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Date:   Sun, 2 May 2021 18:32:20 +0100
From:   Jonathan Cameron <jic23@kernel.org>
To:     Tomasz Duszynski <tomasz.duszynski@octakon.com>
Cc:     <linux-iio@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <devicetree@vger.kernel.org>, <lars@metafoo.de>,
        <robh+dt@kernel.org>
Subject: Re: [PATCH v2 1/3] iio: sps30: separate core and interface specific
 code
Message-ID: <20210502183220.0ed8ff1c@jic23-huawei>
In-Reply-To: <20210502134431.42647-2-tomasz.duszynski@octakon.com>
References: <20210502134431.42647-1-tomasz.duszynski@octakon.com>
        <20210502134431.42647-2-tomasz.duszynski@octakon.com>
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On Sun, 2 May 2021 15:44:29 +0200
Tomasz Duszynski <tomasz.duszynski@octakon.com> wrote:

> 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>
A comment way down the end.   Basically says that dropping the i2c_device_id
table is fine with me, but does occasionally cause problems as it's still used
IIRC by greybus.  Maybe someone will one day connect one of these to greybus :)

Otherwise, looks good to me.


Jonathan

> ---
>  MAINTAINERS                      |   1 +
>  drivers/iio/chemical/Kconfig     |  16 +-
>  drivers/iio/chemical/Makefile    |   1 +
>  drivers/iio/chemical/sps30.c     | 269 ++++++-------------------------
>  drivers/iio/chemical/sps30.h     |  35 ++++
>  drivers/iio/chemical/sps30_i2c.c | 251 ++++++++++++++++++++++++++++
>  6 files changed, 347 insertions(+), 226 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..2b45a76ab7bc 100644
> --- a/drivers/iio/chemical/Kconfig
> +++ b/drivers/iio/chemical/Kconfig
> @@ -132,17 +132,21 @@ config SENSIRION_SGP30
>  	  module will be called sgp30.
>  
>  config SPS30
> -	tristate "SPS30 particulate matter sensor"
> -	depends on I2C
> -	select CRC8
> +	tristate
>  	select IIO_BUFFER
>  	select IIO_TRIGGERED_BUFFER
> +
> +config SPS30_I2C
> +	tristate "SPS30 particulate matter sensor I2C driver"
> +	depends on I2C
> +	select SPS30
> +	select CRC8
>  	help
> -	  Say Y here to build support for the Sensirion SPS30 particulate
> -	  matter sensor.
> +	  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.
> +	  be called sps30_i2c.
>  
>  config VZ89X
>  	tristate "SGX Sensortech MiCS VZ89X VOC sensor"
> 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..d51314505115 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_cpup(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 = state->ops->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 = state->ops->read_meas(state, (__be32 *)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((__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 = state->ops->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 = state->ops->clean_fan(state);
>  	mutex_unlock(&state->lock);
>  	if (ret)
>  		return ret;
> @@ -349,31 +207,29 @@ 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];
> +	__be32 val;
>  	int ret;
>  
>  	mutex_lock(&state->lock);
> -	ret = sps30_do_cmd(state, SPS30_READ_AUTO_CLEANING_PERIOD, tmp, 4);
> +	ret = state->ops->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(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 +238,8 @@ 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 = state->ops->write_cleaning_period(state, cpu_to_be32(val));
>  	if (ret) {
>  		mutex_unlock(&state->lock);
>  		return ret;
> @@ -397,7 +251,7 @@ 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 +314,65 @@ 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)
> +		state->ops->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 = state->ops->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_GPL(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..a58ee43cf45d
> --- /dev/null
> +++ b/drivers/iio/chemical/sps30.h
> @@ -0,0 +1,35 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _SPS30_H
> +#define _SPS30_H
> +
> +#include <linux/types.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, __be32 *meas, size_t num);
> +	int (*reset)(struct sps30_state *state);
> +	int (*clean_fan)(struct sps30_state *state);
> +	int (*read_cleaning_period)(struct sps30_state *state, __be32 *period);
> +	int (*write_cleaning_period)(struct sps30_state *state, __be32 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);
> +
> +#endif
> diff --git a/drivers/iio/chemical/sps30_i2c.c b/drivers/iio/chemical/sps30_i2c.c
> new file mode 100644
> index 000000000000..123ef23bf0eb
> --- /dev/null
> +++ b/drivers/iio/chemical/sps30_i2c.c
> @@ -0,0 +1,251 @@
> +// 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, unsigned char *txbuf, size_t txsize,
> +			  unsigned char *rxbuf, size_t 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, size_t arg_size,
> +			     void *rsp, size_t 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.
> +	 */
> +	unsigned char buf[SPS30_I2C_MAX_BUF_SIZE];
> +	unsigned char *tmp;
> +	unsigned char crc;
> +	size_t i;
> +	int ret;
> +
> +	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 */
> +	unsigned 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)
> +{
> +	unsigned 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, __be32 *meas, size_t num)
> +{
> +	/* measurements are ready within a second */
> +	if (msleep_interruptible(1000))
> +		return -EINTR;
> +
> +	if (!sps30_i2c_meas_ready(state))
> +		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, __be32 *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, __be32 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 */
> +	unsigned 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" },

This drops the i2c_device_id table.   I personally don't mind doing that, but
it will cause trouble for anyone trying to use greybus or similar with this part
(as IIRC they still rely on that id table).

> +	{ }
> +};
> +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");