[PATCH v2 0/2] iio: pressure: add Sensirion SDP31 driver

[PATCH v2 0/2] iio: pressure: add Sensirion SDP31 driver

[Muhammad Abu Bakar]

This series adds support for the Sensirion SDP31 differential pressure
sensor, an I2C device that also reports temperature.

The SDP31 uses a completely different I2C command protocol from the
already supported SDP500 (command-triggered measurements with a per-word
CRC-8), so extending the sdp500 driver does not make sense. No compatible
parts from other vendors were found.

Patch 1 adds the device tree binding.
Patch 2 adds the IIO driver, which exposes differential pressure and
temperature channels and validates each measurement using the sensor's
CRC-8 checksum.

The driver was developed and tested on an SDP31 wired to the I2C bus of
a Raspberry Pi 4.

Changes since v1:
- Explain in this cover letter why a new driver is added instead of
  extending the sdp500 driver.
- dt-bindings: make vdd-supply required, and enable the regulator in the
  driver using devm_regulator_get_enable().
- Move the MAINTAINERS entry into the dt-bindings patch; the driver patch
  only adds its own file.
- Populate the CRC-8 table with DO_ONCE() to avoid a race between
  concurrent probes.
- Use devm_mutex_init() and take the lock inside sdp31_measure() using
  guard(mutex).
- Build the command with __be16/cpu_to_be16() and parse the reply with
  get_unaligned_be16().
- Use a named initializer in the i2c_device_id table.
- Minor cleanups: local struct device *dev, single-line dev_err_probe(),
  and a comment on the mutex.

v1: https://lore.kernel.org/linux-iio/20260919223650.13396-1-m.abubakar365@yahoo.com/

Muhammad Abu Bakar (2):
  dt-bindings: iio: pressure: add Sensirion SDP31
  iio: pressure: add Sensirion SDP31 driver

 .../iio/pressure/sensirion,sdp31.yaml         |  41 ++++
 MAINTAINERS                                   |   6 +
 drivers/iio/pressure/Kconfig                  |  11 +
 drivers/iio/pressure/Makefile                 |   1 +
 drivers/iio/pressure/sdp31.c                  | 209 ++++++++++++++++++
 5 files changed, 268 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/pressure/sensirion,sdp31.yaml
 create mode 100644 drivers/iio/pressure/sdp31.c

-- 
2.43.0

[PATCH v2 1/2] dt-bindings: iio: pressure: add Sensirion SDP31

[Muhammad Abu Bakar]

Add device tree bindings for the Sensirion SDP31 differential pressure
sensor, an I2C device that also reports temperature.

Signed-off-by: Muhammad Abu Bakar <m.abubakar365@yahoo.com>
---
 .../iio/pressure/sensirion,sdp31.yaml         | 41 +++++++++++++++++++
 MAINTAINERS                                   |  5 +++
 2 files changed, 46 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/pressure/sensirion,sdp31.yaml

diff --git a/Documentation/devicetree/bindings/iio/pressure/sensirion,sdp31.yaml b/Documentation/devicetree/bindings/iio/pressure/sensirion,sdp31.yaml
new file mode 100644
index 000000000..a98e7c97e
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/pressure/sensirion,sdp31.yaml
@@ -0,0 +1,41 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/pressure/sensirion,sdp31.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Sensirion SDP31 differential pressure sensor
+
+maintainers:
+  - Muhammad Abu Bakar <m.abubakar365@yahoo.com>
+
+description: |
+  Differential pressure sensor from Sensirion with an I2C interface.
+
+properties:
+  compatible:
+    const: sensirion,sdp31
+
+  reg:
+    maxItems: 1
+
+  vdd-supply: true
+
+required:
+  - compatible
+  - reg
+  - vdd-supply
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c {
+      #address-cells = <1>;
+      #size-cells = <0>;
+      pressure@21 {
+        compatible = "sensirion,sdp31";
+        reg = <0x21>;
+        vdd-supply = <&vdd_3v3>;
+      };
+    };
diff --git a/MAINTAINERS b/MAINTAINERS
index 214aeee76..e285147be 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -24855,6 +24855,11 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/iio/chemical/sensirion,scd4x.yaml
 F:	drivers/iio/chemical/scd4x.c
 
+SENSIRION SDP31 DIFFERENTIAL PRESSURE SENSOR DRIVER
+M:	Muhammad Abu Bakar <m.abubakar365@yahoo.com>
+S:	Maintained
+F:	Documentation/devicetree/bindings/iio/pressure/sensirion,sdp31.yaml
+
 SENSIRION SDP500 DIFFERENTIAL PRESSURE SENSOR DRIVER
 M:	Petar Stoykov <petar.stoykov@prodrive-technologies.com>
 S:	Maintained
-- 
2.43.0

Re: [PATCH v2 1/2] dt-bindings: iio: pressure: add Sensirion SDP31

[Krzysztof Kozlowski]

On Sun, Sep 20, 2026 at 09:47:23PM +0500, Muhammad Abu Bakar wrote:
> Add device tree bindings for the Sensirion SDP31 differential pressure
> sensor, an I2C device that also reports temperature.

I don't see how you addressed previous feedback.

Best regards,
Krzysztof

[PATCH v2 2/2] iio: pressure: add Sensirion SDP31 driver

[Muhammad Abu Bakar]

Add an IIO driver for the Sensirion SDP31 differential pressure sensor.
The device is accessed over I2C and reports differential pressure and
temperature. Each measurement is validated using the sensor's CRC-8
checksum.

Tested on an SDP31 connected to a Raspberry Pi 4 I2C bus.

Signed-off-by: Muhammad Abu Bakar <m.abubakar365@yahoo.com>
---
 MAINTAINERS                   |   1 +
 drivers/iio/pressure/Kconfig  |  11 ++
 drivers/iio/pressure/Makefile |   1 +
 drivers/iio/pressure/sdp31.c  | 209 ++++++++++++++++++++++++++++++++++
 4 files changed, 222 insertions(+)
 create mode 100644 drivers/iio/pressure/sdp31.c

diff --git a/MAINTAINERS b/MAINTAINERS
index e285147be..a053a530e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -24859,6 +24859,7 @@ SENSIRION SDP31 DIFFERENTIAL PRESSURE SENSOR DRIVER
 M:	Muhammad Abu Bakar <m.abubakar365@yahoo.com>
 S:	Maintained
 F:	Documentation/devicetree/bindings/iio/pressure/sensirion,sdp31.yaml
+F:	drivers/iio/pressure/sdp31.c
 
 SENSIRION SDP500 DIFFERENTIAL PRESSURE SENSOR DRIVER
 M:	Petar Stoykov <petar.stoykov@prodrive-technologies.com>
diff --git a/drivers/iio/pressure/Kconfig b/drivers/iio/pressure/Kconfig
index 838a8340c..58172639c 100644
--- a/drivers/iio/pressure/Kconfig
+++ b/drivers/iio/pressure/Kconfig
@@ -286,6 +286,17 @@ config MS5637
 	  This driver can also be built as a module. If so, the module will
 	  be called ms5637.
 
+config SDP31
+	tristate "Sensirion SDP31 differential pressure sensor I2C driver"
+	depends on I2C
+	select CRC8
+	help
+	  Say Y here to build support for Sensirion SDP31 differential pressure
+	  sensor I2C driver.
+
+	  To compile this driver as a module, choose M here: the core module
+	  will be called sdp31.
+
 config SDP500
 	tristate "Sensirion SDP500 differential pressure sensor I2C driver"
 	depends on I2C
diff --git a/drivers/iio/pressure/Makefile b/drivers/iio/pressure/Makefile
index bc0d11a20..5279a0ebd 100644
--- a/drivers/iio/pressure/Makefile
+++ b/drivers/iio/pressure/Makefile
@@ -35,6 +35,7 @@ obj-$(CONFIG_MS5611) += ms5611_core.o
 obj-$(CONFIG_MS5611_I2C) += ms5611_i2c.o
 obj-$(CONFIG_MS5611_SPI) += ms5611_spi.o
 obj-$(CONFIG_MS5637) += ms5637.o
+obj-$(CONFIG_SDP31) += sdp31.o
 obj-$(CONFIG_SDP500) += sdp500.o
 obj-$(CONFIG_IIO_ST_PRESS) += st_pressure.o
 st_pressure-y := st_pressure_core.o
diff --git a/drivers/iio/pressure/sdp31.c b/drivers/iio/pressure/sdp31.c
new file mode 100644
index 000000000..e661a7af8
--- /dev/null
+++ b/drivers/iio/pressure/sdp31.c
@@ -0,0 +1,209 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <linux/cleanup.h>
+#include <linux/crc8.h>
+#include <linux/delay.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/once.h>
+#include <linux/regulator/consumer.h>
+#include <linux/unaligned.h>
+
+#include <linux/iio/iio.h>
+
+#define SDP31_CMD_TRIG_DP    0x362F
+#define SDP31_MEAS_DELAY_MS  50
+#define SDP31_TEMP_SCALE     5
+#define SDP31_CRC8_POLY      0x31
+#define SDP31_CRC8_INIT      0xff
+
+DECLARE_CRC8_TABLE(sdp31_crc8_table);
+
+struct sdp31_data {
+	struct i2c_client *client;
+	struct mutex lock; /* serializes access to the sensor */
+	u16 dp_scale;
+};
+
+struct sdp31_reading {
+	s16 pressure;
+	s16 temp;
+	u16 scale;
+};
+
+/* #2: build the command as a be16 and send it directly. */
+static int sdp31_send_cmd(struct i2c_client *client, u16 cmd)
+{
+	__be16 buf = cpu_to_be16(cmd);
+	int ret = i2c_master_send(client, (u8 *)&buf, sizeof(buf));
+
+	if (ret < 0)
+		return ret;
+	return (ret == sizeof(buf)) ? 0 : -EIO;
+}
+
+static int sdp31_check_crc(const u8 *word)
+{
+	if (crc8(sdp31_crc8_table, word, 2, SDP31_CRC8_INIT) != word[2])
+		return -EIO;
+	return 0;
+}
+
+/* #3: takes sdp31_data and holds the lock for the whole transaction. */
+static int sdp31_measure(struct sdp31_data *data, struct sdp31_reading *out)
+{
+	u8 rx[9];
+	int ret;
+
+	guard(mutex)(&data->lock);
+
+	ret = sdp31_send_cmd(data->client, SDP31_CMD_TRIG_DP);
+	if (ret)
+		return ret;
+
+	msleep(SDP31_MEAS_DELAY_MS);
+
+	ret = i2c_master_recv(data->client, rx, sizeof(rx));
+	if (ret < 0)
+		return ret;
+	if (ret != sizeof(rx))
+		return -EIO;
+
+	if (sdp31_check_crc(&rx[0]) ||
+	    sdp31_check_crc(&rx[3]) ||
+	    sdp31_check_crc(&rx[6]))
+		return -EIO;
+
+	/* #4: use the unaligned big-endian helper instead of manual shifts. */
+	out->pressure = (s16)get_unaligned_be16(&rx[0]);
+	out->temp = (s16)get_unaligned_be16(&rx[3]);
+	out->scale = get_unaligned_be16(&rx[6]);
+	return 0;
+}
+
+static int sdp31_read_raw(struct iio_dev *indio_dev,
+			  struct iio_chan_spec const *chan,
+			  int *val, int *val2, long mask)
+{
+	struct sdp31_data *data = iio_priv(indio_dev);
+	struct sdp31_reading r;
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = sdp31_measure(data, &r);   /* locking now lives inside */
+		if (ret)
+			return ret;
+		switch (chan->type) {
+		case IIO_PRESSURE:
+			*val = r.pressure;
+			return IIO_VAL_INT;
+		case IIO_TEMP:
+			*val = r.temp;
+			return IIO_VAL_INT;
+		default:
+			return -EINVAL;
+		}
+	case IIO_CHAN_INFO_SCALE:
+		switch (chan->type) {
+		case IIO_PRESSURE:
+			*val = 1;
+			*val2 = data->dp_scale * 1000;
+			return IIO_VAL_FRACTIONAL;
+		case IIO_TEMP:
+			*val = SDP31_TEMP_SCALE;
+			return IIO_VAL_INT;
+		default:
+			return -EINVAL;
+		}
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info sdp31_info = {
+	.read_raw = sdp31_read_raw,
+};
+
+static const struct iio_chan_spec sdp31_channels[] = {
+	{
+		.type = IIO_PRESSURE,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+				      BIT(IIO_CHAN_INFO_SCALE),
+	},
+	{
+		.type = IIO_TEMP,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+				      BIT(IIO_CHAN_INFO_SCALE),
+	},
+};
+
+static int sdp31_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;   /* #5 */
+	struct iio_dev *indio_dev;
+	struct sdp31_data *data;
+	struct sdp31_reading r;
+	int ret;
+
+	/* #9: get and enable the sensor's supply (auto-disabled on remove). */
+	ret = devm_regulator_get_enable(dev, "vdd");
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to enable regulator\n");
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	data = iio_priv(indio_dev);
+	data->client = client;
+
+	ret = devm_mutex_init(dev, &data->lock);   /* #6 */
+	if (ret)
+		return ret;
+
+	/* #7: populate the shared CRC table exactly once, race-free. */
+	DO_ONCE(crc8_populate_msb, sdp31_crc8_table, SDP31_CRC8_POLY);
+
+	/* Confirm the sensor is present and learn its scale factor. */
+	ret = sdp31_measure(data, &r);
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to read from sensor\n");  /* #8 */
+	if (!r.scale)
+		return dev_err_probe(dev, -EINVAL, "invalid scale factor\n");
+	data->dp_scale = r.scale;
+
+	indio_dev->name = "sdp31";
+	indio_dev->info = &sdp31_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = sdp31_channels;
+	indio_dev->num_channels = ARRAY_SIZE(sdp31_channels);
+
+	return devm_iio_device_register(dev, indio_dev);
+}
+
+static const struct i2c_device_id sdp31_id[] = {
+	{ .name = "sdp31" },   /* #10: named initializer */
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, sdp31_id);
+
+static const struct of_device_id sdp31_of_match[] = {
+	{ .compatible = "sensirion,sdp31" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, sdp31_of_match);
+
+static struct i2c_driver sdp31_driver = {
+	.driver = {
+		.name = "sdp31",
+		.of_match_table = sdp31_of_match,
+	},
+	.probe = sdp31_probe,
+	.id_table = sdp31_id,
+};
+module_i2c_driver(sdp31_driver);
+
+MODULE_AUTHOR("Muhammad Abu Bakar");
+MODULE_DESCRIPTION("Sensirion SDP31 differential pressure sensor");
+MODULE_LICENSE("GPL");
-- 
2.43.0

Re: [PATCH v2 2/2] iio: pressure: add Sensirion SDP31 driver

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] iio: sdp31: missing sensor power-on delay after vdd enable
--

commit 29a27ea5bbd1f787014c3c0a7f644c621fff7ae3
Author: Muhammad Abu Bakar <m.abubakar365@yahoo.com>

iio: pressure: add Sensirion SDP31 driver

Add an IIO driver for the Sensirion SDP31 differential pressure sensor.
The device is accessed over I2C and reports differential pressure and
temperature. Each measurement is validated using the sensor's CRC-8
checksum.

> diff --git a/drivers/iio/pressure/sdp31.c b/drivers/iio/pressure/sdp31.c
> new file mode 100644
> index 0000000000000..e661a7af86271
> --- /dev/null
> +++ b/drivers/iio/pressure/sdp31.c
[ ... ]
> +static int sdp31_probe(struct i2c_client *client)
> +{
> +	struct device *dev = &client->dev;   /* #5 */
> +	struct iio_dev *indio_dev;
> +	struct sdp31_data *data;
> +	struct sdp31_reading r;
> +	int ret;
> +
> +	/* #9: get and enable the sensor's supply (auto-disabled on remove). */
> +	ret = devm_regulator_get_enable(dev, "vdd");
> +	if (ret)
> +		return dev_err_probe(dev, ret, "failed to enable regulator\n");
> +
> +	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	data = iio_priv(indio_dev);
> +	data->client = client;
> +
> +	ret = devm_mutex_init(dev, &data->lock);   /* #6 */
> +	if (ret)
> +		return ret;
> +
> +	/* #7: populate the shared CRC table exactly once, race-free. */
> +	DO_ONCE(crc8_populate_msb, sdp31_crc8_table, SDP31_CRC8_POLY);
> +
> +	/* Confirm the sensor is present and learn its scale factor. */
> +	ret = sdp31_measure(data, &r);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "failed to read from sensor\n");  /* #8 */

[Severity: Medium]
Will this I2C transaction fail if the sensor is still booting?

The driver calls devm_regulator_get_enable() to turn on the vdd supply and
then almost immediately calls sdp31_measure() to communicate with the sensor.
If the regulator physically toggles power, the sensor might still be in its
hardware initialization sequence and could NACK the initial I2C trigger
command.

Does this need a startup delay between enabling the regulator and the first I2C
transaction to ensure the sensor is fully ready to process commands, preventing
an unconditional probe failure on such platforms?

> +	if (!r.scale)
> +		return dev_err_probe(dev, -EINVAL, "invalid scale factor\n");
> +	data->dp_scale = r.scale;

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260920164724.32019-1-m.abubakar365@yahoo.com?part=2

Re: [PATCH v2 2/2] iio: pressure: add Sensirion SDP31 driver

[Jonathan Cameron]

On Sun, 20 Sep 2026 21:47:24 +0500
Muhammad Abu Bakar <m.abubakar365@yahoo.com> wrote:

> Add an IIO driver for the Sensirion SDP31 differential pressure sensor.
> The device is accessed over I2C and reports differential pressure and
> temperature. Each measurement is validated using the sensor's CRC-8
> checksum.
> 
> Tested on an SDP31 connected to a Raspberry Pi 4 I2C bus.
> 
> Signed-off-by: Muhammad Abu Bakar <m.abubakar365@yahoo.com>
Hi Muhammad,

You seem to have a bunch of comments in the code calling out changes
from earlier versions.  Those may well be helpful whilst developing
(or are they LLM generated?). Either way we don't want to merge them
into the upstream kernel.

Otherwise a few minor comments inline

Thanks,

Jonathan

> diff --git a/drivers/iio/pressure/sdp31.c b/drivers/iio/pressure/sdp31.c
> new file mode 100644
> index 000000000..e661a7af8
> --- /dev/null
> +++ b/drivers/iio/pressure/sdp31.c
> @@ -0,0 +1,209 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +#include <linux/cleanup.h>
> +#include <linux/crc8.h>
> +#include <linux/delay.h>
> +#include <linux/i2c.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/once.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/unaligned.h>
> +
> +#include <linux/iio/iio.h>
> +
> +#define SDP31_CMD_TRIG_DP    0x362F
> +#define SDP31_MEAS_DELAY_MS  50
> +#define SDP31_TEMP_SCALE     5

I'd rather see this one at last just inline in the place I'd
look for the scale.  The define isn't adding anything that isn't
better indicated by how it is used.

> +#define SDP31_CRC8_POLY      0x31
> +#define SDP31_CRC8_INIT      0xff

> +
> +/* #2: build the command as a be16 and send it directly. */
> +static int sdp31_send_cmd(struct i2c_client *client, u16 cmd)
> +{
> +	__be16 buf = cpu_to_be16(cmd);
> +	int ret = i2c_master_send(client, (u8 *)&buf, sizeof(buf));
Tiny thing but I'd split into
	int ret;

	ret = i2c_masster_send();
	if (ret < 0)

as more important to have the code visibly coupled with the
error check than the declaration of ret.

> +
> +	if (ret < 0)
> +		return ret;
> +	return (ret == sizeof(buf)) ? 0 : -EIO;
> +}
> +
> +static int sdp31_check_crc(const u8 *word)
> +{
> +	if (crc8(sdp31_crc8_table, word, 2, SDP31_CRC8_INIT) != word[2])
> +		return -EIO;
As below. I'd have a blank line here.

> +	return 0;
> +}
> +
> +/* #3: takes sdp31_data and holds the lock for the whole transaction. */
> +static int sdp31_measure(struct sdp31_data *data, struct sdp31_reading *out)
> +{
> +	u8 rx[9];
> +	int ret;
> +
> +	guard(mutex)(&data->lock);
> +
> +	ret = sdp31_send_cmd(data->client, SDP31_CMD_TRIG_DP);
> +	if (ret)
> +		return ret;
> +
> +	msleep(SDP31_MEAS_DELAY_MS);
> +
> +	ret = i2c_master_recv(data->client, rx, sizeof(rx));
> +	if (ret < 0)
> +		return ret;
> +	if (ret != sizeof(rx))
> +		return -EIO;
> +
> +	if (sdp31_check_crc(&rx[0]) ||
> +	    sdp31_check_crc(&rx[3]) ||
> +	    sdp31_check_crc(&rx[6]))
> +		return -EIO;
> +
> +	/* #4: use the unaligned big-endian helper instead of manual shifts. */
> +	out->pressure = (s16)get_unaligned_be16(&rx[0]);
> +	out->temp = (s16)get_unaligned_be16(&rx[3]);
> +	out->scale = get_unaligned_be16(&rx[6]);

Trivial but it helps readability a little to have a blank line before simple
return statements like this.

> +	return 0;
> +}
> +
> +static int sdp31_read_raw(struct iio_dev *indio_dev,
> +			  struct iio_chan_spec const *chan,
> +			  int *val, int *val2, long mask)
> +{
> +	struct sdp31_data *data = iio_priv(indio_dev);
> +	struct sdp31_reading r;
> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		ret = sdp31_measure(data, &r);   /* locking now lives inside */
> +		if (ret)
> +			return ret;
> +		switch (chan->type) {
> +		case IIO_PRESSURE:
> +			*val = r.pressure;
> +			return IIO_VAL_INT;
> +		case IIO_TEMP:
> +			*val = r.temp;
> +			return IIO_VAL_INT;
> +		default:
> +			return -EINVAL;
> +		}
> +	case IIO_CHAN_INFO_SCALE:
> +		switch (chan->type) {
> +		case IIO_PRESSURE:
> +			*val = 1;
> +			*val2 = data->dp_scale * 1000;
> +			return IIO_VAL_FRACTIONAL;
> +		case IIO_TEMP:
> +			*val = SDP31_TEMP_SCALE;

As above. *val = 5; is better than a define that brings
no value other than making anyone reading the code go look
to see what value it has.

> +			return IIO_VAL_INT;
> +		default:
> +			return -EINVAL;
> +		}
> +	default:
> +		return -EINVAL;
> +	}
> +}

> +
> +static int sdp31_probe(struct i2c_client *client)
> +{
> +	struct device *dev = &client->dev;   /* #5 */
> +	struct iio_dev *indio_dev;
> +	struct sdp31_data *data;
> +	struct sdp31_reading r;
> +	int ret;
> +
> +	/* #9: get and enable the sensor's supply (auto-disabled on remove). */
> +	ret = devm_regulator_get_enable(dev, "vdd");
> +	if (ret)
> +		return dev_err_probe(dev, ret, "failed to enable regulator\n");
> +
> +	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	data = iio_priv(indio_dev);
> +	data->client = client;
> +
> +	ret = devm_mutex_init(dev, &data->lock);   /* #6 */
> +	if (ret)
> +		return ret;
> +
> +	/* #7: populate the shared CRC table exactly once, race-free. */
> +	DO_ONCE(crc8_populate_msb, sdp31_crc8_table, SDP31_CRC8_POLY);
> +
> +	/* Confirm the sensor is present and learn its scale factor. */
> +	ret = sdp31_measure(data, &r);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "failed to read from sensor\n");  /* #8 */

As below, these need clearing out.

> +	if (!r.scale)
> +		return dev_err_probe(dev, -EINVAL, "invalid scale factor\n");
> +	data->dp_scale = r.scale;
> +
> +	indio_dev->name = "sdp31";
> +	indio_dev->info = &sdp31_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = sdp31_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(sdp31_channels);
> +
> +	return devm_iio_device_register(dev, indio_dev);
> +}
> +
> +static const struct i2c_device_id sdp31_id[] = {
> +	{ .name = "sdp31" },   /* #10: named initializer */

I'm guessing this is an LLM trying to be helpful and highlight changes?
We don't want that record of changes in an upstream driver.

> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, sdp31_id);

Re: [PATCH v2 0/2] iio: pressure: add Sensirion SDP31 driver

[Krzysztof Kozlowski]

On Sun, Sep 20, 2026 at 09:47:22PM +0500, Muhammad Abu Bakar wrote:
> This series adds support for the Sensirion SDP31 differential pressure
> sensor, an I2C device that also reports temperature.
> 
> The SDP31 uses a completely different I2C command protocol from the
> already supported SDP500 (command-triggered measurements with a per-word
> CRC-8), so extending the sdp500 driver does not make sense. No compatible
> parts from other vendors were found.
> 
> Patch 1 adds the device tree binding.
> Patch 2 adds the IIO driver, which exposes differential pressure and
> temperature channels and validates each measurement using the sensor's
> CRC-8 checksum.
> 
> The driver was developed and tested on an SDP31 wired to the I2C bus of
> a Raspberry Pi 4.
> 
> Changes since v1:
> - Explain in this cover letter why a new driver is added instead of
>   extending the sdp500 driver.
> - dt-bindings: make vdd-supply required, and enable the regulator in the
>   driver using devm_regulator_get_enable().
> - Move the MAINTAINERS entry into the dt-bindings patch; the driver patch
>   only adds its own file.
> - Populate the CRC-8 table with DO_ONCE() to avoid a race between
>   concurrent probes.
> - Use devm_mutex_init() and take the lock inside sdp31_measure() using
>   guard(mutex).
> - Build the command with __be16/cpu_to_be16() and parse the reply with
>   get_unaligned_be16().
> - Use a named initializer in the i2c_device_id table.
> - Minor cleanups: local struct device *dev, single-line dev_err_probe(),
>   and a comment on the mutex.
> 
> v1: https://lore.kernel.org/linux-iio/20260919223650.13396-1-m.abubakar365@yahoo.com/

Link does not work.

Best regards,
Krzysztof