[v3,1/2] Documentation: v4l: Flip handling for RAW sensors

Commit Message

Jacopo Mondi July 10, 2023, 1:22 p.m. UTC

Document the requirement of notifying to userspace the possible
re-ordering of the color sample components when a vertical or horizontal
flip is applied to a RAW camera sensor.

Signed-off-by: Jacopo Mondi <[e-mail]>
Reviewed-by: Dave Stevenson <[e-mail]>
---
 Documentation/driver-api/media/camera-sensor.rst | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

Patch

diff --git a/Documentation/driver-api/media/camera-sensor.rst b/Documentation/driver-api/media/camera-sensor.rst
index 93f4f2536c25..cd915ca119ea 100644
--- a/Documentation/driver-api/media/camera-sensor.rst
+++ b/Documentation/driver-api/media/camera-sensor.rst
@@ -173,3 +173,19 @@  V4L2_CID_VFLIP controls with the values programmed by the register sequences.
 The default values of these controls shall be 0 (disabled). Especially these
 controls shall not be inverted, independently of the sensor's mounting
 rotation.
+
+Flip handling for raw camera color sensors
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Applying vertical and horizontal flips on raw camera sensors inverts the color
+sample reading direction on the sensor's pixel array. This may cause the
+re-ordering of the color samples on the sensor's output frame. As an example, a
+raw camera sensor with a Bayer pattern color filter array with a native RGGB
+Bayer order will produce frames with GRBG component ordering when an horizontal
+flip is applied. Camera sensor drivers where inverting the reading order
+direction causes a re-ordering of the color components are required to register
+the ``V4L2_CID_VFLIP`` and ``V4L2_CID_HFLIP`` controls with the
+``V4L2_CTRL_FLAG_MODIFY_LAYOUT`` flag enabled to notify userspace that enabling
+a flip can potentially change the output buffer content layout. Flips should
+also be taken into account when enumerating and handling media bus formats
+on the camera sensor source pads.