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From:   Tomasz Duszynski <tomasz.duszynski@octakon.com>
To:     <linux-iio@vger.kernel.org>
CC:     <linux-kernel@vger.kernel.org>, <devicetree@vger.kernel.org>,
        <jic23@kernel.org>, <lars@metafoo.de>, <robh+dt@kernel.org>,
        Tomasz Duszynski <tomasz.duszynski@octakon.com>
Subject: [PATCH 1/3] iio: sps30: separate core and interface specific code
Date:   Sun, 25 Apr 2021 15:55:44 +0200
Message-ID: <20210425135546.57343-2-tomasz.duszynski@octakon.com>
In-Reply-To: <20210425135546.57343-1-tomasz.duszynski@octakon.com>
References: <20210425135546.57343-1-tomasz.duszynski@octakon.com>
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Precedence: bulk

Move code responsible for handling i2c communication to a separate file.
Rationale for this change is preparation for adding support for serial
communication.

Signed-off-by: Tomasz Duszynski <tomasz.duszynski@octakon.com>
---
 MAINTAINERS                      |   1 +
 drivers/iio/chemical/Kconfig     |  13 +-
 drivers/iio/chemical/Makefile    |   1 +
 drivers/iio/chemical/sps30.c     | 270 ++++++-------------------------
 drivers/iio/chemical/sps30.h     |  73 +++++++++
 drivers/iio/chemical/sps30_i2c.c | 256 +++++++++++++++++++++++++++++
 6 files changed, 391 insertions(+), 223 deletions(-)
 create mode 100644 drivers/iio/chemical/sps30.h
 create mode 100644 drivers/iio/chemical/sps30_i2c.c

diff --git a/MAINTAINERS b/MAINTAINERS
index ccc59fd7e5c0..4b39a9c48736 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -16137,6 +16137,7 @@ M:	Tomasz Duszynski <tduszyns@gmail.com>
 S:	Maintained
 F:	Documentation/devicetree/bindings/iio/chemical/sensirion,sps30.yaml
 F:	drivers/iio/chemical/sps30.c
+F:	drivers/iio/chemical/sps30_i2c.c
 
 SERIAL DEVICE BUS
 M:	Rob Herring <robh@kernel.org>
diff --git a/drivers/iio/chemical/Kconfig b/drivers/iio/chemical/Kconfig
index 10bb431bc3ce..82af5f62fbc6 100644
--- a/drivers/iio/chemical/Kconfig
+++ b/drivers/iio/chemical/Kconfig
@@ -133,8 +133,6 @@ config SENSIRION_SGP30
 
 config SPS30
 	tristate "SPS30 particulate matter sensor"
-	depends on I2C
-	select CRC8
 	select IIO_BUFFER
 	select IIO_TRIGGERED_BUFFER
 	help
@@ -144,6 +142,17 @@ config SPS30
 	  To compile this driver as a module, choose M here: the module will
 	  be called sps30.
 
+config SPS30_I2C
+	tristate "SPS30 particulate matter sensor I2C driver"
+	depends on SPS30 && I2C
+	select CRC8
+	help
+	  Say Y here to build support for the Sensirion SPS30 I2C interface
+	  driver.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called sps30_i2c.
+
 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 fef63dd5bf92..41c264a229c0 100644
--- a/drivers/iio/chemical/Makefile
+++ b/drivers/iio/chemical/Makefile
@@ -17,4 +17,5 @@ obj-$(CONFIG_SCD30_I2C) += scd30_i2c.o
 obj-$(CONFIG_SCD30_SERIAL) += scd30_serial.o
 obj-$(CONFIG_SENSIRION_SGP30)	+= sgp30.o
 obj-$(CONFIG_SPS30) += sps30.o
+obj-$(CONFIG_SPS30_I2C) += sps30_i2c.o
 obj-$(CONFIG_VZ89X)		+= vz89x.o
diff --git a/drivers/iio/chemical/sps30.c b/drivers/iio/chemical/sps30.c
index 7486591588c3..ec9db99e324c 100644
--- a/drivers/iio/chemical/sps30.c
+++ b/drivers/iio/chemical/sps30.c
@@ -3,11 +3,8 @@
  * 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>
@@ -19,27 +16,14 @@
 #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
+#include "sps30.h"
+
 /* 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,
@@ -52,114 +36,9 @@ enum {
 	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);
-		fallthrough;
-	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)
+static s32 sps30_float_to_int_clamped(__be32 fp)
 {
-	int val = get_unaligned_be32(fp);
+	int val = be32_to_cpu(fp);
 	int mantissa = val & GENMASK(22, 0);
 	/* this is fine since passed float is always non-negative */
 	int exp = val >> 23;
@@ -188,38 +67,35 @@ static s32 sps30_float_to_int_clamped(const u8 *fp)
 
 static int sps30_do_meas(struct sps30_state *state, s32 *data, int size)
 {
-	int i, ret, tries = 5;
-	u8 tmp[16];
+	int i, ret;
 
 	if (state->state == RESET) {
-		ret = sps30_do_cmd(state, SPS30_START_MEAS, NULL, 0);
+		ret = sps30_start_meas(state);
 		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;
+	ret = sps30_read_meas(state, data, size);
+	if (ret)
+		return ret;
 
-		/* new measurements ready to be read */
-		if (tmp[1] == 1)
-			break;
+	for (i = 0; i < size; i++)
+		data[i] = sps30_float_to_int_clamped((__force __be32)data[i]);
 
-		msleep_interruptible(300);
-	}
+	return 0;
+}
 
-	if (tries == -1)
-		return -ETIMEDOUT;
+static int sps30_do_reset(struct sps30_state *state)
+{
+	int ret;
 
-	ret = sps30_do_cmd(state, SPS30_READ_DATA, tmp, sizeof(int) * size);
+	ret = sps30_reset(state);
 	if (ret)
 		return ret;
 
-	for (i = 0; i < size; i++)
-		data[i] = sps30_float_to_int_clamped(&tmp[4 * i]);
+	state->state = RESET;
 
 	return 0;
 }
@@ -310,24 +186,6 @@ static int sps30_read_raw(struct iio_dev *indio_dev,
 	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)
@@ -340,7 +198,7 @@ static ssize_t start_cleaning_store(struct device *dev,
 		return -EINVAL;
 
 	mutex_lock(&state->lock);
-	ret = sps30_do_cmd(state, SPS30_START_FAN_CLEANING, NULL, 0);
+	ret = sps30_clean_fan(state);
 	mutex_unlock(&state->lock);
 	if (ret)
 		return ret;
@@ -349,31 +207,28 @@ static ssize_t start_cleaning_store(struct device *dev,
 }
 
 static ssize_t cleaning_period_show(struct device *dev,
-				      struct device_attribute *attr,
-				      char *buf)
+				    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;
+	int val, ret;
 
 	mutex_lock(&state->lock);
-	ret = sps30_do_cmd(state, SPS30_READ_AUTO_CLEANING_PERIOD, tmp, 4);
+	ret = sps30_read_cleaning_period(state, &val);
 	mutex_unlock(&state->lock);
 	if (ret)
 		return ret;
 
-	return sprintf(buf, "%d\n", get_unaligned_be32(tmp));
+	return sprintf(buf, "%d\n", be32_to_cpu((__force __be32)val));
 }
 
-static ssize_t cleaning_period_store(struct device *dev,
-				       struct device_attribute *attr,
-				       const char *buf, size_t len)
+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;
@@ -382,10 +237,8 @@ static ssize_t cleaning_period_store(struct device *dev,
 	    (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);
+	ret = sps30_write_cleaning_period(state, (__force int)cpu_to_be32(val));
 	if (ret) {
 		mutex_unlock(&state->lock);
 		return ret;
@@ -397,7 +250,7 @@ static ssize_t cleaning_period_store(struct device *dev,
 	 * sensor requires reset in order to return up to date self cleaning
 	 * period
 	 */
-	ret = sps30_do_cmd_reset(state);
+	ret = sps30_do_reset(state);
 	if (ret)
 		dev_warn(dev,
 			 "period changed but reads will return the old value\n");
@@ -460,90 +313,65 @@ static const struct iio_chan_spec sps30_channels[] = {
 	IIO_CHAN_SOFT_TIMESTAMP(4),
 };
 
-static void sps30_stop_meas(void *data)
+static void sps30_devm_stop_meas(void *data)
 {
 	struct sps30_state *state = data;
 
-	sps30_do_cmd(state, SPS30_STOP_MEAS, NULL, 0);
+	if (state->state == MEASURING)
+		sps30_stop_meas(state);
 }
 
 static const unsigned long sps30_scan_masks[] = { 0x0f, 0x00 };
 
-static int sps30_probe(struct i2c_client *client)
+int sps30_probe(struct device *dev, const char *name, void *priv, const struct sps30_ops *ops)
 {
 	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));
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*state));
 	if (!indio_dev)
 		return -ENOMEM;
 
+	dev_set_drvdata(dev, indio_dev);
+
 	state = iio_priv(indio_dev);
-	i2c_set_clientdata(client, indio_dev);
-	state->client = client;
-	state->state = RESET;
+	state->dev = dev;
+	state->priv = priv;
+	state->ops = ops;
+	mutex_init(&state->lock);
+
 	indio_dev->info = &sps30_info;
-	indio_dev->name = client->name;
+	indio_dev->name = 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);
+	ret = sps30_do_reset(state);
 	if (ret) {
-		dev_err(&client->dev, "failed to reset device\n");
+		dev_err(dev, "failed to reset device\n");
 		return ret;
 	}
 
-	ret = sps30_do_cmd(state, SPS30_READ_SERIAL, buf, sizeof(buf));
+	ret = sps30_show_info(state);
 	if (ret) {
-		dev_err(&client->dev, "failed to read serial number\n");
+		dev_err(dev, "failed to read device info\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);
+	ret = devm_add_action_or_reset(dev, sps30_devm_stop_meas, state);
 	if (ret)
 		return ret;
 
-	ret = devm_iio_triggered_buffer_setup(&client->dev, indio_dev, NULL,
+	ret = devm_iio_triggered_buffer_setup(dev, indio_dev, NULL,
 					      sps30_trigger_handler, NULL);
 	if (ret)
 		return ret;
 
-	return devm_iio_device_register(&client->dev, indio_dev);
+	return devm_iio_device_register(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);
+EXPORT_SYMBOL(sps30_probe);
 
 MODULE_AUTHOR("Tomasz Duszynski <tduszyns@gmail.com>");
 MODULE_DESCRIPTION("Sensirion SPS30 particulate matter sensor driver");
diff --git a/drivers/iio/chemical/sps30.h b/drivers/iio/chemical/sps30.h
new file mode 100644
index 000000000000..d2b7140fdeb4
--- /dev/null
+++ b/drivers/iio/chemical/sps30.h
@@ -0,0 +1,73 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _SPS30_H
+#define _SPS30_H
+
+struct sps30_state;
+struct sps30_ops {
+	int (*start_meas)(struct sps30_state *state);
+	int (*stop_meas)(struct sps30_state *state);
+	int (*read_meas)(struct sps30_state *state, int *meas, int num);
+	int (*reset)(struct sps30_state *state);
+	int (*clean_fan)(struct sps30_state *state);
+	int (*read_cleaning_period)(struct sps30_state *state, int *period);
+	int (*write_cleaning_period)(struct sps30_state *state, int period);
+	int (*show_info)(struct sps30_state *state);
+};
+
+struct sps30_state {
+	/* serialize access to the device */
+	struct mutex lock;
+	struct device *dev;
+	int state;
+	/*
+	 * priv pointer is solely for serdev driver private data. We keep it
+	 * here because driver_data inside dev has been already used for iio and
+	 * struct serdev_device doesn't have one.
+	 */
+	void *priv;
+	const struct sps30_ops *ops;
+};
+
+int sps30_probe(struct device *dev, const char *name, void *priv, const struct sps30_ops *ops);
+
+static inline int sps30_start_meas(struct sps30_state *state)
+{
+	return state->ops->start_meas(state);
+}
+
+static inline int sps30_stop_meas(struct sps30_state *state)
+{
+	return state->ops->stop_meas(state);
+}
+
+static inline int sps30_read_meas(struct sps30_state *state, void *meas, int num)
+{
+	return state->ops->read_meas(state, meas, num);
+}
+
+static inline int sps30_clean_fan(struct sps30_state *state)
+{
+	return state->ops->clean_fan(state);
+}
+
+static inline int sps30_write_cleaning_period(struct sps30_state *state, int period)
+{
+	return state->ops->write_cleaning_period(state, period);
+}
+
+static inline int sps30_read_cleaning_period(struct sps30_state *state, int *period)
+{
+	return state->ops->read_cleaning_period(state, period);
+}
+
+static inline int sps30_show_info(struct sps30_state *state)
+{
+	return state->ops->show_info(state);
+}
+
+static inline int sps30_reset(struct sps30_state *state)
+{
+	return state->ops->reset(state);
+}
+
+#endif
diff --git a/drivers/iio/chemical/sps30_i2c.c b/drivers/iio/chemical/sps30_i2c.c
new file mode 100644
index 000000000000..97146cd50aa5
--- /dev/null
+++ b/drivers/iio/chemical/sps30_i2c.c
@@ -0,0 +1,256 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Sensirion SPS30 particulate matter sensor i2c driver
+ *
+ * Copyright (c) 2020 Tomasz Duszynski <tomasz.duszynski@octakon.com>
+ *
+ * I2C slave address: 0x69
+ */
+#include <asm/unaligned.h>
+#include <linux/crc8.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/i2c.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/types.h>
+
+#include "sps30.h"
+
+#define SPS30_I2C_CRC8_POLYNOMIAL 0x31
+/* max number of bytes needed to store PM measurements or serial string */
+#define SPS30_I2C_MAX_BUF_SIZE 48
+
+DECLARE_CRC8_TABLE(sps30_i2c_crc8_table);
+
+#define SPS30_I2C_START_MEAS 0x0010
+#define SPS30_I2C_STOP_MEAS 0x0104
+#define SPS30_I2C_READ_MEAS 0x0300
+#define SPS30_I2C_MEAS_READY 0x0202
+#define SPS30_I2C_RESET 0xd304
+#define SPS30_I2C_CLEAN_FAN 0x5607
+#define SPS30_I2C_PERIOD 0x8004
+#define SPS30_I2C_READ_SERIAL 0xd033
+#define SPS30_I2C_READ_VERSION 0xd100
+
+static int sps30_i2c_xfer(struct sps30_state *state, char *txbuf, int txsize,
+			  char *rxbuf, int rxsize)
+{
+	struct i2c_client *client = to_i2c_client(state->dev);
+	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(client, txbuf, txsize);
+	if (ret < 0)
+		return ret;
+	if (ret != txsize)
+		return -EIO;
+
+	if (!rxsize)
+		return 0;
+
+	ret = i2c_master_recv(client, rxbuf, rxsize);
+	if (ret < 0)
+		return ret;
+	if (ret != rxsize)
+		return -EIO;
+
+	return 0;
+}
+
+static int sps30_i2c_command(struct sps30_state *state, u16 cmd, void *arg, int arg_size,
+			     void *rsp, int rsp_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.
+	 */
+	char buf[SPS30_I2C_MAX_BUF_SIZE];
+	int i, ret;
+	char *tmp;
+	char crc;
+
+	put_unaligned_be16(cmd, buf);
+	i = 2;
+
+	if (rsp) {
+		/* each two bytes are followed by a crc8 */
+		rsp_size += rsp_size / 2;
+	} else {
+		tmp = arg;
+
+		while (arg_size) {
+			buf[i] = *tmp++;
+			buf[i + 1] = *tmp++;
+			buf[i + 2] = crc8(sps30_i2c_crc8_table, buf + i, 2, CRC8_INIT_VALUE);
+			arg_size -= 2;
+			i += 3;
+		}
+	}
+
+	ret = sps30_i2c_xfer(state, buf, i, buf, rsp_size);
+	if (ret)
+		return ret;
+
+	/* validate received data and strip off crc bytes */
+	tmp = rsp;
+	for (i = 0; i < rsp_size; i += 3) {
+		crc = crc8(sps30_i2c_crc8_table, buf + i, 2, CRC8_INIT_VALUE);
+		if (crc != buf[i + 2]) {
+			dev_err(state->dev, "data integrity check failed\n");
+			return -EIO;
+		}
+
+		*tmp++ = buf[i];
+		*tmp++ = buf[i + 1];
+	}
+
+	return 0;
+}
+
+static int sps30_i2c_start_meas(struct sps30_state *state)
+{
+	/* request BE IEEE754 formatted data */
+	char buf[] = { 0x03, 0x00 };
+
+	return sps30_i2c_command(state, SPS30_I2C_START_MEAS, buf, sizeof(buf), NULL, 0);
+}
+
+static int sps30_i2c_stop_meas(struct sps30_state *state)
+{
+	return sps30_i2c_command(state, SPS30_I2C_STOP_MEAS, NULL, 0, NULL, 0);
+}
+
+static int sps30_i2c_reset(struct sps30_state *state)
+{
+	int ret;
+
+	ret = sps30_i2c_command(state, SPS30_I2C_RESET, NULL, 0, NULL, 0);
+	msleep(500);
+	/*
+	 * 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_i2c_stop_meas(state);
+
+	return ret;
+}
+
+static bool sps30_i2c_meas_ready(struct sps30_state *state)
+{
+	char buf[2];
+	int ret;
+
+	ret = sps30_i2c_command(state, SPS30_I2C_MEAS_READY, NULL, 0, buf, sizeof(buf));
+	if (ret)
+		return false;
+
+	return buf[1];
+}
+
+static int sps30_i2c_read_meas(struct sps30_state *state, int *meas, int num)
+{
+	int tries = 3;
+
+	do {
+		if (sps30_i2c_meas_ready(state))
+			break;
+
+		if (msleep_interruptible(500))
+			return -EINTR;
+	} while (--tries);
+
+	if (!tries)
+		return -ETIMEDOUT;
+
+	return sps30_i2c_command(state, SPS30_I2C_READ_MEAS, NULL, 0, meas, sizeof(num) * num);
+}
+
+static int sps30_i2c_clean_fan(struct sps30_state *state)
+{
+	return sps30_i2c_command(state, SPS30_I2C_CLEAN_FAN, NULL, 0, NULL, 0);
+}
+
+static int sps30_i2c_read_cleaning_period(struct sps30_state *state, int *period)
+{
+	return sps30_i2c_command(state, SPS30_I2C_PERIOD, NULL, 0, period, sizeof(*period));
+}
+
+static int sps30_i2c_write_cleaning_period(struct sps30_state *state, int period)
+{
+	return sps30_i2c_command(state, SPS30_I2C_PERIOD, &period, sizeof(period), NULL, 0);
+}
+
+static int sps30_i2c_show_info(struct sps30_state *state)
+{
+	/* extra nul just in case */
+	char buf[32 + 1] = { 0x00 };
+	int ret;
+
+	ret = sps30_i2c_command(state, SPS30_I2C_READ_SERIAL, NULL, 0, buf, sizeof(buf) - 1);
+	if (ret)
+		return ret;
+
+	dev_info(state->dev, "serial number: %s\n", buf);
+
+	ret = sps30_i2c_command(state, SPS30_I2C_READ_VERSION, NULL, 0, buf, 2);
+	if (ret)
+		return ret;
+
+	dev_info(state->dev, "fw version: %u.%u\n", buf[0], buf[1]);
+
+	return 0;
+}
+
+static const struct sps30_ops sps30_i2c_ops = {
+	.start_meas = sps30_i2c_start_meas,
+	.stop_meas = sps30_i2c_stop_meas,
+	.read_meas = sps30_i2c_read_meas,
+	.reset = sps30_i2c_reset,
+	.clean_fan = sps30_i2c_clean_fan,
+	.read_cleaning_period = sps30_i2c_read_cleaning_period,
+	.write_cleaning_period = sps30_i2c_write_cleaning_period,
+	.show_info = sps30_i2c_show_info,
+};
+
+static int sps30_i2c_probe(struct i2c_client *client)
+{
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+		return -EOPNOTSUPP;
+
+	crc8_populate_msb(sps30_i2c_crc8_table, SPS30_I2C_CRC8_POLYNOMIAL);
+
+	return sps30_probe(&client->dev, client->name, NULL, &sps30_i2c_ops);
+}
+
+static const struct of_device_id sps30_i2c_of_match[] = {
+	{ .compatible = "sensirion,sps30" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, sps30_i2c_of_match);
+
+static struct i2c_driver sps30_i2c_driver = {
+	.driver = {
+		.name = KBUILD_MODNAME,
+		.of_match_table = sps30_i2c_of_match,
+	},
+	.probe_new = sps30_i2c_probe,
+};
+module_i2c_driver(sps30_i2c_driver);
+
+MODULE_AUTHOR("Tomasz Duszynski <tomasz.duszynski@octakon.com>");
+MODULE_DESCRIPTION("Sensirion SPS30 particulate matter sensor i2c driver");
+MODULE_LICENSE("GPL v2");
-- 
2.31.1