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Diffstat (limited to 'Documentation/DocBook/v4l/media-func-ioctl.xml')
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| 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> | ||