10 VIDIOC_EXPBUF - Export a buffer as a DMABUF file descriptor.
16 .. c:function:: int ioctl( int fd, VIDIOC_EXPBUF, struct v4l2_exportbuffer *argp )
24 File descriptor returned by :ref:`open() <func-open>`.
27 Pointer to struct :c:type:`v4l2_exportbuffer`.
33 This ioctl is an extension to the :ref:`memory mapping <mmap>` I/O
34 method, therefore it is available only for ``V4L2_MEMORY_MMAP`` buffers.
35 It can be used to export a buffer as a DMABUF file at any time after
36 buffers have been allocated with the
37 :ref:`VIDIOC_REQBUFS` ioctl.
39 To export a buffer, applications fill struct
40 :c:type:`v4l2_exportbuffer`. The ``type`` field is
41 set to the same buffer type as was previously used with struct
42 :c:type:`v4l2_requestbuffers` ``type``.
43 Applications must also set the ``index`` field. Valid index numbers
44 range from zero to the number of buffers allocated with
45 :ref:`VIDIOC_REQBUFS` (struct
46 :c:type:`v4l2_requestbuffers` ``count``) minus
47 one. For the multi-planar API, applications set the ``plane`` field to
48 the index of the plane to be exported. Valid planes range from zero to
49 the maximal number of valid planes for the currently active format. For
50 the single-planar API, applications must set ``plane`` to zero.
51 Additional flags may be posted in the ``flags`` field. Refer to a manual
52 for open() for details. Currently only O_CLOEXEC, O_RDONLY, O_WRONLY,
53 and O_RDWR are supported. All other fields must be set to zero. In the
54 case of multi-planar API, every plane is exported separately using
55 multiple :ref:`VIDIOC_EXPBUF` calls.
57 After calling :ref:`VIDIOC_EXPBUF` the ``fd`` field will be set by a
58 driver. This is a DMABUF file descriptor. The application may pass it to
59 other DMABUF-aware devices. Refer to :ref:`DMABUF importing <dmabuf>`
60 for details about importing DMABUF files into V4L2 nodes. It is
61 recommended to close a DMABUF file when it is no longer used to allow
62 the associated memory to be reclaimed.
71 int buffer_export(int v4lfd, enum v4l2_buf_type bt, int index, int *dmafd)
73 struct v4l2_exportbuffer expbuf;
75 memset(&expbuf, 0, sizeof(expbuf));
78 if (ioctl(v4lfd, VIDIOC_EXPBUF, &expbuf) == -1) {
79 perror("VIDIOC_EXPBUF");
91 int buffer_export_mp(int v4lfd, enum v4l2_buf_type bt, int index,
92 int dmafd[], int n_planes)
96 for (i = 0; i < n_planes; ++i) {
97 struct v4l2_exportbuffer expbuf;
99 memset(&expbuf, 0, sizeof(expbuf));
101 expbuf.index = index;
103 if (ioctl(v4lfd, VIDIOC_EXPBUF, &expbuf) == -1) {
104 perror("VIDIOC_EXPBUF");
109 dmafd[i] = expbuf.fd;
116 .. c:type:: v4l2_exportbuffer
118 .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
120 .. flat-table:: struct v4l2_exportbuffer
127 - Type of the buffer, same as struct
128 :c:type:`v4l2_format` ``type`` or struct
129 :c:type:`v4l2_requestbuffers` ``type``, set
130 by the application. See :c:type:`v4l2_buf_type`
133 - Number of the buffer, set by the application. This field is only
134 used for :ref:`memory mapping <mmap>` I/O and can range from
135 zero to the number of buffers allocated with the
136 :ref:`VIDIOC_REQBUFS` and/or
137 :ref:`VIDIOC_CREATE_BUFS` ioctls.
140 - Index of the plane to be exported when using the multi-planar API.
141 Otherwise this value must be set to zero.
144 - Flags for the newly created file, currently only ``O_CLOEXEC``,
145 ``O_RDONLY``, ``O_WRONLY``, and ``O_RDWR`` are supported, refer to
146 the manual of open() for more details.
149 - The DMABUF file descriptor associated with a buffer. Set by the
153 - Reserved field for future use. Drivers and applications must set
160 On success 0 is returned, on error -1 and the ``errno`` variable is set
161 appropriately. The generic error codes are described at the
162 :ref:`Generic Error Codes <gen-errors>` chapter.
165 A queue is not in MMAP mode or DMABUF exporting is not supported or
166 ``flags`` or ``type`` or ``index`` or ``plane`` fields are invalid.