->fan_dynamics[attr->index]);
+	int rpm;
+
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+
+	rpm = RPM_FROM_REG(data->tach[attr->index], sr);
+
+	return sprintf(buf, "%d\n", rpm);
+}
+
+static ssize_t get_fan_target(struct device *dev,
+			      struct device_attribute *devattr, char *buf)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
+	struct max31790_data *data = max31790_update_device(dev);
+	int sr = get_tach_period(data->fan_dynamics[attr->index]);
+	int rpm;
+
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+
+	rpm = RPM_FROM_REG(data->target_count[attr->index], sr);
+
+	return sprintf(buf, "%d\n", rpm);
+}
+
+static ssize_t set_fan_target(struct device *dev,
+			      struct device_attribute *devattr,
+			      const char *buf, size_t count)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
+	struct max31790_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+	u8 bits;
+	int sr;
+	int target_count;
+	unsigned long rpm;
+	int err;
+
+	err = kstrtoul(buf, 10, &rpm);
+	if (err)
+		return err;
+
+	mutex_lock(&data->update_lock);
+
+	rpm = clamp_val(rpm, FAN_RPM_MIN, FAN_RPM_MAX);
+	bits = bits_for_tach_period(rpm);
+	data->fan_dynamics[attr->index] =
+			((data->fan_dynamics[attr->index]
+			  & ~MAX31790_FAN_DYN_SR_MASK)
+			 | (bits << MAX31790_FAN_DYN_SR_SHIFT));
+	err = i2c_smbus_write_byte_data(client,
+			MAX31790_REG_FAN_DYNAMICS(attr->index),
+			data->fan_dynamics[attr->index]);
+
+	if (err < 0) {
+		mutex_unlock(&data->update_lock);
+		return err;
+	}
+
+	sr = get_tach_period(data->fan_dynamics[attr->index]);
+	target_count = RPM_TO_REG(rpm, sr);
+	target_count = clamp_val(target_count, 0x1, 0x7FF);
+
+	data->target_count[attr->index] = target_count << 5;
+
+	err = i2c_smbus_write_word_swapped(client,
+			MAX31790_REG_TARGET_COUNT(attr->index),
+			data->target_count[attr->index]);
+
+	mutex_unlock(&data->update_lock);
+
+	if (err < 0)
+		return err;
+
+	return count;
+}
+
+static ssize_t get_pwm(struct device *dev,
+		       struct device_attribute *devattr, char *buf)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
+	struct max31790_data *data = max31790_update_device(dev);
+	int pwm;
+
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+
+	pwm = data->pwm[attr->index] >> 8;
+
+	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 sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
+	struct max31790_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+	unsigned long pwm;
+	int err;
+
+	err = kstrtoul(buf, 10, &pwm);
+	if (err)
+		return err;
+
+	if (pwm > 255)
+		return -EINVAL;
+
+	mutex_lock(&data->update_lock);
+
+	data->pwm[attr->index] = pwm << 8;
+	err = i2c_smbus_write_word_swapped(client,
+			MAX31790_REG_PWMOUT(attr->index),
+			data->pwm[attr->index]);
+
+	mutex_unlock(&data->update_lock);
+
+	if (err < 0)
+		return err;
+
+	return count;
+}
+
+static ssize_t get_pwm_enable(struct device *dev,
+			      struct device_attribute *devattr, char *buf)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
+	struct max31790_data *data = max31790_update_device(dev);
+	int mode;
+
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+
+	if (data->fan_config[attr->index] & MAX31790_FAN_CFG_RPM_MODE)
+		mode = 2;
+	else if (data->fan_config[attr->index] & MAX31790_FAN_CFG_TACH_INPUT_EN)
+		mode = 1;
+	else
+		mode = 0;
+
+	return sprintf(buf, "%d\n", mode);
+}
+
+static ssize_t set_pwm_enable(struct device *dev,
+			      struct device_attribute *devattr,
+			      const char *buf, size_t count)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
+	struct max31790_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+	unsigned long mode;
+	int err;
+
+	err = kstrtoul(buf, 10, &mode);
+	if (err)
+		return err;
+
+	switch (mode) {
+	case 0:
+		data->fan_config[attr->index] =
+			data->fan_config[attr->index]
+			& ~(MAX31790_FAN_CFG_TACH_INPUT_EN
+			    | MAX31790_FAN_CFG_RPM_MODE);
+		break;
+	case 1:
+		data->fan_config[attr->index] =
+			(data->fan_config[attr->index]
+			 | MAX31790_FAN_CFG_TACH_INPUT_EN)
+			& ~MAX31790_FAN_CFG_RPM_MODE;
+		break;
+	case 2:
+		data->fan_config[attr->index] =
+			data->fan_config[attr->index]
+			| MAX31790_FAN_CFG_TACH_INPUT_EN
+			| MAX31790_FAN_CFG_RPM_MODE;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	mutex_lock(&data->update_lock);
+
+	err = i2c_smbus_write_byte_data(client,
+			MAX31790_REG_FAN_CONFIG(attr->index),
+			data->fan_config[attr->index]);
+
+	mutex_unlock(&data->update_lock);
+
+	if (err < 0)
+		return err;
+
+	return count;
+}
+
+static ssize_t get_fan_fault(struct device *dev,
+			     struct device_attribute *devattr, char *buf)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
+	struct max31790_data *data = max31790_update_device(dev);
+	int fault;
+
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+
+	fault = !!(data->fault_status & (1 << attr->index));
+
+	return sprintf(buf, "%d\n", fault);
+}
+
+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(fan5_input, S_IRUGO, get_fan, NULL, 4);
+static SENSOR_DEVICE_ATTR(fan6_input, S_IRUGO, get_fan, NULL, 5);
+
+static SENSOR_DEVICE_ATTR(fan1_fault, S_IRUGO, get_fan_fault, NULL, 0);
+static SENSOR_DEVICE_ATTR(fan2_fault, S_IRUGO, get_fan_fault, NULL, 1);
+static SENSOR_DEVICE_ATTR(fan3_fault, S_IRUGO, get_fan_fault, NULL, 2);
+static SENSOR_DEVICE_ATTR(fan4_fault, S_IRUGO, get_fan_fault, NULL, 3);
+static SENSOR_DEVICE_ATTR(fan5_fault, S_IRUGO, get_fan_fault, NULL, 4);
+static SENSOR_DEVICE_ATTR(fan6_fault, S_IRUGO, get_fan_fault, NULL, 5);
+
+static SENSOR_DEVICE_ATTR(fan7_input, S_IRUGO, get_fan, NULL, 6);
+static SENSOR_DEVICE_ATTR(fan8_input, S_IRUGO, get_fan, NULL, 7);
+static SENSOR_DEVICE_ATTR(fan9_input, S_IRUGO, get_fan, NULL, 8);
+static SENSOR_DEVICE_ATTR(fan10_input, S_IRUGO, get_fan, NULL, 9);
+static SENSOR_DEVICE_ATTR(fan11_input, S_IRUGO, get_fan, NULL, 10);
+static SENSOR_DEVICE_ATTR(fan12_input, S_IRUGO, get_fan, NULL, 11);
+
+static SENSOR_DEVICE_ATTR(fan7_fault, S_IRUGO, get_fan_fault, NULL, 6);
+static SENSOR_DEVICE_ATTR(fan8_fault, S_IRUGO, get_fan_fault, NULL, 7);
+static SENSOR_DEVICE_ATTR(fan9_fault, S_IRUGO, get_fan_fault, NULL, 8);
+static SENSOR_DEVICE_ATTR(fan10_fault, S_IRUGO, get_fan_fault, NULL, 9);
+static SENSOR_DEVICE_ATTR(fan11_fault, S_IRUGO, get_fan_fault, NULL, 10);
+static SENSOR_DEVICE_ATTR(fan12_fault, S_IRUGO, get_fan_fault, NULL, 11);
+
+static SENSOR_DEVICE_ATTR(fan1_target, S_IWUSR | S_IRUGO,
+		get_fan_target, set_fan_target, 0);
+static SENSOR_DEVICE_ATTR(fan2_target, S_IWUSR | S_IRUGO,
+		get_fan_target, set_fan_target, 1);
+static SENSOR_DEVICE_ATTR(fan3_target, S_IWUSR | S_IRUGO,
+		get_fan_target, set_fan_target, 2);
+static SENSOR_DEVICE_ATTR(fan4_target, S_IWUSR | S_IRUGO,
+		get_fan_target, set_fan_target, 3);
+static SENSOR_DEVICE_ATTR(fan5_target, S_IWUSR | S_IRUGO,
+		get_fan_target, set_fan_target, 4);
+static SENSOR_DEVICE_ATTR(fan6_target, S_IWUSR | S_IRUGO,
+		get_fan_target, set_fan_target, 5);
+
+static SENSOR_DEVICE_ATTR(pwm1, S_IWUSR | S_IRUGO, get_pwm, set_pwm, 0);
+static SENSOR_DEVICE_ATTR(pwm2, S_IWUSR | S_IRUGO, get_pwm, set_pwm, 1);
+static SENSOR_DEVICE_ATTR(pwm3, S_IWUSR | S_IRUGO, get_pwm, set_pwm, 2);
+static SENSOR_DEVICE_ATTR(pwm4, S_IWUSR | S_IRUGO, get_pwm, set_pwm, 3);
+static SENSOR_DEVICE_ATTR(pwm5, S_IWUSR | S_IRUGO, get_pwm, set_pwm, 4);
+static SENSOR_DEVICE_ATTR(pwm6, S_IWUSR | S_IRUGO, get_pwm, set_pwm, 5);
+
+static SENSOR_DEVICE_ATTR(pwm1_enable, S_IWUSR | S_IRUGO,
+		get_pwm_enable, set_pwm_enable, 0);
+static SENSOR_DEVICE_ATTR(pwm2_enable, S_IWUSR | S_IRUGO,
+		get_pwm_enable, set_pwm_enable, 1);
+static SENSOR_DEVICE_ATTR(pwm3_enable, S_IWUSR | S_IRUGO,
+		get_pwm_enable, set_pwm_enable, 2);
+static SENSOR_DEVICE_ATTR(pwm4_enable, S_IWUSR | S_IRUGO,
+		get_pwm_enable, set_pwm_enable, 3);
+static SENSOR_DEVICE_ATTR(pwm5_enable, S_IWUSR | S_IRUGO,
+		get_pwm_enable, set_pwm_enable, 4);
+static SENSOR_DEVICE_ATTR(pwm6_enable, S_IWUSR | S_IRUGO,
+		get_pwm_enable, set_pwm_enable, 5);
+
+static struct attribute *max31790_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_fan5_input.dev_attr.attr,
+	&sensor_dev_attr_fan6_input.dev_attr.attr,
+
+	&sensor_dev_attr_fan1_fault.dev_attr.attr,
+	&sensor_dev_attr_fan2_fault.dev_attr.attr,
+	&sensor_dev_attr_fan3_fault.dev_attr.attr,
+	&sensor_dev_attr_fan4_fault.dev_attr.attr,
+	&sensor_dev_attr_fan5_fault.dev_attr.attr,
+	&sensor_dev_attr_fan6_fault.dev_attr.attr,
+
+	&sensor_dev_attr_fan7_input.dev_attr.attr,
+	&sensor_dev_attr_fan8_input.dev_attr.attr,
+	&sensor_dev_attr_fan9_input.dev_attr.attr,
+	&sensor_dev_attr_fan10_input.dev_attr.attr,
+	&sensor_dev_attr_fan11_input.dev_attr.attr,
+	&sensor_dev_attr_fan12_input.dev_attr.attr,
+
+	&sensor_dev_attr_fan7_fault.dev_attr.attr,
+	&sensor_dev_attr_fan8_fault.dev_attr.attr,
+	&sensor_dev_attr_fan9_fault.dev_attr.attr,
+	&sensor_dev_attr_fan10_fault.dev_attr.attr,
+	&sensor_dev_attr_fan11_fault.dev_attr.attr,
+	&sensor_dev_attr_fan12_fault.dev_attr.attr,
+
+	&sensor_dev_attr_fan1_target.dev_attr.attr,
+	&sensor_dev_attr_fan2_target.dev_attr.attr,
+	&sensor_dev_attr_fan3_target.dev_attr.attr,
+	&sensor_dev_attr_fan4_target.dev_attr.attr,
+	&sensor_dev_attr_fan5_target.dev_attr.attr,
+	&sensor_dev_attr_fan6_target.dev_attr.attr,
+
+	&sensor_dev_attr_pwm1.dev_attr.attr,
+	&sensor_dev_attr_pwm2.dev_attr.attr,
+	&sensor_dev_attr_pwm3.dev_attr.attr,
+	&sensor_dev_attr_pwm4.dev_attr.attr,
+	&sensor_dev_attr_pwm5.dev_attr.attr,
+	&sensor_dev_attr_pwm6.dev_attr.attr,
+
+	&sensor_dev_attr_pwm1_enable.dev_attr.attr,
+	&sensor_dev_attr_pwm2_enable.dev_attr.attr,
+	&sensor_dev_attr_pwm3_enable.dev_attr.attr,
+	&sensor_dev_attr_pwm4_enable.dev_attr.attr,
+	&sensor_dev_attr_pwm5_enable.dev_attr.attr,
+	&sensor_dev_attr_pwm6_enable.dev_attr.attr,
+	NULL
+};
+
+static umode_t max31790_attrs_visible(struct kobject *kobj,
+				     struct attribute *a, int n)
+{
+	struct device *dev = container_of(kobj, struct device, kobj);
+	struct max31790_data *data = dev_get_drvdata(dev);
+	struct device_attribute *devattr =
+			container_of(a, struct device_attribute, attr);
+	int index = to_sensor_dev_attr(devattr)->index % NR_CHANNEL;
+	u8 fan_config;
+
+	fan_config = data->fan_config[index];
+
+	if (n >= NR_CHANNEL * 2 && n < NR_CHANNEL * 4 &&
+	    !(fan_config & MAX31790_FAN_CFG_TACH_INPUT))
+		return 0;
+	if (n >= NR_CHANNEL * 4 && (fan_config & MAX31790_FAN_CFG_TACH_INPUT))
+		return 0;
+
+	return a->mode;
+}
+
+static const struct attribute_group max31790_group = {
+	.attrs = max31790_attrs,
+	.is_visible = max31790_attrs_visible,
+};
+__ATTRIBUTE_GROUPS(max31790);
+
+static int max31790_init_client(struct i2c_client *client,
+				struct max31790_data *data)
+{
+	int i, rv;
+
+	for (i = 0; i < NR_CHANNEL; i++) {
+		rv = i2c_smbus_read_byte_data(client,
+				MAX31790_REG_FAN_CONFIG(i));
+		if (rv < 0)
+			return rv;
+		data->fan_config[i] = rv;
+
+		rv = i2c_smbus_read_byte_data(client,
+				MAX31790_REG_FAN_DYNAMICS(i));
+		if (rv < 0)
+			return rv;
+		data->fan_dynamics[i] = rv;
+	}
+
+	return 0;
+}
+
+static int max31790_probe(struct i2c_client *client,
+			  const struct i2c_device_id *id)
+{
+	struct i2c_adapter *adapter = client->adapter;
+	struct device *dev = &client->dev;
+	struct max31790_data *data;
+	struct device *hwmon_dev;
+	int err;
+
+	if (!i2c_check_functionality(adapter,
+			I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA))
+		return -ENODEV;
+
+	data = devm_kzalloc(dev, sizeof(struct max31790_data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->client = client;
+	mutex_init(&data->update_lock);
+
+	/*
+	 * Initialize the max31790 chip
+	 */
+	err = max31790_init_client(client, data);
+	if (err)
+		return err;
+
+	hwmon_dev = devm_hwmon_device_register_with_groups(dev,
+			client->name, data, max31790_groups);
+
+	return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+static const struct i2c_device_id max31790_id[] = {
+	{ "max31790", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, max31790_id);
+
+static struct i2c_driver max31790_driver = {
+	.class		= I2C_CLASS_HWMON,
+	.probe		= max31790_probe,
+	.driver = {
+		.name	= "max31790",
+	},
+	.id_table	= max31790_id,
+};
+
+module_i2c_driver(max31790_driver);
+
+MODULE_AUTHOR("Il Han <corone.il.han@gmail.com>");
+MODULE_DESCRIPTION("MAX31790 sensor driver");
+MODULE_LICENSE("GPL");