Documentation/userspace-api/media/mediactl/media-ioc-request-alloc.rst
.. 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
MEDIA_IOC_REQUEST_ALLOC - Allocate a request
.. c:macro:: MEDIA_IOC_REQUEST_ALLOC
int ioctl(int fd, MEDIA_IOC_REQUEST_ALLOC, int *argp)
fd
File descriptor returned by :c:func:open().
argp
Pointer to an integer.
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.
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.