.. 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 `, 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 `, :ref:`VIDIOC_G_EXT_CTRLS `, :ref:`VIDIOC_S_EXT_CTRLS ` and :ref:`VIDIOC_TRY_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 ` 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 ` 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 ` chapter. ENOTTY The driver has no support for requests.