1.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-no-invariants-or-later
2.. c:namespace:: MC
3
4.. _request-func-ioctl:
5
6***************
7request ioctl()
8***************
9
10Name
11====
12
13request-ioctl - Control a request file descriptor
14
15Synopsis
16========
17
18.. code-block:: c
19
20    #include <sys/ioctl.h>
21
22``int ioctl(int fd, int cmd, void *argp)``
23
24Arguments
25=========
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, for
32    example :ref:`MEDIA_REQUEST_IOC_QUEUE`.
33
34``argp``
35    Pointer to a request-specific structure.
36
37Description
38===========
39
40The :ref:`ioctl() <request-func-ioctl>` function manipulates request
41parameters. The argument ``fd`` must be an open file descriptor.
42
43The ioctl ``cmd`` code specifies the request function to be called. It
44has encoded in it whether the argument is an input, output or read/write
45parameter, and the size of the argument ``argp`` in bytes.
46
47Macros and structures definitions specifying request ioctl commands and
48their parameters are located in the media.h header file. All request ioctl
49commands, their respective function and parameters are specified in
50:ref:`media-user-func`.
51
52Return Value
53============
54
55On success 0 is returned, on error -1 and the ``errno`` variable is set
56appropriately. The generic error codes are described at the
57:ref:`Generic Error Codes <gen-errors>` chapter.
58
59Command-specific error codes are listed in the individual command
60descriptions.
61
62When an ioctl that takes an output or read/write parameter fails, the
63parameter remains unmodified.
64