CooCenter-System-kernel/Documentation/DocBook/media/v4l/vidioc-s-hw-freq-seek.xml

<refentry id="vidioc-s-hw-freq-seek">
  <refmeta>
    <refentrytitle>ioctl VIDIOC_S_HW_FREQ_SEEK</refentrytitle>
    &manvol;
  </refmeta>

  <refnamediv>
    <refname>VIDIOC_S_HW_FREQ_SEEK</refname>
    <refpurpose>Perform a hardware frequency seek</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_hw_freq_seek
*<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_S_HW_FREQ_SEEK</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><parameter>argp</parameter></term>
	<listitem>
	  <para></para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Description</title>

    <para>Start a hardware frequency seek from the current frequency.
To do this applications initialize the <structfield>tuner</structfield>,
<structfield>type</structfield>, <structfield>seek_upward</structfield>,
<structfield>wrap_around</structfield>, <structfield>spacing</structfield>,
<structfield>rangelow</structfield> and <structfield>rangehigh</structfield>
fields, and zero out the <structfield>reserved</structfield> array of a
&v4l2-hw-freq-seek; and call the <constant>VIDIOC_S_HW_FREQ_SEEK</constant>
ioctl with a pointer to this structure.</para>

    <para>The <structfield>rangelow</structfield> and
<structfield>rangehigh</structfield> fields can be set to a non-zero value to
tell the driver to search a specific band. If the &v4l2-tuner;
<structfield>capability</structfield> field has the
<constant>V4L2_TUNER_CAP_HWSEEK_PROG_LIM</constant> flag set, these values
must fall within one of the bands returned by &VIDIOC-ENUM-FREQ-BANDS;. If
the <constant>V4L2_TUNER_CAP_HWSEEK_PROG_LIM</constant> flag is not set,
then these values must exactly match those of one of the bands returned by
&VIDIOC-ENUM-FREQ-BANDS;. If the current frequency of the tuner does not fall
within the selected band it will be clamped to fit in the band before the
seek is started.</para>

    <para>If an error is returned, then the original frequency will
    be restored.</para>

    <para>This ioctl is supported if the <constant>V4L2_CAP_HW_FREQ_SEEK</constant> capability is set.</para>

    <para>If this ioctl is called from a non-blocking filehandle, then &EAGAIN; is
    returned and no seek takes place.</para>

    <table pgwide="1" frame="none" id="v4l2-hw-freq-seek">
      <title>struct <structname>v4l2_hw_freq_seek</structname></title>
      <tgroup cols="3">
	&cs-str;
	<tbody valign="top">
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>tuner</structfield></entry>
	    <entry>The tuner index number. This is the
same value as in the &v4l2-input; <structfield>tuner</structfield>
field and the &v4l2-tuner; <structfield>index</structfield> field.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>type</structfield></entry>
	    <entry>The tuner type. This is the same value as in the
&v4l2-tuner; <structfield>type</structfield> field. See <xref
	    linkend="v4l2-tuner-type" /></entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>seek_upward</structfield></entry>
	    <entry>If non-zero, seek upward from the current frequency, else seek downward.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>wrap_around</structfield></entry>
	    <entry>If non-zero, wrap around when at the end of the frequency range, else stop seeking.
	    The &v4l2-tuner; <structfield>capability</structfield> field will tell you what the
	    hardware supports.
	    </entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>spacing</structfield></entry>
	    <entry>If non-zero, defines the hardware seek resolution in Hz. The driver selects the nearest value that is supported by the device. If spacing is zero a reasonable default value is used.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>rangelow</structfield></entry>
	    <entry>If non-zero, the lowest tunable frequency of the band to
search in units of 62.5 kHz, or if the &v4l2-tuner;
<structfield>capability</structfield> field has the
<constant>V4L2_TUNER_CAP_LOW</constant> flag set, in units of 62.5 Hz or if the &v4l2-tuner;
<structfield>capability</structfield> field has the
<constant>V4L2_TUNER_CAP_1HZ</constant> flag set, in units of 1 Hz.
If <structfield>rangelow</structfield> is zero a reasonable default value
is used.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>rangehigh</structfield></entry>
	    <entry>If non-zero, the highest tunable frequency of the band to
search in units of 62.5 kHz, or if the &v4l2-tuner;
<structfield>capability</structfield> field has the
<constant>V4L2_TUNER_CAP_LOW</constant> flag set, in units of 62.5 Hz or if the &v4l2-tuner;
<structfield>capability</structfield> field has the
<constant>V4L2_TUNER_CAP_1HZ</constant> flag set, in units of 1 Hz.
If <structfield>rangehigh</structfield> is zero a reasonable default value
is used.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>reserved</structfield>[5]</entry>
	    <entry>Reserved for future extensions. Applications
	    must set the array to zero.</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>
  </refsect1>

  <refsect1>
    &return-value;

    <variablelist>
      <varlistentry>
	<term><errorcode>EINVAL</errorcode></term>
	<listitem>
	  <para>The <structfield>tuner</structfield> index is out of
bounds, the <structfield>wrap_around</structfield> value is not supported or
one of the values in the <structfield>type</structfield>,
<structfield>rangelow</structfield> or <structfield>rangehigh</structfield>
fields is wrong.</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><errorcode>EAGAIN</errorcode></term>
	<listitem>
	  <para>Attempted to call <constant>VIDIOC_S_HW_FREQ_SEEK</constant>
	  with the filehandle in non-blocking mode.</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><errorcode>ENODATA</errorcode></term>
	<listitem>
	  <para>The hardware seek found no channels.</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><errorcode>EBUSY</errorcode></term>
	<listitem>
	  <para>Another hardware seek is already in progress.</para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>
</refentry>