iio: magn: Add support for BMC150 magnetometer

Add support for the Bosh BMC150 Magnetometer.
The specification can be downloaded from:
http://ae-bst.resource.bosch.com/media/products/dokumente/bmc150/BST-BMC150-DS000-04.pdf.
The chip contains both an accelerometer and a magnetometer.
This patch adds support only for the magnetometer part.

The temperature compensation formulas are based on bmm050_api.c
authored by contact@bosch.sensortec.com.
Signed-off-by: Irina Tirdea <irina.tirdea@intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/magnetometer/Kconfig

@@ -76,4 +76,18 @@ config IIO_ST_MAGN_SPI_3AXIS
 	depends on IIO_ST_MAGN_3AXIS
 	depends on IIO_ST_SENSORS_SPI
 
+config BMC150_MAGN
+	tristate "Bosch BMC150 Magnetometer Driver"
+	depends on I2C
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
+	help
+	  Say yes here to build support for the BMC150 magnetometer.
+
+	  Currently this only supports the device via an i2c interface.
+
+	  This is a combo module with both accelerometer and magnetometer.
+	  This driver is only implementing magnetometer part, which has
+	  its own address and register map.
+
 endmenu

drivers/iio/magnetometer/Makefile

@@ -13,3 +13,5 @@ st_magn-$(CONFIG_IIO_BUFFER) += st_magn_buffer.o
 
 obj-$(CONFIG_IIO_ST_MAGN_I2C_3AXIS) += st_magn_i2c.o
 obj-$(CONFIG_IIO_ST_MAGN_SPI_3AXIS) += st_magn_spi.o
+
+obj-$(CONFIG_BMC150_MAGN) += bmc150_magn.o