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[media] DocBook media: clarify v4l2_buffer/plane fields 

Be more specific as to who has to fill in each field/flag: the driver
or the application.

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 2014-03-07 10:16:48 -03:00 committed by Mauro Carvalho Chehab
parent 26092ffb72
commit 22a437cd63
1 changed files with 36 additions and 18 deletions
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54
Documentation/DocBook/media/v4l/io.xml
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@ -676,10 +676,11 @@ plane structures.</para>
<entry>__u32</entry>
<entry><structfield>index</structfield></entry>
<entry></entry>
<entry>Number of the buffer, set by the application. This
field is only used for <link linkend="mmap">memory mapping</link> I/O
and can range from zero to the number of buffers allocated
with the &VIDIOC-REQBUFS; ioctl (&v4l2-requestbuffers; <structfield>count</structfield>) minus one.</entry>
<entry>Number of the buffer, set by the application except
when calling &VIDIOC-DQBUF;, then it is set by the driver.
This field can range from zero to the number of buffers allocated
with the &VIDIOC-REQBUFS; ioctl (&v4l2-requestbuffers; <structfield>count</structfield>),
plus any buffers allocated with &VIDIOC-CREATE-BUFS; minus one.</entry>
</row>
<row>
<entry>__u32</entry>
@ -698,7 +699,7 @@ 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 an output stream.</entry>
refers to an input stream, applications when it refers to an output stream.</entry>
</row>
<row>
<entry>__u32</entry>
@ -715,7 +716,7 @@ linkend="buffer-flags" />.</entry>
buffer, see <xref linkend="v4l2-field" />. This field is not used when
the buffer contains VBI data. Drivers must set it when
<structfield>type</structfield> refers to an input stream,
applications when an output stream.</entry>
applications when it refers to an output stream.</entry>
</row>
<row>
<entry>struct timeval</entry>
@ -729,7 +730,9 @@ applications when an output stream.</entry>
stores the time at which the last data byte was actually sent out
in the <structfield>timestamp</structfield> field. This permits
applications to monitor the drift between the video and system
clock.</para></entry>
clock. For output streams that use <constant>V4L2_BUF_FLAG_TIMESTAMP_COPY</constant>
the application has to fill in the timestamp which will be copied
by the driver to the capture stream.</para></entry>
</row>
<row>
<entry>&v4l2-timecode;</entry>
@ -822,7 +825,8 @@ is the file descriptor associated with a DMABUF buffer.</entry>
<entry><structfield>length</structfield></entry>
<entry></entry>
<entry>Size of the buffer (not the payload) in bytes for the
single-planar API. For the multi-planar API the application sets
single-planar API. This is set by the driver based on the calls to
&VIDIOC-REQBUFS; and/or &VIDIOC-CREATE-BUFS;. For the multi-planar API the application sets
this to the number of elements in the <structfield>planes</structfield>
array. The driver will fill in the actual number of valid elements in
that array.
@ -856,13 +860,15 @@ should set this to 0.</entry>
<entry><structfield>bytesused</structfield></entry>
<entry></entry>
<entry>The number of bytes occupied by data in the plane
(its payload).</entry>
(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>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>length</structfield></entry>
<entry></entry>
<entry>Size in bytes of the plane (not its payload).</entry>
<entry>Size in bytes of the plane (not its payload). This is set by the driver
based on the calls to &VIDIOC-REQBUFS; and/or &VIDIOC-CREATE-BUFS;.</entry>
</row>
<row>
<entry>union</entry>
@ -901,7 +907,9 @@ should set this to 0.</entry>
<entry>__u32</entry>
<entry><structfield>data_offset</structfield></entry>
<entry></entry>
<entry>Offset in bytes to video data in the plane, if applicable.
<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.
</entry>
</row>
<row>
@ -1031,7 +1039,7 @@ buffer cannot be on both queues at the same time, the
<constant>V4L2_BUF_FLAG_QUEUED</constant> and
<constant>V4L2_BUF_FLAG_DONE</constant> flag are mutually exclusive.
They can be both cleared however, then the buffer is in "dequeued"
state, in the application domain to say so.</entry>
state, in the application domain so to say.</entry>
</row>
<row>
<entry><constant>V4L2_BUF_FLAG_ERROR</constant></entry>
@ -1049,27 +1057,35 @@ state, in the application domain to say so.</entry>
<entry>Drivers set or clear this flag when calling the
<constant>VIDIOC_DQBUF</constant> ioctl. It may be set by video
capture devices when the buffer contains a compressed image which is a
key frame (or field), &ie; can be decompressed on its own.</entry>
key frame (or field), &ie; can be decompressed on its own. Also know as
an I-frame. Applications can set this bit when <structfield>type</structfield>
refers to an output stream.</entry>
</row>
<row>
<entry><constant>V4L2_BUF_FLAG_PFRAME</constant></entry>
<entry>0x00000010</entry>
<entry>Similar to <constant>V4L2_BUF_FLAG_KEYFRAME</constant>
this flags predicted frames or fields which contain only differences to a
previous key frame.</entry>
previous key frame. Applications can set this bit when <structfield>type</structfield>
refers to an output stream.</entry>
</row>
<row>
<entry><constant>V4L2_BUF_FLAG_BFRAME</constant></entry>
<entry>0x00000020</entry>
<entry>Similar to <constant>V4L2_BUF_FLAG_PFRAME</constant>
this is a bidirectional predicted frame or field. [ooc tbd]</entry>
<entry>Similar to <constant>V4L2_BUF_FLAG_KEYFRAME</constant>
this flags a bi-directional predicted frame or field which contains only
the differences between the current frame and both the preceding and following
key frames to specify its content. Applications can set this bit when
<structfield>type</structfield> refers to an output stream.</entry>
</row>
<row>
<entry><constant>V4L2_BUF_FLAG_TIMECODE</constant></entry>
<entry>0x00000100</entry>
<entry>The <structfield>timecode</structfield> field is valid.
Drivers set or clear this flag when the <constant>VIDIOC_DQBUF</constant>
ioctl is called.</entry>
ioctl is called. Applications can set this bit and the corresponding
<structfield>timecode</structfield> structure when <structfield>type</structfield>
refers to an output stream.</entry>
</row>
<row>
<entry><constant>V4L2_BUF_FLAG_PREPARED</constant></entry>
@ -1141,7 +1157,9 @@ in which case caches have not been used.</entry>
the frame. Logical 'and' operation between the
<structfield>flags</structfield> field and
<constant>V4L2_BUF_FLAG_TSTAMP_SRC_MASK</constant> produces the
value of the timestamp source.</entry>
value of the timestamp source. Applications must set the timestamp
source when <structfield>type</structfield> refers to an output stream
and <constant>V4L2_BUF_FLAG_TIMESTAMP_COPY</constant> is set.</entry>
</row>
<row>
<entry><constant>V4L2_BUF_FLAG_TSTAMP_SRC_EOF</constant></entry>