[PATCH 0/3] iio: sps30: add support for serial interface

[PATCH 0/3] iio: sps30: add support for serial interface

[Tomasz Duszynski]

One can communicate with sensor either over i2c or serial interface.
This series add support for the latter. And in order to do that existing
codebase needs to be separated into core and interface specific
components.

Tomasz Duszynski (3):
  iio: sps30: separate core and interface specific code
  iio: sps30: add support for serial interface
  dt-bindings: iio: chemical: sps30: update binding with serial example

 .../iio/chemical/sensirion,sps30.yaml         |   7 +-
 MAINTAINERS                                   |   2 +
 drivers/iio/chemical/Kconfig                  |  23 +-
 drivers/iio/chemical/Makefile                 |   2 +
 drivers/iio/chemical/sps30.c                  | 270 ++---------
 drivers/iio/chemical/sps30.h                  |  73 +++
 drivers/iio/chemical/sps30_i2c.c              | 256 +++++++++++
 drivers/iio/chemical/sps30_serial.c           | 420 ++++++++++++++++++
 8 files changed, 829 insertions(+), 224 deletions(-)
 create mode 100644 drivers/iio/chemical/sps30.h
 create mode 100644 drivers/iio/chemical/sps30_i2c.c
 create mode 100644 drivers/iio/chemical/sps30_serial.c

--
2.31.1

[PATCH 1/3] iio: sps30: separate core and interface specific code

[Tomasz Duszynski]

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

Re: [PATCH 1/3] iio: sps30: separate core and interface specific code

[Lars-Peter Clausen]

On 4/25/21 3:55 PM, Tomasz Duszynski 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>

Hi,

The whole series looks really great. Couple of small comments inline.

> [...]
> 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
Since the base module is not very useful without any of the drivers 
enabled, what you can do here is, make the base module 
non-user-selectable, e.g. remove the description text after the tristate 
and then do a `select SPS30` both here from he I2C module and the serial 
module.
> +	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
> [...]
> +EXPORT_SYMBOL(sps30_probe);
EXPORT_SYMBOL_GPL()
>   
>   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);

The interface for {read,write}_cleaning_period() should use __be32, 
since that is what is being passed around.

I was a bit confused when reviewing the uart driver why we can just 
memcpy an int into the output buffer without endianess problems.

> +	int (*show_info)(struct sps30_state *state);
> +};
> +
[...]

Re: [PATCH 1/3] iio: sps30: separate core and interface specific code

[Tomasz Duszynski]

On Sun, Apr 25, 2021 at 05:16:14PM +0200, Lars-Peter Clausen wrote:
> On 4/25/21 3:55 PM, Tomasz Duszynski 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>
>
> Hi,
>
> The whole series looks really great. Couple of small comments inline.
>
> > [...]
> > 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
> Since the base module is not very useful without any of the drivers enabled,
> what you can do here is, make the base module non-user-selectable, e.g.
> remove the description text after the tristate and then do a `select SPS30`
> both here from he I2C module and the serial module.

Right. Current form was helpful in debugging and eventually I forgot to
change it to something reasonable. Thanks for catching this.

> > +	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
> > [...]
> > +EXPORT_SYMBOL(sps30_probe);
> EXPORT_SYMBOL_GPL()

Ack.

> >   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);
>
> The interface for {read,write}_cleaning_period() should use __be32, since
> that is what is being passed around.
>
> I was a bit confused when reviewing the uart driver why we can just memcpy
> an int into the output buffer without endianess problems.
>

Agree that indeed might be confusing at first read since as you said
all endianess conversions are handled in core and other components just
take everything verbatim - which isn't that obvious.

> > +	int (*show_info)(struct sps30_state *state);
> > +};
> > +
> [...]

Re: [PATCH 1/3] iio: sps30: separate core and interface specific code

[Jonathan Cameron]

On Sun, 25 Apr 2021 15:55:44 +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>

Hi Tomasz,

This seems rather less minimal than I'd usually expect for this sort of refactor
but (other than a few things commented on inline) it seems like all the other
bits of refactoring are sensible to me.

Thanks,

Jonathan

> ---
>  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"

One option here is to simplify the Kconfig memu options by
dropping the text above so the option is hidden then selecting
this option (rather than depends) for the bus specific drivers.

> -	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));

As below, I'm not seeing the necessity of this cast.  Just make val a
__be32 and deal with parameters being passed around as that type.

>  }
>  
> -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));

I guess this is related to the below question of the type of period parameter.
I'd make it a be32 directly if that's what it actually is!

>  	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);

As mentioned below, I think period should be a fixed width type.

> +	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);

I'm not convinced the following wrappers are worthwhile.
Most of these are only called in one or two places and having the
ops structure exposed in the calls doesn't really matter much for readability etc.

> +}
> +
> +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));

Do you not want a fixed size type of period?  u32 or something like that?

> +}
> +
> +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");

Re: [PATCH 1/3] iio: sps30: separate core and interface specific code

[Andy Shevchenko]

On Sun, Apr 25, 2021 at 6:46 PM Jonathan Cameron <jic23@kernel.org> wrote:
> On Sun, 25 Apr 2021 15:55:44 +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.

Lars and Jonathan made very good reviews, nothing to add from my side,
thanks, guys!

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 1/3] iio: sps30: separate core and interface specific code

[Tomasz Duszynski]

On Sun, Apr 25, 2021 at 04:46:13PM +0100, Jonathan Cameron wrote:
> On Sun, 25 Apr 2021 15:55:44 +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>
>
> Hi Tomasz,
>
> This seems rather less minimal than I'd usually expect for this sort of refactor
> but (other than a few things commented on inline) it seems like all the other
> bits of refactoring are sensible to me.

Good. I though about splitting the work into more patches but
eventually I realized it's going to create more noise than
really necessary.

>
> Thanks,
>
> Jonathan
>
> > ---
> >  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"
>
> One option here is to simplify the Kconfig memu options by
> dropping the text above so the option is hidden then selecting
> this option (rather than depends) for the bus specific drivers.
>

Ack.

> > -	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));
>
> As below, I'm not seeing the necessity of this cast.  Just make val a
> __be32 and deal with parameters being passed around as that type.
>

Sure.

> >  }
> >
> > -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));
>
> I guess this is related to the below question of the type of period parameter.
> I'd make it a be32 directly if that's what it actually is!
>

Sure.

> >  	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);
>
> As mentioned below, I think period should be a fixed width type.
>
> > +	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);
>
> I'm not convinced the following wrappers are worthwhile.
> Most of these are only called in one or two places and having the
> ops structure exposed in the calls doesn't really matter much for readability etc.
>

No strong opinions here. Will drop them altogether in v2.

> > +}
> > +
> > +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));
>
> Do you not want a fixed size type of period?  u32 or something like that?
>
> > +}
> > +
> > +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");
>

[PATCH 2/3] iio: sps30: add support for serial interface

[Tomasz Duszynski]

Sensor has support for both i2c and serial communication interfaces.
Both offer very similar set of features. Minor differences don't impact
overall functionality like doing measurements, etc.

Support for i2c have already been added, this patch adds support
for the latter ie. serial interface.

Signed-off-by: Tomasz Duszynski <tomasz.duszynski@octakon.com>
---
 MAINTAINERS                         |   1 +
 drivers/iio/chemical/Kconfig        |  10 +
 drivers/iio/chemical/Makefile       |   1 +
 drivers/iio/chemical/sps30_serial.c | 420 ++++++++++++++++++++++++++++
 4 files changed, 432 insertions(+)
 create mode 100644 drivers/iio/chemical/sps30_serial.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 4b39a9c48736..cab9a63ad2cf 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -16138,6 +16138,7 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/iio/chemical/sensirion,sps30.yaml
 F:	drivers/iio/chemical/sps30.c
 F:	drivers/iio/chemical/sps30_i2c.c
+F:	drivers/iio/chemical/sps30_serial.c
 
 SERIAL DEVICE BUS
 M:	Rob Herring <robh@kernel.org>
diff --git a/drivers/iio/chemical/Kconfig b/drivers/iio/chemical/Kconfig
index 82af5f62fbc6..6909b4754b9e 100644
--- a/drivers/iio/chemical/Kconfig
+++ b/drivers/iio/chemical/Kconfig
@@ -153,6 +153,16 @@ config SPS30_I2C
 	  To compile this driver as a module, choose M here: the module will
 	  be called sps30_i2c.
 
+config SPS30_SERIAL
+	tristate "SPS30 particulate matter sensor serial driver"
+	depends on SPS30 && SERIAL_DEV_BUS
+	help
+	  Say Y here to build support for the Sensirion SPS30 serial interface
+	  driver.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called sps30_serial.
+
 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 41c264a229c0..4898690cc155 100644
--- a/drivers/iio/chemical/Makefile
+++ b/drivers/iio/chemical/Makefile
@@ -18,4 +18,5 @@ 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-$(CONFIG_SPS30_SERIAL) += sps30_serial.o
 obj-$(CONFIG_VZ89X)		+= vz89x.o
diff --git a/drivers/iio/chemical/sps30_serial.c b/drivers/iio/chemical/sps30_serial.c
new file mode 100644
index 000000000000..5adeeed9bc8f
--- /dev/null
+++ b/drivers/iio/chemical/sps30_serial.c
@@ -0,0 +1,420 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Sensirion SPS30 particulate matter sensor serial driver
+ *
+ * Copyright (c) 2021 Tomasz Duszynski <tomasz.duszynski@octakon.com>
+ */
+#include <linux/completion.h>
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/iio/iio.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/serdev.h>
+
+#include "sps30.h"
+
+#define SPS30_SERIAL_SOF_EOF 0x7e
+#define SPS30_SERIAL_TIMEOUT msecs_to_jiffies(20)
+#define SPS30_SERIAL_MAX_BUF_SIZE 263
+#define SPS30_SERIAL_ESCAPE_CHAR 0x7d
+
+#define SPS30_SERIAL_FRAME_MIN_SIZE 7
+#define SPS30_SERIAL_FRAME_ADR_OFFSET 1
+#define SPS30_SERIAL_FRAME_CMD_OFFSET 2
+#define SPS30_SERIAL_FRAME_MOSI_LEN_OFFSET 3
+#define SPS30_SERIAL_FRAME_MISO_STATE_OFFSET 3
+#define SPS30_SERIAL_FRAME_MISO_LEN_OFFSET 4
+#define SPS30_SERIAL_FRAME_MISO_DATA_OFFSET 5
+
+#define SPS30_SERIAL_START_MEAS 0x00
+#define SPS30_SERIAL_STOP_MEAS 0x01
+#define SPS30_SERIAL_READ_MEAS 0x03
+#define SPS30_SERIAL_RESET 0xd3
+#define SPS30_SERIAL_CLEAN_FAN 0x56
+#define SPS30_SERIAL_PERIOD 0x80
+#define SPS30_SERIAL_DEV_INFO 0xd0
+#define SPS30_SERIAL_READ_VERSION 0xd1
+
+struct sps30_serial_priv {
+	struct completion new_frame;
+	char buf[SPS30_SERIAL_MAX_BUF_SIZE];
+	int num;
+	unsigned int chksum;
+	bool escaped;
+	bool done;
+};
+
+static int sps30_serial_xfer(struct sps30_state *state, const char *buf, int size)
+{
+	struct serdev_device *serdev = to_serdev_device(state->dev);
+	struct sps30_serial_priv *priv = state->priv;
+	int ret;
+
+	priv->num = 0;
+	priv->chksum = 0;
+	priv->escaped = false;
+	priv->done = false;
+
+	ret = serdev_device_write(serdev, buf, size, SPS30_SERIAL_TIMEOUT);
+	if (ret < 0)
+		return ret;
+	if (ret != size)
+		return -EIO;
+
+	ret = wait_for_completion_interruptible_timeout(&priv->new_frame, SPS30_SERIAL_TIMEOUT);
+	if (ret < 0)
+		return ret;
+	if (!ret)
+		return -ETIMEDOUT;
+
+	return 0;
+}
+
+static struct {
+	char byte;
+	char byte2;
+} sps30_serial_bytes[] = {
+	{ 0x11, 0x31 },
+	{ 0x13, 0x33 },
+	{ 0x7e, 0x5e },
+	{ 0x7d, 0x5d },
+};
+
+static int sps30_serial_put_byte(char *buf, char byte)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(sps30_serial_bytes); i++) {
+		if (sps30_serial_bytes[i].byte != byte)
+			continue;
+
+		buf[0] = SPS30_SERIAL_ESCAPE_CHAR;
+		buf[1] = sps30_serial_bytes[i].byte2;
+
+		return 2;
+	}
+
+	buf[0] = byte;
+
+	return 1;
+}
+
+static char sps30_serial_get_byte(bool escaped, char byte2)
+{
+	int i;
+
+	if (!escaped)
+		return byte2;
+
+	for (i = 0; i < ARRAY_SIZE(sps30_serial_bytes); i++) {
+		if (sps30_serial_bytes[i].byte2 != byte2)
+			continue;
+
+		return sps30_serial_bytes[i].byte;
+	}
+
+	return 0;
+}
+
+static int sps30_serial_prep_frame(char *buf, char cmd, const char *arg, int arg_size)
+{
+	unsigned int chksum;
+	unsigned char byte;
+	int i, num = 0;
+
+	buf[num++] = SPS30_SERIAL_SOF_EOF;
+	buf[num++] = 0;
+
+	byte = cmd;
+	num += sps30_serial_put_byte(buf + num, byte);
+	chksum = byte;
+
+	byte = (unsigned char)arg_size;
+	num += sps30_serial_put_byte(buf + num, byte);
+	chksum += byte;
+
+	for (i = 0; i < arg_size; i++) {
+		byte = arg[i];
+		num += sps30_serial_put_byte(buf + num, byte);
+		chksum += byte;
+	}
+
+	byte = (unsigned char)~chksum;
+	num += sps30_serial_put_byte(buf + num, byte);
+
+	buf[num++] = SPS30_SERIAL_SOF_EOF;
+
+	return num;
+}
+
+static bool sps30_serial_frame_valid(struct sps30_state *state, const char *buf)
+{
+	struct sps30_serial_priv *priv = state->priv;
+
+	if ((priv->num < SPS30_SERIAL_FRAME_MIN_SIZE) ||
+	    (priv->num != SPS30_SERIAL_FRAME_MIN_SIZE +
+	     priv->buf[SPS30_SERIAL_FRAME_MISO_LEN_OFFSET])) {
+		dev_err(state->dev, "frame has invalid number of bytes\n");
+		return false;
+	}
+
+	if ((priv->buf[SPS30_SERIAL_FRAME_ADR_OFFSET] != buf[SPS30_SERIAL_FRAME_ADR_OFFSET]) ||
+	    (priv->buf[SPS30_SERIAL_FRAME_CMD_OFFSET] != buf[SPS30_SERIAL_FRAME_CMD_OFFSET])) {
+		dev_err(state->dev, "frame has wrong ADR and CMD bytes\n");
+		return false;
+	}
+
+	if (priv->buf[SPS30_SERIAL_FRAME_MISO_STATE_OFFSET]) {
+		dev_err(state->dev, "frame with non-zero state received (0x%02x)\n",
+			priv->buf[SPS30_SERIAL_FRAME_MISO_STATE_OFFSET]);
+		//return false;
+	}
+
+	if (priv->buf[priv->num - 2] != priv->chksum) {
+		dev_err(state->dev, "frame integrity check failed\n");
+		return false;
+	}
+
+	return true;
+}
+
+static int sps30_serial_command(struct sps30_state *state, char cmd, void *arg, int arg_size,
+				void *rsp, int rsp_size)
+{
+	struct sps30_serial_priv *priv = state->priv;
+	char buf[SPS30_SERIAL_MAX_BUF_SIZE];
+	int ret, size;
+
+	size = sps30_serial_prep_frame(buf, cmd, arg, arg_size);
+	ret = sps30_serial_xfer(state, buf, size);
+	if (ret)
+		return ret;
+
+	if (!sps30_serial_frame_valid(state, buf))
+		return -EIO;
+
+	if (rsp) {
+		rsp_size = clamp((int)priv->buf[SPS30_SERIAL_FRAME_MISO_LEN_OFFSET], 0, rsp_size);
+		memcpy(rsp, &priv->buf[SPS30_SERIAL_FRAME_MISO_DATA_OFFSET], rsp_size);
+	}
+
+	return rsp_size;
+}
+
+static int sps30_serial_receive_buf(struct serdev_device *serdev, const unsigned char *buf,
+				    size_t size)
+{
+	struct iio_dev *indio_dev = dev_get_drvdata(&serdev->dev);
+	struct sps30_serial_priv *priv;
+	struct sps30_state *state;
+	unsigned char byte;
+	int i;
+
+	if (!indio_dev)
+		return 0;
+
+	state = iio_priv(indio_dev);
+	priv = state->priv;
+
+	/* just in case device put some unexpected data on the bus */
+	if (priv->done)
+		return size;
+
+	/* wait for the start of frame */
+	if (!priv->num && size && buf[0] != SPS30_SERIAL_SOF_EOF)
+		return 1;
+
+	if (priv->num + size >= ARRAY_SIZE(priv->buf))
+		size = ARRAY_SIZE(priv->buf) - priv->num;
+
+	for (i = 0; i < size; i++) {
+		byte = buf[i];
+		/* remove stuffed bytes on-the-fly */
+		if (byte == SPS30_SERIAL_ESCAPE_CHAR) {
+			priv->escaped = true;
+			continue;
+		}
+
+		byte = sps30_serial_get_byte(priv->escaped, byte);
+		if (priv->escaped && !byte)
+			dev_warn(state->dev, "unrecognized escaped char (0x%02x)\n", byte);
+		priv->chksum += byte;
+		/* incrementing here would complete rx just after reading SOF */
+		priv->buf[priv->num] = byte;
+
+		if (priv->num++ && !priv->escaped && byte == SPS30_SERIAL_SOF_EOF) {
+			/* SOF, EOF and checksum itself are not checksummed */
+			priv->chksum -= 2 * SPS30_SERIAL_SOF_EOF + priv->buf[priv->num - 2];
+			priv->chksum = (unsigned char)~priv->chksum;
+			priv->done = true;
+			complete(&priv->new_frame);
+			i++;
+			break;
+		}
+
+		priv->escaped = false;
+	}
+
+	return i;
+}
+
+static const struct serdev_device_ops sps30_serial_device_ops = {
+	.receive_buf = sps30_serial_receive_buf,
+	.write_wakeup = serdev_device_write_wakeup,
+};
+
+static int sps30_serial_start_meas(struct sps30_state *state)
+{
+	/* request BE IEEE754 formatted data */
+	char buf[] = { 0x01, 0x03 };
+
+	return sps30_serial_command(state, SPS30_SERIAL_START_MEAS, buf, sizeof(buf), NULL, 0);
+}
+
+static int sps30_serial_stop_meas(struct sps30_state *state)
+{
+	return sps30_serial_command(state, SPS30_SERIAL_STOP_MEAS, NULL, 0, NULL, 0);
+}
+
+static int sps30_serial_reset(struct sps30_state *state)
+{
+	int ret;
+
+	ret = sps30_serial_command(state, SPS30_SERIAL_RESET, NULL, 0, NULL, 0);
+	msleep(500);
+
+	return ret;
+}
+
+static int sps30_serial_read_meas(struct sps30_state *state, int *meas, int num)
+{
+	int ret, tries = 3;
+
+	do {
+		ret = sps30_serial_command(state, SPS30_SERIAL_READ_MEAS, NULL, 0,
+					   meas, num * sizeof(num));
+		if (ret < 0)
+			return ret;
+		/* if measurements aren't ready sensor returns empty frame */
+		if (ret == num * sizeof(int))
+			break;
+
+		if (msleep_interruptible(500))
+			return -EINTR;
+	} while (--tries);
+
+	return !tries ? -ETIMEDOUT : 0;
+}
+
+static int sps30_serial_clean_fan(struct sps30_state *state)
+{
+	return sps30_serial_command(state, SPS30_SERIAL_CLEAN_FAN, NULL, 0, NULL, 0);
+}
+
+static int sps30_serial_read_cleaning_period(struct sps30_state *state, int *period)
+{
+	char buf[] = { 0x00 };
+	int ret;
+
+	ret = sps30_serial_command(state, SPS30_SERIAL_PERIOD, buf, sizeof(buf),
+				   period, sizeof(*period));
+	if (ret < 0)
+		return ret;
+	if (ret != sizeof(*period))
+		return -EIO;
+
+	return 0;
+}
+
+static int sps30_serial_write_cleaning_period(struct sps30_state *state, int period)
+{
+	char buf[5] = { 0x00 };
+
+	memcpy(buf + 1, &period, sizeof(period));
+
+	return sps30_serial_command(state, SPS30_SERIAL_PERIOD, buf, sizeof(buf), NULL, 0);
+}
+
+static int sps30_serial_show_info(struct sps30_state *state)
+{
+	/* extra nul byte just in case serial number isn't a valid string */
+	char buf[32 + 1] = { 0x00 };
+	struct device *dev = state->dev;
+	int ret;
+
+	/* tell device to return serial number */
+	buf[0] = 0x03;
+	ret = sps30_serial_command(state, SPS30_SERIAL_DEV_INFO, buf, 1, buf, sizeof(buf) - 1);
+	if (ret < 0)
+		return ret;
+
+	dev_info(dev, "serial number: %s\n", buf);
+
+	ret = sps30_serial_command(state, SPS30_SERIAL_READ_VERSION, NULL, 0, buf, sizeof(buf) - 1);
+	if (ret < 0)
+		return ret;
+	if (ret < 2)
+		return -EIO;
+
+	dev_info(dev, "fw version: %u.%u\n", buf[0], buf[1]);
+
+	return 0;
+}
+
+static const struct sps30_ops sps30_serial_ops = {
+	.start_meas = sps30_serial_start_meas,
+	.stop_meas = sps30_serial_stop_meas,
+	.read_meas = sps30_serial_read_meas,
+	.reset = sps30_serial_reset,
+	.clean_fan = sps30_serial_clean_fan,
+	.read_cleaning_period = sps30_serial_read_cleaning_period,
+	.write_cleaning_period = sps30_serial_write_cleaning_period,
+	.show_info = sps30_serial_show_info,
+};
+
+static int sps30_serial_probe(struct serdev_device *serdev)
+{
+	struct device *dev = &serdev->dev;
+	struct sps30_serial_priv *priv;
+	int ret;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	init_completion(&priv->new_frame);
+	serdev_device_set_client_ops(serdev, &sps30_serial_device_ops);
+
+	ret = devm_serdev_device_open(dev, serdev);
+	if (ret)
+		return ret;
+
+	serdev_device_set_baudrate(serdev, 115200);
+	serdev_device_set_flow_control(serdev, false);
+
+	ret = serdev_device_set_parity(serdev, SERDEV_PARITY_NONE);
+	if (ret)
+		return ret;
+
+	return sps30_probe(dev, KBUILD_MODNAME, priv, &sps30_serial_ops);
+}
+
+static const struct of_device_id sps30_serial_of_match[] = {
+	{ .compatible = "sensirion,sps30" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, sps30_serial_of_match);
+
+static struct serdev_device_driver sps30_serial_driver = {
+	.driver = {
+		.name = KBUILD_MODNAME,
+		.of_match_table = sps30_serial_of_match,
+	},
+	.probe = sps30_serial_probe,
+};
+module_serdev_device_driver(sps30_serial_driver);
+
+MODULE_AUTHOR("Tomasz Duszynski <tomasz.duszynski@octakon.com>");
+MODULE_DESCRIPTION("Sensirion SPS30 particulate matter sensor serial driver");
+MODULE_LICENSE("GPL v2");
-- 
2.31.1

Re: [PATCH 2/3] iio: sps30: add support for serial interface

[Lars-Peter Clausen]

On 4/25/21 3:55 PM, Tomasz Duszynski wrote:
> [...]
>
> +struct sps30_serial_priv {
> +	struct completion new_frame;
> +	char buf[SPS30_SERIAL_MAX_BUF_SIZE];
The driver uses char, but the serdev API uses unsigned char. Just to 
avoid any surprises I'd use unsigned char for all the buffers in the 
driver as well.
> +	int num;
> +	unsigned int chksum;
> +	bool escaped;
> +	bool done;
> +};
> +
> +static int sps30_serial_xfer(struct sps30_state *state, const char *buf, int size)
> +{
> +	struct serdev_device *serdev = to_serdev_device(state->dev);
> +	struct sps30_serial_priv *priv = state->priv;
> +	int ret;
> +
> +	priv->num = 0;
> +	priv->chksum = 0;
> +	priv->escaped = false;
> +	priv->done = false;
Hm... no locking with regards to the serdev callback. I guess the 
assumption is that we'll never receive any data without explicitly 
requesting it.
> +
> +	ret = serdev_device_write(serdev, buf, size, SPS30_SERIAL_TIMEOUT);
> +	if (ret < 0)
> +		return ret;
> +	if (ret != size)
> +		return -EIO;
> +
> +	ret = wait_for_completion_interruptible_timeout(&priv->new_frame, SPS30_SERIAL_TIMEOUT);
> +	if (ret < 0)
> +		return ret;
> +	if (!ret)
> +		return -ETIMEDOUT;
> +
> +	return 0;
> +}
> [...]
> +static bool sps30_serial_frame_valid(struct sps30_state *state, const char *buf)
> +{
> +	struct sps30_serial_priv *priv = state->priv;
> +
> +	if ((priv->num < SPS30_SERIAL_FRAME_MIN_SIZE) ||
> +	    (priv->num != SPS30_SERIAL_FRAME_MIN_SIZE +
> +	     priv->buf[SPS30_SERIAL_FRAME_MISO_LEN_OFFSET])) {
> +		dev_err(state->dev, "frame has invalid number of bytes\n");
> +		return false;
> +	}
> +
> +	if ((priv->buf[SPS30_SERIAL_FRAME_ADR_OFFSET] != buf[SPS30_SERIAL_FRAME_ADR_OFFSET]) ||
> +	    (priv->buf[SPS30_SERIAL_FRAME_CMD_OFFSET] != buf[SPS30_SERIAL_FRAME_CMD_OFFSET])) {
> +		dev_err(state->dev, "frame has wrong ADR and CMD bytes\n");
> +		return false;
> +	}
> +
> +	if (priv->buf[SPS30_SERIAL_FRAME_MISO_STATE_OFFSET]) {
> +		dev_err(state->dev, "frame with non-zero state received (0x%02x)\n",
> +			priv->buf[SPS30_SERIAL_FRAME_MISO_STATE_OFFSET]);
> +		//return false;
What's with the out commented line?
> +	}
> +
> +	if (priv->buf[priv->num - 2] != priv->chksum) {
> +		dev_err(state->dev, "frame integrity check failed\n");
> +		return false;
> +	}
> +
> +	return true;
> +}
> +
> +static int sps30_serial_command(struct sps30_state *state, char cmd, void *arg, int arg_size,
> +				void *rsp, int rsp_size)
> +{
> +	struct sps30_serial_priv *priv = state->priv;
> +	char buf[SPS30_SERIAL_MAX_BUF_SIZE];
> +	int ret, size;
> +
> +	size = sps30_serial_prep_frame(buf, cmd, arg, arg_size);
> +	ret = sps30_serial_xfer(state, buf, size);
> +	if (ret)
> +		return ret;
> +
> +	if (!sps30_serial_frame_valid(state, buf))
> +		return -EIO;
> +
> +	if (rsp) {
> +		rsp_size = clamp((int)priv->buf[SPS30_SERIAL_FRAME_MISO_LEN_OFFSET], 0, rsp_size);
If buf is unsigned char this can be a min_t(unsigned int, ...). And 
maybe also make rsp_size unsigned int.
> +		memcpy(rsp, &priv->buf[SPS30_SERIAL_FRAME_MISO_DATA_OFFSET], rsp_size);
> +	}
> +
> +	return rsp_size;
> +}
> +
> +static int sps30_serial_receive_buf(struct serdev_device *serdev, const unsigned char *buf,
> +				    size_t size)
> +{
> +	struct iio_dev *indio_dev = dev_get_drvdata(&serdev->dev);
> +	struct sps30_serial_priv *priv;
> +	struct sps30_state *state;
> +	unsigned char byte;
> +	int i;
> +
> +	if (!indio_dev)
> +		return 0;

> +
> +	state = iio_priv(indio_dev);
> +	priv = state->priv;
> +
> +	/* just in case device put some unexpected data on the bus */
> +	if (priv->done)
> +		return size;
> +
> +	/* wait for the start of frame */
> +	if (!priv->num && size && buf[0] != SPS30_SERIAL_SOF_EOF)
> +		return 1;
> +
> +	if (priv->num + size >= ARRAY_SIZE(priv->buf))
> +		size = ARRAY_SIZE(priv->buf) - priv->num;
> +
> +	for (i = 0; i < size; i++) {
> +		byte = buf[i];
> +		/* remove stuffed bytes on-the-fly */
> +		if (byte == SPS30_SERIAL_ESCAPE_CHAR) {
> +			priv->escaped = true;
> +			continue;
> +		}
> +
> +		byte = sps30_serial_get_byte(priv->escaped, byte);
> +		if (priv->escaped && !byte)
> +			dev_warn(state->dev, "unrecognized escaped char (0x%02x)\n", byte);
> +		priv->chksum += byte;
> +		/* incrementing here would complete rx just after reading SOF */
> +		priv->buf[priv->num] = byte;
> +
> +		if (priv->num++ && !priv->escaped && byte == SPS30_SERIAL_SOF_EOF) {

This is a bit to tricky for my taste.

How about.

priv->num++

if (priv->num > 1 && ...)

> +			/* SOF, EOF and checksum itself are not checksummed */
> +			priv->chksum -= 2 * SPS30_SERIAL_SOF_EOF + priv->buf[priv->num - 2];
> +			priv->chksum = (unsigned char)~priv->chksum;
To keep the whole checksum stuff simpler, maybe just compute it in 
sps30_serial_frame_valid() over the whole set of data.
> +			priv->done = true;
> +			complete(&priv->new_frame);
> +			i++;
> +			break;
> +		}
> +
> +		priv->escaped = false;
> +	}
> +
> +	return i;
> +}
> [...]
> +static int sps30_serial_probe(struct serdev_device *serdev)
> +{
> [...]
> +	return sps30_probe(dev, KBUILD_MODNAME, priv, &sps30_serial_ops);
Usually the IIO device name should just be the part number. Ideally the 
application should not care about the backend. I'd just pass "sps30" 
here for the name.
> +}

Re: [PATCH 2/3] iio: sps30: add support for serial interface

[Tomasz Duszynski]

On Sun, Apr 25, 2021 at 05:52:47PM +0200, Lars-Peter Clausen wrote:
> On 4/25/21 3:55 PM, Tomasz Duszynski wrote:
> > [...]
> >
> > +struct sps30_serial_priv {
> > +	struct completion new_frame;
> > +	char buf[SPS30_SERIAL_MAX_BUF_SIZE];
> The driver uses char, but the serdev API uses unsigned char. Just to avoid
> any surprises I'd use unsigned char for all the buffers in the driver as
> well.

Sure, will use unsigned variant consistently then.

> > +	int num;
> > +	unsigned int chksum;
> > +	bool escaped;
> > +	bool done;
> > +};
> > +
> > +static int sps30_serial_xfer(struct sps30_state *state, const char *buf, int size)
> > +{
> > +	struct serdev_device *serdev = to_serdev_device(state->dev);
> > +	struct sps30_serial_priv *priv = state->priv;
> > +	int ret;
> > +
> > +	priv->num = 0;
> > +	priv->chksum = 0;
> > +	priv->escaped = false;
> > +	priv->done = false;
> Hm... no locking with regards to the serdev callback. I guess the assumption
> is that we'll never receive any data without explicitly requesting it.

Correct, sensor shouldn't put anything on the bus without explicic
request. Nonetheless I added some flag just in case.

> > +
> > +	ret = serdev_device_write(serdev, buf, size, SPS30_SERIAL_TIMEOUT);
> > +	if (ret < 0)
> > +		return ret;
> > +	if (ret != size)
> > +		return -EIO;
> > +
> > +	ret = wait_for_completion_interruptible_timeout(&priv->new_frame, SPS30_SERIAL_TIMEOUT);
> > +	if (ret < 0)
> > +		return ret;
> > +	if (!ret)
> > +		return -ETIMEDOUT;
> > +
> > +	return 0;
> > +}
> > [...]
> > +static bool sps30_serial_frame_valid(struct sps30_state *state, const char *buf)
> > +{
> > +	struct sps30_serial_priv *priv = state->priv;
> > +
> > +	if ((priv->num < SPS30_SERIAL_FRAME_MIN_SIZE) ||
> > +	    (priv->num != SPS30_SERIAL_FRAME_MIN_SIZE +
> > +	     priv->buf[SPS30_SERIAL_FRAME_MISO_LEN_OFFSET])) {
> > +		dev_err(state->dev, "frame has invalid number of bytes\n");
> > +		return false;
> > +	}
> > +
> > +	if ((priv->buf[SPS30_SERIAL_FRAME_ADR_OFFSET] != buf[SPS30_SERIAL_FRAME_ADR_OFFSET]) ||
> > +	    (priv->buf[SPS30_SERIAL_FRAME_CMD_OFFSET] != buf[SPS30_SERIAL_FRAME_CMD_OFFSET])) {
> > +		dev_err(state->dev, "frame has wrong ADR and CMD bytes\n");
> > +		return false;
> > +	}
> > +
> > +	if (priv->buf[SPS30_SERIAL_FRAME_MISO_STATE_OFFSET]) {
> > +		dev_err(state->dev, "frame with non-zero state received (0x%02x)\n",
> > +			priv->buf[SPS30_SERIAL_FRAME_MISO_STATE_OFFSET]);
> > +		//return false;
> What's with the out commented line?

Good catch. This shouldn't be commented - not sure how that two slashes
got here.

> > +	}
> > +
> > +	if (priv->buf[priv->num - 2] != priv->chksum) {
> > +		dev_err(state->dev, "frame integrity check failed\n");
> > +		return false;
> > +	}
> > +
> > +	return true;
> > +}
> > +
> > +static int sps30_serial_command(struct sps30_state *state, char cmd, void *arg, int arg_size,
> > +				void *rsp, int rsp_size)
> > +{
> > +	struct sps30_serial_priv *priv = state->priv;
> > +	char buf[SPS30_SERIAL_MAX_BUF_SIZE];
> > +	int ret, size;
> > +
> > +	size = sps30_serial_prep_frame(buf, cmd, arg, arg_size);
> > +	ret = sps30_serial_xfer(state, buf, size);
> > +	if (ret)
> > +		return ret;
> > +
> > +	if (!sps30_serial_frame_valid(state, buf))
> > +		return -EIO;
> > +
> > +	if (rsp) {
> > +		rsp_size = clamp((int)priv->buf[SPS30_SERIAL_FRAME_MISO_LEN_OFFSET], 0, rsp_size);
> If buf is unsigned char this can be a min_t(unsigned int, ...). And maybe
> also make rsp_size unsigned int.

Okay.

> > +		memcpy(rsp, &priv->buf[SPS30_SERIAL_FRAME_MISO_DATA_OFFSET], rsp_size);
> > +	}
> > +
> > +	return rsp_size;
> > +}
> > +
> > +static int sps30_serial_receive_buf(struct serdev_device *serdev, const unsigned char *buf,
> > +				    size_t size)
> > +{
> > +	struct iio_dev *indio_dev = dev_get_drvdata(&serdev->dev);
> > +	struct sps30_serial_priv *priv;
> > +	struct sps30_state *state;
> > +	unsigned char byte;
> > +	int i;
> > +
> > +	if (!indio_dev)
> > +		return 0;
>
> > +
> > +	state = iio_priv(indio_dev);
> > +	priv = state->priv;
> > +
> > +	/* just in case device put some unexpected data on the bus */
> > +	if (priv->done)
> > +		return size;
> > +
> > +	/* wait for the start of frame */
> > +	if (!priv->num && size && buf[0] != SPS30_SERIAL_SOF_EOF)
> > +		return 1;
> > +
> > +	if (priv->num + size >= ARRAY_SIZE(priv->buf))
> > +		size = ARRAY_SIZE(priv->buf) - priv->num;
> > +
> > +	for (i = 0; i < size; i++) {
> > +		byte = buf[i];
> > +		/* remove stuffed bytes on-the-fly */
> > +		if (byte == SPS30_SERIAL_ESCAPE_CHAR) {
> > +			priv->escaped = true;
> > +			continue;
> > +		}
> > +
> > +		byte = sps30_serial_get_byte(priv->escaped, byte);
> > +		if (priv->escaped && !byte)
> > +			dev_warn(state->dev, "unrecognized escaped char (0x%02x)\n", byte);
> > +		priv->chksum += byte;
> > +		/* incrementing here would complete rx just after reading SOF */
> > +		priv->buf[priv->num] = byte;
> > +
> > +		if (priv->num++ && !priv->escaped && byte == SPS30_SERIAL_SOF_EOF) {
>
> This is a bit to tricky for my taste.
>

Less than ideal but didn't come up with anything better which is why I
put extra comment a few lines above.

> How about.
>
> priv->num++
>
> if (priv->num > 1 && ...)
>

Makes sense.

> > +			/* SOF, EOF and checksum itself are not checksummed */
> > +			priv->chksum -= 2 * SPS30_SERIAL_SOF_EOF + priv->buf[priv->num - 2];
> > +			priv->chksum = (unsigned char)~priv->chksum;
> To keep the whole checksum stuff simpler, maybe just compute it in
> sps30_serial_frame_valid() over the whole set of data.

Okay that fits there as well. Advantage here is chksum is computed on
the fly though.

> > +			priv->done = true;
> > +			complete(&priv->new_frame);
> > +			i++;
> > +			break;
> > +		}
> > +
> > +		priv->escaped = false;
> > +	}
> > +
> > +	return i;
> > +}
> > [...]
> > +static int sps30_serial_probe(struct serdev_device *serdev)
> > +{
> > [...]
> > +	return sps30_probe(dev, KBUILD_MODNAME, priv, &sps30_serial_ops);
> Usually the IIO device name should just be the part number. Ideally the
> application should not care about the backend. I'd just pass "sps30" here
> for the name.

Fair enough.

Thanks for review.

> > +}
>
>

Re: [PATCH 2/3] iio: sps30: add support for serial interface

[Jonathan Cameron]

On Sun, 25 Apr 2021 15:55:45 +0200
Tomasz Duszynski <tomasz.duszynski@octakon.com> wrote:

> Sensor has support for both i2c and serial communication interfaces.
> Both offer very similar set of features. Minor differences don't impact
> overall functionality like doing measurements, etc.
> 
> Support for i2c have already been added, this patch adds support
> for the latter ie. serial interface.
> 
> Signed-off-by: Tomasz Duszynski <tomasz.duszynski@octakon.com>

Hi Tomasz,

A few things inline that need tidying up.

I'm far from an expert on serdev drivers though so I'm not 100% sure on that
side of things.

Thanks,

Jonathan

> ---
>  MAINTAINERS                         |   1 +
>  drivers/iio/chemical/Kconfig        |  10 +
>  drivers/iio/chemical/Makefile       |   1 +
>  drivers/iio/chemical/sps30_serial.c | 420 ++++++++++++++++++++++++++++
>  4 files changed, 432 insertions(+)
>  create mode 100644 drivers/iio/chemical/sps30_serial.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 4b39a9c48736..cab9a63ad2cf 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -16138,6 +16138,7 @@ S:	Maintained
>  F:	Documentation/devicetree/bindings/iio/chemical/sensirion,sps30.yaml
>  F:	drivers/iio/chemical/sps30.c
>  F:	drivers/iio/chemical/sps30_i2c.c
> +F:	drivers/iio/chemical/sps30_serial.c
>  
>  SERIAL DEVICE BUS
>  M:	Rob Herring <robh@kernel.org>
> diff --git a/drivers/iio/chemical/Kconfig b/drivers/iio/chemical/Kconfig
> index 82af5f62fbc6..6909b4754b9e 100644
> --- a/drivers/iio/chemical/Kconfig
> +++ b/drivers/iio/chemical/Kconfig
> @@ -153,6 +153,16 @@ config SPS30_I2C
>  	  To compile this driver as a module, choose M here: the module will
>  	  be called sps30_i2c.
>  
> +config SPS30_SERIAL
> +	tristate "SPS30 particulate matter sensor serial driver"
> +	depends on SPS30 && SERIAL_DEV_BUS
> +	help
> +	  Say Y here to build support for the Sensirion SPS30 serial interface
> +	  driver.
> +
> +	  To compile this driver as a module, choose M here: the module will
> +	  be called sps30_serial.
> +
>  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 41c264a229c0..4898690cc155 100644
> --- a/drivers/iio/chemical/Makefile
> +++ b/drivers/iio/chemical/Makefile
> @@ -18,4 +18,5 @@ 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-$(CONFIG_SPS30_SERIAL) += sps30_serial.o
>  obj-$(CONFIG_VZ89X)		+= vz89x.o
> diff --git a/drivers/iio/chemical/sps30_serial.c b/drivers/iio/chemical/sps30_serial.c
> new file mode 100644
> index 000000000000..5adeeed9bc8f
> --- /dev/null
> +++ b/drivers/iio/chemical/sps30_serial.c
> @@ -0,0 +1,420 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Sensirion SPS30 particulate matter sensor serial driver
> + *
> + * Copyright (c) 2021 Tomasz Duszynski <tomasz.duszynski@octakon.com>
> + */
> +#include <linux/completion.h>
> +#include <linux/device.h>
> +#include <linux/errno.h>
> +#include <linux/iio/iio.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>
> +#include <linux/serdev.h>
> +
> +#include "sps30.h"
> +
> +#define SPS30_SERIAL_SOF_EOF 0x7e
> +#define SPS30_SERIAL_TIMEOUT msecs_to_jiffies(20)
> +#define SPS30_SERIAL_MAX_BUF_SIZE 263
> +#define SPS30_SERIAL_ESCAPE_CHAR 0x7d
> +
> +#define SPS30_SERIAL_FRAME_MIN_SIZE 7
> +#define SPS30_SERIAL_FRAME_ADR_OFFSET 1
> +#define SPS30_SERIAL_FRAME_CMD_OFFSET 2
> +#define SPS30_SERIAL_FRAME_MOSI_LEN_OFFSET 3
> +#define SPS30_SERIAL_FRAME_MISO_STATE_OFFSET 3
> +#define SPS30_SERIAL_FRAME_MISO_LEN_OFFSET 4
> +#define SPS30_SERIAL_FRAME_MISO_DATA_OFFSET 5
> +
> +#define SPS30_SERIAL_START_MEAS 0x00
> +#define SPS30_SERIAL_STOP_MEAS 0x01
> +#define SPS30_SERIAL_READ_MEAS 0x03
> +#define SPS30_SERIAL_RESET 0xd3
> +#define SPS30_SERIAL_CLEAN_FAN 0x56
> +#define SPS30_SERIAL_PERIOD 0x80
> +#define SPS30_SERIAL_DEV_INFO 0xd0
> +#define SPS30_SERIAL_READ_VERSION 0xd1
> +
> +struct sps30_serial_priv {
> +	struct completion new_frame;
> +	char buf[SPS30_SERIAL_MAX_BUF_SIZE];
> +	int num;
> +	unsigned int chksum;
> +	bool escaped;
> +	bool done;
> +};
> +
> +static int sps30_serial_xfer(struct sps30_state *state, const char *buf, int size)
> +{
> +	struct serdev_device *serdev = to_serdev_device(state->dev);
> +	struct sps30_serial_priv *priv = state->priv;
> +	int ret;
> +
> +	priv->num = 0;
> +	priv->chksum = 0;
> +	priv->escaped = false;
> +	priv->done = false;
> +
> +	ret = serdev_device_write(serdev, buf, size, SPS30_SERIAL_TIMEOUT);
> +	if (ret < 0)
> +		return ret;
> +	if (ret != size)
> +		return -EIO;
> +
> +	ret = wait_for_completion_interruptible_timeout(&priv->new_frame, SPS30_SERIAL_TIMEOUT);
> +	if (ret < 0)
> +		return ret;
> +	if (!ret)
> +		return -ETIMEDOUT;
> +
> +	return 0;
> +}
> +
> +static struct {
> +	char byte;
> +	char byte2;
> +} sps30_serial_bytes[] = {
> +	{ 0x11, 0x31 },
> +	{ 0x13, 0x33 },
> +	{ 0x7e, 0x5e },
> +	{ 0x7d, 0x5d },
> +};
> +
> +static int sps30_serial_put_byte(char *buf, char byte)
> +{
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(sps30_serial_bytes); i++) {
> +		if (sps30_serial_bytes[i].byte != byte)
> +			continue;
> +
> +		buf[0] = SPS30_SERIAL_ESCAPE_CHAR;
> +		buf[1] = sps30_serial_bytes[i].byte2;
> +
> +		return 2;
> +	}
> +
> +	buf[0] = byte;
> +
> +	return 1;
> +}
> +
> +static char sps30_serial_get_byte(bool escaped, char byte2)
> +{
> +	int i;
> +
> +	if (!escaped)
> +		return byte2;
> +
> +	for (i = 0; i < ARRAY_SIZE(sps30_serial_bytes); i++) {
> +		if (sps30_serial_bytes[i].byte2 != byte2)
> +			continue;
> +
> +		return sps30_serial_bytes[i].byte;
> +	}
> +
> +	return 0;
> +}
> +
> +static int sps30_serial_prep_frame(char *buf, char cmd, const char *arg, int arg_size)
> +{
> +	unsigned int chksum;
> +	unsigned char byte;
> +	int i, num = 0;
> +
> +	buf[num++] = SPS30_SERIAL_SOF_EOF;
> +	buf[num++] = 0;
> +
> +	byte = cmd;
> +	num += sps30_serial_put_byte(buf + num, byte);
> +	chksum = byte;
> +
> +	byte = (unsigned char)arg_size;
> +	num += sps30_serial_put_byte(buf + num, byte);
> +	chksum += byte;
> +
> +	for (i = 0; i < arg_size; i++) {
> +		byte = arg[i];
> +		num += sps30_serial_put_byte(buf + num, byte);
> +		chksum += byte;
> +	}
> +
> +	byte = (unsigned char)~chksum;
> +	num += sps30_serial_put_byte(buf + num, byte);
> +
> +	buf[num++] = SPS30_SERIAL_SOF_EOF;
> +
> +	return num;
> +}
> +
> +static bool sps30_serial_frame_valid(struct sps30_state *state, const char *buf)
> +{
> +	struct sps30_serial_priv *priv = state->priv;
> +
> +	if ((priv->num < SPS30_SERIAL_FRAME_MIN_SIZE) ||
> +	    (priv->num != SPS30_SERIAL_FRAME_MIN_SIZE +
> +	     priv->buf[SPS30_SERIAL_FRAME_MISO_LEN_OFFSET])) {
> +		dev_err(state->dev, "frame has invalid number of bytes\n");
> +		return false;
> +	}
> +
> +	if ((priv->buf[SPS30_SERIAL_FRAME_ADR_OFFSET] != buf[SPS30_SERIAL_FRAME_ADR_OFFSET]) ||
> +	    (priv->buf[SPS30_SERIAL_FRAME_CMD_OFFSET] != buf[SPS30_SERIAL_FRAME_CMD_OFFSET])) {
> +		dev_err(state->dev, "frame has wrong ADR and CMD bytes\n");
> +		return false;
> +	}
> +
> +	if (priv->buf[SPS30_SERIAL_FRAME_MISO_STATE_OFFSET]) {
> +		dev_err(state->dev, "frame with non-zero state received (0x%02x)\n",
> +			priv->buf[SPS30_SERIAL_FRAME_MISO_STATE_OFFSET]);
> +		//return false;

?

> +	}
> +
> +	if (priv->buf[priv->num - 2] != priv->chksum) {
> +		dev_err(state->dev, "frame integrity check failed\n");
> +		return false;
> +	}
> +
> +	return true;
> +}
> +
> +static int sps30_serial_command(struct sps30_state *state, char cmd, void *arg, int arg_size,
> +				void *rsp, int rsp_size)
> +{
> +	struct sps30_serial_priv *priv = state->priv;
> +	char buf[SPS30_SERIAL_MAX_BUF_SIZE];
> +	int ret, size;
> +
> +	size = sps30_serial_prep_frame(buf, cmd, arg, arg_size);
> +	ret = sps30_serial_xfer(state, buf, size);
> +	if (ret)
> +		return ret;
> +
> +	if (!sps30_serial_frame_valid(state, buf))
> +		return -EIO;
> +
> +	if (rsp) {
> +		rsp_size = clamp((int)priv->buf[SPS30_SERIAL_FRAME_MISO_LEN_OFFSET], 0, rsp_size);
> +		memcpy(rsp, &priv->buf[SPS30_SERIAL_FRAME_MISO_DATA_OFFSET], rsp_size);
> +	}
> +
> +	return rsp_size;
> +}
> +
> +static int sps30_serial_receive_buf(struct serdev_device *serdev, const unsigned char *buf,
> +				    size_t size)
> +{
> +	struct iio_dev *indio_dev = dev_get_drvdata(&serdev->dev);
> +	struct sps30_serial_priv *priv;
> +	struct sps30_state *state;
> +	unsigned char byte;
> +	int i;
> +
> +	if (!indio_dev)
> +		return 0;
> +
> +	state = iio_priv(indio_dev);
> +	priv = state->priv;
> +
> +	/* just in case device put some unexpected data on the bus */
> +	if (priv->done)
> +		return size;
> +
> +	/* wait for the start of frame */
> +	if (!priv->num && size && buf[0] != SPS30_SERIAL_SOF_EOF)
> +		return 1;
> +
> +	if (priv->num + size >= ARRAY_SIZE(priv->buf))
> +		size = ARRAY_SIZE(priv->buf) - priv->num;
> +
> +	for (i = 0; i < size; i++) {
> +		byte = buf[i];
> +		/* remove stuffed bytes on-the-fly */
> +		if (byte == SPS30_SERIAL_ESCAPE_CHAR) {
> +			priv->escaped = true;
> +			continue;
> +		}
> +
> +		byte = sps30_serial_get_byte(priv->escaped, byte);
> +		if (priv->escaped && !byte)
> +			dev_warn(state->dev, "unrecognized escaped char (0x%02x)\n", byte);
> +		priv->chksum += byte;
> +		/* incrementing here would complete rx just after reading SOF */
> +		priv->buf[priv->num] = byte;
> +
> +		if (priv->num++ && !priv->escaped && byte == SPS30_SERIAL_SOF_EOF) {
> +			/* SOF, EOF and checksum itself are not checksummed */
> +			priv->chksum -= 2 * SPS30_SERIAL_SOF_EOF + priv->buf[priv->num - 2];
> +			priv->chksum = (unsigned char)~priv->chksum;
> +			priv->done = true;
> +			complete(&priv->new_frame);
> +			i++;
> +			break;
> +		}
> +
> +		priv->escaped = false;
> +	}
> +
> +	return i;
> +}
> +
> +static const struct serdev_device_ops sps30_serial_device_ops = {
> +	.receive_buf = sps30_serial_receive_buf,
> +	.write_wakeup = serdev_device_write_wakeup,
> +};
> +
> +static int sps30_serial_start_meas(struct sps30_state *state)
> +{
> +	/* request BE IEEE754 formatted data */
> +	char buf[] = { 0x01, 0x03 };
> +
> +	return sps30_serial_command(state, SPS30_SERIAL_START_MEAS, buf, sizeof(buf), NULL, 0);
> +}
> +
> +static int sps30_serial_stop_meas(struct sps30_state *state)
> +{
> +	return sps30_serial_command(state, SPS30_SERIAL_STOP_MEAS, NULL, 0, NULL, 0);
> +}
> +
> +static int sps30_serial_reset(struct sps30_state *state)
> +{
> +	int ret;
> +
> +	ret = sps30_serial_command(state, SPS30_SERIAL_RESET, NULL, 0, NULL, 0);
> +	msleep(500);
> +
> +	return ret;
> +}
> +
> +static int sps30_serial_read_meas(struct sps30_state *state, int *meas, int num)
> +{
> +	int ret, tries = 3;
> +

For any repeat loops like this, please add a comment to explain why you picked 3
retries.  (it works is a valid comment, but obviously datasheet reference is better :)

> +	do {
> +		ret = sps30_serial_command(state, SPS30_SERIAL_READ_MEAS, NULL, 0,
> +					   meas, num * sizeof(num));
> +		if (ret < 0)
> +			return ret;
> +		/* if measurements aren't ready sensor returns empty frame */
> +		if (ret == num * sizeof(int))
> +			break;
> +
> +		if (msleep_interruptible(500))
> +			return -EINTR;
> +	} while (--tries);
> +
> +	return !tries ? -ETIMEDOUT : 0;
> +}
> +
> +static int sps30_serial_clean_fan(struct sps30_state *state)
> +{
> +	return sps30_serial_command(state, SPS30_SERIAL_CLEAN_FAN, NULL, 0, NULL, 0);
> +}
> +
> +static int sps30_serial_read_cleaning_period(struct sps30_state *state, int *period)
> +{
> +	char buf[] = { 0x00 };
> +	int ret;
> +
> +	ret = sps30_serial_command(state, SPS30_SERIAL_PERIOD, buf, sizeof(buf),
> +				   period, sizeof(*period));
> +	if (ret < 0)
> +		return ret;
> +	if (ret != sizeof(*period))
> +		return -EIO;
> +
> +	return 0;
> +}
> +
> +static int sps30_serial_write_cleaning_period(struct sps30_state *state, int period)
> +{
> +	char buf[5] = { 0x00 };
> +
> +	memcpy(buf + 1, &period, sizeof(period));

Same issue with what size period could in theory be. Also should be no problem keeping
it in the __be32 type throughout.

> +
> +	return sps30_serial_command(state, SPS30_SERIAL_PERIOD, buf, sizeof(buf), NULL, 0);
> +}
> +
> +static int sps30_serial_show_info(struct sps30_state *state)
> +{
> +	/* extra nul byte just in case serial number isn't a valid string */
> +	char buf[32 + 1] = { 0x00 };
> +	struct device *dev = state->dev;
> +	int ret;
> +
> +	/* tell device to return serial number */
> +	buf[0] = 0x03;
> +	ret = sps30_serial_command(state, SPS30_SERIAL_DEV_INFO, buf, 1, buf, sizeof(buf) - 1);
> +	if (ret < 0)
> +		return ret;
> +
> +	dev_info(dev, "serial number: %s\n", buf);
> +
> +	ret = sps30_serial_command(state, SPS30_SERIAL_READ_VERSION, NULL, 0, buf, sizeof(buf) - 1);
> +	if (ret < 0)
> +		return ret;
> +	if (ret < 2)
> +		return -EIO;
> +
> +	dev_info(dev, "fw version: %u.%u\n", buf[0], buf[1]);
> +
> +	return 0;
> +}
> +
> +static const struct sps30_ops sps30_serial_ops = {
> +	.start_meas = sps30_serial_start_meas,
> +	.stop_meas = sps30_serial_stop_meas,
> +	.read_meas = sps30_serial_read_meas,
> +	.reset = sps30_serial_reset,
> +	.clean_fan = sps30_serial_clean_fan,
> +	.read_cleaning_period = sps30_serial_read_cleaning_period,
> +	.write_cleaning_period = sps30_serial_write_cleaning_period,
> +	.show_info = sps30_serial_show_info,
> +};
> +
> +static int sps30_serial_probe(struct serdev_device *serdev)
> +{
> +	struct device *dev = &serdev->dev;
> +	struct sps30_serial_priv *priv;
> +	int ret;
> +
> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	init_completion(&priv->new_frame);
> +	serdev_device_set_client_ops(serdev, &sps30_serial_device_ops);
> +
> +	ret = devm_serdev_device_open(dev, serdev);
> +	if (ret)
> +		return ret;
> +
> +	serdev_device_set_baudrate(serdev, 115200);
> +	serdev_device_set_flow_control(serdev, false);
> +
> +	ret = serdev_device_set_parity(serdev, SERDEV_PARITY_NONE);
> +	if (ret)
> +		return ret;
> +
> +	return sps30_probe(dev, KBUILD_MODNAME, priv, &sps30_serial_ops);
> +}
> +
> +static const struct of_device_id sps30_serial_of_match[] = {
> +	{ .compatible = "sensirion,sps30" },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, sps30_serial_of_match);
> +
> +static struct serdev_device_driver sps30_serial_driver = {
> +	.driver = {
> +		.name = KBUILD_MODNAME,
> +		.of_match_table = sps30_serial_of_match,
> +	},
> +	.probe = sps30_serial_probe,
> +};
> +module_serdev_device_driver(sps30_serial_driver);
> +
> +MODULE_AUTHOR("Tomasz Duszynski <tomasz.duszynski@octakon.com>");
> +MODULE_DESCRIPTION("Sensirion SPS30 particulate matter sensor serial driver");
> +MODULE_LICENSE("GPL v2");

Re: [PATCH 2/3] iio: sps30: add support for serial interface

[Tomasz Duszynski]

On Sun, Apr 25, 2021 at 04:53:44PM +0100, Jonathan Cameron wrote:
> On Sun, 25 Apr 2021 15:55:45 +0200
> Tomasz Duszynski <tomasz.duszynski@octakon.com> wrote:
>
> > Sensor has support for both i2c and serial communication interfaces.
> > Both offer very similar set of features. Minor differences don't impact
> > overall functionality like doing measurements, etc.
> >
> > Support for i2c have already been added, this patch adds support
> > for the latter ie. serial interface.
> >
> > Signed-off-by: Tomasz Duszynski <tomasz.duszynski@octakon.com>
>
> Hi Tomasz,
>
> A few things inline that need tidying up.
>
> I'm far from an expert on serdev drivers though so I'm not 100% sure on that
> side of things.
>
> Thanks,
>
> Jonathan
>
> > ---
> >  MAINTAINERS                         |   1 +
> >  drivers/iio/chemical/Kconfig        |  10 +
> >  drivers/iio/chemical/Makefile       |   1 +
> >  drivers/iio/chemical/sps30_serial.c | 420 ++++++++++++++++++++++++++++
> >  4 files changed, 432 insertions(+)
> >  create mode 100644 drivers/iio/chemical/sps30_serial.c
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 4b39a9c48736..cab9a63ad2cf 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -16138,6 +16138,7 @@ S:	Maintained
> >  F:	Documentation/devicetree/bindings/iio/chemical/sensirion,sps30.yaml
> >  F:	drivers/iio/chemical/sps30.c
> >  F:	drivers/iio/chemical/sps30_i2c.c
> > +F:	drivers/iio/chemical/sps30_serial.c
> >
> >  SERIAL DEVICE BUS
> >  M:	Rob Herring <robh@kernel.org>
> > diff --git a/drivers/iio/chemical/Kconfig b/drivers/iio/chemical/Kconfig
> > index 82af5f62fbc6..6909b4754b9e 100644
> > --- a/drivers/iio/chemical/Kconfig
> > +++ b/drivers/iio/chemical/Kconfig
> > @@ -153,6 +153,16 @@ config SPS30_I2C
> >  	  To compile this driver as a module, choose M here: the module will
> >  	  be called sps30_i2c.
> >
> > +config SPS30_SERIAL
> > +	tristate "SPS30 particulate matter sensor serial driver"
> > +	depends on SPS30 && SERIAL_DEV_BUS
> > +	help
> > +	  Say Y here to build support for the Sensirion SPS30 serial interface
> > +	  driver.
> > +
> > +	  To compile this driver as a module, choose M here: the module will
> > +	  be called sps30_serial.
> > +
> >  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 41c264a229c0..4898690cc155 100644
> > --- a/drivers/iio/chemical/Makefile
> > +++ b/drivers/iio/chemical/Makefile
> > @@ -18,4 +18,5 @@ 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-$(CONFIG_SPS30_SERIAL) += sps30_serial.o
> >  obj-$(CONFIG_VZ89X)		+= vz89x.o
> > diff --git a/drivers/iio/chemical/sps30_serial.c b/drivers/iio/chemical/sps30_serial.c
> > new file mode 100644
> > index 000000000000..5adeeed9bc8f
> > --- /dev/null
> > +++ b/drivers/iio/chemical/sps30_serial.c
> > @@ -0,0 +1,420 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Sensirion SPS30 particulate matter sensor serial driver
> > + *
> > + * Copyright (c) 2021 Tomasz Duszynski <tomasz.duszynski@octakon.com>
> > + */
> > +#include <linux/completion.h>
> > +#include <linux/device.h>
> > +#include <linux/errno.h>
> > +#include <linux/iio/iio.h>
> > +#include <linux/mod_devicetable.h>
> > +#include <linux/module.h>
> > +#include <linux/serdev.h>
> > +
> > +#include "sps30.h"
> > +
> > +#define SPS30_SERIAL_SOF_EOF 0x7e
> > +#define SPS30_SERIAL_TIMEOUT msecs_to_jiffies(20)
> > +#define SPS30_SERIAL_MAX_BUF_SIZE 263
> > +#define SPS30_SERIAL_ESCAPE_CHAR 0x7d
> > +
> > +#define SPS30_SERIAL_FRAME_MIN_SIZE 7
> > +#define SPS30_SERIAL_FRAME_ADR_OFFSET 1
> > +#define SPS30_SERIAL_FRAME_CMD_OFFSET 2
> > +#define SPS30_SERIAL_FRAME_MOSI_LEN_OFFSET 3
> > +#define SPS30_SERIAL_FRAME_MISO_STATE_OFFSET 3
> > +#define SPS30_SERIAL_FRAME_MISO_LEN_OFFSET 4
> > +#define SPS30_SERIAL_FRAME_MISO_DATA_OFFSET 5
> > +
> > +#define SPS30_SERIAL_START_MEAS 0x00
> > +#define SPS30_SERIAL_STOP_MEAS 0x01
> > +#define SPS30_SERIAL_READ_MEAS 0x03
> > +#define SPS30_SERIAL_RESET 0xd3
> > +#define SPS30_SERIAL_CLEAN_FAN 0x56
> > +#define SPS30_SERIAL_PERIOD 0x80
> > +#define SPS30_SERIAL_DEV_INFO 0xd0
> > +#define SPS30_SERIAL_READ_VERSION 0xd1
> > +
> > +struct sps30_serial_priv {
> > +	struct completion new_frame;
> > +	char buf[SPS30_SERIAL_MAX_BUF_SIZE];
> > +	int num;
> > +	unsigned int chksum;
> > +	bool escaped;
> > +	bool done;
> > +};
> > +
> > +static int sps30_serial_xfer(struct sps30_state *state, const char *buf, int size)
> > +{
> > +	struct serdev_device *serdev = to_serdev_device(state->dev);
> > +	struct sps30_serial_priv *priv = state->priv;
> > +	int ret;
> > +
> > +	priv->num = 0;
> > +	priv->chksum = 0;
> > +	priv->escaped = false;
> > +	priv->done = false;
> > +
> > +	ret = serdev_device_write(serdev, buf, size, SPS30_SERIAL_TIMEOUT);
> > +	if (ret < 0)
> > +		return ret;
> > +	if (ret != size)
> > +		return -EIO;
> > +
> > +	ret = wait_for_completion_interruptible_timeout(&priv->new_frame, SPS30_SERIAL_TIMEOUT);
> > +	if (ret < 0)
> > +		return ret;
> > +	if (!ret)
> > +		return -ETIMEDOUT;
> > +
> > +	return 0;
> > +}
> > +
> > +static struct {
> > +	char byte;
> > +	char byte2;
> > +} sps30_serial_bytes[] = {
> > +	{ 0x11, 0x31 },
> > +	{ 0x13, 0x33 },
> > +	{ 0x7e, 0x5e },
> > +	{ 0x7d, 0x5d },
> > +};
> > +
> > +static int sps30_serial_put_byte(char *buf, char byte)
> > +{
> > +	int i;
> > +
> > +	for (i = 0; i < ARRAY_SIZE(sps30_serial_bytes); i++) {
> > +		if (sps30_serial_bytes[i].byte != byte)
> > +			continue;
> > +
> > +		buf[0] = SPS30_SERIAL_ESCAPE_CHAR;
> > +		buf[1] = sps30_serial_bytes[i].byte2;
> > +
> > +		return 2;
> > +	}
> > +
> > +	buf[0] = byte;
> > +
> > +	return 1;
> > +}
> > +
> > +static char sps30_serial_get_byte(bool escaped, char byte2)
> > +{
> > +	int i;
> > +
> > +	if (!escaped)
> > +		return byte2;
> > +
> > +	for (i = 0; i < ARRAY_SIZE(sps30_serial_bytes); i++) {
> > +		if (sps30_serial_bytes[i].byte2 != byte2)
> > +			continue;
> > +
> > +		return sps30_serial_bytes[i].byte;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int sps30_serial_prep_frame(char *buf, char cmd, const char *arg, int arg_size)
> > +{
> > +	unsigned int chksum;
> > +	unsigned char byte;
> > +	int i, num = 0;
> > +
> > +	buf[num++] = SPS30_SERIAL_SOF_EOF;
> > +	buf[num++] = 0;
> > +
> > +	byte = cmd;
> > +	num += sps30_serial_put_byte(buf + num, byte);
> > +	chksum = byte;
> > +
> > +	byte = (unsigned char)arg_size;
> > +	num += sps30_serial_put_byte(buf + num, byte);
> > +	chksum += byte;
> > +
> > +	for (i = 0; i < arg_size; i++) {
> > +		byte = arg[i];
> > +		num += sps30_serial_put_byte(buf + num, byte);
> > +		chksum += byte;
> > +	}
> > +
> > +	byte = (unsigned char)~chksum;
> > +	num += sps30_serial_put_byte(buf + num, byte);
> > +
> > +	buf[num++] = SPS30_SERIAL_SOF_EOF;
> > +
> > +	return num;
> > +}
> > +
> > +static bool sps30_serial_frame_valid(struct sps30_state *state, const char *buf)
> > +{
> > +	struct sps30_serial_priv *priv = state->priv;
> > +
> > +	if ((priv->num < SPS30_SERIAL_FRAME_MIN_SIZE) ||
> > +	    (priv->num != SPS30_SERIAL_FRAME_MIN_SIZE +
> > +	     priv->buf[SPS30_SERIAL_FRAME_MISO_LEN_OFFSET])) {
> > +		dev_err(state->dev, "frame has invalid number of bytes\n");
> > +		return false;
> > +	}
> > +
> > +	if ((priv->buf[SPS30_SERIAL_FRAME_ADR_OFFSET] != buf[SPS30_SERIAL_FRAME_ADR_OFFSET]) ||
> > +	    (priv->buf[SPS30_SERIAL_FRAME_CMD_OFFSET] != buf[SPS30_SERIAL_FRAME_CMD_OFFSET])) {
> > +		dev_err(state->dev, "frame has wrong ADR and CMD bytes\n");
> > +		return false;
> > +	}
> > +
> > +	if (priv->buf[SPS30_SERIAL_FRAME_MISO_STATE_OFFSET]) {
> > +		dev_err(state->dev, "frame with non-zero state received (0x%02x)\n",
> > +			priv->buf[SPS30_SERIAL_FRAME_MISO_STATE_OFFSET]);
> > +		//return false;
>
> ?
>
> > +	}
> > +
> > +	if (priv->buf[priv->num - 2] != priv->chksum) {
> > +		dev_err(state->dev, "frame integrity check failed\n");
> > +		return false;
> > +	}
> > +
> > +	return true;
> > +}
> > +
> > +static int sps30_serial_command(struct sps30_state *state, char cmd, void *arg, int arg_size,
> > +				void *rsp, int rsp_size)
> > +{
> > +	struct sps30_serial_priv *priv = state->priv;
> > +	char buf[SPS30_SERIAL_MAX_BUF_SIZE];
> > +	int ret, size;
> > +
> > +	size = sps30_serial_prep_frame(buf, cmd, arg, arg_size);
> > +	ret = sps30_serial_xfer(state, buf, size);
> > +	if (ret)
> > +		return ret;
> > +
> > +	if (!sps30_serial_frame_valid(state, buf))
> > +		return -EIO;
> > +
> > +	if (rsp) {
> > +		rsp_size = clamp((int)priv->buf[SPS30_SERIAL_FRAME_MISO_LEN_OFFSET], 0, rsp_size);
> > +		memcpy(rsp, &priv->buf[SPS30_SERIAL_FRAME_MISO_DATA_OFFSET], rsp_size);
> > +	}
> > +
> > +	return rsp_size;
> > +}
> > +
> > +static int sps30_serial_receive_buf(struct serdev_device *serdev, const unsigned char *buf,
> > +				    size_t size)
> > +{
> > +	struct iio_dev *indio_dev = dev_get_drvdata(&serdev->dev);
> > +	struct sps30_serial_priv *priv;
> > +	struct sps30_state *state;
> > +	unsigned char byte;
> > +	int i;
> > +
> > +	if (!indio_dev)
> > +		return 0;
> > +
> > +	state = iio_priv(indio_dev);
> > +	priv = state->priv;
> > +
> > +	/* just in case device put some unexpected data on the bus */
> > +	if (priv->done)
> > +		return size;
> > +
> > +	/* wait for the start of frame */
> > +	if (!priv->num && size && buf[0] != SPS30_SERIAL_SOF_EOF)
> > +		return 1;
> > +
> > +	if (priv->num + size >= ARRAY_SIZE(priv->buf))
> > +		size = ARRAY_SIZE(priv->buf) - priv->num;
> > +
> > +	for (i = 0; i < size; i++) {
> > +		byte = buf[i];
> > +		/* remove stuffed bytes on-the-fly */
> > +		if (byte == SPS30_SERIAL_ESCAPE_CHAR) {
> > +			priv->escaped = true;
> > +			continue;
> > +		}
> > +
> > +		byte = sps30_serial_get_byte(priv->escaped, byte);
> > +		if (priv->escaped && !byte)
> > +			dev_warn(state->dev, "unrecognized escaped char (0x%02x)\n", byte);
> > +		priv->chksum += byte;
> > +		/* incrementing here would complete rx just after reading SOF */
> > +		priv->buf[priv->num] = byte;
> > +
> > +		if (priv->num++ && !priv->escaped && byte == SPS30_SERIAL_SOF_EOF) {
> > +			/* SOF, EOF and checksum itself are not checksummed */
> > +			priv->chksum -= 2 * SPS30_SERIAL_SOF_EOF + priv->buf[priv->num - 2];
> > +			priv->chksum = (unsigned char)~priv->chksum;
> > +			priv->done = true;
> > +			complete(&priv->new_frame);
> > +			i++;
> > +			break;
> > +		}
> > +
> > +		priv->escaped = false;
> > +	}
> > +
> > +	return i;
> > +}
> > +
> > +static const struct serdev_device_ops sps30_serial_device_ops = {
> > +	.receive_buf = sps30_serial_receive_buf,
> > +	.write_wakeup = serdev_device_write_wakeup,
> > +};
> > +
> > +static int sps30_serial_start_meas(struct sps30_state *state)
> > +{
> > +	/* request BE IEEE754 formatted data */
> > +	char buf[] = { 0x01, 0x03 };
> > +
> > +	return sps30_serial_command(state, SPS30_SERIAL_START_MEAS, buf, sizeof(buf), NULL, 0);
> > +}
> > +
> > +static int sps30_serial_stop_meas(struct sps30_state *state)
> > +{
> > +	return sps30_serial_command(state, SPS30_SERIAL_STOP_MEAS, NULL, 0, NULL, 0);
> > +}
> > +
> > +static int sps30_serial_reset(struct sps30_state *state)
> > +{
> > +	int ret;
> > +
> > +	ret = sps30_serial_command(state, SPS30_SERIAL_RESET, NULL, 0, NULL, 0);
> > +	msleep(500);
> > +
> > +	return ret;
> > +}
> > +
> > +static int sps30_serial_read_meas(struct sps30_state *state, int *meas, int num)
> > +{
> > +	int ret, tries = 3;
> > +
>
> For any repeat loops like this, please add a comment to explain why you picked 3
> retries.  (it works is a valid comment, but obviously datasheet reference is better :)
>

According to the spec sensor spits out data each second but sometimes it
looks as if they are available in 500ms or so. Picking 3 for the number of
tries covers two cases.

> > +	do {
> > +		ret = sps30_serial_command(state, SPS30_SERIAL_READ_MEAS, NULL, 0,
> > +					   meas, num * sizeof(num));
> > +		if (ret < 0)
> > +			return ret;
> > +		/* if measurements aren't ready sensor returns empty frame */
> > +		if (ret == num * sizeof(int))
> > +			break;
> > +
> > +		if (msleep_interruptible(500))
> > +			return -EINTR;
> > +	} while (--tries);
> > +
> > +	return !tries ? -ETIMEDOUT : 0;
> > +}
> > +
> > +static int sps30_serial_clean_fan(struct sps30_state *state)
> > +{
> > +	return sps30_serial_command(state, SPS30_SERIAL_CLEAN_FAN, NULL, 0, NULL, 0);
> > +}
> > +
> > +static int sps30_serial_read_cleaning_period(struct sps30_state *state, int *period)
> > +{
> > +	char buf[] = { 0x00 };
> > +	int ret;
> > +
> > +	ret = sps30_serial_command(state, SPS30_SERIAL_PERIOD, buf, sizeof(buf),
> > +				   period, sizeof(*period));
> > +	if (ret < 0)
> > +		return ret;
> > +	if (ret != sizeof(*period))
> > +		return -EIO;
> > +
> > +	return 0;
> > +}
> > +
> > +static int sps30_serial_write_cleaning_period(struct sps30_state *state, int period)
> > +{
> > +	char buf[5] = { 0x00 };
> > +
> > +	memcpy(buf + 1, &period, sizeof(period));
>
> Same issue with what size period could in theory be. Also should be no problem keeping
> it in the __be32 type throughout.
>
> > +
> > +	return sps30_serial_command(state, SPS30_SERIAL_PERIOD, buf, sizeof(buf), NULL, 0);
> > +}
> > +
> > +static int sps30_serial_show_info(struct sps30_state *state)
> > +{
> > +	/* extra nul byte just in case serial number isn't a valid string */
> > +	char buf[32 + 1] = { 0x00 };
> > +	struct device *dev = state->dev;
> > +	int ret;
> > +
> > +	/* tell device to return serial number */
> > +	buf[0] = 0x03;
> > +	ret = sps30_serial_command(state, SPS30_SERIAL_DEV_INFO, buf, 1, buf, sizeof(buf) - 1);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	dev_info(dev, "serial number: %s\n", buf);
> > +
> > +	ret = sps30_serial_command(state, SPS30_SERIAL_READ_VERSION, NULL, 0, buf, sizeof(buf) - 1);
> > +	if (ret < 0)
> > +		return ret;
> > +	if (ret < 2)
> > +		return -EIO;
> > +
> > +	dev_info(dev, "fw version: %u.%u\n", buf[0], buf[1]);
> > +
> > +	return 0;
> > +}
> > +
> > +static const struct sps30_ops sps30_serial_ops = {
> > +	.start_meas = sps30_serial_start_meas,
> > +	.stop_meas = sps30_serial_stop_meas,
> > +	.read_meas = sps30_serial_read_meas,
> > +	.reset = sps30_serial_reset,
> > +	.clean_fan = sps30_serial_clean_fan,
> > +	.read_cleaning_period = sps30_serial_read_cleaning_period,
> > +	.write_cleaning_period = sps30_serial_write_cleaning_period,
> > +	.show_info = sps30_serial_show_info,
> > +};
> > +
> > +static int sps30_serial_probe(struct serdev_device *serdev)
> > +{
> > +	struct device *dev = &serdev->dev;
> > +	struct sps30_serial_priv *priv;
> > +	int ret;
> > +
> > +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> > +	if (!priv)
> > +		return -ENOMEM;
> > +
> > +	init_completion(&priv->new_frame);
> > +	serdev_device_set_client_ops(serdev, &sps30_serial_device_ops);
> > +
> > +	ret = devm_serdev_device_open(dev, serdev);
> > +	if (ret)
> > +		return ret;
> > +
> > +	serdev_device_set_baudrate(serdev, 115200);
> > +	serdev_device_set_flow_control(serdev, false);
> > +
> > +	ret = serdev_device_set_parity(serdev, SERDEV_PARITY_NONE);
> > +	if (ret)
> > +		return ret;
> > +
> > +	return sps30_probe(dev, KBUILD_MODNAME, priv, &sps30_serial_ops);
> > +}
> > +
> > +static const struct of_device_id sps30_serial_of_match[] = {
> > +	{ .compatible = "sensirion,sps30" },
> > +	{ }
> > +};
> > +MODULE_DEVICE_TABLE(of, sps30_serial_of_match);
> > +
> > +static struct serdev_device_driver sps30_serial_driver = {
> > +	.driver = {
> > +		.name = KBUILD_MODNAME,
> > +		.of_match_table = sps30_serial_of_match,
> > +	},
> > +	.probe = sps30_serial_probe,
> > +};
> > +module_serdev_device_driver(sps30_serial_driver);
> > +
> > +MODULE_AUTHOR("Tomasz Duszynski <tomasz.duszynski@octakon.com>");
> > +MODULE_DESCRIPTION("Sensirion SPS30 particulate matter sensor serial driver");
> > +MODULE_LICENSE("GPL v2");
>

[PATCH 3/3] dt-bindings: iio: chemical: sps30: update binding with serial example

[Tomasz Duszynski]

sps30 has gained support for serial communication so add example to the
binding file. While at it remove reg property from list of required
properties because it's no-op in case of serial communication.

Signed-off-by: Tomasz Duszynski <tomasz.duszynski@octakon.com>
---
 .../devicetree/bindings/iio/chemical/sensirion,sps30.yaml  | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/iio/chemical/sensirion,sps30.yaml b/Documentation/devicetree/bindings/iio/chemical/sensirion,sps30.yaml
index a93d1972a5c2..967500b7e773 100644
--- a/Documentation/devicetree/bindings/iio/chemical/sensirion,sps30.yaml
+++ b/Documentation/devicetree/bindings/iio/chemical/sensirion,sps30.yaml
@@ -22,7 +22,6 @@ properties:
 
 required:
   - compatible
-  - reg
 
 additionalProperties: false
 
@@ -37,5 +36,11 @@ examples:
         reg = <0x69>;
       };
     };
+  - |
+    serial {
+      air-pollution-sensor {
+        compatible = "sensirion,sps30";
+      };
+    };
 
 ...
-- 
2.31.1