[PATCH 2/2] media: v4l2-ctrls: Document V4L2_CID_NOTIFY_GAIN_XXX controls

[David Plowman <david.plowman@raspberrypi.com>]

Add documentation for each of the controls

V4L2_CID_NOTIFY_GAIN_RED
V4L2_CID_NOTIFY_GAIN_GREENR
V4L2_CID_NOTIFY_GAIN_BLUE
V4L2_CID_NOTIFY_GAIN_GREENB

These controls are required by sensors that need to know what colour
gains will be applied to pixels by downstream processing (such as by
an ISP), though the sensor does not apply these gains itself.

Signed-off-by: David Plowman <david.plowman@raspberrypi.com>
---
 .../media/v4l/ext-ctrls-image-source.rst      | 28 +++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-image-source.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-image-source.rst
index de43f5c8486d..f824d6c36ae8 100644
--- a/Documentation/userspace-api/media/v4l/ext-ctrls-image-source.rst
+++ b/Documentation/userspace-api/media/v4l/ext-ctrls-image-source.rst
@@ -72,3 +72,31 @@ Image Source Control IDs
     * - __u32
       - ``height``
       - Height of the area.
+
+``V4L2_CID_NOTIFY_GAIN_RED (integer)``
+    Notify the sensor what gain will be applied to red pixels by the
+    subsequent processing (such as by an ISP). The sensor is merely
+    informed of this value in case it performs processing that requires
+    it, but it is not applied to the output pixels themselves. The
+    units are determined by the sensor driver.
+
+``V4L2_CID_NOTIFY_GAIN_GREENR (integer)``
+    Notify the sensor what gain will be applied to green pixels (on
+    red rows) by subsequent processing (such as by an ISP). The sensor
+    is merely informed of this value in case it performs processing
+    that requires it, but it is not applied to the output pixels
+    themselves. The units are determined by the sensor driver.
+
+``V4L2_CID_NOTIFY_GAIN_BLUE (integer)``
+    Notify the sensor what gain will be applied to blue pixels by the
+    subsequent processing (such as by an ISP). The sensor is merely
+    informed of this value in case it performs processing that requires
+    it, but it is not applied to the output pixels themselves. The
+    units are determined by the sensor driver.
+
+``V4L2_CID_NOTIFY_GAIN_GREENB (integer)``
+    Notify the sensor what gain will be applied to green pixels (on
+    blue rows) by subsequent processing (such as by an ISP). The sensor
+    is merely informed of this value in case it performs processing
+    that requires it, but it is not applied to the output pixels
+    themselves. The units are determined by the sensor driver.
-- 
2.17.1