iio: core: Introduce IIO_CHAN_INFO_CALIBEMISSIVITY

Contact-less IR temperature sensors measure the temperature of an object
by using its thermal radiation.  Surfaces with different emissivity
ratios emit different amounts of energy at the same temperature.

IIO_CHAN_INFO_CALIBEMISSIVITY allows the user to inform the sensor of the
emissivity of the object in front of it, in order to effectively measure
its temperature.

A device providing such setting is Melexis's MLX90614:
http://melexis.com/Assets/IR-sensor-thermometer-MLX90614-Datasheet-5152.aspx.

Signed-off-by: Vianney le Clément de Saint-Marcq <vianney.leclement@essensium.com>
Cc: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
index 3befcb19f414..866b4ec4aab6 100644
--- a/Documentation/ABI/testing/sysfs-bus-iio
+++ b/Documentation/ABI/testing/sysfs-bus-iio
@@ -1364,3 +1364,14 @@ Description:
                 hwfifo_watermak_min but not equal to any of the values in this
                 list, the driver will chose an appropriate value for the
                 hardware fifo watermark level.
+
+What:           /sys/bus/iio/devices/iio:deviceX/in_temp_calibemissivity
+What:           /sys/bus/iio/devices/iio:deviceX/in_tempX_calibemissivity
+What:           /sys/bus/iio/devices/iio:deviceX/in_temp_object_calibemissivity
+What:           /sys/bus/iio/devices/iio:deviceX/in_tempX_object_calibemissivity
+KernelVersion:  4.1
+Contact:        linux-iio@vger.kernel.org
+Description:
+                The emissivity ratio of the surface in the field of view of the
+                contactless temperature sensor.  Emissivity varies from 0 to 1,
+                with 1 being the emissivity of a black body.