[PATCH 2/2] iio: pressure: add Sensirion SDP31 driver
From: Muhammad Abu Bakar
Date: Sat Sep 19 2026 - 18:40:38 EST
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@xxxxxxxxx>
---
MAINTAINERS | 6 ++
drivers/iio/pressure/Kconfig | 11 ++
drivers/iio/pressure/Makefile | 1 +
drivers/iio/pressure/sdp31.c | 194 ++++++++++++++++++++++++++++++++++
4 files changed, 212 insertions(+)
create mode 100644 drivers/iio/pressure/sdp31.c
diff --git a/MAINTAINERS b/MAINTAINERS
index 214aeee76..a053a530e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -24855,6 +24855,12 @@ 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@xxxxxxxxx>
+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@xxxxxxxxxxxxxxxxxxxxxxxxx>
S: Maintained
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..934a3afcd
--- /dev/null
+++ b/drivers/iio/pressure/sdp31.c
@@ -0,0 +1,194 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/delay.h>
+#include <linux/mutex.h>
+#include <linux/crc8.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 multi-step measurements */
+ u16 dp_scale; /* diff-pressure scale factor read from the sensor */
+};
+
+struct sdp31_reading {
+ s16 pressure;
+ s16 temp;
+ u16 scale;
+};
+
+static int sdp31_send_cmd(struct i2c_client *client, u16 cmd)
+{
+ u8 buf[2] = { cmd >> 8, cmd & 0xff };
+ int ret = i2c_master_send(client, 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;
+}
+
+static int sdp31_measure(struct i2c_client *client, struct sdp31_reading *out)
+{
+ u8 rx[9];
+ int ret;
+
+ ret = sdp31_send_cmd(client, SDP31_CMD_TRIG_DP);
+ if (ret)
+ return ret;
+
+ msleep(SDP31_MEAS_DELAY_MS);
+
+ ret = i2c_master_recv(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;
+
+ out->pressure = (s16)((rx[0] << 8) | rx[1]);
+ out->temp = (s16)((rx[3] << 8) | rx[4]);
+ out->scale = (rx[6] << 8) | rx[7];
+ 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:
+ mutex_lock(&data->lock);
+ ret = sdp31_measure(data->client, &r);
+ mutex_unlock(&data->lock);
+ 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:
+ /* raw / dp_scale = Pa; /1000 => kPa (IIO unit) */
+ *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 iio_dev *indio_dev;
+ struct sdp31_data *data;
+ struct sdp31_reading r;
+ int ret;
+
+ indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+ if (!indio_dev)
+ return -ENOMEM;
+
+ data = iio_priv(indio_dev);
+ data->client = client;
+ mutex_init(&data->lock);
+
+ crc8_populate_msb(sdp31_crc8_table, SDP31_CRC8_POLY);
+
+ /* Confirm the sensor is present and learn its scale factor. */
+ ret = sdp31_measure(client, &r);
+ if (ret)
+ return dev_err_probe(&client->dev, ret,
+ "failed to read from sensor\n");
+ if (!r.scale)
+ return dev_err_probe(&client->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(&client->dev, indio_dev);
+}
+
+static const struct i2c_device_id sdp31_id[] = {
+ { "sdp31" },
+ { }
+};
+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