xref: /linux/Documentation/userspace-api/media/cec/cec-func-ioctl.rst (revision 4b4193256c8d3bc3a5397b5cd9494c2ad386317d) 
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2.. document under the terms of the GNU Free Documentation License,
3.. Version 1.1 or any later version published by the Free Software
4.. Foundation, with no Invariant Sections, no Front-Cover Texts
5.. and no Back-Cover Texts. A copy of the license is included at
6.. Documentation/userspace-api/media/fdl-appendix.rst.
7..
8.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
9
10.. _cec-func-ioctl:
11
12***********
13cec ioctl()
14***********
15
16Name
17====
18
19cec-ioctl - Control a cec device
20
21Synopsis
22========
23
24.. code-block:: c
25
26    #include <sys/ioctl.h>
27
28
29.. c:function:: int ioctl( int fd, int request, void *argp )
30   :name: cec-ioctl
31
32Arguments
33=========
34
35``fd``
36    File descriptor returned by :c:func:`open() <cec-open>`.
37
38``request``
39    CEC ioctl request code as defined in the cec.h header file, for
40    example :ref:`CEC_ADAP_G_CAPS <CEC_ADAP_G_CAPS>`.
41
42``argp``
43    Pointer to a request-specific structure.
44
45
46Description
47===========
48
49The :c:func:`ioctl() <cec-ioctl>` function manipulates cec device parameters. The
50argument ``fd`` must be an open file descriptor.
51
52The ioctl ``request`` code specifies the cec function to be called. It
53has encoded in it whether the argument is an input, output or read/write
54parameter, and the size of the argument ``argp`` in bytes.
55
56Macros and structures definitions specifying cec ioctl requests and
57their parameters are located in the cec.h header file. All cec ioctl
58requests, their respective function and parameters are specified in
59:ref:`cec-user-func`.
60
61
62Return Value
63============
64
65On success 0 is returned, on error -1 and the ``errno`` variable is set
66appropriately. The generic error codes are described at the
67:ref:`Generic Error Codes <gen-errors>` chapter.
68
69Request-specific error codes are listed in the individual requests
70descriptions.
71
72When an ioctl that takes an output or read/write parameter fails, the
73parameter remains unmodified.
74