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authorHans Verkuil <hverkuil@xs4all.nl>2014-07-21 10:16:47 -0300
committerMauro Carvalho Chehab <m.chehab@samsung.com>2014-07-25 19:17:15 -0300
commit592d1349f719db7c071ba9f4ade272be114b4196 (patch)
tree23a7eebf1bb1258f783f55721166486442270756 /Documentation/DocBook/media
parente87b540be2dd02552fb9244d50ae8b4e4619a34b (diff)
[media] Docbook/media: improve data_offset/bytesused documentation
This patch explicitly documents the relationship between bytesused and data_offset. Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
Diffstat (limited to 'Documentation/DocBook/media')
-rw-r--r--Documentation/DocBook/media/v4l/io.xml7
1 files changed, 6 insertions, 1 deletions
diff --git a/Documentation/DocBook/media/v4l/io.xml b/Documentation/DocBook/media/v4l/io.xml
index 8c4ee746a731..e5e8325aa3d7 100644
--- a/Documentation/DocBook/media/v4l/io.xml
+++ b/Documentation/DocBook/media/v4l/io.xml
@@ -870,7 +870,8 @@ should set this to 0.</entry>
If the application sets this to 0 for an output stream, then
<structfield>bytesused</structfield> will be set to the size of the
plane (see the <structfield>length</structfield> field of this struct)
- by the driver.</entry>
+ by the driver. Note that the actual image data starts at
+ <structfield>data_offset</structfield> which may not be 0.</entry>
</row>
<row>
<entry>__u32</entry>
@@ -919,6 +920,10 @@ should set this to 0.</entry>
<entry>Offset in bytes to video data in the plane.
Drivers must set this field when <structfield>type</structfield>
refers to an input stream, applications when it refers to an output stream.
+ Note that data_offset is included in <structfield>bytesused</structfield>.
+ So the size of the image in the plane is
+ <structfield>bytesused</structfield>-<structfield>data_offset</structfield> at
+ offset <structfield>data_offset</structfield> from the start of the plane.
</entry>
</row>
<row>