[PATCH v2 4/7] iio: core: Introduce IIO_CHAN_INFO_EMISSIVITY

["Vianney le Clément de Saint-Marcq" <vianney.leclement@essensium.com>]

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_EMISSIVITY 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>

---

v2: new patch
---
 Documentation/ABI/testing/sysfs-bus-iio | 11 +++++++++++
 drivers/iio/industrialio-core.c         |  1 +
 include/linux/iio/iio.h                 |  1 +
 3 files changed, 13 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
index 9a70c31..a8b103a 100644
--- a/Documentation/ABI/testing/sysfs-bus-iio
+++ b/Documentation/ABI/testing/sysfs-bus-iio
@@ -1249,3 +1249,14 @@ Contact:	linux-iio@vger.kernel.org
 Description:
 		Specifies number of seconds in which we compute the steps
 		that occur in order to decide if the consumer is making steps.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_temp_emissivity
+What:		/sys/bus/iio/devices/iio:deviceX/in_tempX_emissivity
+What:		/sys/bus/iio/devices/iio:deviceX/in_temp_object_emissivity
+What:		/sys/bus/iio/devices/iio:deviceX/in_tempX_object_emissivity
+KernelVersion:	4.0
+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.
diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index aaba9d3..902d03b 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -128,6 +128,7 @@ static const char * const iio_chan_info_postfix[] = {
 	[IIO_CHAN_INFO_CALIBWEIGHT] = "calibweight",
 	[IIO_CHAN_INFO_DEBOUNCE_COUNT] = "debounce_count",
 	[IIO_CHAN_INFO_DEBOUNCE_TIME] = "debounce_time",
+	[IIO_CHAN_INFO_EMISSIVITY] = "emissivity",
 };
 
 /**
diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
index 80d8550..24bd0bdd 100644
--- a/include/linux/iio/iio.h
+++ b/include/linux/iio/iio.h
@@ -43,6 +43,7 @@ enum iio_chan_info_enum {
 	IIO_CHAN_INFO_CALIBWEIGHT,
 	IIO_CHAN_INFO_DEBOUNCE_COUNT,
 	IIO_CHAN_INFO_DEBOUNCE_TIME,
+	IIO_CHAN_INFO_EMISSIVITY,
 };
 
 enum iio_shared_by {
-- 
2.3.3