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-rw-r--r--Documentation/DocBook/media/v4l/io.xml15
1 files changed, 12 insertions, 3 deletions
diff --git a/Documentation/DocBook/media/v4l/io.xml b/Documentation/DocBook/media/v4l/io.xml
index 97a69bf6f3eb..a086a5db7a18 100644
--- a/Documentation/DocBook/media/v4l/io.xml
+++ b/Documentation/DocBook/media/v4l/io.xml
@@ -125,7 +125,7 @@ location of the buffers in device memory can be determined with the
<structfield>m.offset</structfield> and <structfield>length</structfield>
returned in a &v4l2-buffer; are passed as sixth and second parameter to the
<function>mmap()</function> function. When using the multi-planar API,
-struct &v4l2-buffer; contains an array of &v4l2-plane; structures, each
+&v4l2-buffer; contains an array of &v4l2-plane; structures, each
containing its own <structfield>m.offset</structfield> and
<structfield>length</structfield>. When using the multi-planar API, every
plane of every buffer has to be mapped separately, so the number of
@@ -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>