Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 2ddb77bb authored by Hans Verkuil's avatar Hans Verkuil Committed by Mauro Carvalho Chehab
Browse files

[media] DocBook v4l: update bytesperline handling 



The documentation says that the bytesperline field in v4l2_pix_format refers
to the largest plane in the case of planar formats (i.e. multiple planes
stores in a single buffer).

For almost all planar formats the first plane is also the largest (or equal)
plane, except for two formats: V4L2_PIX_FMT_NV24/NV42. For this YUV 4:4:4
format the second chroma plane is twice the size of the first luma plane.

Looking at the very few drivers that support this format the bytesperline
value that they report is actually that of the first plane and not that
of the largest plane.

Rather than fixing the drivers it makes more sense to update the documentation
since it is very difficult to use the largest plane for this. You would have
to check what the format is in order to know to which plane bytesperline
belongs, which makes calculations much more difficult.

This patch updates the documentation accordingly.

Signed-off-by: default avatarHans Verkuil <hans.verkuil@cisco.com>
Acked-by: default avatarLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: default avatarSakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@osg.samsung.com>
parent 3259aa57

Documentation/DocBook/media/v4l/pixfmt.xml

+2 −2
Original line number Diff line number Diff line
@@ -80,9 +80,9 @@ padding bytes after the last line of an image cross a system page 
boundary. Input devices may write padding bytes, the value is

undefined. Output devices ignore the contents of padding

bytes.</para><para>When the image format is planar the

<structfield>bytesperline</structfield> value applies to the largest

<structfield>bytesperline</structfield> value applies to the first

plane and is divided by the same factor as the

<structfield>width</structfield> field for any smaller planes. For

<structfield>width</structfield> field for the other planes. For

example the Cb and Cr planes of a YUV 4:2:0 image have half as many

padding bytes following each line as the Y plane. To avoid ambiguities

drivers must return a <structfield>bytesperline</structfield> value

Documentation/DocBook/media/v4l/vidioc-g-fbuf.xml

+2 −2
Original line number Diff line number Diff line
@@ -240,9 +240,9 @@ where padding bytes after the last line of an image cross a system 
page boundary. Capture devices may write padding bytes, the value is

undefined. Output devices ignore the contents of padding

bytes.</para><para>When the image format is planar the

<structfield>bytesperline</structfield> value applies to the largest

<structfield>bytesperline</structfield> value applies to the first

plane and is divided by the same factor as the

<structfield>width</structfield> field for any smaller planes. For

<structfield>width</structfield> field for the other planes. For

example the Cb and Cr planes of a YUV 4:2:0 image have half as many

padding bytes following each line as the Y plane. To avoid ambiguities

drivers must return a <structfield>bytesperline</structfield> value