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authorHans Verkuil <hans.verkuil@cisco.com>2014-04-07 10:01:28 -0300
committerMauro Carvalho Chehab <m.chehab@samsung.com>2014-04-16 18:53:52 -0300
commitb050b29e071a0b11262ad513700ab073f58c45b2 (patch)
tree39a449e59b218f0b7a663f4f3886d6d7156e88ad
parent3050040b4ed95a8e3fa243d57f78a1d7fb1ab77b (diff)
[media] DocBook media: update bytesused field description
For output buffers the application has to set the bytesused field. In reality applications often do not set this since drivers that deal with fix image sizes just override it anyway. The vb2 framework will replace this field with the length field if bytesused was set to 0 by the application, which is what happens in practice. Document this behavior. Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com> Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com> Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
-rw-r--r--Documentation/DocBook/media/v4l/io.xml13
1 files changed, 11 insertions, 2 deletions
diff --git a/Documentation/DocBook/media/v4l/io.xml b/Documentation/DocBook/media/v4l/io.xml
index 97a69bf6f3eb..188e6211abd1 100644
--- a/Documentation/DocBook/media/v4l/io.xml
+++ b/Documentation/DocBook/media/v4l/io.xml
@@ -699,7 +699,12 @@ linkend="v4l2-buf-type" /></entry>
buffer. It depends on the negotiated data format and may change with
each buffer for compressed variable size data like JPEG images.
Drivers must set this field when <structfield>type</structfield>
-refers to an input stream, applications when it refers to an output stream.</entry>
+refers to an input stream, applications when it refers to an output stream.
+If the application sets this to 0 for an output stream, then
+<structfield>bytesused</structfield> will be set to the size of the
+buffer (see the <structfield>length</structfield> field of this struct) by
+the driver. For multiplanar formats this field is ignored and the
+<structfield>planes</structfield> pointer is used instead.</entry>
</row>
<row>
<entry>__u32</entry>
@@ -861,7 +866,11 @@ should set this to 0.</entry>
<entry></entry>
<entry>The number of bytes occupied by data in the plane
(its payload). Drivers must set this field when <structfield>type</structfield>
- refers to an input stream, applications when it refers to an output stream.</entry>
+ refers to an input stream, applications when it refers to an output stream.
+ 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>
</row>
<row>
<entry>__u32</entry>

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