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1.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-no-invariants-or-later2.. c:namespace:: MC3 4.. _request-func-ioctl:5 6***************7request ioctl()8***************9 10Name11====12 13request-ioctl - Control a request file descriptor14 15Synopsis16========17 18.. code-block:: c19 20 #include <sys/ioctl.h>21 22``int ioctl(int fd, int cmd, void *argp)``23 24Arguments25=========26 27``fd``28 File descriptor returned by :ref:`MEDIA_IOC_REQUEST_ALLOC`.29 30``cmd``31 The request ioctl command code as defined in the media.h header file, for32 example :ref:`MEDIA_REQUEST_IOC_QUEUE`.33 34``argp``35 Pointer to a request-specific structure.36 37Description38===========39 40The :ref:`ioctl() <request-func-ioctl>` function manipulates request41parameters. The argument ``fd`` must be an open file descriptor.42 43The ioctl ``cmd`` code specifies the request function to be called. It44has encoded in it whether the argument is an input, output or read/write45parameter, and the size of the argument ``argp`` in bytes.46 47Macros and structures definitions specifying request ioctl commands and48their parameters are located in the media.h header file. All request ioctl49commands, their respective function and parameters are specified in50:ref:`media-user-func`.51 52Return Value53============54 55On success 0 is returned, on error -1 and the ``errno`` variable is set56appropriately. The generic error codes are described at the57:ref:`Generic Error Codes <gen-errors>` chapter.58 59Command-specific error codes are listed in the individual command60descriptions.61 62When an ioctl that takes an output or read/write parameter fails, the63parameter remains unmodified.64