Synopsis
========
-.. cpp:function:: int ioctl( int fd, int request, struct v4l2_buffer *argp )
+.. c:function:: int ioctl( int fd, VIDIOC_QBUF, struct v4l2_buffer *argp )
+ :name: VIDIOC_QBUF
+
+.. c:function:: int ioctl( int fd, VIDIOC_DQBUF, struct v4l2_buffer *argp )
+ :name: VIDIOC_DQBUF
Arguments
``fd``
File descriptor returned by :ref:`open() <func-open>`.
-``request``
- VIDIOC_QBUF, VIDIOC_DQBUF
-
``argp``
The semantics depend on the selected I/O method.
To enqueue a buffer applications set the ``type`` field of a struct
-:ref:`v4l2_buffer <v4l2-buffer>` to the same buffer type as was
-previously used with struct :ref:`v4l2_format <v4l2-format>` ``type``
-and struct :ref:`v4l2_requestbuffers <v4l2-requestbuffers>` ``type``.
+:c:type:`v4l2_buffer` to the same buffer type as was
+previously used with struct :c:type:`v4l2_format` ``type``
+and struct :c:type:`v4l2_requestbuffers` ``type``.
Applications must also set the ``index`` field. Valid index numbers
range from zero to the number of buffers allocated with
:ref:`VIDIOC_REQBUFS` (struct
-:ref:`v4l2_requestbuffers <v4l2-requestbuffers>` ``count``) minus
-one. The contents of the struct :ref:`struct v4l2_buffer <v4l2-buffer>` returned
+:c:type:`v4l2_requestbuffers` ``count``) minus
+one. The contents of the struct :c:type:`v4l2_buffer` returned
by a :ref:`VIDIOC_QUERYBUF` ioctl will do as well.
When the buffer is intended for output (``type`` is
``V4L2_BUF_TYPE_VIDEO_OUTPUT``, ``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE``,
``reserved2`` and ``reserved`` fields must be set to 0. When using the
:ref:`multi-planar API <planar-apis>`, the ``m.planes`` field must
contain a userspace pointer to a filled-in array of struct
-:ref:`v4l2_plane <v4l2-plane>` and the ``length`` field must be set
+:c:type:`v4l2_plane` and the ``length`` field must be set
to the number of elements in that array.
To enqueue a :ref:`memory mapped <mmap>` buffer applications set the
``memory`` field to ``V4L2_MEMORY_USERPTR``, the ``m.userptr`` field to
the address of the buffer and ``length`` to its size. When the
multi-planar API is used, ``m.userptr`` and ``length`` members of the
-passed array of struct :ref:`v4l2_plane <v4l2-plane>` have to be used
+passed array of struct :c:type:`v4l2_plane` have to be used
instead. When ``VIDIOC_QBUF`` is called with a pointer to this structure
the driver sets the ``V4L2_BUF_FLAG_QUEUED`` flag and clears the
``V4L2_BUF_FLAG_MAPPED`` and ``V4L2_BUF_FLAG_DONE`` flags in the
``memory`` field to ``V4L2_MEMORY_DMABUF`` and the ``m.fd`` field to a
file descriptor associated with a DMABUF buffer. When the multi-planar
API is used the ``m.fd`` fields of the passed array of struct
-:ref:`v4l2_plane <v4l2-plane>` have to be used instead. When
+:c:type:`v4l2_plane` have to be used instead. When
``VIDIOC_QBUF`` is called with a pointer to this structure the driver
sets the ``V4L2_BUF_FLAG_QUEUED`` flag and clears the
``V4L2_BUF_FLAG_MAPPED`` and ``V4L2_BUF_FLAG_DONE`` flags in the
Applications call the ``VIDIOC_DQBUF`` ioctl to dequeue a filled
(capturing) or displayed (output) buffer from the driver's outgoing
queue. They just set the ``type``, ``memory`` and ``reserved`` fields of
-a struct :ref:`v4l2_buffer <v4l2-buffer>` as above, when
+a struct :c:type:`v4l2_buffer` as above, when
``VIDIOC_DQBUF`` is called with a pointer to this structure the driver
fills the remaining fields or returns an error code. The driver may also
set ``V4L2_BUF_FLAG_ERROR`` in the ``flags`` field. It indicates a
:ref:`open() <func-open>` function, ``VIDIOC_DQBUF`` returns
immediately with an ``EAGAIN`` error code when no buffer is available.
-The :ref:`struct v4l2_buffer <v4l2-buffer>` structure is specified in
+The struct :c:type:`v4l2_buffer` structure is specified in
:ref:`buffer`.
projects / cascardo / linux.git / blobdiff