1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2.. c:namespace:: V4L
3
4.. _VIDIOC_PREPARE_BUF:
5
6************************
7ioctl VIDIOC_PREPARE_BUF
8************************
9
10Name
11====
12
13VIDIOC_PREPARE_BUF - Prepare a buffer for I/O
14
15Synopsis
16========
17
18.. c:macro:: VIDIOC_PREPARE_BUF
19
20``int ioctl(int fd, VIDIOC_PREPARE_BUF, struct v4l2_buffer *argp)``
21
22Arguments
23=========
24
25``fd``
26    File descriptor returned by :c:func:`open()`.
27
28``argp``
29    Pointer to struct :c:type:`v4l2_buffer`.
30
31Description
32===========
33
34Applications can optionally call the :ref:`VIDIOC_PREPARE_BUF` ioctl to
35pass ownership of the buffer to the driver before actually enqueuing it,
36using the :ref:`VIDIOC_QBUF <VIDIOC_QBUF>` ioctl, and to prepare it for future I/O. Such
37preparations may include cache invalidation or cleaning. Performing them
38in advance saves time during the actual I/O.
39
40The struct :c:type:`v4l2_buffer` structure is specified in
41:ref:`buffer`.
42
43Return Value
44============
45
46On success 0 is returned, on error -1 and the ``errno`` variable is set
47appropriately. The generic error codes are described at the
48:ref:`Generic Error Codes <gen-errors>` chapter.
49
50EBUSY
51    File I/O is in progress.
52
53EINVAL
54    The buffer ``type`` is not supported, or the ``index`` is out of
55    bounds, or no buffers have been allocated yet, or the ``userptr`` or
56    ``length`` are invalid.
57