drivers: iio: chemical: Add support for Sensirion SCD4x CO2 sensor

This is a driver for the SCD4x CO2 sensor from Sensirion. The sensor is
able to measure CO2 concentration, temperature and relative humdity.
The sensor uses a photoacoustic principle for measuring CO2 concentration.
An I2C interface is supported by this driver in order to communicate with
the sensor.
Signed-off-by: Roan van Dijk <roan@protonic.nl>
Link: https://lore.kernel.org/r/20211008101706.755942-4-roan@protonic.nlSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/chemical/Kconfig

@@ -118,6 +118,19 @@ config SCD30_SERIAL
 	  To compile this driver as a module, choose M here: the module will
 	  be called scd30_serial.
 
+config SCD4X
+	tristate "SCD4X carbon dioxide sensor driver"
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
+	depends on I2C
+	select CRC8
+	help
+	  Say Y here to build support for the Sensirion SCD4X sensor with carbon
+	  dioxide, relative humidity and temperature sensing capabilities.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called scd4x.
+
 config SENSIRION_SGP30
 	tristate "Sensirion SGPxx gas sensors"
 	depends on I2C

drivers/iio/chemical/Makefile

@@ -15,6 +15,7 @@ obj-$(CONFIG_PMS7003) += pms7003.o
 obj-$(CONFIG_SCD30_CORE) += scd30_core.o
 obj-$(CONFIG_SCD30_I2C) += scd30_i2c.o
 obj-$(CONFIG_SCD30_SERIAL) += scd30_serial.o
+obj-$(CONFIG_SCD4X) += scd4x.o
 obj-$(CONFIG_SENSEAIR_SUNRISE_CO2) += sunrise_co2.o
 obj-$(CONFIG_SENSIRION_SGP30)	+= sgp30.o
 obj-$(CONFIG_SENSIRION_SGP40)	+= sgp40.o