OpenCloudOS-Kernel/Documentation/DocBook/v4l/vidioc-query-dv-preset.xml

<refentry id="vidioc-query-dv-preset">
  <refmeta>
    <refentrytitle>ioctl VIDIOC_QUERY_DV_PRESET</refentrytitle>
    &manvol;
  </refmeta>

  <refnamediv>
    <refname>VIDIOC_QUERY_DV_PRESET</refname>
    <refpurpose>Sense the DV preset received by the current
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>struct v4l2_dv_preset *<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_QUERY_DV_PRESET</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><parameter>argp</parameter></term>
	<listitem>
	  <para></para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Description</title>

    <para>The hardware may be able to detect the current DV preset
automatically, similar to sensing the video standard. To do so, applications
call <constant> VIDIOC_QUERY_DV_PRESET</constant> with a pointer to a
&v4l2-dv-preset; type. Once the hardware detects a preset, that preset is
returned in the preset field of &v4l2-dv-preset;. If the preset could not be
detected because there was no signal, or the signal was unreliable, or the
signal did not map to a supported preset, then the value V4L2_DV_INVALID is
returned.</para>
  </refsect1>

  <refsect1>
    &return-value;
    <variablelist>
      <varlistentry>
	<term><errorcode>EINVAL</errorcode></term>
	<listitem>
	  <para>This ioctl is not supported.</para>
	</listitem>
    </varlistentry>
      <varlistentry>
	<term><errorcode>EBUSY</errorcode></term>
	<listitem>
	  <para>The device is busy and therefore can not sense the preset</para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>
</refentry>

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