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[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>
This commit is contained in:
Hans Verkuil 2014-07-21 10:16:47 -03:00 committed by Mauro Carvalho Chehab
parent e87b540be2
commit 592d1349f7
1 changed files with 6 additions and 1 deletions
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7
Documentation/DocBook/media/v4l/io.xml
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@ -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>