[RFC v5 05/15] media: Documentation: Add scaling and post-scaler crop for common raw

[Sakari Ailus <sakari.ailus@linux.intel.com>]

Document scaling and post-scaler digital crop operations for the common
raw sensor model.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
---
 .../media/v4l/subdev-config-model.rst         | 24 +++++++++++++++----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/Documentation/userspace-api/media/v4l/subdev-config-model.rst b/Documentation/userspace-api/media/v4l/subdev-config-model.rst
index b0bd09772ceb..f15e5495cc34 100644
--- a/Documentation/userspace-api/media/v4l/subdev-config-model.rst
+++ b/Documentation/userspace-api/media/v4l/subdev-config-model.rst
@@ -118,11 +118,18 @@ sub-sampling to achieve the desired size.
 
 The digital crop operation takes place after binning and sub-sampling. It is
 configured by setting the ``V4L2_SEL_TGT_CROP`` rectangle on (pad, stream) pair
-0/0. The resulting image size is further output by the sensor.
+0/0.
+
+The scaling operation is performed after the digital crop. It is configured by
+setting the ``V4L2_SEL_TGT_COMPOSE`` rectangle on (pad, stream) pair 0/0,
+relative to the digital crop.
 
 The sensor's output mbus code is configured by setting the format on the (pad,
-stream) pair 0/0. When setting the format, always use the same width and height
-as for the digital crop setting.
+stream) pair 0/0. The width and height fields are used to configure post-scaler
+digital crop if supported by the driver, affecting the right and bottom edges of
+the frame. If post-scaler digital crop is not supported, the width and height
+fields of the format will match the compose rectangle sizes applied on the same
+0/0 (pad, stream) pair.
 
 Drivers may only support some of even none of these configurations, in which
 case they do not expose the corresponding selection rectangles. If any selection
@@ -180,12 +187,19 @@ Also refer to :ref:`Selection targets <v4l2-selection-targets-table>`.
       - X
       - Digital crop. This rectangle is relative to the ``V4L2_SEL_TGT_COMPOSE``
         rectangle on (pad, stream) pair 1/0.
+    * - 0/0
+      - ``V4L2_SEL_TGT_COMPOSE``
+      - \-
+      - X
+      - Scaling. This rectangle is relative to the ``V4L2_SEL_TGT_CROP``
+        rectangle on (pad, stream) pair 0/0.
     * - 0/0
       - Format
       - X
       - X
-      - Image data source format. Always assign the width and height fields of
-        the format to the same values than for the ``V4L2_SEL_TGT_CROP``
+      - Image data source format and post-scaler crop. The width and height
+        fields of the format, used to configure post-scaler crop on the right
+        and bottom edges of the image, are related to the ``V4L2_SEL_TGT_COMPOSE``
         rectangle on (pad, stream) pair 0/0. The media bus code reflects the
         pixel data output of the sensor.
     * - 0/1
-- 
2.39.5