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