drivers/iio/chemical/sps30.c - linux/kernel/git/bpf/bpf - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Sensirion SPS30 particulate matter sensor driver
  *
  * Copyright (c) Tomasz Duszynski <tduszyns@gmail.com>
  *
  * I2C slave address: 0x69
  */

 #include <asm/unaligned.h>
 #include <linux/crc8.h>
 #include <linux/delay.h>
 #include <linux/i2c.h>
 #include <linux/iio/buffer.h>
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
 #include <linux/iio/trigger_consumer.h>
 #include <linux/iio/triggered_buffer.h>
 #include <linux/kernel.h>
 #include <linux/module.h>

 #define SPS30_CRC8_POLYNOMIAL 0x31
 /* max number of bytes needed to store PM measurements or serial string */
 #define SPS30_MAX_READ_SIZE 48
 /* sensor measures reliably up to 3000 ug / m3 */
 #define SPS30_MAX_PM 3000
 /* minimum and maximum self cleaning periods in seconds */
 #define SPS30_AUTO_CLEANING_PERIOD_MIN 0
 #define SPS30_AUTO_CLEANING_PERIOD_MAX 604800

 /* SPS30 commands */
 #define SPS30_START_MEAS 0x0010
 #define SPS30_STOP_MEAS 0x0104
 #define SPS30_RESET 0xd304
 #define SPS30_READ_DATA_READY_FLAG 0x0202
 #define SPS30_READ_DATA 0x0300
 #define SPS30_READ_SERIAL 0xd033
 #define SPS30_START_FAN_CLEANING 0x5607
 #define SPS30_AUTO_CLEANING_PERIOD 0x8004
 /* not a sensor command per se, used only to distinguish write from read */
 #define SPS30_READ_AUTO_CLEANING_PERIOD 0x8005

 enum {
 	PM1,
 	PM2P5,
 	PM4,
 	PM10,
 };

 enum {
 	RESET,
 	MEASURING,
 };

 struct sps30_state {
 	struct i2c_client *client;
 	/*
 	 * Guards against concurrent access to sensor registers.
 	 * Must be held whenever sequence of commands is to be executed.
 	 */
 	struct mutex lock;
 	int state;
 };

 DECLARE_CRC8_TABLE(sps30_crc8_table);

 static int sps30_write_then_read(struct sps30_state *state, u8 *txbuf,
 				 int txsize, u8 *rxbuf, int rxsize)
 {
 	int ret;

 	/*
 	 * Sensor does not support repeated start so instead of
 	 * sending two i2c messages in a row we just send one by one.
 	 */
 	ret = i2c_master_send(state->client, txbuf, txsize);
 	if (ret != txsize)
 		return ret < 0 ? ret : -EIO;

 	if (!rxbuf)
 		return 0;

 	ret = i2c_master_recv(state->client, rxbuf, rxsize);
 	if (ret != rxsize)
 		return ret < 0 ? ret : -EIO;

 	return 0;
 }

 static int sps30_do_cmd(struct sps30_state *state, u16 cmd, u8 *data, int size)
 {
 	/*
 	 * Internally sensor stores measurements in a following manner:
 	 *
 	 * PM1: upper two bytes, crc8, lower two bytes, crc8
 	 * PM2P5: upper two bytes, crc8, lower two bytes, crc8
 	 * PM4: upper two bytes, crc8, lower two bytes, crc8
 	 * PM10: upper two bytes, crc8, lower two bytes, crc8
 	 *
 	 * What follows next are number concentration measurements and
 	 * typical particle size measurement which we omit.
 	 */
 	u8 buf[SPS30_MAX_READ_SIZE] = { cmd >> 8, cmd };
 	int i, ret = 0;

 	switch (cmd) {
 	case SPS30_START_MEAS:
 		buf[2] = 0x03;
 		buf[3] = 0x00;
 		buf[4] = crc8(sps30_crc8_table, &buf[2], 2, CRC8_INIT_VALUE);
 		ret = sps30_write_then_read(state, buf, 5, NULL, 0);
 		break;
 	case SPS30_STOP_MEAS:
 	case SPS30_RESET:
 	case SPS30_START_FAN_CLEANING:
 		ret = sps30_write_then_read(state, buf, 2, NULL, 0);
 		break;
 	case SPS30_READ_AUTO_CLEANING_PERIOD:
 		buf[0] = SPS30_AUTO_CLEANING_PERIOD >> 8;
 		buf[1] = (u8)(SPS30_AUTO_CLEANING_PERIOD & 0xff);
 		/* fall through */
 	case SPS30_READ_DATA_READY_FLAG:
 	case SPS30_READ_DATA:
 	case SPS30_READ_SERIAL:
 		/* every two data bytes are checksummed */
 		size += size / 2;
 		ret = sps30_write_then_read(state, buf, 2, buf, size);
 		break;
 	case SPS30_AUTO_CLEANING_PERIOD:
 		buf[2] = data[0];
 		buf[3] = data[1];
 		buf[4] = crc8(sps30_crc8_table, &buf[2], 2, CRC8_INIT_VALUE);
 		buf[5] = data[2];
 		buf[6] = data[3];
 		buf[7] = crc8(sps30_crc8_table, &buf[5], 2, CRC8_INIT_VALUE);
 		ret = sps30_write_then_read(state, buf, 8, NULL, 0);
 		break;
 	}

 	if (ret)
 		return ret;

 	/* validate received data and strip off crc bytes */
 	for (i = 0; i < size; i += 3) {
 		u8 crc = crc8(sps30_crc8_table, &buf[i], 2, CRC8_INIT_VALUE);

 		if (crc != buf[i + 2]) {
 			dev_err(&state->client->dev,
 				"data integrity check failed\n");
 			return -EIO;
 		}

 		*data++ = buf[i];
 		*data++ = buf[i + 1];
 	}

 	return 0;
 }

 static s32 sps30_float_to_int_clamped(const u8 *fp)
 {
 	int val = get_unaligned_be32(fp);
 	int mantissa = val & GENMASK(22, 0);
 	/* this is fine since passed float is always non-negative */
 	int exp = val >> 23;
 	int fraction, shift;

 	/* special case 0 */
 	if (!exp && !mantissa)
 		return 0;

 	exp -= 127;
 	if (exp < 0) {
 		/* return values ranging from 1 to 99 */
 		return ((((1 << 23) + mantissa) * 100) >> 23) >> (-exp);
 	}

 	/* return values ranging from 100 to 300000 */
 	shift = 23 - exp;
 	val = (1 << exp) + (mantissa >> shift);
 	if (val >= SPS30_MAX_PM)
 		return SPS30_MAX_PM * 100;

 	fraction = mantissa & GENMASK(shift - 1, 0);

 	return val * 100 + ((fraction * 100) >> shift);
 }

 static int sps30_do_meas(struct sps30_state *state, s32 *data, int size)
 {
 	int i, ret, tries = 5;
 	u8 tmp[16];

 	if (state->state == RESET) {
 		ret = sps30_do_cmd(state, SPS30_START_MEAS, NULL, 0);
 		if (ret)
 			return ret;

 		state->state = MEASURING;
 	}

 	while (tries--) {
 		ret = sps30_do_cmd(state, SPS30_READ_DATA_READY_FLAG, tmp, 2);
 		if (ret)
 			return -EIO;

 		/* new measurements ready to be read */
 		if (tmp[1] == 1)
 			break;

 		msleep_interruptible(300);
 	}

 	if (tries == -1)
 		return -ETIMEDOUT;

 	ret = sps30_do_cmd(state, SPS30_READ_DATA, tmp, sizeof(int) * size);
 	if (ret)
 		return ret;

 	for (i = 0; i < size; i++)
 		data[i] = sps30_float_to_int_clamped(&tmp[4 * i]);

 	return 0;
 }

 static irqreturn_t sps30_trigger_handler(int irq, void *p)
 {
 	struct iio_poll_func *pf = p;
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct sps30_state *state = iio_priv(indio_dev);
 	int ret;
 	s32 data[4 + 2]; /* PM1, PM2P5, PM4, PM10, timestamp */

 	mutex_lock(&state->lock);
 	ret = sps30_do_meas(state, data, 4);
 	mutex_unlock(&state->lock);
 	if (ret)
 		goto err;

 	iio_push_to_buffers_with_timestamp(indio_dev, data,
 					   iio_get_time_ns(indio_dev));
 err:
 	iio_trigger_notify_done(indio_dev->trig);

 	return IRQ_HANDLED;
 }

 static int sps30_read_raw(struct iio_dev *indio_dev,
 			  struct iio_chan_spec const *chan,
 			  int *val, int *val2, long mask)
 {
 	struct sps30_state *state = iio_priv(indio_dev);
 	int data[4], ret = -EINVAL;

 	switch (mask) {
 	case IIO_CHAN_INFO_PROCESSED:
 		switch (chan->type) {
 		case IIO_MASSCONCENTRATION:
 			mutex_lock(&state->lock);
 			/* read up to the number of bytes actually needed */
 			switch (chan->channel2) {
 			case IIO_MOD_PM1:
 				ret = sps30_do_meas(state, data, 1);
 				break;
 			case IIO_MOD_PM2P5:
 				ret = sps30_do_meas(state, data, 2);
 				break;
 			case IIO_MOD_PM4:
 				ret = sps30_do_meas(state, data, 3);
 				break;
 			case IIO_MOD_PM10:
 				ret = sps30_do_meas(state, data, 4);
 				break;
 			}
 			mutex_unlock(&state->lock);
 			if (ret)
 				return ret;

 			*val = data[chan->address] / 100;
 			*val2 = (data[chan->address] % 100) * 10000;

 			return IIO_VAL_INT_PLUS_MICRO;
 		default:
 			return -EINVAL;
 		}
 	case IIO_CHAN_INFO_SCALE:
 		switch (chan->type) {
 		case IIO_MASSCONCENTRATION:
 			switch (chan->channel2) {
 			case IIO_MOD_PM1:
 			case IIO_MOD_PM2P5:
 			case IIO_MOD_PM4:
 			case IIO_MOD_PM10:
 				*val = 0;
 				*val2 = 10000;

 				return IIO_VAL_INT_PLUS_MICRO;
 			default:
 				return -EINVAL;
 			}
 		default:
 			return -EINVAL;
 		}
 	}

 	return -EINVAL;
 }

 static int sps30_do_cmd_reset(struct sps30_state *state)
 {
 	int ret;

 	ret = sps30_do_cmd(state, SPS30_RESET, NULL, 0);
 	msleep(300);
 	/*
 	 * Power-on-reset causes sensor to produce some glitch on i2c bus and
 	 * some controllers end up in error state. Recover simply by placing
 	 * some data on the bus, for example STOP_MEAS command, which
 	 * is NOP in this case.
 	 */
 	sps30_do_cmd(state, SPS30_STOP_MEAS, NULL, 0);
 	state->state = RESET;

 	return ret;
 }

 static ssize_t start_cleaning_store(struct device *dev,
 				    struct device_attribute *attr,
 				    const char *buf, size_t len)
 {
 	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 	struct sps30_state *state = iio_priv(indio_dev);
 	int val, ret;

 	if (kstrtoint(buf, 0, &val) || val != 1)
 		return -EINVAL;

 	mutex_lock(&state->lock);
 	ret = sps30_do_cmd(state, SPS30_START_FAN_CLEANING, NULL, 0);
 	mutex_unlock(&state->lock);
 	if (ret)
 		return ret;

 	return len;
 }

 static ssize_t cleaning_period_show(struct device *dev,
 				      struct device_attribute *attr,
 				      char *buf)
 {
 	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 	struct sps30_state *state = iio_priv(indio_dev);
 	u8 tmp[4];
 	int ret;

 	mutex_lock(&state->lock);
 	ret = sps30_do_cmd(state, SPS30_READ_AUTO_CLEANING_PERIOD, tmp, 4);
 	mutex_unlock(&state->lock);
 	if (ret)
 		return ret;

 	return sprintf(buf, "%d\n", get_unaligned_be32(tmp));
 }

 static ssize_t cleaning_period_store(struct device *dev,
 				       struct device_attribute *attr,
 				       const char *buf, size_t len)
 {
 	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 	struct sps30_state *state = iio_priv(indio_dev);
 	int val, ret;
 	u8 tmp[4];

 	if (kstrtoint(buf, 0, &val))
 		return -EINVAL;

 	if ((val < SPS30_AUTO_CLEANING_PERIOD_MIN) ||
 	    (val > SPS30_AUTO_CLEANING_PERIOD_MAX))
 		return -EINVAL;

 	put_unaligned_be32(val, tmp);

 	mutex_lock(&state->lock);
 	ret = sps30_do_cmd(state, SPS30_AUTO_CLEANING_PERIOD, tmp, 0);
 	if (ret) {
 		mutex_unlock(&state->lock);
 		return ret;
 	}

 	msleep(20);

 	/*
 	 * sensor requires reset in order to return up to date self cleaning
 	 * period
 	 */
 	ret = sps30_do_cmd_reset(state);
 	if (ret)
 		dev_warn(dev,
 			 "period changed but reads will return the old value\n");

 	mutex_unlock(&state->lock);

 	return len;
 }

 static ssize_t cleaning_period_available_show(struct device *dev,
 					      struct device_attribute *attr,
 					      char *buf)
 {
 	return snprintf(buf, PAGE_SIZE, "[%d %d %d]\n",
 			SPS30_AUTO_CLEANING_PERIOD_MIN, 1,
 			SPS30_AUTO_CLEANING_PERIOD_MAX);
 }

 static IIO_DEVICE_ATTR_WO(start_cleaning, 0);
 static IIO_DEVICE_ATTR_RW(cleaning_period, 0);
 static IIO_DEVICE_ATTR_RO(cleaning_period_available, 0);

 static struct attribute *sps30_attrs[] = {
 	&iio_dev_attr_start_cleaning.dev_attr.attr,
 	&iio_dev_attr_cleaning_period.dev_attr.attr,
 	&iio_dev_attr_cleaning_period_available.dev_attr.attr,
 	NULL
 };

 static const struct attribute_group sps30_attr_group = {
 	.attrs = sps30_attrs,
 };

 static const struct iio_info sps30_info = {
 	.attrs = &sps30_attr_group,
 	.read_raw = sps30_read_raw,
 };

 #define SPS30_CHAN(_index, _mod) { \
 	.type = IIO_MASSCONCENTRATION, \
 	.modified = 1, \
 	.channel2 = IIO_MOD_ ## _mod, \
 	.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), \
 	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
 	.address = _mod, \
 	.scan_index = _index, \
 	.scan_type = { \
 		.sign = 'u', \
 		.realbits = 19, \
 		.storagebits = 32, \
 		.endianness = IIO_CPU, \
 	}, \
 }

 static const struct iio_chan_spec sps30_channels[] = {
 	SPS30_CHAN(0, PM1),
 	SPS30_CHAN(1, PM2P5),
 	SPS30_CHAN(2, PM4),
 	SPS30_CHAN(3, PM10),
 	IIO_CHAN_SOFT_TIMESTAMP(4),
 };

 static void sps30_stop_meas(void *data)
 {
 	struct sps30_state *state = data;

 	sps30_do_cmd(state, SPS30_STOP_MEAS, NULL, 0);
 }

 static const unsigned long sps30_scan_masks[] = { 0x0f, 0x00 };

 static int sps30_probe(struct i2c_client *client)
 {
 	struct iio_dev *indio_dev;
 	struct sps30_state *state;
 	u8 buf[32];
 	int ret;

 	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
 		return -EOPNOTSUPP;

 	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*state));
 	if (!indio_dev)
 		return -ENOMEM;

 	state = iio_priv(indio_dev);
 	i2c_set_clientdata(client, indio_dev);
 	state->client = client;
 	state->state = RESET;
 	indio_dev->dev.parent = &client->dev;
 	indio_dev->info = &sps30_info;
 	indio_dev->name = client->name;
 	indio_dev->channels = sps30_channels;
 	indio_dev->num_channels = ARRAY_SIZE(sps30_channels);
 	indio_dev->modes = INDIO_DIRECT_MODE;
 	indio_dev->available_scan_masks = sps30_scan_masks;

 	mutex_init(&state->lock);
 	crc8_populate_msb(sps30_crc8_table, SPS30_CRC8_POLYNOMIAL);

 	ret = sps30_do_cmd_reset(state);
 	if (ret) {
 		dev_err(&client->dev, "failed to reset device\n");
 		return ret;
 	}

 	ret = sps30_do_cmd(state, SPS30_READ_SERIAL, buf, sizeof(buf));
 	if (ret) {
 		dev_err(&client->dev, "failed to read serial number\n");
 		return ret;
 	}
 	/* returned serial number is already NUL terminated */
 	dev_info(&client->dev, "serial number: %s\n", buf);

 	ret = devm_add_action_or_reset(&client->dev, sps30_stop_meas, state);
 	if (ret)
 		return ret;

 	ret = devm_iio_triggered_buffer_setup(&client->dev, indio_dev, NULL,
 					      sps30_trigger_handler, NULL);
 	if (ret)
 		return ret;

 	return devm_iio_device_register(&client->dev, indio_dev);
 }

 static const struct i2c_device_id sps30_id[] = {
 	{ "sps30" },
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, sps30_id);

 static const struct of_device_id sps30_of_match[] = {
 	{ .compatible = "sensirion,sps30" },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, sps30_of_match);

 static struct i2c_driver sps30_driver = {
 	.driver = {
 		.name = "sps30",
 		.of_match_table = sps30_of_match,
 	},
 	.id_table = sps30_id,
 	.probe_new = sps30_probe,
 };
 module_i2c_driver(sps30_driver);

 MODULE_AUTHOR("Tomasz Duszynski <tduszyns@gmail.com>");
 MODULE_DESCRIPTION("Sensirion SPS30 particulate matter sensor driver");
 MODULE_LICENSE("GPL v2");
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Sensirion SPS30 particulate matter sensor driver
	*
	* Copyright (c) Tomasz Duszynski <tduszyns@gmail.com>
	*
	* I2C slave address: 0x69
	*/

	#include <asm/unaligned.h>
	#include <linux/crc8.h>
	#include <linux/delay.h>
	#include <linux/i2c.h>
	#include <linux/iio/buffer.h>
	#include <linux/iio/iio.h>
	#include <linux/iio/sysfs.h>
	#include <linux/iio/trigger_consumer.h>
	#include <linux/iio/triggered_buffer.h>
	#include <linux/kernel.h>
	#include <linux/module.h>

	#define SPS30_CRC8_POLYNOMIAL 0x31
	/* max number of bytes needed to store PM measurements or serial string */
	#define SPS30_MAX_READ_SIZE 48
	/* sensor measures reliably up to 3000 ug / m3 */
	#define SPS30_MAX_PM 3000
	/* minimum and maximum self cleaning periods in seconds */
	#define SPS30_AUTO_CLEANING_PERIOD_MIN 0
	#define SPS30_AUTO_CLEANING_PERIOD_MAX 604800

	/* SPS30 commands */
	#define SPS30_START_MEAS 0x0010
	#define SPS30_STOP_MEAS 0x0104
	#define SPS30_RESET 0xd304
	#define SPS30_READ_DATA_READY_FLAG 0x0202
	#define SPS30_READ_DATA 0x0300
	#define SPS30_READ_SERIAL 0xd033
	#define SPS30_START_FAN_CLEANING 0x5607
	#define SPS30_AUTO_CLEANING_PERIOD 0x8004
	/* not a sensor command per se, used only to distinguish write from read */
	#define SPS30_READ_AUTO_CLEANING_PERIOD 0x8005

	enum {
	PM1,
	PM2P5,
	PM4,
	PM10,
	};

	enum {
	RESET,
	MEASURING,
	};

	struct sps30_state {
	struct i2c_client *client;
	/*
	* Guards against concurrent access to sensor registers.
	* Must be held whenever sequence of commands is to be executed.
	*/
	struct mutex lock;
	int state;
	};

	DECLARE_CRC8_TABLE(sps30_crc8_table);

	static int sps30_write_then_read(struct sps30_state state, u8 txbuf,
	int txsize, u8 *rxbuf, int rxsize)
	{
	int ret;

	/*
	* Sensor does not support repeated start so instead of
	* sending two i2c messages in a row we just send one by one.
	*/
	ret = i2c_master_send(state->client, txbuf, txsize);
	if (ret != txsize)
	return ret < 0 ? ret : -EIO;

	if (!rxbuf)
	return 0;

	ret = i2c_master_recv(state->client, rxbuf, rxsize);
	if (ret != rxsize)
	return ret < 0 ? ret : -EIO;

	return 0;
	}

	static int sps30_do_cmd(struct sps30_state state, u16 cmd, u8 data, int size)
	{
	/*
	* Internally sensor stores measurements in a following manner:
	*
	* PM1: upper two bytes, crc8, lower two bytes, crc8
	* PM2P5: upper two bytes, crc8, lower two bytes, crc8
	* PM4: upper two bytes, crc8, lower two bytes, crc8
	* PM10: upper two bytes, crc8, lower two bytes, crc8
	*
	* What follows next are number concentration measurements and
	* typical particle size measurement which we omit.
	*/
	u8 buf[SPS30_MAX_READ_SIZE] = { cmd >> 8, cmd };
	int i, ret = 0;

	switch (cmd) {
	case SPS30_START_MEAS:
	buf[2] = 0x03;
	buf[3] = 0x00;
	buf[4] = crc8(sps30_crc8_table, &buf[2], 2, CRC8_INIT_VALUE);
	ret = sps30_write_then_read(state, buf, 5, NULL, 0);
	break;
	case SPS30_STOP_MEAS:
	case SPS30_RESET:
	case SPS30_START_FAN_CLEANING:
	ret = sps30_write_then_read(state, buf, 2, NULL, 0);
	break;
	case SPS30_READ_AUTO_CLEANING_PERIOD:
	buf[0] = SPS30_AUTO_CLEANING_PERIOD >> 8;
	buf[1] = (u8)(SPS30_AUTO_CLEANING_PERIOD & 0xff);
	/* fall through */
	case SPS30_READ_DATA_READY_FLAG:
	case SPS30_READ_DATA:
	case SPS30_READ_SERIAL:
	/* every two data bytes are checksummed */
	size += size / 2;
	ret = sps30_write_then_read(state, buf, 2, buf, size);
	break;
	case SPS30_AUTO_CLEANING_PERIOD:
	buf[2] = data[0];
	buf[3] = data[1];
	buf[4] = crc8(sps30_crc8_table, &buf[2], 2, CRC8_INIT_VALUE);
	buf[5] = data[2];
	buf[6] = data[3];
	buf[7] = crc8(sps30_crc8_table, &buf[5], 2, CRC8_INIT_VALUE);
	ret = sps30_write_then_read(state, buf, 8, NULL, 0);
	break;
	}

	if (ret)
	return ret;

	/* validate received data and strip off crc bytes */
	for (i = 0; i < size; i += 3) {
	u8 crc = crc8(sps30_crc8_table, &buf[i], 2, CRC8_INIT_VALUE);

	if (crc != buf[i + 2]) {
	dev_err(&state->client->dev,
	"data integrity check failed\n");
	return -EIO;
	}

	*data++ = buf[i];
	*data++ = buf[i + 1];
	}

	return 0;
	}

	static s32 sps30_float_to_int_clamped(const u8 *fp)
	{
	int val = get_unaligned_be32(fp);
	int mantissa = val & GENMASK(22, 0);
	/* this is fine since passed float is always non-negative */
	int exp = val >> 23;
	int fraction, shift;

	/* special case 0 */
	if (!exp && !mantissa)
	return 0;

	exp -= 127;
	if (exp < 0) {
	/* return values ranging from 1 to 99 */
	return ((((1 << 23) + mantissa) * 100) >> 23) >> (-exp);
	}

	/* return values ranging from 100 to 300000 */
	shift = 23 - exp;
	val = (1 << exp) + (mantissa >> shift);
	if (val >= SPS30_MAX_PM)
	return SPS30_MAX_PM * 100;

	fraction = mantissa & GENMASK(shift - 1, 0);

	return val * 100 + ((fraction * 100) >> shift);
	}

	static int sps30_do_meas(struct sps30_state state, s32 data, int size)
	{
	int i, ret, tries = 5;
	u8 tmp[16];

	if (state->state == RESET) {
	ret = sps30_do_cmd(state, SPS30_START_MEAS, NULL, 0);
	if (ret)
	return ret;

	state->state = MEASURING;
	}

	while (tries--) {
	ret = sps30_do_cmd(state, SPS30_READ_DATA_READY_FLAG, tmp, 2);
	if (ret)
	return -EIO;

	/* new measurements ready to be read */
	if (tmp[1] == 1)
	break;

	msleep_interruptible(300);
	}

	if (tries == -1)
	return -ETIMEDOUT;

	ret = sps30_do_cmd(state, SPS30_READ_DATA, tmp, sizeof(int) * size);
	if (ret)
	return ret;

	for (i = 0; i < size; i++)
	data[i] = sps30_float_to_int_clamped(&tmp[4 * i]);

	return 0;
	}

	static irqreturn_t sps30_trigger_handler(int irq, void *p)
	{
	struct iio_poll_func *pf = p;
	struct iio_dev *indio_dev = pf->indio_dev;
	struct sps30_state *state = iio_priv(indio_dev);
	int ret;
	s32 data[4 + 2]; /* PM1, PM2P5, PM4, PM10, timestamp */

	mutex_lock(&state->lock);
	ret = sps30_do_meas(state, data, 4);
	mutex_unlock(&state->lock);
	if (ret)
	goto err;

	iio_push_to_buffers_with_timestamp(indio_dev, data,
	iio_get_time_ns(indio_dev));
	err:
	iio_trigger_notify_done(indio_dev->trig);

	return IRQ_HANDLED;
	}

	static int sps30_read_raw(struct iio_dev *indio_dev,
	struct iio_chan_spec const *chan,
	int val, int val2, long mask)
	{
	struct sps30_state *state = iio_priv(indio_dev);
	int data[4], ret = -EINVAL;

	switch (mask) {
	case IIO_CHAN_INFO_PROCESSED:
	switch (chan->type) {
	case IIO_MASSCONCENTRATION:
	mutex_lock(&state->lock);
	/* read up to the number of bytes actually needed */
	switch (chan->channel2) {
	case IIO_MOD_PM1:
	ret = sps30_do_meas(state, data, 1);
	break;
	case IIO_MOD_PM2P5:
	ret = sps30_do_meas(state, data, 2);
	break;
	case IIO_MOD_PM4:
	ret = sps30_do_meas(state, data, 3);
	break;
	case IIO_MOD_PM10:
	ret = sps30_do_meas(state, data, 4);
	break;
	}
	mutex_unlock(&state->lock);
	if (ret)
	return ret;

	*val = data[chan->address] / 100;
	val2 = (data[chan->address] % 100) 10000;

	return IIO_VAL_INT_PLUS_MICRO;
	default:
	return -EINVAL;
	}
	case IIO_CHAN_INFO_SCALE:
	switch (chan->type) {
	case IIO_MASSCONCENTRATION:
	switch (chan->channel2) {
	case IIO_MOD_PM1:
	case IIO_MOD_PM2P5:
	case IIO_MOD_PM4:
	case IIO_MOD_PM10:
	*val = 0;
	*val2 = 10000;

	return IIO_VAL_INT_PLUS_MICRO;
	default:
	return -EINVAL;
	}
	default:
	return -EINVAL;
	}
	}

	return -EINVAL;
	}

	static int sps30_do_cmd_reset(struct sps30_state *state)
	{
	int ret;

	ret = sps30_do_cmd(state, SPS30_RESET, NULL, 0);
	msleep(300);
	/*
	* Power-on-reset causes sensor to produce some glitch on i2c bus and
	* some controllers end up in error state. Recover simply by placing
	* some data on the bus, for example STOP_MEAS command, which
	* is NOP in this case.
	*/
	sps30_do_cmd(state, SPS30_STOP_MEAS, NULL, 0);
	state->state = RESET;

	return ret;
	}

	static ssize_t start_cleaning_store(struct device *dev,
	struct device_attribute *attr,
	const char *buf, size_t len)
	{
	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
	struct sps30_state *state = iio_priv(indio_dev);
	int val, ret;

	if (kstrtoint(buf, 0, &val) \|\| val != 1)
	return -EINVAL;

	mutex_lock(&state->lock);
	ret = sps30_do_cmd(state, SPS30_START_FAN_CLEANING, NULL, 0);
	mutex_unlock(&state->lock);
	if (ret)
	return ret;

	return len;
	}

	static ssize_t cleaning_period_show(struct device *dev,
	struct device_attribute *attr,
	char *buf)
	{
	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
	struct sps30_state *state = iio_priv(indio_dev);
	u8 tmp[4];
	int ret;

	mutex_lock(&state->lock);
	ret = sps30_do_cmd(state, SPS30_READ_AUTO_CLEANING_PERIOD, tmp, 4);
	mutex_unlock(&state->lock);
	if (ret)
	return ret;

	return sprintf(buf, "%d\n", get_unaligned_be32(tmp));
	}

	static ssize_t cleaning_period_store(struct device *dev,
	struct device_attribute *attr,
	const char *buf, size_t len)
	{
	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
	struct sps30_state *state = iio_priv(indio_dev);
	int val, ret;
	u8 tmp[4];

	if (kstrtoint(buf, 0, &val))
	return -EINVAL;

	if ((val < SPS30_AUTO_CLEANING_PERIOD_MIN) \|\|
	(val > SPS30_AUTO_CLEANING_PERIOD_MAX))
	return -EINVAL;

	put_unaligned_be32(val, tmp);

	mutex_lock(&state->lock);
	ret = sps30_do_cmd(state, SPS30_AUTO_CLEANING_PERIOD, tmp, 0);
	if (ret) {
	mutex_unlock(&state->lock);
	return ret;
	}

	msleep(20);

	/*
	* sensor requires reset in order to return up to date self cleaning
	* period
	*/
	ret = sps30_do_cmd_reset(state);
	if (ret)
	dev_warn(dev,
	"period changed but reads will return the old value\n");

	mutex_unlock(&state->lock);

	return len;
	}

	static ssize_t cleaning_period_available_show(struct device *dev,
	struct device_attribute *attr,
	char *buf)
	{
	return snprintf(buf, PAGE_SIZE, "[%d %d %d]\n",
	SPS30_AUTO_CLEANING_PERIOD_MIN, 1,
	SPS30_AUTO_CLEANING_PERIOD_MAX);
	}

	static IIO_DEVICE_ATTR_WO(start_cleaning, 0);
	static IIO_DEVICE_ATTR_RW(cleaning_period, 0);
	static IIO_DEVICE_ATTR_RO(cleaning_period_available, 0);

	static struct attribute *sps30_attrs[] = {
	&iio_dev_attr_start_cleaning.dev_attr.attr,
	&iio_dev_attr_cleaning_period.dev_attr.attr,
	&iio_dev_attr_cleaning_period_available.dev_attr.attr,
	NULL
	};

	static const struct attribute_group sps30_attr_group = {
	.attrs = sps30_attrs,
	};

	static const struct iio_info sps30_info = {
	.attrs = &sps30_attr_group,
	.read_raw = sps30_read_raw,
	};

	#define SPS30_CHAN(_index, _mod) { \
	.type = IIO_MASSCONCENTRATION, \
	.modified = 1, \
	.channel2 = IIO_MOD_ ## _mod, \
	.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), \
	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
	.address = _mod, \
	.scan_index = _index, \
	.scan_type = { \
	.sign = 'u', \
	.realbits = 19, \
	.storagebits = 32, \
	.endianness = IIO_CPU, \
	}, \
	}

	static const struct iio_chan_spec sps30_channels[] = {
	SPS30_CHAN(0, PM1),
	SPS30_CHAN(1, PM2P5),
	SPS30_CHAN(2, PM4),
	SPS30_CHAN(3, PM10),
	IIO_CHAN_SOFT_TIMESTAMP(4),
	};

	static void sps30_stop_meas(void *data)
	{
	struct sps30_state *state = data;

	sps30_do_cmd(state, SPS30_STOP_MEAS, NULL, 0);
	}

	static const unsigned long sps30_scan_masks[] = { 0x0f, 0x00 };

	static int sps30_probe(struct i2c_client *client)
	{
	struct iio_dev *indio_dev;
	struct sps30_state *state;
	u8 buf[32];
	int ret;

	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
	return -EOPNOTSUPP;

	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*state));
	if (!indio_dev)
	return -ENOMEM;

	state = iio_priv(indio_dev);
	i2c_set_clientdata(client, indio_dev);
	state->client = client;
	state->state = RESET;
	indio_dev->dev.parent = &client->dev;
	indio_dev->info = &sps30_info;
	indio_dev->name = client->name;
	indio_dev->channels = sps30_channels;
	indio_dev->num_channels = ARRAY_SIZE(sps30_channels);
	indio_dev->modes = INDIO_DIRECT_MODE;
	indio_dev->available_scan_masks = sps30_scan_masks;

	mutex_init(&state->lock);
	crc8_populate_msb(sps30_crc8_table, SPS30_CRC8_POLYNOMIAL);

	ret = sps30_do_cmd_reset(state);
	if (ret) {
	dev_err(&client->dev, "failed to reset device\n");
	return ret;
	}

	ret = sps30_do_cmd(state, SPS30_READ_SERIAL, buf, sizeof(buf));
	if (ret) {
	dev_err(&client->dev, "failed to read serial number\n");
	return ret;
	}
	/* returned serial number is already NUL terminated */
	dev_info(&client->dev, "serial number: %s\n", buf);

	ret = devm_add_action_or_reset(&client->dev, sps30_stop_meas, state);
	if (ret)
	return ret;

	ret = devm_iio_triggered_buffer_setup(&client->dev, indio_dev, NULL,
	sps30_trigger_handler, NULL);
	if (ret)
	return ret;

	return devm_iio_device_register(&client->dev, indio_dev);
	}

	static const struct i2c_device_id sps30_id[] = {
	{ "sps30" },
	{ }
	};
	MODULE_DEVICE_TABLE(i2c, sps30_id);

	static const struct of_device_id sps30_of_match[] = {
	{ .compatible = "sensirion,sps30" },
	{ }
	};
	MODULE_DEVICE_TABLE(of, sps30_of_match);

	static struct i2c_driver sps30_driver = {
	.driver = {
	.name = "sps30",
	.of_match_table = sps30_of_match,
	},
	.id_table = sps30_id,
	.probe_new = sps30_probe,
	};
	module_i2c_driver(sps30_driver);

	MODULE_AUTHOR("Tomasz Duszynski <tduszyns@gmail.com>");
	MODULE_DESCRIPTION("Sensirion SPS30 particulate matter sensor driver");
	MODULE_LICENSE("GPL v2");