CooCenter-System-kernel/Documentation/DocBook/media/v4l/vidioc-g-input.xml

<refentry id="vidioc-g-input">
  <refmeta>
    <refentrytitle>ioctl VIDIOC_G_INPUT, VIDIOC_S_INPUT</refentrytitle>
    &manvol;
  </refmeta>

  <refnamediv>
    <refname>VIDIOC_G_INPUT</refname>
    <refname>VIDIOC_S_INPUT</refname>
    <refpurpose>Query or select the current video input</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <funcsynopsis>
      <funcprototype>
	<funcdef>int <function>ioctl</function></funcdef>
	<paramdef>int <parameter>fd</parameter></paramdef>
	<paramdef>int <parameter>request</parameter></paramdef>
	<paramdef>int *<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>VIDIOC_G_INPUT, VIDIOC_S_INPUT</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><parameter>argp</parameter></term>
	<listitem>
	  <para></para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Description</title>

    <para>To query the current video input applications call the
<constant>VIDIOC_G_INPUT</constant> ioctl with a pointer to an integer
where the driver stores the number of the input, as in the
&v4l2-input; <structfield>index</structfield> field. This ioctl will
fail only when there are no video inputs, returning
<errorcode>EINVAL</errorcode>.</para>

    <para>To select a video input applications store the number of the
desired input in an integer and call the
<constant>VIDIOC_S_INPUT</constant> ioctl with a pointer to this
integer. Side effects are possible. For example inputs may support
different video standards, so the driver may implicitly switch the
current standard. Because of these possible side effects applications
must select an input before querying or negotiating any other parameters.</para>

    <para>Information about video inputs is available using the
&VIDIOC-ENUMINPUT; ioctl.</para>
  </refsect1>

  <refsect1>
    &return-value;

    <variablelist>
      <varlistentry>
	<term><errorcode>EINVAL</errorcode></term>
	<listitem>
	  <para>The number of the video input is out of bounds.</para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>
</refentry>