1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
3 .. _VIDIOC_PREPARE_BUF:
5 ************************
6 ioctl VIDIOC_PREPARE_BUF
7 ************************
12 VIDIOC_PREPARE_BUF - Prepare a buffer for I/O
18 .. c:function:: int ioctl( int fd, VIDIOC_PREPARE_BUF, struct v4l2_buffer *argp )
19 :name: VIDIOC_PREPARE_BUF
26 File descriptor returned by :ref:`open() <func-open>`.
29 Pointer to struct :c:type:`v4l2_buffer`.
35 Applications can optionally call the :ref:`VIDIOC_PREPARE_BUF` ioctl to
36 pass ownership of the buffer to the driver before actually enqueuing it,
37 using the :ref:`VIDIOC_QBUF <VIDIOC_QBUF>` ioctl, and to prepare it for future I/O. Such
38 preparations may include cache invalidation or cleaning. Performing them
39 in advance saves time during the actual I/O.
41 The struct :c:type:`v4l2_buffer` structure is specified in
48 On success 0 is returned, on error -1 and the ``errno`` variable is set
49 appropriately. The generic error codes are described at the
50 :ref:`Generic Error Codes <gen-errors>` chapter.
53 File I/O is in progress.
56 The buffer ``type`` is not supported, or the ``index`` is out of
57 bounds, or no buffers have been allocated yet, or the ``userptr`` or
58 ``length`` are invalid.