linux/Documentation/DocBook/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_ENUM_LINKS</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>EBUSY</errorcode></term>
	<listitem>
	  <para>The link properties can't be changed because the link is
	  currently busy. This can be caused, for instance, by an active media
	  stream (audio or video) on the link. The ioctl shouldn't be retried if
	  no other action is performed before to fix the problem.</para>
	</listitem>
      </varlistentry>
      <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>