61 lines
1.4 KiB
ReStructuredText
61 lines
1.4 KiB
ReStructuredText
|
.. -*- coding: utf-8; mode: rst -*-
|
||
|
|
|
||
|
|
.. _VIDIOC_PREPARE_BUF:
|
||
|
|
|
||
|
|
************************
|
||
|
|
ioctl VIDIOC_PREPARE_BUF
|
||
|
|
************************
|
||
|
|
|
||
|
|
Name
|
||
|
|
====
|
||
|
|
|
||
|
|
VIDIOC_PREPARE_BUF - Prepare a buffer for I/O
|
||
|
|
|
||
|
|
|
||
|
|
Synopsis
|
||
|
|
========
|
||
|
|
|
||
|
|
.. c:function:: int ioctl( int fd, VIDIOC_PREPARE_BUF, struct v4l2_buffer *argp )
|
||
|
|
:name: VIDIOC_PREPARE_BUF
|
||
|
|
|
||
|
|
|
||
|
|
Arguments
|
||
|
|
=========
|
||
|
|
|
||
|
|
``fd``
|
||
|
|
File descriptor returned by :ref:`open() <func-open>`.
|
||
|
|
|
||
|
|
``argp``
|
||
|
|
|
||
|
|
|
||
|
|
Description
|
||
|
|
===========
|
||
|
|
|
||
|
|
Applications can optionally call the :ref:`VIDIOC_PREPARE_BUF` ioctl to
|
||
|
|
pass ownership of the buffer to the driver before actually enqueuing it,
|
||
|
|
using the :ref:`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 struct :c:type:`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.
|