iio: chemical: Add support for Bosch BME680 sensor

Bosch BME680 is a 4-in-1 sensor with temperature, pressure, humidity
and gas sensing capability. It supports both I2C and SPI communication
protocol for effective data communication.

The device supports two modes:

1. Sleep mode
2. Forced mode

The measurements only takes place when forced mode is triggered and a
single TPHG cycle is performed by the sensor. The sensor automatically
goes to sleep after afterwards.

The device has various calibration constants/parameters programmed into
devices' non-volatile memory(NVM) during production and can't be altered
by the user. These constants are used in the compensation functions to
get the required compensated readings along with the raw data. The
compensation functions/algorithms are provided by Bosch Sensortec GmbH
via their API[1]. As these don't change during the measurement cycle,
therefore we read and store them at the probe. The default configs
supplied by Bosch are also set at probe.

0-day tested with build success.

GSoC-2018: https://summerofcode.withgoogle.com/projects/#6691473790074880
Mentor: Daniel Baluta
[1] https://github.com/BoschSensortec/BME680_driver
Datasheet:
https://ae-bst.resource.bosch.com/media/_tech/media/datasheets/BST-BME680-DS001-00.pdf

Note from Jonathan: The compensation functions are 'interesting' and
could do with a tidy up in future.  However, they work so we can leave that
for another day.

Cc: Daniel Baluta <daniel.baluta@nxp.com>
Signed-off-by: Himanshu Jha <himanshujha199640@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/drivers/iio/chemical/Kconfig b/drivers/iio/chemical/Kconfig
index 5cb5be7612b4..b8e005be4f87 100644
--- a/drivers/iio/chemical/Kconfig
+++ b/drivers/iio/chemical/Kconfig
@@ -21,6 +21,29 @@ config ATLAS_PH_SENSOR
 	 To compile this driver as module, choose M here: the
 	 module will be called atlas-ph-sensor.
 
+config BME680
+	tristate "Bosch Sensortec BME680 sensor driver"
+	depends on (I2C || SPI)
+	select REGMAP
+	select BME680_I2C if I2C
+	select BME680_SPI if SPI
+	help
+	  Say yes here to build support for Bosch Sensortec BME680 sensor with
+	  temperature, pressure, humidity and gas sensing capability.
+
+	  This driver can also be built as a module. If so, the module for I2C
+	  would be called bme680_i2c and bme680_spi for SPI support.
+
+config BME680_I2C
+	tristate
+	depends on I2C && BME680
+	select REGMAP_I2C
+
+config BME680_SPI
+	tristate
+	depends on SPI && BME680
+	select REGMAP_SPI
+
 config CCS811
 	tristate "AMS CCS811 VOC sensor"
 	depends on I2C