66 lines
1.8 KiB
ReStructuredText
66 lines
1.8 KiB
ReStructuredText
|
.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-no-invariants-or-later
|
||
|
|
.. c:namespace:: MC
|
||
|
|
|
||
|
|
.. _media_ioc_request_alloc:
|
||
|
|
|
||
|
|
*****************************
|
||
|
|
ioctl MEDIA_IOC_REQUEST_ALLOC
|
||
|
|
*****************************
|
||
|
|
|
||
|
|
Name
|
||
|
|
====
|
||
|
|
|
||
|
|
MEDIA_IOC_REQUEST_ALLOC - Allocate a request
|
||
|
|
|
||
|
|
Synopsis
|
||
|
|
========
|
||
|
|
|
||
|
|
.. c:macro:: MEDIA_IOC_REQUEST_ALLOC
|
||
|
|
|
||
|
|
``int ioctl(int fd, MEDIA_IOC_REQUEST_ALLOC, int *argp)``
|
||
|
|
|
||
|
|
Arguments
|
||
|
|
=========
|
||
|
|
|
||
|
|
``fd``
|
||
|
|
File descriptor returned by :c:func:`open()`.
|
||
|
|
|
||
|
|
``argp``
|
||
|
|
Pointer to an integer.
|
||
|
|
|
||
|
|
Description
|
||
|
|
===========
|
||
|
|
|
||
|
|
If the media device supports :ref:`requests <media-request-api>`, then
|
||
|
|
this ioctl can be used to allocate a request. If it is not supported, then
|
||
|
|
``errno`` is set to ``ENOTTY``. A request is accessed through a file descriptor
|
||
|
|
that is returned in ``*argp``.
|
||
|
|
|
||
|
|
If the request was successfully allocated, then the request file descriptor
|
||
|
|
can be passed to the :ref:`VIDIOC_QBUF <VIDIOC_QBUF>`,
|
||
|
|
:ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>`,
|
||
|
|
:ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` and
|
||
|
|
:ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` ioctls.
|
||
|
|
|
||
|
|
In addition, the request can be queued by calling
|
||
|
|
:ref:`MEDIA_REQUEST_IOC_QUEUE` and re-initialized by calling
|
||
|
|
:ref:`MEDIA_REQUEST_IOC_REINIT`.
|
||
|
|
|
||
|
|
Finally, the file descriptor can be :ref:`polled <request-func-poll>` to wait
|
||
|
|
for the request to complete.
|
||
|
|
|
||
|
|
The request will remain allocated until all the file descriptors associated
|
||
|
|
with it are closed by :c:func:`close()` and the driver no
|
||
|
|
longer uses the request internally. See also
|
||
|
|
:ref:`here <media-request-life-time>` for more information.
|
||
|
|
|
||
|
|
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.
|
||
|
|
|
||
|
|
ENOTTY
|
||
|
|
The driver has no support for requests.
|