Date:	Mon, 25 Apr 2016 10:42:26 +0200
From:	Pascal Sachs <pascalsachs@...il.com>
To:	jdelvare@...e.com, linux@...ck-us.net
Cc:	corbet@....net, linux-hwmon@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	David Frey <david.frey@...sirion.com>,
	Pascal Sachs <pascal.sachs@...sirion.com>
Subject: [PATCH 1/1 v2] hwmon: add support for Sensirion SHT3x sensors

From: David Frey <david.frey@...sirion.com>

This driver implements support for the Sensirion SHT3x-DIS chip,
a humidity and temperature sensor. Temperature is measured
in degrees celsius, relative humidity is expressed as a percentage.
In the sysfs interface, all values are scaled by 1000,
i.e. the value for 31.5 degrees celsius is 31500.

Signed-off-by: Pascal Sachs <pascal.sachs@...sirion.com>
---
Patch was generated against kernel v4.6-rc5

 Documentation/hwmon/sht3x           |  66 ++++
 drivers/hwmon/Kconfig               |  10 +
 drivers/hwmon/Makefile              |   1 +
 drivers/hwmon/sht3x.c               | 675 ++++++++++++++++++++++++++++++++++++
 drivers/hwmon/twl4030-madc-hwmon.c  |   1 +
 include/linux/platform_data/sht3x.h |  25 ++
 6 files changed, 778 insertions(+)
 create mode 100644 Documentation/hwmon/sht3x
 create mode 100644 drivers/hwmon/sht3x.c
 create mode 100644 include/linux/platform_data/sht3x.h

diff --git a/Documentation/hwmon/sht3x b/Documentation/hwmon/sht3x
new file mode 100644
index 0000000..c04748d
--- /dev/null
+++ b/Documentation/hwmon/sht3x
@@ -0,0 +1,66 @@
+Kernel driver sht3x
+===================
+
+Supported chips:
+  * Sensirion SHT3x-DIS
+    Prefix: 'sht3x'
+    Addresses scanned: none
+    Datasheet: http://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/Humidity/Sensirion_Humidity_Datasheet_SHT3x_DIS.pdf
+
+Author:
+  David Frey <david.frey@...sirion.com>
+  Pascal Sachs <pascal.sachs@...sirion.com>
+
+Description
+-----------
+
+This driver implements support for the Sensirion SHT3x-DIS chip, a humidity
+and temperature sensor. Temperature is measured in degrees celsius, relative
+humidity is expressed as a percentage. In the sysfs interface, all values are
+scaled by 1000, i.e. the value for 31.5 degrees celsius is 31500.
+
+The device communicates with the I2C protocol. Sensors can have the I2C
+addresses 0x44 or 0x45, depending on the wiring. See
+Documentation/i2c/instantiating-devices for methods to instantiate the device.
+
+There are two options configurable by means of sht3x_platform_data:
+1. blocking (pull the I2C clock line down while performing the measurement) or
+   non-blocking mode. Blocking mode will guarantee the fastest result but
+   the I2C bus will be busy during that time. By default, non-blocking mode
+   is used. Make sure clock-stretching works properly on your device if you
+   want to use blocking mode.
+2. high or low accuracy. High accuracy is used by default and using it is
+   strongly recommended.
+
+The sht3x sensor supports a single shot mode as well as 5 periodic measure
+modes, which can be controlled with the frequency sysfs interface.
+The allowed frequencies are as follows:
+  *     0  single shot mode
+  *   500   0.5 Hz periodic measurement
+  *  1000   1   Hz periodic measurement
+  *  2000   2   Hz periodic measurement
+  *  4000   4   Hz periodic measurement
+  * 10000  10   Hz periodic measurement
+
+While in periodic measure mode, read out of humidity and temperature values are
+not supported. Nevertheless it is possible to read out the values with maximal
+the same frequency as the periodic measure mode.
+
+sysfs-Interface
+---------------
+
+temp1_input:        temperature input
+humidity1_input:    humidity input
+temp1_max:          temperature max value
+temp1_max_hyst:     temperature hysteresis value for max limit
+humidity1_max:      humidity max value
+humidity1_max_hyst: humidity hysteresis value for max limit
+temp1_min:          temperature min value
+temp1_min_hyst:     temperature hysteresis value for min limit
+humidity1_min:      humidity min value
+humidity1_min_hyst: humidity hysteresis value for min limit
+frequency:          Measurement frequency, 0 for single shot, frequency in
+                    mHz for periodic measurement
+soft_reset:         Soft reset the internal state of the sensor, clear the
+                    status register, clear the alert and switch back to
+                    single shot mode
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 5c2d13a..76f4c53 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1254,6 +1254,16 @@ config SENSORS_SHT21
 	  This driver can also be built as a module.  If so, the module
 	  will be called sht21.
 
+config SENSORS_SHT3x
+	tristate "Sensiron humidity and temperature sensors. SHT3x and compat."
+	depends on I2C && CRC8
+	help
+	  If you say yes here you get support for the Sensiron SHT30 and SHT31
+	  humidity and temperature sensors.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called sht3x.
+
 config SENSORS_SHTC1
 	tristate "Sensiron humidity and temperature sensors. SHTC1 and compat."
 	depends on I2C
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index 58cc3ac..999ff2d 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -137,6 +137,7 @@ obj-$(CONFIG_SENSORS_SCH5627)	+= sch5627.o
 obj-$(CONFIG_SENSORS_SCH5636)	+= sch5636.o
 obj-$(CONFIG_SENSORS_SHT15)	+= sht15.o
 obj-$(CONFIG_SENSORS_SHT21)	+= sht21.o
+obj-$(CONFIG_SENSORS_SHT3x)	+= sht3x.o
 obj-$(CONFIG_SENSORS_SHTC1)	+= shtc1.o
 obj-$(CONFIG_SENSORS_SIS5595)	+= sis5595.o
 obj-$(CONFIG_SENSORS_SMM665)	+= smm665.o
diff --git a/drivers/hwmon/sht3x.c b/drivers/hwmon/sht3x.c
new file mode 100644
index 0000000..97f72b8
--- /dev/null
+++ b/drivers/hwmon/sht3x.c
@@ -0,0 +1,675 @@
+/* Sensirion SHT3x-DIS humidity and temperature sensor driver.
+ * The SHT3x comes in many different versions, this driver is for the
+ * I2C version only.
+ *
+ * Copyright (C) 2016 Sensirion AG, Switzerland
+ * Author: David Frey <david.frey@...sirion.com>
+ * Author: Pascal Sachs <pascal.sachs@...sirion.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 <asm/page.h>
+#include <linux/crc8.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/platform_data/sht3x.h>
+
+/* commands (high precision mode) */
+static const unsigned char sht3x_cmd_measure_blocking_hpm[]    = { 0x2c, 0x06 };
+static const unsigned char sht3x_cmd_measure_nonblocking_hpm[] = { 0x24, 0x00 };
+
+/* commands (low power mode) */
+static const unsigned char sht3x_cmd_measure_blocking_lpm[]    = { 0x2c, 0x10 };
+static const unsigned char sht3x_cmd_measure_nonblocking_lpm[] = { 0x24, 0x16 };
+
+/* commands for periodic mode */
+static const unsigned char sht3x_cmd_measure_periodic_mode[]   = { 0xe0, 0x00 };
+static const unsigned char sht3x_cmd_break[]                   = { 0x30, 0x93 };
+
+/* other commands */
+static const unsigned char sht3x_cmd_clear_status_reg[]        = { 0x30, 0x41 };
+static const unsigned char sht3x_cmd_soft_reset[]              = { 0x30, 0xa2 };
+
+/* delays for non-blocking i2c commands, both in us */
+#define SHT3X_NONBLOCKING_WAIT_TIME_HPM  15000
+#define SHT3X_NONBLOCKING_WAIT_TIME_LPM   4000
+
+#define SHT3X_WORD_LEN         2
+#define SHT3X_CMD_LENGTH       2
+#define SHT3X_CRC8_LEN         1
+#define SHT3X_RESPONSE_LENGTH  6
+#define SHT3X_CRC8_LEN         1
+#define SHT3X_CRC8_POLYNOMIAL  0x31
+#define SHT3X_CRC8_INIT        0xFF
+#define SHT3X_ID_SHT           0
+#define SHT3X_ID_STS           1
+
+DECLARE_CRC8_TABLE(sht3x_crc8_table);
+
+/* periodic measure commands (high precision mode) */
+static const char periodic_measure_commands_hpm[][SHT3X_CMD_LENGTH] = {
+	/* 0.5 measurements per second */
+	{0x20, 0x32},
+	/* 1 measurements per second */
+	{0x21, 0x30},
+	/* 2 measurements per second */
+	{0x22, 0x36},
+	/* 4 measurements per second */
+	{0x23, 0x34},
+	/* 10 measurements per second */
+	{0x27, 0x37},
+};
+
+/* periodic measure commands (low power mode) */
+static const char periodic_measure_commands_lpm[][SHT3X_CMD_LENGTH] = {
+	/* 0.5 measurements per second */
+	{0x20, 0x2f},
+	/* 1 measurements per second */
+	{0x21, 0x2d},
+	/* 2 measurements per second */
+	{0x22, 0x2b},
+	/* 4 measurements per second */
+	{0x23, 0x29},
+	/* 10 measurements per second */
+	{0x27, 0x2a},
+};
+
+struct sht3x_alert_commands {
+	const char read_command[SHT3X_CMD_LENGTH];
+	const char write_command[SHT3X_CMD_LENGTH];
+};
+
+const struct sht3x_alert_commands alert_commands[] = {
+	/* temp1_max, humidity1_max */
+	{ {0xe1, 0x1f}, {0x61, 0x1d} },
+	/* temp_1_max_hyst, humidity1_max_hyst */
+	{ {0xe1, 0x14}, {0x61, 0x16} },
+	/* temp1_min, humidity1_min */
+	{ {0xe1, 0x02}, {0x61, 0x00} },
+	/* temp_1_min_hyst, humidity1_min_hyst */
+	{ {0xe1, 0x09}, {0x61, 0x0B} },
+};
+
+
+static const u16 mode_to_frequency[] = {
+	    0,
+	  500,
+	 1000,
+	 2000,
+	 4000,
+	10000,
+};
+
+struct sht3x_data {
+	struct i2c_client *client;
+	struct mutex update_lock;
+
+	u8 mode;
+	const unsigned char *command;
+	u32 wait_time;			/* in us*/
+
+	struct sht3x_platform_data setup;
+
+	int temperature;	/* 1000 * temperature in dgr C */
+	u32 humidity;		/* 1000 * relative humidity in %RH */
+};
+
+
+static int find_index(const u16 *list, size_t size, u16 value)
+{
+	size_t index = 0;
+
+	while (index < size && list[index] != value)
+		index++;
+
+	return index == size ? -1 : index;
+}
+
+static int sht3x_read_from_command(struct i2c_client *client,
+				   struct sht3x_data *data,
+				   const char *command,
+				   char *buf, int length, u32 wait_time)
+{
+	int ret;
+
+	mutex_lock(&data->update_lock);
+
+	ret = i2c_master_send(client, command, SHT3X_CMD_LENGTH);
+
+	if (ret != SHT3X_CMD_LENGTH) {
+		ret = ret < 0 ? ret : -EIO;
+		goto out;
+	}
+
+	if (wait_time)
+		usleep_range(wait_time, wait_time + 1000);
+
+	ret = i2c_master_recv(client, buf, length);
+	if (ret != length) {
+		ret = ret < 0 ? ret : -EIO;
+		goto out;
+	}
+
+	ret = 0;
+out:
+	mutex_unlock(&data->update_lock);
+	return ret;
+
+}
+
+static int sht3x_extract_temperature(u16 raw)
+{
+	/*
+	 * From datasheet:
+	 * T = -45 + 175 * ST / 2^16
+	 * Adapted for integer fixed point (3 digit) arithmetic.
+	 */
+	return ((21875 * (int)raw) >> 13) - 45000;
+}
+
+static u32 sht3x_extract_humidity(u16 raw)
+{
+	/*
+	 * From datasheet:
+	 * RH = 100 * SRH / 2^16
+	 * Adapted for integer fixed point (3 digit) arithmetic.
+	 */
+	return (12500 * (int)raw) >> 13;
+}
+
+/* sysfs attributes */
+static struct sht3x_data *sht3x_update_client(struct device *dev)
+{
+	struct sht3x_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+	unsigned char buf[SHT3X_RESPONSE_LENGTH];
+	u16 val;
+	int ret;
+
+	ret = sht3x_read_from_command(client, data,  data->command,
+				      buf, sizeof(buf), data->wait_time);
+	if (ret)
+		return ERR_PTR(ret);
+
+	val = be16_to_cpup((__be16 *) buf);
+	data->temperature = sht3x_extract_temperature(val);
+	val = be16_to_cpup((__be16 *) (buf + 3));
+	data->humidity = sht3x_extract_humidity(val);
+
+	return data;
+}
+
+static ssize_t temp1_input_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct sht3x_data *data = sht3x_update_client(dev);
+
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+
+	return sprintf(buf, "%d\n", data->temperature);
+}
+
+static ssize_t humidity1_input_show(struct device *dev,
+				    struct device_attribute *attr, char *buf)
+{
+	struct sht3x_data *data = sht3x_update_client(dev);
+
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+
+	return sprintf(buf, "%d\n", data->humidity);
+}
+
+static int alert_read_raw(struct device *dev,
+			  struct device_attribute *attr,
+			  char *buffer, int length)
+{
+	int ret;
+	u8 index;
+	const struct sht3x_alert_commands *commands;
+	struct sht3x_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+
+	index = to_sensor_dev_attr(attr)->index;
+	commands = &alert_commands[index];
+
+	ret = sht3x_read_from_command(client, data, commands->read_command,
+				      buffer, length, 0);
+
+	return ret;
+}
+
+static ssize_t temp1_alert_read(struct device *dev,
+				struct device_attribute *attr,
+				int *temperature)
+{
+	int ret;
+	u16 raw;
+	char buffer[SHT3X_RESPONSE_LENGTH];
+
+	ret = alert_read_raw(dev, attr, buffer, SHT3X_RESPONSE_LENGTH);
+	if (ret)
+		return ret;
+
+	raw = be16_to_cpup((__be16 *) buffer);
+
+	/*
+	 * lower 9 bits are temperature MSB
+	 */
+	*temperature = sht3x_extract_temperature((raw & 0x01ff) << 7);
+
+	return 0;
+}
+
+
+static ssize_t temp1_alert_show(struct device *dev,
+				struct device_attribute *attr,
+				char *buf)
+{
+	int ret;
+	int temperature;
+
+	ret = temp1_alert_read(dev, attr, &temperature);
+	if (ret)
+		return ret;
+
+	return scnprintf(buf, PAGE_SIZE, "%d\n", temperature);
+}
+
+
+static ssize_t humidity1_alert_read(struct device *dev,
+				    struct device_attribute *attr,
+				    u32 *humidity)
+{
+	int ret;
+	u16 raw;
+	char buffer[SHT3X_RESPONSE_LENGTH];
+
+	ret = alert_read_raw(dev, attr, buffer, SHT3X_RESPONSE_LENGTH);
+	if (ret)
+		return ret;
+
+	raw = be16_to_cpup((__be16 *) buffer);
+
+	/*
+	 * top 7 bits are the humidity MSB,
+	 */
+	*humidity = sht3x_extract_humidity(raw & 0xfe00);
+
+	return 0;
+}
+
+static ssize_t humidity1_alert_show(struct device *dev,
+				    struct device_attribute *attr,
+				    char *buf)
+{
+	int ret;
+	u32 humidity;
+
+	ret = humidity1_alert_read(dev, attr, &humidity);
+	if (ret)
+		return ret;
+
+	return scnprintf(buf, PAGE_SIZE, "%d\n", humidity);
+}
+
+static size_t alert_store(struct device *dev,
+			  struct device_attribute *attr,
+			  size_t count,
+			  int temperature,
+			  u32 humidity)
+{
+	char buffer[SHT3X_CMD_LENGTH + SHT3X_WORD_LEN + SHT3X_CRC8_LEN];
+	char *position = buffer;
+	int ret;
+	u16 raw;
+	u8 index;
+	struct sht3x_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+	const struct sht3x_alert_commands *commands;
+
+	index = to_sensor_dev_attr(attr)->index;
+	commands = &alert_commands[index];
+
+	memcpy(position, commands->write_command, SHT3X_CMD_LENGTH);
+	position += SHT3X_CMD_LENGTH;
+	/*
+	 * ST = (T + 45) / 175 * 2^16
+	 * SRH = RH / 100 * 2^16
+	 * adapted for fixed point arithmetic and packed the same as
+	 * in alert_show()
+	 */
+	raw = ((u32)(temperature + 45000) * 24543) >> (16 + 7);
+	raw |= (((u32)humidity * 42950) >> 16) & 0xfe00;
+
+	*(__be16 *)(position) = cpu_to_be16(raw);
+	position += SHT3X_WORD_LEN;
+	*position = crc8(sht3x_crc8_table,
+			 (position - SHT3X_WORD_LEN),
+			 SHT3X_WORD_LEN,
+			 SHT3X_CRC8_INIT);
+
+
+	ret = i2c_master_send(client, buffer, sizeof(buffer));
+	if (ret != sizeof(buffer))
+		return ret < 0 ? ret : -EIO;
+
+	return count;
+
+}
+
+static ssize_t temp1_alert_store(struct device *dev,
+				 struct device_attribute *attr,
+				 const char *buf,
+				 size_t count)
+{
+	int temperature;
+	u32 humidity;
+	int ret;
+
+	ret = kstrtoint(buf, 0, &temperature);
+
+	if (ret)
+		return -EINVAL;
+
+	temperature = clamp_val(temperature, -45000, 130000);
+
+	/*
+	 * use old humidity alert value since we can only update
+	 * temperature and humidity alerts together
+	 */
+	ret = humidity1_alert_read(dev, attr, &humidity);
+	if (ret)
+		return ret;
+
+	ret = alert_store(dev, attr, count, temperature, humidity);
+
+	return ret;
+}
+
+static ssize_t humidity1_alert_store(struct device *dev,
+				     struct device_attribute *attr,
+				     const char *buf,
+				     size_t count)
+{
+	int temperature;
+	u32 humidity;
+	int ret;
+
+	ret = kstrtou32(buf, 0, &humidity);
+
+	if (ret)
+		return -EINVAL;
+
+	humidity = clamp_val(humidity, 0, 100000);
+
+	/*
+	 * use old temperature alert value since we can only update
+	 * temperature and humidity alerts together
+	 */
+	ret = temp1_alert_read(dev, attr, &temperature);
+	if (ret)
+		return ret;
+
+	ret = alert_store(dev, attr, count, temperature, humidity);
+
+	return ret;
+}
+
+static void sht3x_select_command(struct sht3x_data *data)
+{
+	/*
+	 * In blocking mode (clock stretching mode) the I2C bus
+	 * is blocked for other traffic, thus the call to i2c_master_recv()
+	 * will wait until the data is ready. For non blocking mode, we
+	 * have to wait ourselves.
+	 */
+	if (data->mode > 0) {
+		data->command = sht3x_cmd_measure_periodic_mode;
+		data->wait_time = 0;
+	} else if (data->setup.blocking_io) {
+		data->command = data->setup.high_precision ?
+				sht3x_cmd_measure_blocking_hpm :
+				sht3x_cmd_measure_blocking_lpm;
+		data->wait_time = 0;
+	} else {
+		if (data->setup.high_precision) {
+			data->command = sht3x_cmd_measure_nonblocking_hpm;
+			data->wait_time = SHT3X_NONBLOCKING_WAIT_TIME_HPM;
+		} else {
+			data->command = sht3x_cmd_measure_nonblocking_lpm;
+			data->wait_time = SHT3X_NONBLOCKING_WAIT_TIME_LPM;
+		}
+	}
+}
+
+static ssize_t frequency_show(struct device *dev,
+			      struct device_attribute *attr,
+			      char *buf) {
+	struct sht3x_data *data = dev_get_drvdata(dev);
+
+	return scnprintf(buf, PAGE_SIZE, "%d\n", mode_to_frequency[data->mode]);
+}
+
+static ssize_t frequency_store(struct device *dev,
+			       struct device_attribute *attr,
+			       const char *buf,
+			       size_t count) {
+	u16 frequency;
+	int mode;
+	int ret;
+	const char *command;
+	struct sht3x_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+
+	ret = kstrtou16(buf, 0, &frequency);
+
+	if (ret)
+		return -EINVAL;
+
+	mode = find_index(mode_to_frequency, sizeof(mode_to_frequency),
+			  frequency);
+
+	/* invalid frequency */
+	if (mode < 0)
+		return -EINVAL;
+
+	/* mode did not change */
+	if (mode == data->mode)
+		return count;
+
+	/* abort periodic measure */
+	ret = i2c_master_send(client, sht3x_cmd_break, SHT3X_CMD_LENGTH);
+	if (ret != SHT3X_CMD_LENGTH)
+		return ret < 0 ? ret : -EIO;
+	data->mode = 0;
+
+	if (mode > 0) {
+		if (data->setup.high_precision)
+			command = periodic_measure_commands_hpm[mode - 1];
+		else
+			command = periodic_measure_commands_lpm[mode - 1];
+
+		/* select mode */
+		ret = i2c_master_send(client, command, SHT3X_CMD_LENGTH);
+		if (ret != SHT3X_CMD_LENGTH)
+			return ret < 0 ? ret : -EIO;
+	}
+
+	/* select mode and command */
+	data->mode = mode;
+	sht3x_select_command(data);
+
+	return count;
+}
+
+static ssize_t soft_reset(struct device *dev,
+			  struct device_attribute *attr,
+			  const char *buf,
+			  size_t count) {
+	int ret;
+	struct sht3x_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+
+	/* break if in periodic measure mode */
+	if (data->mode > 0) {
+		ret = i2c_master_send(client, sht3x_cmd_break,
+				      SHT3X_CMD_LENGTH);
+		if (ret != SHT3X_CMD_LENGTH)
+			return ret < 0 ? ret : -EIO;
+		data->mode = 0;
+	}
+
+	/* clear status register */
+	ret = i2c_master_send(client, sht3x_cmd_clear_status_reg,
+			      SHT3X_CMD_LENGTH);
+	if (ret != SHT3X_CMD_LENGTH)
+		return ret < 0 ? ret : -EIO;
+
+	/* soft reset */
+	ret = i2c_master_send(client, sht3x_cmd_soft_reset, SHT3X_CMD_LENGTH);
+	if (ret != SHT3X_CMD_LENGTH)
+		return ret < 0 ? ret : -EIO;
+
+	return count;
+}
+
+static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, temp1_input_show, NULL, 0);
+static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO, humidity1_input_show,
+			  NULL, 0);
+static SENSOR_DEVICE_ATTR(temp1_max, S_IRUGO | S_IWUSR, temp1_alert_show,
+			  temp1_alert_store, 0);
+static SENSOR_DEVICE_ATTR(humidity1_max, S_IRUGO | S_IWUSR,
+			  humidity1_alert_show, humidity1_alert_store, 0);
+static SENSOR_DEVICE_ATTR(temp1_max_hyst, S_IRUGO | S_IWUSR, temp1_alert_show,
+			  temp1_alert_store, 1);
+static SENSOR_DEVICE_ATTR(humidity1_max_hyst, S_IRUGO | S_IWUSR,
+			  humidity1_alert_show, humidity1_alert_store, 1);
+static SENSOR_DEVICE_ATTR(temp1_min, S_IRUGO | S_IWUSR, temp1_alert_show,
+			  temp1_alert_store, 2);
+static SENSOR_DEVICE_ATTR(humidity1_min, S_IRUGO | S_IWUSR,
+			  humidity1_alert_show, humidity1_alert_store, 2);
+static SENSOR_DEVICE_ATTR(temp1_min_hyst, S_IRUGO | S_IWUSR,
+			  temp1_alert_show, temp1_alert_store, 3);
+static SENSOR_DEVICE_ATTR(humidity1_min_hyst, S_IRUGO | S_IWUSR,
+			  humidity1_alert_show, humidity1_alert_store, 3);
+static SENSOR_DEVICE_ATTR(frequency, S_IRUGO | S_IWUSR, frequency_show,
+			  frequency_store, 0);
+static SENSOR_DEVICE_ATTR(soft_reset, S_IWUSR, NULL, soft_reset, 0);
+
+static struct attribute *sht3x_attrs[] = {
+	&sensor_dev_attr_temp1_input.dev_attr.attr,
+	&sensor_dev_attr_humidity1_input.dev_attr.attr,
+	&sensor_dev_attr_temp1_max.dev_attr.attr,
+	&sensor_dev_attr_temp1_max_hyst.dev_attr.attr,
+	&sensor_dev_attr_humidity1_max.dev_attr.attr,
+	&sensor_dev_attr_humidity1_max_hyst.dev_attr.attr,
+	&sensor_dev_attr_temp1_min.dev_attr.attr,
+	&sensor_dev_attr_temp1_min_hyst.dev_attr.attr,
+	&sensor_dev_attr_humidity1_min.dev_attr.attr,
+	&sensor_dev_attr_humidity1_min_hyst.dev_attr.attr,
+	&sensor_dev_attr_frequency.dev_attr.attr,
+	&sensor_dev_attr_soft_reset.dev_attr.attr,
+	NULL
+};
+
+static struct attribute *sts3x_attrs[] = {
+	&sensor_dev_attr_temp1_input.dev_attr.attr,
+	NULL
+};
+
+ATTRIBUTE_GROUPS(sht3x);
+ATTRIBUTE_GROUPS(sts3x);
+
+static int sht3x_probe(struct i2c_client *client,
+		       const struct i2c_device_id *id)
+{
+	int ret;
+	struct sht3x_data *data;
+	struct device *hwmon_dev;
+	struct i2c_adapter *adap = client->adapter;
+	struct device *dev = &client->dev;
+	const struct attribute_group **attribute_groups;
+
+	/*
+	 * we require full i2c support since the sht3x uses multi-byte read and
+	 * writes as well as multi-byte commands which are not supported by
+	 * the smbus protocol
+	 */
+	if (!i2c_check_functionality(adap, I2C_FUNC_I2C))
+		return -ENODEV;
+
+	ret = i2c_master_send(client, sht3x_cmd_clear_status_reg,
+			      SHT3X_CMD_LENGTH);
+	if (ret != SHT3X_CMD_LENGTH)
+		return ret < 0 ? ret : -ENODEV;
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->setup.blocking_io = false;
+	data->setup.high_precision = true;
+	data->mode = 0;
+	data->client = client;
+	crc8_populate_msb(sht3x_crc8_table, SHT3X_CRC8_POLYNOMIAL);
+
+	if (client->dev.platform_data)
+		data->setup = *(struct sht3x_platform_data *)dev->platform_data;
+	sht3x_select_command(data);
+	mutex_init(&data->update_lock);
+
+	if (id->driver_data == SHT3X_ID_STS)
+		attribute_groups = sts3x_groups;
+	else
+		attribute_groups = sht3x_groups;
+
+	hwmon_dev = devm_hwmon_device_register_with_groups(dev,
+			client->name,
+			data, attribute_groups);
+
+	if (IS_ERR(hwmon_dev))
+		dev_dbg(dev, "unable to register hwmon device\n");
+
+	return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+/* device ID table */
+static const struct i2c_device_id sht3x_id[] = {
+	{"sht3x", SHT3X_ID_SHT},
+	{"sts3x", SHT3X_ID_STS},
+	{}
+};
+
+MODULE_DEVICE_TABLE(i2c, sht3x_id);
+
+static struct i2c_driver sht3x_i2c_driver = {
+	.driver.name = "sht3x",
+	.probe       = sht3x_probe,
+	.id_table    = sht3x_id,
+};
+
+module_i2c_driver(sht3x_i2c_driver);
+
+MODULE_AUTHOR("David Frey <david.frey@...sirion.com>");
+MODULE_AUTHOR("Pascal Sachs <pascal.sachs@...sirion.com>");
+MODULE_DESCRIPTION("Sensirion SHT3x humidity and temperature sensor driver");
+MODULE_LICENSE("GPL");
diff --git a/drivers/hwmon/twl4030-madc-hwmon.c b/drivers/hwmon/twl4030-madc-hwmon.c
index b5caf7f..8201173 100644
--- a/drivers/hwmon/twl4030-madc-hwmon.c
+++ b/drivers/hwmon/twl4030-madc-hwmon.c
@@ -25,6 +25,7 @@
  */
 #include <linux/init.h>
 #include <linux/module.h>
+//FIXME this is used for clamp_val
 #include <linux/kernel.h>
 #include <linux/i2c/twl.h>
 #include <linux/device.h>
diff --git a/include/linux/platform_data/sht3x.h b/include/linux/platform_data/sht3x.h
new file mode 100644
index 0000000..46af9a0
--- /dev/null
+++ b/include/linux/platform_data/sht3x.h
@@ -0,0 +1,25 @@
+/*
+ * Copyright (C) 2015 Sensirion AG, Switzerland
+ * Author: David Frey <david.frey@...sirion.com>
+ * Author: Pascal Sachs <pascal.sachs@...sirion.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.
+ *
+ */
+
+#ifndef __SHT3X_H_
+#define __SHT3X_H_
+
+struct sht3x_platform_data {
+	bool blocking_io;
+	bool high_precision;
+};
+#endif /* __SHT3X_H_ */
-- 
1.9.1

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