blob: fb3ac38b3db207d25ac9965d67a481e2541128e9 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
|
.. -*- coding: utf-8; mode: rst -*-
.. _VIDIOC_PREPARE_BUF:
************************
ioctl VIDIOC_PREPARE_BUF
************************
*man VIDIOC_PREPARE_BUF(2)*
Prepare a buffer for I/O
Synopsis
========
.. c:function:: int ioctl( int fd, int request, struct v4l2_buffer *argp )
Arguments
=========
``fd``
File descriptor returned by :ref:`open() <func-open>`.
``request``
VIDIOC_PREPARE_BUF
``argp``
Description
===========
Applications can optionally call the ``VIDIOC_PREPARE_BUF`` ioctl to
pass ownership of the buffer to the driver before actually enqueuing it,
using the ``VIDIOC_QBUF`` ioctl, and to prepare it for future I/O. Such
preparations may include cache invalidation or cleaning. Performing them
in advance saves time during the actual I/O. In case such cache
operations are not required, the application can use one of
``V4L2_BUF_FLAG_NO_CACHE_INVALIDATE`` and
``V4L2_BUF_FLAG_NO_CACHE_CLEAN`` flags to skip the respective step.
The :c:type:`struct v4l2_buffer` structure is specified in
:ref:`buffer`.
Return Value
============
On success 0 is returned, on error -1 and the ``errno`` variable is set
appropriately. The generic error codes are described at the
:ref:`Generic Error Codes <gen-errors>` chapter.
EBUSY
File I/O is in progress.
EINVAL
The buffer ``type`` is not supported, or the ``index`` is out of
bounds, or no buffers have been allocated yet, or the ``userptr`` or
``length`` are invalid.
.. ------------------------------------------------------------------------------
.. This file was automatically converted from DocBook-XML with the dbxml
.. library (https://github.com/return42/sphkerneldoc). The origin XML comes
.. from the linux kernel, refer to:
..
.. * https://github.com/torvalds/linux/tree/master/Documentation/DocBook
.. ------------------------------------------------------------------------------
|
