-.. 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
The semantics depend on the selected I/O method.
To enqueue a buffer applications set the ``type`` field of a struct
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
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``,
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
``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
to the number of elements in that array.
To enqueue a :ref:`memory mapped <mmap>` buffer applications set the
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
``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
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
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
``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
``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
``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
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
``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
``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.
:ref:`open() <func-open>` function, ``VIDIOC_DQBUF`` returns
immediately with an ``EAGAIN`` error code when no buffer is available.
``VIDIOC_DQBUF`` failed due to an internal error. Can also indicate
temporary problems like signal loss.
``VIDIOC_DQBUF`` failed due to an internal error. Can also indicate
temporary problems like signal loss.
an error, or even stop capturing. Reusing such buffer may be unsafe
though and its details (e.g. ``index``) may not be returned either.
It is recommended that drivers indicate recoverable errors by setting
an error, or even stop capturing. Reusing such buffer may be unsafe
though and its details (e.g. ``index``) may not be returned either.
It is recommended that drivers indicate recoverable errors by setting
projects / cascardo / linux.git / blobdiff