drivers/iio/chemical/sgp30.c - linux/kernel/git/bpf/bpf - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * sgp30.c - Support for Sensirion SGP Gas Sensors
  *
  * Copyright (C) 2018 Andreas Brauchli <andreas.brauchli@sensirion.com>
  *
  * I2C slave address: 0x58
  *
  * Datasheets:
  * https://www.sensirion.com/file/datasheet_sgp30
  * https://www.sensirion.com/file/datasheet_sgpc3
  *
  * TODO:
  * - baseline support
  * - humidity compensation
  * - power mode switching (SGPC3)
  */

 #include <linux/crc8.h>
 #include <linux/delay.h>
 #include <linux/kthread.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/i2c.h>
 #include <linux/of_device.h>
 #include <linux/iio/iio.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			12000
 #define SGP_MEASUREMENT_DURATION_US		50000
 #define SGP_CMD_LEN				SGP_WORD_LEN
 #define SGP_CMD_MAX_BUF_SIZE			(SGP_CMD_LEN + 2 * SGP_WORD_LEN)
 #define SGP_MEASUREMENT_LEN			2
 #define SGP30_MEASURE_INTERVAL_HZ		1
 #define SGPC3_MEASURE_INTERVAL_HZ		2
 #define SGP_VERS_PRODUCT(data)	((((data)->feature_set) & 0xf000) >> 12)
 #define SGP_VERS_RESERVED(data)	((((data)->feature_set) & 0x0800) >> 11)
 #define SGP_VERS_GEN(data)	((((data)->feature_set) & 0x0600) >> 9)
 #define SGP_VERS_ENG_BIT(data)	((((data)->feature_set) & 0x0100) >> 8)
 #define SGP_VERS_MAJOR(data)	((((data)->feature_set) & 0x00e0) >> 5)
 #define SGP_VERS_MINOR(data)	(((data)->feature_set) & 0x001f)

 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,
 };

 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_FEATURE_SET			= SGP_CMD(0x202f),
 	SGP_CMD_GET_SERIAL_ID			= SGP_CMD(0x3682),

 	SGP30_CMD_MEASURE_SIGNAL		= SGP_CMD(0x2050),

 	SGPC3_CMD_MEASURE_RAW			= SGP_CMD(0x2046),
 };

 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];
 };

 enum _iaq_buffer_state {
 	IAQ_BUFFER_EMPTY = 0,
 	IAQ_BUFFER_DEFAULT_VALS,
 	IAQ_BUFFER_VALID,
 };

 struct sgp_data {
 	struct i2c_client *client;
 	struct task_struct *iaq_thread;
 	struct mutex data_lock;
 	unsigned long iaq_init_start_jiffies;
 	unsigned long iaq_defval_skip_jiffies;
 	u16 product_id;
 	u16 feature_set;
 	unsigned long measure_interval_jiffies;
 	enum sgp_cmd iaq_init_cmd;
 	enum sgp_cmd measure_iaq_cmd;
 	enum sgp_cmd measure_gas_signals_cmd;
 	union sgp_reading buffer;
 	union sgp_reading iaq_buffer;
 	enum _iaq_buffer_state iaq_buffer_state;
 };

 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,
 		.modified = 1,
 		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
 		.address = SGP30_IAQ_TVOC_IDX,
 	},
 	{
 		.type = IIO_CONCENTRATION,
 		.channel2 = IIO_MOD_CO2,
 		.modified = 1,
 		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
 		.address = SGP30_IAQ_CO2EQ_IDX,
 	},
 	{
 		.type = IIO_CONCENTRATION,
 		.channel2 = IIO_MOD_ETHANOL,
 		.modified = 1,
 		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
 		.address = SGP30_SIG_ETOH_IDX,
 	},
 	{
 		.type = IIO_CONCENTRATION,
 		.channel2 = IIO_MOD_H2,
 		.modified = 1,
 		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
 		.address = SGP30_SIG_H2_IDX,
 	},
 };

 static const struct iio_chan_spec sgpc3_channels[] = {
 	{
 		.type = IIO_CONCENTRATION,
 		.channel2 = IIO_MOD_VOC,
 		.modified = 1,
 		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
 		.address = SGPC3_IAQ_TVOC_IDX,
 	},
 	{
 		.type = IIO_CONCENTRATION,
 		.channel2 = IIO_MOD_ETHANOL,
 		.modified = 1,
 		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
 		.address = SGPC3_SIG_ETOH_IDX,
 	},
 };

 static const 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
  * @buf:        Raw data buffer
  * @word_count: Num data words stored in the buffer, excluding CRC bytes
  *
  * Return:      0 on success, negative error otherwise.
  */
 static int sgp_verify_buffer(const struct sgp_data *data,
 			     union sgp_reading *buf, size_t word_count)
 {
 	size_t size = word_count * (SGP_WORD_LEN + SGP_CRC8_LEN);
 	int i;
 	u8 crc;
 	u8 *data_buf = &buf->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_cmd() - reads data from 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
  * @buf:         Raw data buffer to use
  * @word_count:  Num words to read, excluding CRC bytes
  *
  * Return:       0 on success, negative error otherwise.
  */
 static int sgp_read_cmd(struct sgp_data *data, enum sgp_cmd cmd,
 			union sgp_reading *buf, 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;

 	ret = i2c_master_send(client, (const char *)&cmd, SGP_CMD_LEN);
 	if (ret != SGP_CMD_LEN)
 		return -EIO;
 	usleep_range(duration_us, duration_us + 1000);

 	if (word_count == 0)
 		return 0;

 	data_buf = &buf->start;
 	ret = i2c_master_recv(client, data_buf, size);
 	if (ret < 0)
 		return ret;
 	if (ret != size)
 		return -EIO;

 	return sgp_verify_buffer(data, buf, word_count);
 }

 /**
  * sgp_measure_iaq() - measure and retrieve IAQ values from sensor
  * The caller must hold data->data_lock for the duration of the call.
  * @data:       SGP data
  *
  * Return:      0 on success, -EBUSY on default values, negative error
  *              otherwise.
  */

 static int sgp_measure_iaq(struct sgp_data *data)
 {
 	int ret;
 	/* data contains default values */
 	bool default_vals = !time_after(jiffies, data->iaq_init_start_jiffies +
 						 data->iaq_defval_skip_jiffies);

 	ret = sgp_read_cmd(data, data->measure_iaq_cmd, &data->iaq_buffer,
 			   SGP_MEASUREMENT_LEN, SGP_MEASUREMENT_DURATION_US);
 	if (ret < 0)
 		return ret;

 	data->iaq_buffer_state = IAQ_BUFFER_DEFAULT_VALS;

 	if (default_vals)
 		return -EBUSY;

 	data->iaq_buffer_state = IAQ_BUFFER_VALID;

 	return 0;
 }

 static void sgp_iaq_thread_sleep_until(const struct sgp_data *data,
 				       unsigned long sleep_jiffies)
 {
 	const long IAQ_POLL = 50000;

 	while (!time_after(jiffies, sleep_jiffies)) {
 		usleep_range(IAQ_POLL, IAQ_POLL + 10000);
 		if (kthread_should_stop() || data->iaq_init_start_jiffies == 0)
 			return;
 	}
 }

 static int sgp_iaq_threadfn(void *p)
 {
 	struct sgp_data *data = (struct sgp_data *)p;
 	unsigned long next_update_jiffies;
 	int ret;

 	while (!kthread_should_stop()) {
 		mutex_lock(&data->data_lock);
 		if (data->iaq_init_start_jiffies == 0) {
 			ret = sgp_read_cmd(data, data->iaq_init_cmd, NULL, 0,
 					   SGP_CMD_DURATION_US);
 			if (ret < 0)
 				goto unlock_sleep_continue;
 			data->iaq_init_start_jiffies = jiffies;
 		}

 		ret = sgp_measure_iaq(data);
 		if (ret && ret != -EBUSY) {
 			dev_warn(&data->client->dev,
 				 "IAQ measurement error [%d]\n", ret);
 		}
 unlock_sleep_continue:
 		next_update_jiffies = jiffies + data->measure_interval_jiffies;
 		mutex_unlock(&data->data_lock);
 		sgp_iaq_thread_sleep_until(data, next_update_jiffies);
 	}

 	return 0;
 }

 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_buffer_state != IAQ_BUFFER_VALID) {
 			mutex_unlock(&data->data_lock);
 			return -EBUSY;
 		}
 		words = data->iaq_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);
 		if (chan->address == SGPC3_SIG_ETOH_IDX) {
 			if (data->iaq_buffer_state == IAQ_BUFFER_EMPTY)
 				ret = -EBUSY;
 			else
 				ret = 0;
 			words = data->iaq_buffer.raw_words;
 		} else {
 			ret = sgp_read_cmd(data, data->measure_gas_signals_cmd,
 					   &data->buffer, SGP_MEASUREMENT_LEN,
 					   SGP_MEASUREMENT_DURATION_US);
 			words = data->buffer.raw_words;
 		}
 		if (ret) {
 			mutex_unlock(&data->data_lock);
 			return ret;
 		}

 		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;
 		default:
 			ret = -EINVAL;
 			break;
 		}
 		mutex_unlock(&data->data_lock);
 		break;
 	default:
 		return -EINVAL;
 	}

 	return ret;
 }

 static int sgp_check_compat(struct sgp_data *data,
 			    unsigned int product_id)
 {
 	const struct sgp_version *supported_versions;
 	u16 ix, num_fs;
 	u16 product, generation, major, minor;

 	/* driver does not match product */
 	generation = SGP_VERS_GEN(data);
 	if (generation != 0) {
 		dev_err(&data->client->dev,
 			"incompatible product generation %d != 0", generation);
 		return -ENODEV;
 	}

 	product = SGP_VERS_PRODUCT(data);
 	if (product != product_id) {
 		dev_err(&data->client->dev,
 			"sensor reports a different product: 0x%04hx\n",
 			product);
 		return -ENODEV;
 	}

 	if (SGP_VERS_RESERVED(data))
 		dev_warn(&data->client->dev, "reserved bit is set\n");

 	/* engineering samples are not supported: no interface guarantees */
 	if (SGP_VERS_ENG_BIT(data))
 		return -ENODEV;

 	switch (product) {
 	case SGP30:
 		supported_versions = supported_versions_sgp30;
 		num_fs = ARRAY_SIZE(supported_versions_sgp30);
 		break;
 	case SGPC3:
 		supported_versions = supported_versions_sgpc3;
 		num_fs = ARRAY_SIZE(supported_versions_sgpc3);
 		break;
 	default:
 		return -ENODEV;
 	}

 	major = SGP_VERS_MAJOR(data);
 	minor = SGP_VERS_MINOR(data);
 	for (ix = 0; ix < num_fs; ix++) {
 		if (major == supported_versions[ix].major &&
 		    minor >= supported_versions[ix].minor)
 			return 0;
 	}
 	dev_err(&data->client->dev, "unsupported sgp version: %d.%d\n",
 		major, minor);

 	return -ENODEV;
 }

 static void sgp_init(struct sgp_data *data)
 {
 	data->iaq_init_cmd = SGP_CMD_IAQ_INIT;
 	data->iaq_init_start_jiffies = 0;
 	data->iaq_buffer_state = IAQ_BUFFER_EMPTY;
 	switch (SGP_VERS_PRODUCT(data)) {
 	case SGP30:
 		data->measure_interval_jiffies = SGP30_MEASURE_INTERVAL_HZ * HZ;
 		data->measure_iaq_cmd = SGP_CMD_IAQ_MEASURE;
 		data->measure_gas_signals_cmd = SGP30_CMD_MEASURE_SIGNAL;
 		data->product_id = SGP30;
 		data->iaq_defval_skip_jiffies = 15 * HZ;
 		break;
 	case SGPC3:
 		data->measure_interval_jiffies = SGPC3_MEASURE_INTERVAL_HZ * HZ;
 		data->measure_iaq_cmd = SGPC3_CMD_MEASURE_RAW;
 		data->measure_gas_signals_cmd = SGPC3_CMD_MEASURE_RAW;
 		data->product_id = SGPC3;
 		data->iaq_defval_skip_jiffies =
 			43 * data->measure_interval_jiffies;
 		break;
 	}
 }

 static const struct iio_info sgp_info = {
 	.read_raw	= sgp_read_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;
 	const struct of_device_id *of_id;
 	unsigned long product_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)
 		product_id = (unsigned long)of_id->data;
 	else
 		product_id = id->driver_data;

 	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);

 	/* get feature set version and write it to client data */
 	ret = sgp_read_cmd(data, SGP_CMD_GET_FEATURE_SET, &data->buffer, 1,
 			   SGP_CMD_DURATION_US);
 	if (ret < 0)
 		return ret;

 	data->feature_set = be16_to_cpu(data->buffer.raw_words[0].value);

 	ret = sgp_check_compat(data, product_id);
 	if (ret)
 		return ret;

 	indio_dev->dev.parent = &client->dev;
 	indio_dev->info = &sgp_info;
 	indio_dev->name = id->name;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 	indio_dev->channels = sgp_devices[product_id].channels;
 	indio_dev->num_channels = sgp_devices[product_id].num_channels;

 	sgp_init(data);

 	ret = devm_iio_device_register(&client->dev, indio_dev);
 	if (ret) {
 		dev_err(&client->dev, "failed to register iio device\n");
 		return ret;
 	}

 	data->iaq_thread = kthread_run(sgp_iaq_threadfn, data,
 				       "%s-iaq", data->client->name);

 	return 0;
 }

 static int sgp_remove(struct i2c_client *client)
 {
 	struct iio_dev *indio_dev = i2c_get_clientdata(client);
 	struct sgp_data *data = iio_priv(indio_dev);

 	if (data->iaq_thread)
 		kthread_stop(data->iaq_thread);

 	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 = "sgp30",
 		.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 SGP gas sensors");
 MODULE_LICENSE("GPL v2");
	// SPDX-License-Identifier: GPL-2.0
	/*
	* sgp30.c - Support for Sensirion SGP Gas Sensors
	*
	* Copyright (C) 2018 Andreas Brauchli <andreas.brauchli@sensirion.com>
	*
	* I2C slave address: 0x58
	*
	* Datasheets:
	* https://www.sensirion.com/file/datasheet_sgp30
	* https://www.sensirion.com/file/datasheet_sgpc3
	*
	* TODO:
	* - baseline support
	* - humidity compensation
	* - power mode switching (SGPC3)
	*/

	#include <linux/crc8.h>
	#include <linux/delay.h>
	#include <linux/kthread.h>
	#include <linux/module.h>
	#include <linux/mutex.h>
	#include <linux/i2c.h>
	#include <linux/of_device.h>
	#include <linux/iio/iio.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 12000
	#define SGP_MEASUREMENT_DURATION_US 50000
	#define SGP_CMD_LEN SGP_WORD_LEN
	#define SGP_CMD_MAX_BUF_SIZE (SGP_CMD_LEN + 2 * SGP_WORD_LEN)
	#define SGP_MEASUREMENT_LEN 2
	#define SGP30_MEASURE_INTERVAL_HZ 1
	#define SGPC3_MEASURE_INTERVAL_HZ 2
	#define SGP_VERS_PRODUCT(data) ((((data)->feature_set) & 0xf000) >> 12)
	#define SGP_VERS_RESERVED(data) ((((data)->feature_set) & 0x0800) >> 11)
	#define SGP_VERS_GEN(data) ((((data)->feature_set) & 0x0600) >> 9)
	#define SGP_VERS_ENG_BIT(data) ((((data)->feature_set) & 0x0100) >> 8)
	#define SGP_VERS_MAJOR(data) ((((data)->feature_set) & 0x00e0) >> 5)
	#define SGP_VERS_MINOR(data) (((data)->feature_set) & 0x001f)

	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,
	};

	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_FEATURE_SET = SGP_CMD(0x202f),
	SGP_CMD_GET_SERIAL_ID = SGP_CMD(0x3682),

	SGP30_CMD_MEASURE_SIGNAL = SGP_CMD(0x2050),

	SGPC3_CMD_MEASURE_RAW = SGP_CMD(0x2046),
	};

	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];
	};

	enum _iaq_buffer_state {
	IAQ_BUFFER_EMPTY = 0,
	IAQ_BUFFER_DEFAULT_VALS,
	IAQ_BUFFER_VALID,
	};

	struct sgp_data {
	struct i2c_client *client;
	struct task_struct *iaq_thread;
	struct mutex data_lock;
	unsigned long iaq_init_start_jiffies;
	unsigned long iaq_defval_skip_jiffies;
	u16 product_id;
	u16 feature_set;
	unsigned long measure_interval_jiffies;
	enum sgp_cmd iaq_init_cmd;
	enum sgp_cmd measure_iaq_cmd;
	enum sgp_cmd measure_gas_signals_cmd;
	union sgp_reading buffer;
	union sgp_reading iaq_buffer;
	enum _iaq_buffer_state iaq_buffer_state;
	};

	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,
	.modified = 1,
	.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
	.address = SGP30_IAQ_TVOC_IDX,
	},
	{
	.type = IIO_CONCENTRATION,
	.channel2 = IIO_MOD_CO2,
	.modified = 1,
	.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
	.address = SGP30_IAQ_CO2EQ_IDX,
	},
	{
	.type = IIO_CONCENTRATION,
	.channel2 = IIO_MOD_ETHANOL,
	.modified = 1,
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
	.address = SGP30_SIG_ETOH_IDX,
	},
	{
	.type = IIO_CONCENTRATION,
	.channel2 = IIO_MOD_H2,
	.modified = 1,
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
	.address = SGP30_SIG_H2_IDX,
	},
	};

	static const struct iio_chan_spec sgpc3_channels[] = {
	{
	.type = IIO_CONCENTRATION,
	.channel2 = IIO_MOD_VOC,
	.modified = 1,
	.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
	.address = SGPC3_IAQ_TVOC_IDX,
	},
	{
	.type = IIO_CONCENTRATION,
	.channel2 = IIO_MOD_ETHANOL,
	.modified = 1,
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
	.address = SGPC3_SIG_ETOH_IDX,
	},
	};

	static const 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
	* @buf: Raw data buffer
	* @word_count: Num data words stored in the buffer, excluding CRC bytes
	*
	* Return: 0 on success, negative error otherwise.
	*/
	static int sgp_verify_buffer(const struct sgp_data *data,
	union sgp_reading *buf, size_t word_count)
	{
	size_t size = word_count * (SGP_WORD_LEN + SGP_CRC8_LEN);
	int i;
	u8 crc;
	u8 *data_buf = &buf->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_cmd() - reads data from 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
	* @buf: Raw data buffer to use
	* @word_count: Num words to read, excluding CRC bytes
	*
	* Return: 0 on success, negative error otherwise.
	*/
	static int sgp_read_cmd(struct sgp_data *data, enum sgp_cmd cmd,
	union sgp_reading *buf, 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;

	ret = i2c_master_send(client, (const char *)&cmd, SGP_CMD_LEN);
	if (ret != SGP_CMD_LEN)
	return -EIO;
	usleep_range(duration_us, duration_us + 1000);

	if (word_count == 0)
	return 0;

	data_buf = &buf->start;
	ret = i2c_master_recv(client, data_buf, size);
	if (ret < 0)
	return ret;
	if (ret != size)
	return -EIO;

	return sgp_verify_buffer(data, buf, word_count);
	}

	/**
	* sgp_measure_iaq() - measure and retrieve IAQ values from sensor
	* The caller must hold data->data_lock for the duration of the call.
	* @data: SGP data
	*
	* Return: 0 on success, -EBUSY on default values, negative error
	* otherwise.
	*/

	static int sgp_measure_iaq(struct sgp_data *data)
	{
	int ret;
	/* data contains default values */
	bool default_vals = !time_after(jiffies, data->iaq_init_start_jiffies +
	data->iaq_defval_skip_jiffies);

	ret = sgp_read_cmd(data, data->measure_iaq_cmd, &data->iaq_buffer,
	SGP_MEASUREMENT_LEN, SGP_MEASUREMENT_DURATION_US);
	if (ret < 0)
	return ret;

	data->iaq_buffer_state = IAQ_BUFFER_DEFAULT_VALS;

	if (default_vals)
	return -EBUSY;

	data->iaq_buffer_state = IAQ_BUFFER_VALID;

	return 0;
	}

	static void sgp_iaq_thread_sleep_until(const struct sgp_data *data,
	unsigned long sleep_jiffies)
	{
	const long IAQ_POLL = 50000;

	while (!time_after(jiffies, sleep_jiffies)) {
	usleep_range(IAQ_POLL, IAQ_POLL + 10000);
	if (kthread_should_stop() \|\| data->iaq_init_start_jiffies == 0)
	return;
	}
	}

	static int sgp_iaq_threadfn(void *p)
	{
	struct sgp_data data = (struct sgp_data )p;
	unsigned long next_update_jiffies;
	int ret;

	while (!kthread_should_stop()) {
	mutex_lock(&data->data_lock);
	if (data->iaq_init_start_jiffies == 0) {
	ret = sgp_read_cmd(data, data->iaq_init_cmd, NULL, 0,
	SGP_CMD_DURATION_US);
	if (ret < 0)
	goto unlock_sleep_continue;
	data->iaq_init_start_jiffies = jiffies;
	}

	ret = sgp_measure_iaq(data);
	if (ret && ret != -EBUSY) {
	dev_warn(&data->client->dev,
	"IAQ measurement error [%d]\n", ret);
	}
	unlock_sleep_continue:
	next_update_jiffies = jiffies + data->measure_interval_jiffies;
	mutex_unlock(&data->data_lock);
	sgp_iaq_thread_sleep_until(data, next_update_jiffies);
	}

	return 0;
	}

	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_buffer_state != IAQ_BUFFER_VALID) {
	mutex_unlock(&data->data_lock);
	return -EBUSY;
	}
	words = data->iaq_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);
	if (chan->address == SGPC3_SIG_ETOH_IDX) {
	if (data->iaq_buffer_state == IAQ_BUFFER_EMPTY)
	ret = -EBUSY;
	else
	ret = 0;
	words = data->iaq_buffer.raw_words;
	} else {
	ret = sgp_read_cmd(data, data->measure_gas_signals_cmd,
	&data->buffer, SGP_MEASUREMENT_LEN,
	SGP_MEASUREMENT_DURATION_US);
	words = data->buffer.raw_words;
	}
	if (ret) {
	mutex_unlock(&data->data_lock);
	return ret;
	}

	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;
	default:
	ret = -EINVAL;
	break;
	}
	mutex_unlock(&data->data_lock);
	break;
	default:
	return -EINVAL;
	}

	return ret;
	}

	static int sgp_check_compat(struct sgp_data *data,
	unsigned int product_id)
	{
	const struct sgp_version *supported_versions;
	u16 ix, num_fs;
	u16 product, generation, major, minor;

	/* driver does not match product */
	generation = SGP_VERS_GEN(data);
	if (generation != 0) {
	dev_err(&data->client->dev,
	"incompatible product generation %d != 0", generation);
	return -ENODEV;
	}

	product = SGP_VERS_PRODUCT(data);
	if (product != product_id) {
	dev_err(&data->client->dev,
	"sensor reports a different product: 0x%04hx\n",
	product);
	return -ENODEV;
	}

	if (SGP_VERS_RESERVED(data))
	dev_warn(&data->client->dev, "reserved bit is set\n");

	/* engineering samples are not supported: no interface guarantees */
	if (SGP_VERS_ENG_BIT(data))
	return -ENODEV;

	switch (product) {
	case SGP30:
	supported_versions = supported_versions_sgp30;
	num_fs = ARRAY_SIZE(supported_versions_sgp30);
	break;
	case SGPC3:
	supported_versions = supported_versions_sgpc3;
	num_fs = ARRAY_SIZE(supported_versions_sgpc3);
	break;
	default:
	return -ENODEV;
	}

	major = SGP_VERS_MAJOR(data);
	minor = SGP_VERS_MINOR(data);
	for (ix = 0; ix < num_fs; ix++) {
	if (major == supported_versions[ix].major &&
	minor >= supported_versions[ix].minor)
	return 0;
	}
	dev_err(&data->client->dev, "unsupported sgp version: %d.%d\n",
	major, minor);

	return -ENODEV;
	}

	static void sgp_init(struct sgp_data *data)
	{
	data->iaq_init_cmd = SGP_CMD_IAQ_INIT;
	data->iaq_init_start_jiffies = 0;
	data->iaq_buffer_state = IAQ_BUFFER_EMPTY;
	switch (SGP_VERS_PRODUCT(data)) {
	case SGP30:
	data->measure_interval_jiffies = SGP30_MEASURE_INTERVAL_HZ * HZ;
	data->measure_iaq_cmd = SGP_CMD_IAQ_MEASURE;
	data->measure_gas_signals_cmd = SGP30_CMD_MEASURE_SIGNAL;
	data->product_id = SGP30;
	data->iaq_defval_skip_jiffies = 15 * HZ;
	break;
	case SGPC3:
	data->measure_interval_jiffies = SGPC3_MEASURE_INTERVAL_HZ * HZ;
	data->measure_iaq_cmd = SGPC3_CMD_MEASURE_RAW;
	data->measure_gas_signals_cmd = SGPC3_CMD_MEASURE_RAW;
	data->product_id = SGPC3;
	data->iaq_defval_skip_jiffies =
	43 * data->measure_interval_jiffies;
	break;
	}
	}

	static const struct iio_info sgp_info = {
	.read_raw = sgp_read_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;
	const struct of_device_id *of_id;
	unsigned long product_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)
	product_id = (unsigned long)of_id->data;
	else
	product_id = id->driver_data;

	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);

	/* get feature set version and write it to client data */
	ret = sgp_read_cmd(data, SGP_CMD_GET_FEATURE_SET, &data->buffer, 1,
	SGP_CMD_DURATION_US);
	if (ret < 0)
	return ret;

	data->feature_set = be16_to_cpu(data->buffer.raw_words[0].value);

	ret = sgp_check_compat(data, product_id);
	if (ret)
	return ret;

	indio_dev->dev.parent = &client->dev;
	indio_dev->info = &sgp_info;
	indio_dev->name = id->name;
	indio_dev->modes = INDIO_DIRECT_MODE;
	indio_dev->channels = sgp_devices[product_id].channels;
	indio_dev->num_channels = sgp_devices[product_id].num_channels;

	sgp_init(data);

	ret = devm_iio_device_register(&client->dev, indio_dev);
	if (ret) {
	dev_err(&client->dev, "failed to register iio device\n");
	return ret;
	}

	data->iaq_thread = kthread_run(sgp_iaq_threadfn, data,
	"%s-iaq", data->client->name);

	return 0;
	}

	static int sgp_remove(struct i2c_client *client)
	{
	struct iio_dev *indio_dev = i2c_get_clientdata(client);
	struct sgp_data *data = iio_priv(indio_dev);

	if (data->iaq_thread)
	kthread_stop(data->iaq_thread);

	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 = "sgp30",
	.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 SGP gas sensors");
	MODULE_LICENSE("GPL v2");