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140d8816 LP |
1 | <refentry id="media-func-ioctl"> |
2 | <refmeta> | |
3 | <refentrytitle>media ioctl()</refentrytitle> | |
4 | &manvol; | |
5 | </refmeta> | |
6 | ||
7 | <refnamediv> | |
8 | <refname>media-ioctl</refname> | |
9 | <refpurpose>Control a media device</refpurpose> | |
10 | </refnamediv> | |
11 | ||
12 | <refsynopsisdiv> | |
13 | <funcsynopsis> | |
14 | <funcsynopsisinfo>#include <sys/ioctl.h></funcsynopsisinfo> | |
15 | <funcprototype> | |
16 | <funcdef>int <function>ioctl</function></funcdef> | |
17 | <paramdef>int <parameter>fd</parameter></paramdef> | |
18 | <paramdef>int <parameter>request</parameter></paramdef> | |
19 | <paramdef>void *<parameter>argp</parameter></paramdef> | |
20 | </funcprototype> | |
21 | </funcsynopsis> | |
22 | </refsynopsisdiv> | |
23 | ||
24 | <refsect1> | |
25 | <title>Arguments</title> | |
26 | ||
27 | <variablelist> | |
28 | <varlistentry> | |
29 | <term><parameter>fd</parameter></term> | |
30 | <listitem> | |
31 | <para>&fd;</para> | |
32 | </listitem> | |
33 | </varlistentry> | |
34 | <varlistentry> | |
35 | <term><parameter>request</parameter></term> | |
36 | <listitem> | |
37 | <para>Media ioctl request code as defined in the media.h header file, | |
38 | for example MEDIA_IOC_SETUP_LINK.</para> | |
39 | </listitem> | |
40 | </varlistentry> | |
41 | <varlistentry> | |
42 | <term><parameter>argp</parameter></term> | |
43 | <listitem> | |
44 | <para>Pointer to a request-specific structure.</para> | |
45 | </listitem> | |
46 | </varlistentry> | |
47 | </variablelist> | |
48 | </refsect1> | |
49 | ||
50 | <refsect1> | |
51 | <title>Description</title> | |
52 | <para>The <function>ioctl()</function> function manipulates media device | |
53 | parameters. The argument <parameter>fd</parameter> must be an open file | |
54 | descriptor.</para> | |
55 | <para>The ioctl <parameter>request</parameter> code specifies the media | |
56 | function to be called. It has encoded in it whether the argument is an | |
57 | input, output or read/write parameter, and the size of the argument | |
58 | <parameter>argp</parameter> in bytes.</para> | |
59 | <para>Macros and structures definitions specifying media ioctl requests and | |
60 | their parameters are located in the media.h header file. All media ioctl | |
61 | requests, their respective function and parameters are specified in | |
62 | <xref linkend="media-user-func" />.</para> | |
63 | </refsect1> | |
64 | ||
65 | <refsect1> | |
66 | <title>Return Value</title> | |
67 | ||
68 | <para><function>ioctl()</function> returns <returnvalue>0</returnvalue> on | |
69 | success. On failure, <returnvalue>-1</returnvalue> is returned, and the | |
70 | <varname>errno</varname> variable is set appropriately. Generic error codes | |
71 | are listed below, and request-specific error codes are listed in the | |
72 | individual requests descriptions.</para> | |
73 | <para>When an ioctl that takes an output or read/write parameter fails, | |
74 | the parameter remains unmodified.</para> | |
75 | ||
76 | <variablelist> | |
77 | <varlistentry> | |
78 | <term><errorcode>EBADF</errorcode></term> | |
79 | <listitem> | |
80 | <para><parameter>fd</parameter> is not a valid open file descriptor. | |
81 | </para> | |
82 | </listitem> | |
83 | </varlistentry> | |
84 | <varlistentry> | |
85 | <term><errorcode>EFAULT</errorcode></term> | |
86 | <listitem> | |
87 | <para><parameter>argp</parameter> references an inaccessible memory | |
88 | area.</para> | |
89 | </listitem> | |
90 | </varlistentry> | |
91 | <varlistentry> | |
92 | <term><errorcode>EINVAL</errorcode></term> | |
93 | <listitem> | |
94 | <para>The <parameter>request</parameter> or the data pointed to by | |
95 | <parameter>argp</parameter> is not valid. This is a very common error | |
96 | code, see the individual ioctl requests listed in | |
97 | <xref linkend="media-user-func" /> for actual causes.</para> | |
98 | </listitem> | |
99 | </varlistentry> | |
100 | <varlistentry> | |
101 | <term><errorcode>ENOMEM</errorcode></term> | |
102 | <listitem> | |
103 | <para>Insufficient kernel memory was available to complete the | |
104 | request.</para> | |
105 | </listitem> | |
106 | </varlistentry> | |
107 | <varlistentry> | |
108 | <term><errorcode>ENOTTY</errorcode></term> | |
109 | <listitem> | |
110 | <para><parameter>fd</parameter> is not associated with a character | |
111 | special device.</para> | |
112 | </listitem> | |
113 | </varlistentry> | |
114 | </variablelist> | |
115 | </refsect1> | |
116 | </refentry> |