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V4L/DVB: media-spec: Fix documentation mistakes regarding I/O streaming

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The media spec contains several errors in the description of the
I/O streaming ioctls, in particular with respect to the userptr
I/O method.

The most important change is that you really need to set count
and index in v4l2_requestbuffer and v4l2_buffer when dealing with
user pointer streaming.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
This commit is contained in:
Hans Verkuil
2010-02-20 09:41:03 -03:00
committed by Mauro Carvalho Chehab
parent 340dde817a
commit 995f5fefb0
4 changed files with 42 additions and 44 deletions
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7
Documentation/DocBook/v4l/vidioc-querybuf.xml
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@@ -54,12 +54,13 @@ buffer at any time after buffers have been allocated with the
&VIDIOC-REQBUFS; ioctl.</para>
<para>Applications set the <structfield>type</structfield> field
of a &v4l2-buffer; to the same buffer type as previously
of a &v4l2-buffer; to the same buffer type as was previously used with
&v4l2-format; <structfield>type</structfield> and &v4l2-requestbuffers;
<structfield>type</structfield>, and the <structfield>index</structfield>
field. Valid index numbers range from zero
to the number of buffers allocated with &VIDIOC-REQBUFS;
(&v4l2-requestbuffers; <structfield>count</structfield>) minus one.
The <structfield>reserved</structfield> field should to set to 0.
After calling <constant>VIDIOC_QUERYBUF</constant> with a pointer to
this structure drivers return an error code or fill the rest of
the structure.</para>
@@ -68,8 +69,8 @@ the structure.</para>
<constant>V4L2_BUF_FLAG_MAPPED</constant>,
<constant>V4L2_BUF_FLAG_QUEUED</constant> and
<constant>V4L2_BUF_FLAG_DONE</constant> flags will be valid. The
<structfield>memory</structfield> field will be set to
<constant>V4L2_MEMORY_MMAP</constant>, the <structfield>m.offset</structfield>
<structfield>memory</structfield> field will be set to the current
I/O method, the <structfield>m.offset</structfield>
contains the offset of the buffer from the start of the device memory,
the <structfield>length</structfield> field its size. The driver may
or may not set the remaining fields and flags, they are meaningless in