[PATCH 1/2] iio: chemical: sgpxx: Support Sensirion SGPxx sensors

[Andreas Brauchli <a.brauchli@elementarea.net>]

Support Sensirion SGP30 and SGPC3 multi-pixel I2C gas sensors

Supported Features:

* Indoor Air Quality (IAQ) concentrations for
  SGP30 and SGPC3:
  - tVOC (in_concentration_voc_input)
  SGP30 only:
  - CO2eq (in_concentration_co2_input)
  IAQ must first be initialized by writing a non-empty value to
  out_iaq_init. After initializing IAQ, at least one IAQ signal must
  be read out every second (SGP30) / every two seconds (SGPC3) for the
  sensor to correctly maintain its internal baseline
* Baseline support for IAQ (in_iaq_baseline, out_iaq_baseline)
* Gas concentration signals for
  SGP30 and SGPC3:
  - Ethanol (in_concentration_ethanol_raw)
  SGP30 only:
  - H2 (in_concentration_h2_raw)
* On-chip self test (in_selftest)
  The self test interferes with IAQ operations. If needed, first
  retrieve the current baseline, then reset it after the self test
* Sensor interface version (in_feature_set_version)
* Sensor serial number (in_serial_id)
* Humidity compensation for SGP30
  With the help of a humidity signal, the gas signals can be
  humidity-compensated.
* Checksummed I2C communication

For all features, refer to the data sheet or the documentation in
Documentation/iio/chemical/sgpxx.txt for more details.

Signed-off-by: Andreas Brauchli <andreas.brauchli@sensirion.com>
---
 Documentation/iio/chemical/sgpxx.txt | 112 +++++
 drivers/iio/chemical/Kconfig         |  13 +
 drivers/iio/chemical/Makefile        |   1 +
 drivers/iio/chemical/sgpxx.c         | 894 +++++++++++++++++++++++++++++++++++
 4 files changed, 1020 insertions(+)
 create mode 100644 Documentation/iio/chemical/sgpxx.txt
 create mode 100644 drivers/iio/chemical/sgpxx.c

diff --git a/Documentation/iio/chemical/sgpxx.txt b/Documentation/iio/chemical/sgpxx.txt
new file mode 100644
index 000000000000..f49b2f365df3
--- /dev/null
+++ b/Documentation/iio/chemical/sgpxx.txt
@@ -0,0 +1,112 @@
+sgpxx: Industrial IO driver for Sensirion i2c Multi-Pixel Gas Sensors
+
+1. Overview
+
+The sgpxx driver supports the Sensirion SGP30 and SGPC3 multi-pixel gas sensors.
+
+Datasheets:
+https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/9_Gas_Sensors/Sensirion_Gas_Sensors_SGP30_Datasheet_EN.pdf
+https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/9_Gas_Sensors/Sensirion_Gas_Sensors_SGPC3_Datasheet_EN.pdf
+
+2. Modes of Operation
+
+2.1. Driver Instantiation
+
+The sgpxx driver must be instantiated on the corresponding i2c bus with the
+product name (sgp30 or sgpc3) and i2c address (0x58).
+
+Example instantiation of an sgp30 on i2c bus 1 (i2c-1):
+
+    $ echo sgp30 0x58 | sudo tee /sys/bus/i2c/devices/i2c-1/new_device
+
+Using the wrong product name results in an instantiation error. Check dmesg.
+
+2.2. Indoor Air Quality (IAQ) concentrations
+
+* tVOC (in_concentration_voc_input) at ppb precision (1e-9)
+* CO2eq (in_concentration_co2_input) at ppm precision (1e-6) -- SGP30 only
+
+2.2.1. IAQ Initialization
+Before Indoor Air Quality (IAQ) values can be read, the IAQ mode must be
+initialized by writing a non-empty value to out_iaq_init:
+
+    $ echo init > out_iaq_init
+
+After initializing IAQ, at least one IAQ signal must be read out every second
+(SGP30) / every two seconds (SGPC3) for the sensor to correctly maintain its
+internal baseline:
+
+    SGP30:
+    $ watch -n1 cat in_concentration_voc_input
+
+    SGPC3:
+    $ watch -n2 cat in_concentration_voc_input
+
+For the first 15s of operation after writing to out_iaq_init, default values are
+retured by the sensor.
+
+2.2.2. Pausing and Resuming IAQ
+
+For best performance and faster startup times, the baseline should be saved
+once every hour, after 12h of operation. The baseline is restored by writing a
+non-empty value to out_iaq_init, followed by writing an unmodified retrieved
+baseline value from in_iaq_baseline to out_iaq_baseline.
+
+    Saving the baseline:
+    $ baseline=$(cat in_iaq_baseline)
+
+    Restoring the baseline:
+    $ echo init > out_iaq_init
+    $ echo -n $baseline > out_iaq_baseline
+
+2.3. Gas Concentration Signals
+
+* Ethanol (in_concentration_ethanol_raw)
+* H2 (in_concentration_h2_raw) -- SGP30 only
+
+The gas signals in_concentration_ethanol_raw and in_concentration_h2_raw may be
+used without prior write to out_iaq_init.
+
+2.4. Humidity Compensation (SGP30)
+
+The SGP30 features an on-chip humidity compensation that requires the
+(in-device) environment's absolute humidity.
+
+Set the absolute humidity by writing the absolute humidity concentration (in
+mg/m^3) to out_concentration_ah_raw. The absolute humidity is obtained by
+converting the relative humidity and temperature. The following units are used:
+AH in mg/m^3, RH in percent (0..100), T in degrees Celsius, and exp() being the
+base-e exponential function.
+
+                  RH            exp(17.62 * T)
+                ----- * 6.112 * --------------
+                100.0            243.12 + T
+  AH = 216.7 * ------------------------------- * 1000
+                        273.15 + T
+
+Writing a value of 0 to out_absolute_humidity disables the humidity
+compensation.
+
+2.5. On-chip self test
+
+    $ cat in_selftest
+
+in_selftest returns OK or FAILED.
+
+The self test interferes with IAQ operations. If needed, first save the current
+baseline, then restore it after the self test:
+
+    $ baseline=$(cat in_iaq_baseline)
+    $ cat in_selftest
+    $ echo init > out_iaq_init
+    $ echo -n $baseline > out_iaq_baseline
+
+If the sensor's current operating duration is less than 12h the baseline should
+not be restored by skipping the last step.
+
+3. Sensor Interface
+
+    $ cat in_feature_set_version
+
+The SGP sensors' minor interface (feature set) version guarantees interface
+stability: a sensor with feature set 1.1 works with a driver for feature set 1.0
diff --git a/drivers/iio/chemical/Kconfig b/drivers/iio/chemical/Kconfig
index 5cb5be7612b4..4574dd687513 100644
--- a/drivers/iio/chemical/Kconfig
+++ b/drivers/iio/chemical/Kconfig
@@ -38,6 +38,19 @@ config IAQCORE
 	  iAQ-Core Continuous/Pulsed VOC (Volatile Organic Compounds)
 	  sensors
 
+config SENSIRION_SGPXX
+	tristate "Sensirion SGPxx gas sensors"
+	depends on I2C
+	select CRC8
+	help
+	  Say Y here to build I2C interface support for the following
+	  Sensirion SGP gas sensors:
+	    * SGP30 gas sensor
+	    * SGPC3 gas sensor
+
+	  To compile this driver as module, choose M here: the
+	  module will be called sgpxx.
+
 config VZ89X
 	tristate "SGX Sensortech MiCS VZ89X VOC sensor"
 	depends on I2C
diff --git a/drivers/iio/chemical/Makefile b/drivers/iio/chemical/Makefile
index a629b29d1e0b..6090a0ae3981 100644
--- a/drivers/iio/chemical/Makefile
+++ b/drivers/iio/chemical/Makefile
@@ -6,4 +6,5 @@
 obj-$(CONFIG_ATLAS_PH_SENSOR)	+= atlas-ph-sensor.o
 obj-$(CONFIG_CCS811)		+= ccs811.o
 obj-$(CONFIG_IAQCORE)		+= ams-iaq-core.o
+obj-$(CONFIG_SENSIRION_SGPXX)	+= sgpxx.o
 obj-$(CONFIG_VZ89X)		+= vz89x.o
diff --git a/drivers/iio/chemical/sgpxx.c b/drivers/iio/chemical/sgpxx.c
new file mode 100644
index 000000000000..aea55e41d4cc
--- /dev/null
+++ b/drivers/iio/chemical/sgpxx.c
@@ -0,0 +1,894 @@
+/*
+ * sgpxx.c - Support for Sensirion SGP Gas Sensors
+ *
+ * Copyright (C) 2017 Andreas Brauchli <andreas.brauchli@sensirion.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.
+ *
+ * Datasheets:
+ * https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/9_Gas_Sensors/Sensirion_Gas_Sensors_SGP30_Datasheet_EN.pdf
+ * https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/9_Gas_Sensors/Sensirion_Gas_Sensors_SGPC3_Datasheet_EN.pdf
+ */
+
+#include <linux/crc8.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/init.h>
+#include <linux/i2c.h>
+#include <linux/of_device.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/sysfs.h>
+
+#define SGP_WORD_LEN			2
+#define SGP_CRC8_POLYNOMIAL		0x31
+#define SGP_CRC8_INIT			0xff
+#define SGP_CRC8_LEN			1
+#define SGP_CMD(cmd_word)		cpu_to_be16(cmd_word)
+#define SGP_CMD_DURATION_US		50000
+#define SGP_SELFTEST_DURATION_US	220000
+#define SGP_CMD_HANDLING_DURATION_US	10000
+#define SGP_CMD_LEN			SGP_WORD_LEN
+#define SGP30_MEASUREMENT_LEN		2
+#define SGPC3_MEASUREMENT_LEN		2
+#define SGP30_MEASURE_INTERVAL_HZ	1
+#define SGPC3_MEASURE_INTERVAL_HZ	2
+#define SGP_SELFTEST_OK			0xd400
+
+DECLARE_CRC8_TABLE(sgp_crc8_table);
+
+enum sgp_product_id {
+	SGP30 = 0,
+	SGPC3
+};
+
+enum sgp30_channel_idx {
+	SGP30_IAQ_TVOC_IDX = 0,
+	SGP30_IAQ_CO2EQ_IDX,
+	SGP30_SIG_ETOH_IDX,
+	SGP30_SIG_H2_IDX,
+	SGP30_SET_AH_IDX,
+};
+
+enum sgpc3_channel_idx {
+	SGPC3_IAQ_TVOC_IDX = 10,
+	SGPC3_SIG_ETOH_IDX,
+};
+
+enum sgp_cmd {
+	SGP_CMD_IAQ_INIT		= SGP_CMD(0x2003),
+	SGP_CMD_IAQ_MEASURE		= SGP_CMD(0x2008),
+	SGP_CMD_GET_BASELINE		= SGP_CMD(0x2015),
+	SGP_CMD_SET_BASELINE		= SGP_CMD(0x201e),
+	SGP_CMD_GET_FEATURE_SET		= SGP_CMD(0x202f),
+	SGP_CMD_GET_SERIAL_ID		= SGP_CMD(0x3682),
+	SGP_CMD_MEASURE_TEST		= SGP_CMD(0x2032),
+
+	SGP30_CMD_MEASURE_SIGNAL	= SGP_CMD(0x2050),
+	SGP30_CMD_SET_ABSOLUTE_HUMIDITY = SGP_CMD(0x2061),
+
+	SGPC3_CMD_IAQ_INIT0		= SGP_CMD(0x2089),
+	SGPC3_CMD_IAQ_INIT16		= SGP_CMD(0x2024),
+	SGPC3_CMD_IAQ_INIT64		= SGP_CMD(0x2003),
+	SGPC3_CMD_IAQ_INIT184		= SGP_CMD(0x206a),
+	SGPC3_CMD_MEASURE_RAW		= SGP_CMD(0x2046),
+};
+
+enum sgp_measure_mode {
+	SGP_MEASURE_MODE_UNKNOWN,
+	SGP_MEASURE_MODE_IAQ,
+	SGP_MEASURE_MODE_SIGNAL,
+	SGP_MEASURE_MODE_ALL,
+};
+
+struct sgp_version {
+	u8 major;
+	u8 minor;
+};
+
+struct sgp_crc_word {
+	__be16 value;
+	u8 crc8;
+} __attribute__((__packed__));
+
+union sgp_reading {
+	u8 start;
+	struct sgp_crc_word raw_words[4];
+};
+
+struct sgp_data {
+	struct i2c_client *client;
+	struct mutex data_lock; /* mutex to lock access to data buffer */
+	struct mutex i2c_lock; /* mutex to lock access to i2c */
+	unsigned long last_update;
+
+	u64 serial_id;
+	u16 chip_id;
+	u16 feature_set;
+	u16 measurement_len;
+	int measure_interval_hz;
+	enum sgp_cmd measure_iaq_cmd;
+	enum sgp_cmd measure_signal_cmd;
+	enum sgp_measure_mode measure_mode;
+	char *baseline_format;
+	bool iaq_initialized;
+	u8 baseline_len;
+	union sgp_reading buffer;
+};
+
+struct sgp_device {
+	const struct iio_chan_spec *channels;
+	int num_channels;
+};
+
+static const struct sgp_version supported_versions_sgp30[] = {
+	{
+		.major = 1,
+		.minor = 0,
+	}
+};
+
+static const struct sgp_version supported_versions_sgpc3[] = {
+	{
+		.major = 0,
+		.minor = 4,
+	}
+};
+
+static const struct iio_chan_spec sgp30_channels[] = {
+	{
+		.type = IIO_CONCENTRATION,
+		.channel2 = IIO_MOD_VOC,
+		.datasheet_name = "TVOC signal",
+		.scan_index = 0,
+		.modified = 1,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
+		.address = SGP30_IAQ_TVOC_IDX,
+	},
+	{
+		.type = IIO_CONCENTRATION,
+		.channel2 = IIO_MOD_CO2,
+		.datasheet_name = "CO2eq signal",
+		.scan_index = 1,
+		.modified = 1,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
+		.address = SGP30_IAQ_CO2EQ_IDX,
+	},
+	{
+		.type = IIO_CONCENTRATION,
+		.info_mask_separate =
+			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
+		.address = SGP30_SIG_ETOH_IDX,
+		.extend_name = "ethanol",
+		.datasheet_name = "Ethanol signal",
+		.scan_index = 2,
+		.scan_type = {
+			.endianness = IIO_BE,
+		},
+	},
+	{
+		.type = IIO_CONCENTRATION,
+		.info_mask_separate =
+			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
+		.address = SGP30_SIG_H2_IDX,
+		.extend_name = "h2",
+		.datasheet_name = "H2 signal",
+		.scan_index = 3,
+		.scan_type = {
+			.endianness = IIO_BE,
+		},
+	},
+	IIO_CHAN_SOFT_TIMESTAMP(4),
+	{
+		.type = IIO_CONCENTRATION,
+		.address = SGP30_SET_AH_IDX,
+		.extend_name = "ah",
+		.datasheet_name = "absolute humidty",
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+		.output = 1,
+		.scan_index = 5
+	},
+};
+
+static const struct iio_chan_spec sgpc3_channels[] = {
+	{
+		.type = IIO_CONCENTRATION,
+		.channel2 = IIO_MOD_VOC,
+		.datasheet_name = "TVOC signal",
+		.modified = 1,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
+		.address = SGPC3_IAQ_TVOC_IDX,
+	},
+	{
+		.type = IIO_CONCENTRATION,
+		.info_mask_separate =
+			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
+		.address = SGPC3_SIG_ETOH_IDX,
+		.extend_name = "ethanol",
+		.datasheet_name = "Ethanol signal",
+		.scan_index = 0,
+		.scan_type = {
+			.endianness = IIO_BE,
+		},
+	},
+	IIO_CHAN_SOFT_TIMESTAMP(2),
+};
+
+static struct sgp_device sgp_devices[] = {
+	[SGP30] = {
+		.channels = sgp30_channels,
+		.num_channels = ARRAY_SIZE(sgp30_channels),
+	},
+	[SGPC3] = {
+		.channels = sgpc3_channels,
+		.num_channels = ARRAY_SIZE(sgpc3_channels),
+	},
+};
+
+/**
+ * sgp_verify_buffer() - verify the checksums of the data buffer words
+ *
+ * @data:       SGP data containing the raw buffer
+ * @word_count: Num data words stored in the buffer, excluding CRC bytes
+ *
+ * Return:      0 on success, negative error code otherwise
+ */
+static int sgp_verify_buffer(struct sgp_data *data, size_t word_count)
+{
+	size_t size = word_count * (SGP_WORD_LEN + SGP_CRC8_LEN);
+	int i;
+	u8 crc;
+	u8 *data_buf = &data->buffer.start;
+
+	for (i = 0; i < size; i += SGP_WORD_LEN + SGP_CRC8_LEN) {
+		crc = crc8(sgp_crc8_table, &data_buf[i], SGP_WORD_LEN,
+			   SGP_CRC8_INIT);
+		if (crc != data_buf[i + SGP_WORD_LEN]) {
+			dev_err(&data->client->dev, "CRC error\n");
+			return -EIO;
+		}
+	}
+	return 0;
+}
+
+/**
+ * sgp_read_from_cmd() - reads data from SGP sensor after issuing a command
+ * The caller must hold data->data_lock for the duration of the call.
+ * @data:        SGP data
+ * @cmd:         SGP Command to issue
+ * @word_count:  Num words to read, excluding CRC bytes
+ *
+ * Return:       0 on success, negative error otherwise.
+ */
+static int sgp_read_from_cmd(struct sgp_data *data,
+			     enum sgp_cmd cmd,
+			     size_t word_count,
+			     unsigned long duration_us)
+{
+	int ret;
+	struct i2c_client *client = data->client;
+	size_t size = word_count * (SGP_WORD_LEN + SGP_CRC8_LEN);
+	u8 *data_buf = &data->buffer.start;
+
+	mutex_lock(&data->i2c_lock);
+	ret = i2c_master_send(client, (const char *)&cmd, SGP_CMD_LEN);
+	if (ret != SGP_CMD_LEN) {
+		mutex_unlock(&data->i2c_lock);
+		return -EIO;
+	}
+	usleep_range(duration_us, duration_us + 1000);
+
+	ret = i2c_master_recv(client, data_buf, size);
+	mutex_unlock(&data->i2c_lock);
+
+	if (ret < 0)
+		ret = -ETXTBSY;
+	else if (ret != size)
+		ret = -EINTR;
+	else
+		ret = sgp_verify_buffer(data, word_count);
+
+	return ret;
+}
+
+/**
+ * sgp_i2c_write_from_cmd() - write data to SGP sensor with a command
+ * @data:       SGP data
+ * @cmd:        SGP Command to issue
+ * @buf:        Data to write
+ * @buf_size:   Data size of the buffer
+ *
+ * Return:      0 on success, negative error otherwise.
+ */
+static int sgp_write_from_cmd(struct sgp_data *data,
+			      enum sgp_cmd cmd,
+			      u16 *buf,
+			      size_t buf_size,
+			      unsigned long duration_us)
+{
+	int ret, ix;
+	u16 buf_idx = 0;
+	u16 buffer_size = SGP_CMD_LEN + buf_size *
+		(SGP_WORD_LEN + SGP_CRC8_LEN);
+	u8 buffer[buffer_size];
+
+	/* assemble buffer */
+	*((u16 *)&buffer[0]) = cmd;
+	buf_idx += SGP_CMD_LEN;
+	for (ix = 0; ix < buf_size; ix++) {
+		*((u16 *)&buffer[buf_idx]) = ntohs(buf[ix] & 0xffff);
+		buf_idx += SGP_WORD_LEN;
+		buffer[buf_idx] = crc8(sgp_crc8_table,
+				       &buffer[buf_idx - SGP_WORD_LEN],
+				       SGP_WORD_LEN, SGP_CRC8_INIT);
+		buf_idx += SGP_CRC8_LEN;
+	}
+	mutex_lock(&data->i2c_lock);
+	ret = i2c_master_send(data->client, buffer, buffer_size);
+	if (ret != buffer_size) {
+		ret = -EIO;
+		goto unlock_return_count;
+	}
+	ret = 0;
+	/* Wait inside lock to ensure the chip is ready before next command */
+	usleep_range(duration_us, duration_us + 1000);
+
+unlock_return_count:
+	mutex_unlock(&data->i2c_lock);
+	return ret;
+}
+
+/**
+ * sgp_get_measurement() - retrieve measurement result from sensor
+ * The caller must hold data->data_lock for the duration of the call.
+ * @data:           SGP data
+ * @cmd:            SGP Command to issue
+ * @measure_mode:   SGP measurement mode
+ *
+ * Return:      0 on success, negative error otherwise.
+ */
+static int sgp_get_measurement(struct sgp_data *data, enum sgp_cmd cmd,
+			       enum sgp_measure_mode measure_mode)
+{
+	int ret;
+
+	/* if all channels are measured, we don't need to distinguish between
+	 * different measure modes
+	 */
+	if (data->measure_mode == SGP_MEASURE_MODE_ALL)
+		measure_mode = SGP_MEASURE_MODE_ALL;
+
+	/* Always measure if measure mode changed
+	 * SGP30 should only be polled once a second
+	 * SGPC3 should only be polled once every two seconds
+	 */
+	if (measure_mode == data->measure_mode &&
+	    !time_after(jiffies,
+			data->last_update + data->measure_interval_hz * HZ)) {
+		return 0;
+	}
+
+	ret = sgp_read_from_cmd(data, cmd, data->measurement_len,
+				SGP_CMD_DURATION_US);
+
+	if (ret < 0)
+		return ret;
+
+	data->measure_mode = measure_mode;
+	data->last_update = jiffies;
+
+	return 0;
+}
+
+static int sgp_absolute_humidity_store(struct sgp_data *data,
+				       int val, int val2)
+{
+	u32 ah;
+	u16 ah_scaled;
+
+	if (val < 0 || val > 256 || (val == 256 && val2 > 0))
+		return -EINVAL;
+
+	ah = val * 1000 + val2 / 1000;
+	/* ah_scaled = (u16)((ah / 1000.0) * 256.0) */
+	ah_scaled = (u16)(((u64)ah * 256 * 16777) >> 24);
+
+	/* ensure we don't disable AH compensation due to rounding */
+	if (ah > 0 && ah_scaled == 0)
+		ah_scaled = 1;
+
+	return sgp_write_from_cmd(data, SGP30_CMD_SET_ABSOLUTE_HUMIDITY,
+				  &ah_scaled, 1, SGP_CMD_HANDLING_DURATION_US);
+}
+
+static int sgp_read_raw(struct iio_dev *indio_dev,
+			struct iio_chan_spec const *chan, int *val,
+			int *val2, long mask)
+{
+	struct sgp_data *data = iio_priv(indio_dev);
+	struct sgp_crc_word *words;
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_PROCESSED:
+		mutex_lock(&data->data_lock);
+		if (!data->iaq_initialized) {
+			dev_warn(&data->client->dev,
+				 "IAQ potentially uninitialized\n");
+		}
+		ret = sgp_get_measurement(data, data->measure_iaq_cmd,
+					  SGP_MEASURE_MODE_IAQ);
+		if (ret)
+			goto unlock_fail;
+		words = data->buffer.raw_words;
+		switch (chan->address) {
+		case SGP30_IAQ_TVOC_IDX:
+		case SGPC3_IAQ_TVOC_IDX:
+			*val = 0;
+			*val2 = be16_to_cpu(words[1].value);
+			ret = IIO_VAL_INT_PLUS_NANO;
+			break;
+		case SGP30_IAQ_CO2EQ_IDX:
+			*val = 0;
+			*val2 = be16_to_cpu(words[0].value);
+			ret = IIO_VAL_INT_PLUS_MICRO;
+			break;
+		default:
+			ret = -EINVAL;
+			break;
+		}
+		mutex_unlock(&data->data_lock);
+		break;
+	case IIO_CHAN_INFO_RAW:
+		mutex_lock(&data->data_lock);
+		ret = sgp_get_measurement(data, data->measure_signal_cmd,
+					  SGP_MEASURE_MODE_SIGNAL);
+		if (ret)
+			goto unlock_fail;
+		words = data->buffer.raw_words;
+		switch (chan->address) {
+		case SGP30_SIG_ETOH_IDX:
+			*val = be16_to_cpu(words[1].value);
+			ret = IIO_VAL_INT;
+			break;
+		case SGPC3_SIG_ETOH_IDX:
+		case SGP30_SIG_H2_IDX:
+			*val = be16_to_cpu(words[0].value);
+			ret = IIO_VAL_INT;
+			break;
+		}
+unlock_fail:
+		mutex_unlock(&data->data_lock);
+		break;
+	case IIO_CHAN_INFO_SCALE:
+		switch (chan->address) {
+		case SGP30_SIG_ETOH_IDX:
+		case SGPC3_SIG_ETOH_IDX:
+		case SGP30_SIG_H2_IDX:
+			*val = 0;
+			*val2 = 1953125;
+			ret = IIO_VAL_INT_PLUS_NANO;
+			break;
+		default:
+			ret = -EINVAL;
+			break;
+		}
+		break;
+	default:
+		ret = -EINVAL;
+	}
+	return ret;
+}
+
+static int sgp_write_raw(struct iio_dev *indio_dev,
+			 struct iio_chan_spec const *chan,
+			 int val, int val2, long mask)
+{
+	struct sgp_data *data = iio_priv(indio_dev);
+	int ret;
+
+	switch (chan->address) {
+	case SGP30_SET_AH_IDX:
+		ret = sgp_absolute_humidity_store(data, val, val2);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
+	return ret;
+}
+
+static ssize_t sgp_iaq_init_store(struct device *dev,
+				  struct device_attribute *attr,
+				  const char *buf, size_t count)
+{
+	struct sgp_data *data = iio_priv(dev_to_iio_dev(dev));
+	u32 init_time;
+	enum sgp_cmd cmd;
+	int ret;
+
+	cmd = SGP_CMD_IAQ_INIT;
+	if (data->chip_id == SGPC3) {
+		ret = kstrtou32(buf, 10, &init_time);
+
+		if (ret)
+			return -EINVAL;
+
+		switch (init_time) {
+		case 0:
+			cmd = SGPC3_CMD_IAQ_INIT0;
+			break;
+		case 16:
+			cmd = SGPC3_CMD_IAQ_INIT16;
+			break;
+		case 64:
+			cmd = SGPC3_CMD_IAQ_INIT64;
+			break;
+		case 184:
+			cmd = SGPC3_CMD_IAQ_INIT184;
+			break;
+		default:
+			return -EINVAL;
+		}
+	}
+
+	mutex_lock(&data->data_lock);
+	ret = sgp_read_from_cmd(data, cmd, 0, SGP_CMD_DURATION_US);
+
+	if (ret < 0)
+		goto unlock_fail;
+
+	data->iaq_initialized = true;
+	mutex_unlock(&data->data_lock);
+	return count;
+
+unlock_fail:
+	mutex_unlock(&data->data_lock);
+	return ret;
+}
+
+static ssize_t sgp_iaq_baseline_show(struct device *dev,
+				     struct device_attribute *attr,
+				     char *buf)
+{
+	struct sgp_data *data = iio_priv(dev_to_iio_dev(dev));
+	u32 baseline;
+	u16 baseline_word;
+	int ret, ix;
+
+	mutex_lock(&data->data_lock);
+	ret = sgp_read_from_cmd(data, SGP_CMD_GET_BASELINE, data->baseline_len,
+				SGP_CMD_DURATION_US);
+
+	if (ret < 0)
+		goto unlock_fail;
+
+	baseline = 0;
+	for (ix = 0; ix < data->baseline_len; ix++) {
+		baseline_word = be16_to_cpu(data->buffer.raw_words[ix].value);
+		baseline |= baseline_word << (16 * ix);
+	}
+
+	mutex_unlock(&data->data_lock);
+	return sprintf(buf, data->baseline_format, baseline);
+
+unlock_fail:
+	mutex_unlock(&data->data_lock);
+	return ret;
+}
+
+static ssize_t sgp_iaq_baseline_store(struct device *dev,
+				      struct device_attribute *attr,
+				      const char *buf, size_t count)
+{
+	struct sgp_data *data = iio_priv(dev_to_iio_dev(dev));
+	int newline = (count > 0 && buf[count - 1] == '\n');
+	u16 words[2];
+	int ret = 0;
+
+	/* 1 word (4 chars) per signal */
+	if (count - newline == (data->baseline_len * 4)) {
+		if (data->baseline_len == 1)
+			ret = sscanf(buf, "%04hx", &words[0]);
+		else if (data->baseline_len == 2)
+			ret = sscanf(buf, "%04hx%04hx", &words[0], &words[1]);
+		else
+			return -EIO;
+	}
+
+	/* Check if baseline format is correct */
+	if (ret != data->baseline_len) {
+		dev_err(&data->client->dev, "invalid baseline format\n");
+		return -EIO;
+	}
+
+	ret = sgp_write_from_cmd(data, SGP_CMD_SET_BASELINE, words,
+				 data->baseline_len, SGP_CMD_DURATION_US);
+	if (ret < 0)
+		return -EIO;
+
+	return count;
+}
+
+static ssize_t sgp_selftest_show(struct device *dev,
+				 struct device_attribute *attr, char *buf)
+{
+	struct sgp_data *data = iio_priv(dev_to_iio_dev(dev));
+	u16 measure_test;
+	int ret;
+
+	mutex_lock(&data->data_lock);
+	data->iaq_initialized = false;
+	ret = sgp_read_from_cmd(data, SGP_CMD_MEASURE_TEST, 1,
+				SGP_SELFTEST_DURATION_US);
+
+	if (ret != 0)
+		goto unlock_fail;
+
+	measure_test = be16_to_cpu(data->buffer.raw_words[0].value);
+	mutex_unlock(&data->data_lock);
+
+	return sprintf(buf, "%s\n",
+		       measure_test ^ SGP_SELFTEST_OK ? "FAILED" : "OK");
+
+unlock_fail:
+	mutex_unlock(&data->data_lock);
+	return ret;
+}
+
+static ssize_t sgp_serial_id_show(struct device *dev,
+				  struct device_attribute *attr, char *buf)
+{
+	struct sgp_data *data = iio_priv(dev_to_iio_dev(dev));
+
+	return sprintf(buf, "%llu\n", data->serial_id);
+}
+
+static ssize_t sgp_feature_set_version_show(struct device *dev,
+					    struct device_attribute *attr,
+					    char *buf)
+{
+	struct sgp_data *data = iio_priv(dev_to_iio_dev(dev));
+
+	return sprintf(buf, "%hu.%hu\n", (data->feature_set & 0x00e0) >> 5,
+		       data->feature_set & 0x001f);
+}
+
+static int sgp_get_serial_id(struct sgp_data *data)
+{
+	int ret;
+	struct sgp_crc_word *words;
+
+	mutex_lock(&data->data_lock);
+	ret = sgp_read_from_cmd(data, SGP_CMD_GET_SERIAL_ID, 3,
+				SGP_CMD_DURATION_US);
+	if (ret != 0)
+		goto unlock_fail;
+
+	words = data->buffer.raw_words;
+	data->serial_id = (u64)(be16_to_cpu(words[2].value) & 0xffff)       |
+			  (u64)(be16_to_cpu(words[1].value) & 0xffff) << 16 |
+			  (u64)(be16_to_cpu(words[0].value) & 0xffff) << 32;
+
+unlock_fail:
+	mutex_unlock(&data->data_lock);
+	return ret;
+}
+
+static int setup_and_check_sgp_data(struct sgp_data *data,
+				    unsigned int chip_id)
+{
+	u16 minor, major, product, eng, ix, num_fs, reserved;
+	struct sgp_version *supported_versions;
+
+	product = (data->feature_set & 0xf000) >> 12;
+	reserved = (data->feature_set & 0x0e00) >> 9;
+	eng = (data->feature_set & 0x0100) >> 8;
+	major = (data->feature_set & 0x00e0) >> 5;
+	minor = data->feature_set & 0x001f;
+
+	/* driver does not match product */
+	if (product != chip_id) {
+		dev_err(&data->client->dev,
+			"sensor reports a different product: 0x%04hx\n",
+			product);
+		return -ENODEV;
+	}
+
+	if (reserved != 0)
+		dev_warn(&data->client->dev, "reserved bits set: 0x%04hx\n",
+			 reserved);
+
+	/* engineering samples are not supported */
+	if (eng != 0)
+		return -ENODEV;
+
+	data->iaq_initialized = false;
+	switch (product) {
+	case SGP30:
+		supported_versions =
+			(struct sgp_version *)supported_versions_sgp30;
+		num_fs = ARRAY_SIZE(supported_versions_sgp30);
+		data->measurement_len = SGP30_MEASUREMENT_LEN;
+		data->measure_interval_hz = SGP30_MEASURE_INTERVAL_HZ;
+		data->measure_iaq_cmd = SGP_CMD_IAQ_MEASURE;
+		data->measure_signal_cmd = SGP30_CMD_MEASURE_SIGNAL;
+		data->chip_id = SGP30;
+		data->baseline_len = 2;
+		data->baseline_format = "%08x\n";
+		data->measure_mode = SGP_MEASURE_MODE_UNKNOWN;
+		break;
+	case SGPC3:
+		supported_versions =
+			(struct sgp_version *)supported_versions_sgpc3;
+		num_fs = ARRAY_SIZE(supported_versions_sgpc3);
+		data->measurement_len = SGPC3_MEASUREMENT_LEN;
+		data->measure_interval_hz = SGPC3_MEASURE_INTERVAL_HZ;
+		data->measure_iaq_cmd = SGPC3_CMD_MEASURE_RAW;
+		data->measure_signal_cmd = SGPC3_CMD_MEASURE_RAW;
+		data->chip_id = SGPC3;
+		data->baseline_len = 1;
+		data->baseline_format = "%04x\n";
+		data->measure_mode = SGP_MEASURE_MODE_ALL;
+		break;
+	default:
+		return -ENODEV;
+	};
+
+	for (ix = 0; ix < num_fs; ix++) {
+		if (supported_versions[ix].major == major &&
+		    minor >= supported_versions[ix].minor)
+			return 0;
+	}
+
+	dev_err(&data->client->dev, "unsupported sgp version: %d.%d\n",
+		major, minor);
+	return -ENODEV;
+}
+
+static IIO_DEVICE_ATTR(in_serial_id, 0444, sgp_serial_id_show, NULL, 0);
+static IIO_DEVICE_ATTR(in_feature_set_version, 0444,
+		       sgp_feature_set_version_show, NULL, 0);
+static IIO_DEVICE_ATTR(in_selftest, 0444, sgp_selftest_show, NULL, 0);
+static IIO_DEVICE_ATTR(out_iaq_init, 0220, NULL, sgp_iaq_init_store, 0);
+static IIO_DEVICE_ATTR(in_iaq_baseline, 0444, sgp_iaq_baseline_show, NULL, 0);
+static IIO_DEVICE_ATTR(out_iaq_baseline, 0220, NULL, sgp_iaq_baseline_store, 0);
+
+static struct attribute *sgp_attributes[] = {
+	&iio_dev_attr_in_serial_id.dev_attr.attr,
+	&iio_dev_attr_in_feature_set_version.dev_attr.attr,
+	&iio_dev_attr_in_selftest.dev_attr.attr,
+	&iio_dev_attr_out_iaq_init.dev_attr.attr,
+	&iio_dev_attr_in_iaq_baseline.dev_attr.attr,
+	&iio_dev_attr_out_iaq_baseline.dev_attr.attr,
+	NULL
+};
+
+static const struct attribute_group sgp_attr_group = {
+	.attrs = sgp_attributes,
+};
+
+static const struct iio_info sgp_info = {
+	.attrs		= &sgp_attr_group,
+	.read_raw	= sgp_read_raw,
+	.write_raw	= sgp_write_raw,
+};
+
+static const struct of_device_id sgp_dt_ids[] = {
+	{ .compatible = "sensirion,sgp30", .data = (void *)SGP30 },
+	{ .compatible = "sensirion,sgpc3", .data = (void *)SGPC3 },
+	{ }
+};
+
+static int sgp_probe(struct i2c_client *client,
+		     const struct i2c_device_id *id)
+{
+	struct iio_dev *indio_dev;
+	struct sgp_data *data;
+	struct sgp_device *chip;
+	const struct of_device_id *of_id;
+	unsigned long chip_id;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	of_id = of_match_device(sgp_dt_ids, &client->dev);
+	if (!of_id)
+		chip_id = id->driver_data;
+	else
+		chip_id = (unsigned long)of_id->data;
+
+	chip = &sgp_devices[chip_id];
+	data = iio_priv(indio_dev);
+	i2c_set_clientdata(client, indio_dev);
+	data->client = client;
+	crc8_populate_msb(sgp_crc8_table, SGP_CRC8_POLYNOMIAL);
+	mutex_init(&data->data_lock);
+	mutex_init(&data->i2c_lock);
+
+	/* get serial id and write it to client data */
+	ret = sgp_get_serial_id(data);
+
+	if (ret != 0)
+		return ret;
+
+	/* get feature set version and write it to client data */
+	ret = sgp_read_from_cmd(data, SGP_CMD_GET_FEATURE_SET, 1,
+				SGP_CMD_DURATION_US);
+	if (ret != 0)
+		return ret;
+
+	data->feature_set = be16_to_cpu(data->buffer.raw_words[0].value);
+
+	ret = setup_and_check_sgp_data(data, chip_id);
+	if (ret < 0)
+		goto fail_free;
+
+	/* so initial reading will complete */
+	data->last_update = jiffies - data->measure_interval_hz * HZ;
+
+	indio_dev->dev.parent = &client->dev;
+	indio_dev->info = &sgp_info;
+	indio_dev->name = dev_name(&client->dev);
+	indio_dev->modes = INDIO_BUFFER_SOFTWARE | INDIO_DIRECT_MODE;
+
+	indio_dev->channels = chip->channels;
+	indio_dev->num_channels = chip->num_channels;
+
+	ret = devm_iio_device_register(&client->dev, indio_dev);
+	if (!ret)
+		return ret;
+
+	dev_err(&client->dev, "failed to register iio device\n");
+
+fail_free:
+	mutex_destroy(&data->i2c_lock);
+	mutex_destroy(&data->data_lock);
+	iio_device_free(indio_dev);
+	return ret;
+}
+
+static int sgp_remove(struct i2c_client *client)
+{
+	struct iio_dev *indio_dev = i2c_get_clientdata(client);
+
+	devm_iio_device_unregister(&client->dev, indio_dev);
+	return 0;
+}
+
+static const struct i2c_device_id sgp_id[] = {
+	{ "sgp30", SGP30 },
+	{ "sgpc3", SGPC3 },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(i2c, sgp_id);
+MODULE_DEVICE_TABLE(of, sgp_dt_ids);
+
+static struct i2c_driver sgp_driver = {
+	.driver = {
+		.name	= "sgpxx",
+		.of_match_table = of_match_ptr(sgp_dt_ids),
+	},
+	.probe = sgp_probe,
+	.remove = sgp_remove,
+	.id_table = sgp_id,
+};
+module_i2c_driver(sgp_driver);
+
+MODULE_AUTHOR("Andreas Brauchli <andreas.brauchli@sensirion.com>");
+MODULE_AUTHOR("Pascal Sachs <pascal.sachs@sensirion.com>");
+MODULE_DESCRIPTION("Sensirion SGPxx gas sensors");
+MODULE_LICENSE("GPL v2");
+MODULE_VERSION("0.5.0");
-- 
2.14.1