iio: distance: srf08: add driver ABI documentation

Add sysfs-bus-iio-distance-srf08 for individual attributes of the driver,
especially:
 - sensitivity which the device documentation calls gain for amplifying the
   signal
 - max_range for limiting the maximum distance for expected echos and
   therefore limiting the time waiting for telegrams

Signed-off-by: Andreas Klinger <ak@it-klinger.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/Documentation/ABI/testing/sysfs-bus-iio-distance-srf08 b/Documentation/ABI/testing/sysfs-bus-iio-distance-srf08
new file mode 100644 (file)
index 0000000..0a1ca14
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-iio-distance-srf08
@@ -0,0 +1,22 @@
+What           /sys/bus/iio/devices/iio:deviceX/sensor_sensitivity
+Date:          January 2017
+KernelVersion: 4.11
+Contact:       linux-iio@vger.kernel.org
+Description:
+               Show or set the gain boost of the amp, from 0-31 range.
+               default 31
+
+What           /sys/bus/iio/devices/iio:deviceX/sensor_max_range
+Date:          January 2017
+KernelVersion: 4.11
+Contact:       linux-iio@vger.kernel.org
+Description:
+                Show or set the maximum range between the sensor and the
+               first object echoed in meters. Default value is 6.020.
+               This setting limits the time the driver is waiting for a
+               echo.
+               Showing the range of available values is represented as the
+               minimum value, the step and the maximum value, all enclosed
+               in square brackets.
+               Example:
+               [0.043 0.043 11.008]