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<refentry id="media-func-ioctl">
<refmeta>
<refentrytitle>media ioctl()</refentrytitle>
&manvol;
</refmeta>
<refnamediv>
<refname>media-ioctl</refname>
<refpurpose>Control a media device</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include <sys/ioctl.h></funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>ioctl</function></funcdef>
<paramdef>int <parameter>fd</parameter></paramdef>
<paramdef>int <parameter>request</parameter></paramdef>
<paramdef>void *<parameter>argp</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>fd</parameter></term>
<listitem>
<para>&fd;</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>request</parameter></term>
<listitem>
<para>Media ioctl request code as defined in the media.h header file,
for example MEDIA_IOC_SETUP_LINK.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>argp</parameter></term>
<listitem>
<para>Pointer to a request-specific structure.</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>The <function>ioctl()</function> function manipulates media device
parameters. The argument <parameter>fd</parameter> must be an open file
descriptor.</para>
<para>The ioctl <parameter>request</parameter> code specifies the media
function to be called. It has encoded in it whether the argument is an
input, output or read/write parameter, and the size of the argument
<parameter>argp</parameter> in bytes.</para>
<para>Macros and structures definitions specifying media ioctl requests and
their parameters are located in the media.h header file. All media ioctl
requests, their respective function and parameters are specified in
<xref linkend="media-user-func" />.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para><function>ioctl()</function> returns <returnvalue>0</returnvalue> on
success. On failure, <returnvalue>-1</returnvalue> is returned, and the
<varname>errno</varname> variable is set appropriately. Generic error codes
are listed below, and request-specific error codes are listed in the
individual requests descriptions.</para>
<para>When an ioctl that takes an output or read/write parameter fails,
the parameter remains unmodified.</para>
<variablelist>
<varlistentry>
<term><errorcode>EBADF</errorcode></term>
<listitem>
<para><parameter>fd</parameter> is not a valid open file descriptor.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><errorcode>EFAULT</errorcode></term>
<listitem>
<para><parameter>argp</parameter> references an inaccessible memory
area.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><errorcode>EINVAL</errorcode></term>
<listitem>
<para>The <parameter>request</parameter> or the data pointed to by
<parameter>argp</parameter> is not valid. This is a very common error
code, see the individual ioctl requests listed in
<xref linkend="media-user-func" /> for actual causes.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><errorcode>ENOMEM</errorcode></term>
<listitem>
<para>Insufficient kernel memory was available to complete the
request.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><errorcode>ENOTTY</errorcode></term>
<listitem>
<para><parameter>fd</parameter> is not associated with a character
special device.</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
</refentry>
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