linux-stable-rt/Documentation/DocBook/media/v4l/media-ioc-setup-link.xml

<refentry id="media-ioc-setup-link">
  <refmeta>
    <refentrytitle>ioctl MEDIA_IOC_SETUP_LINK</refentrytitle>
    &manvol;
  </refmeta>

  <refnamediv>
    <refname>MEDIA_IOC_SETUP_LINK</refname>
    <refpurpose>Modify the properties of a link</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <funcsynopsis>
      <funcprototype>
	<funcdef>int <function>ioctl</function></funcdef>
	<paramdef>int <parameter>fd</parameter></paramdef>
	<paramdef>int <parameter>request</parameter></paramdef>
	<paramdef>struct media_link_desc *<parameter>argp</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Arguments</title>

    <variablelist>
      <varlistentry>
	<term><parameter>fd</parameter></term>
	<listitem>
	  <para>File descriptor returned by
	  <link linkend='media-func-open'><function>open()</function></link>.</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><parameter>request</parameter></term>
	<listitem>
	  <para>MEDIA_IOC_SETUP_LINK</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><parameter>argp</parameter></term>
	<listitem>
	  <para></para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Description</title>

    <para>To change link properties applications fill a &media-link-desc; with
    link identification information (source and sink pad) and the new requested
    link flags. They then call the MEDIA_IOC_SETUP_LINK ioctl with a pointer to
    that structure.</para>
    <para>The only configurable property is the <constant>ENABLED</constant>
    link flag to enable/disable a link. Links marked with the
    <constant>IMMUTABLE</constant> link flag can not be enabled or disabled.
    </para>
    <para>Link configuration has no side effect on other links. If an enabled
    link at the sink pad prevents the link from being enabled, the driver
    returns with an &EBUSY;.</para>
    <para>Only links marked with the <constant>DYNAMIC</constant> link flag can
    be enabled/disabled while streaming media data. Attempting to enable or
    disable a streaming non-dynamic link will return an &EBUSY;.</para>
    <para>If the specified link can't be found the driver returns with an
    &EINVAL;.</para>
  </refsect1>

  <refsect1>
    &return-value;

    <variablelist>
      <varlistentry>
	<term><errorcode>EINVAL</errorcode></term>
	<listitem>
	  <para>The &media-link-desc; references a non-existing link, or the
	  link is immutable and an attempt to modify its configuration was made.
	  </para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>
</refentry>