Documentation/DocBook/v4l/media-ioc-setup-link.xml

   1 <refentry id="media-ioc-setup-link">
   2   <refmeta>
   3     <refentrytitle>ioctl MEDIA_IOC_SETUP_LINK</refentrytitle>
   4     &manvol;
   5   </refmeta>
   6
   7   <refnamediv>
   8     <refname>MEDIA_IOC_SETUP_LINK</refname>
   9     <refpurpose>Modify the properties of a link</refpurpose>
  10   </refnamediv>
  11
  12   <refsynopsisdiv>
  13     <funcsynopsis>
  14       <funcprototype>
  15         <funcdef>int <function>ioctl</function></funcdef>
  16         <paramdef>int <parameter>fd</parameter></paramdef>
  17         <paramdef>int <parameter>request</parameter></paramdef>
  18         <paramdef>struct media_link_desc *<parameter>argp</parameter></paramdef>
  19       </funcprototype>
  20     </funcsynopsis>
  21   </refsynopsisdiv>
  22
  23   <refsect1>
  24     <title>Arguments</title>
  25
  26     <variablelist>
  27       <varlistentry>
  28         <term><parameter>fd</parameter></term>
  29         <listitem>
  30           <para>File descriptor returned by
  31           <link linkend='media-func-open'><function>open()</function></link>.</para>
  32         </listitem>
  33       </varlistentry>
  34       <varlistentry>
  35         <term><parameter>request</parameter></term>
  36         <listitem>
  37           <para>MEDIA_IOC_ENUM_LINKS</para>
  38         </listitem>
  39       </varlistentry>
  40       <varlistentry>
  41         <term><parameter>argp</parameter></term>
  42         <listitem>
  43           <para></para>
  44         </listitem>
  45       </varlistentry>
  46     </variablelist>
  47   </refsect1>
  48
  49   <refsect1>
  50     <title>Description</title>
  51
  52     <para>To change link properties applications fill a &media-link-desc; with
  53     link identification information (source and sink pad) and the new requested
  54     link flags. They then call the MEDIA_IOC_SETUP_LINK ioctl with a pointer to
  55     that structure.</para>
  56     <para>The only configurable property is the <constant>ENABLED</constant>
  57     link flag to enable/disable a link. Links marked with the
  58     <constant>IMMUTABLE</constant> link flag can not be enabled or disabled.
  59     </para>
  60     <para>Link configuration has no side effect on other links. If an enabled
  61     link at the sink pad prevents the link from being enabled, the driver
  62     returns with an &EBUSY;.</para>
  63     <para>Only links marked with the <constant>DYNAMIC</constant> link flag can
  64     be enabled/disabled while streaming media data. Attempting to enable or
  65     disable a streaming non-dynamic link will return an &EBUSY;.</para>
  66     <para>If the specified link can't be found the driver returns with an
  67     &EINVAL;.</para>
  68   </refsect1>
  69
  70   <refsect1>
  71     &return-value;
  72
  73     <variablelist>
  74       <varlistentry>
  75         <term><errorcode>EBUSY</errorcode></term>
  76         <listitem>
  77           <para>The link properties can't be changed because the link is
  78           currently busy. This can be caused, for instance, by an active media
  79           stream (audio or video) on the link. The ioctl shouldn't be retried if
  80           no other action is performed before to fix the problem.</para>
  81         </listitem>
  82       </varlistentry>
  83       <varlistentry>
  84         <term><errorcode>EINVAL</errorcode></term>
  85         <listitem>
  86           <para>The &media-link-desc; references a non-existing link, or the
  87           link is immutable and an attempt to modify its configuration was made.
  88           </para>
  89         </listitem>
  90       </varlistentry>
  91     </variablelist>
  92   </refsect1>
  93 </refentry>