Documentation/DocBook/media/v4l/vidioc-g-tuner.xml - linux - Git at Google

 <refentry id="vidioc-g-tuner">
   <refmeta>
     <refentrytitle>ioctl VIDIOC_G_TUNER, VIDIOC_S_TUNER</refentrytitle>
     &manvol;
   </refmeta>

   <refnamediv>
     <refname>VIDIOC_G_TUNER</refname>
     <refname>VIDIOC_S_TUNER</refname>
     <refpurpose>Get or set tuner attributes</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_tuner
 *<parameter>argp</parameter></paramdef>
       </funcprototype>
     </funcsynopsis>
     <funcsynopsis>
       <funcprototype>
 	<funcdef>int <function>ioctl</function></funcdef>
 	<paramdef>int <parameter>fd</parameter></paramdef>
 	<paramdef>int <parameter>request</parameter></paramdef>
 	<paramdef>const struct v4l2_tuner
 *<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_TUNER, VIDIOC_S_TUNER</para>
 	</listitem>
       </varlistentry>
       <varlistentry>
 	<term><parameter>argp</parameter></term>
 	<listitem>
 	  <para></para>
 	</listitem>
       </varlistentry>
     </variablelist>
   </refsect1>

   <refsect1>
     <title>Description</title>

     <para>To query the attributes of a tuner applications initialize the
 <structfield>index</structfield> field and zero out the
 <structfield>reserved</structfield> array of a &v4l2-tuner; and call the
 <constant>VIDIOC_G_TUNER</constant> ioctl with a pointer to this
 structure. Drivers fill the rest of the structure or return an
 &EINVAL; when the index is out of bounds. To enumerate all tuners
 applications shall begin at index zero, incrementing by one until the
 driver returns <errorcode>EINVAL</errorcode>.</para>

     <para>Tuners have two writable properties, the audio mode and
 the radio frequency. To change the audio mode, applications initialize
 the <structfield>index</structfield>,
 <structfield>audmode</structfield> and
 <structfield>reserved</structfield> fields and call the
 <constant>VIDIOC_S_TUNER</constant> ioctl. This will
 <emphasis>not</emphasis> change the current tuner, which is determined
 by the current video input. Drivers may choose a different audio mode
 if the requested mode is invalid or unsupported. Since this is a
 <!-- FIXME -->write-only ioctl, it does not return the actually
 selected audio mode.</para>

     <para>To change the radio frequency the &VIDIOC-S-FREQUENCY; ioctl
 is available.</para>

     <table pgwide="1" frame="none" id="v4l2-tuner">
       <title>struct <structname>v4l2_tuner</structname></title>
       <tgroup cols="3">
 	<colspec colname="c1" colwidth="1*" />
 	<colspec colname="c2" colwidth="1*" />
 	<colspec colname="c3" colwidth="1*" />
 	<colspec colname="c4" colwidth="1*" />
 	<spanspec spanname="hspan" namest="c3" nameend="c4" />
 	<tbody valign="top">
 	  <row>
 	    <entry>__u32</entry>
 	    <entry><structfield>index</structfield></entry>
 	    <entry spanname="hspan">Identifies the tuner, set by the
 application.</entry>
 	  </row>
 	  <row>
 	    <entry>__u8</entry>
 	    <entry><structfield>name</structfield>[32]</entry>
 	    <entry spanname="hspan"><para>Name of the tuner, a
 NUL-terminated ASCII string. This information is intended for the
 user.<!-- FIXME Video inputs already have a name, the purpose of this
 field is not quite clear.--></para></entry>
 	  </row>
 	  <row>
 	    <entry>__u32</entry>
 	    <entry><structfield>type</structfield></entry>
 	    <entry spanname="hspan">Type of the tuner, see <xref
 		linkend="v4l2-tuner-type" />.</entry>
 	  </row>
 	  <row>
 	    <entry>__u32</entry>
 	    <entry><structfield>capability</structfield></entry>
 	    <entry spanname="hspan"><para>Tuner capability flags, see
 <xref linkend="tuner-capability" />. Audio flags indicate the ability
 to decode audio subprograms. They will <emphasis>not</emphasis>
 change, for example with the current video standard.</para><para>When
 the structure refers to a radio tuner the
 <constant>V4L2_TUNER_CAP_LANG1</constant>,
 <constant>V4L2_TUNER_CAP_LANG2</constant> and
 <constant>V4L2_TUNER_CAP_NORM</constant> flags can't be used.</para>
 <para>If multiple frequency bands are supported, then
 <structfield>capability</structfield> is the union of all
 <structfield>capability</structfield> fields of each &v4l2-frequency-band;.
 </para></entry>
 	  </row>
 	  <row>
 	    <entry>__u32</entry>
 	    <entry><structfield>rangelow</structfield></entry>
 	    <entry spanname="hspan">The lowest tunable frequency in
 units of 62.5 kHz, or if the <structfield>capability</structfield>
 flag <constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
 Hz. If multiple frequency bands are supported, then
 <structfield>rangelow</structfield> is the lowest frequency
 of all the frequency bands.</entry>
 	  </row>
 	  <row>
 	    <entry>__u32</entry>
 	    <entry><structfield>rangehigh</structfield></entry>
 	    <entry spanname="hspan">The highest tunable frequency in
 units of 62.5 kHz, or if the <structfield>capability</structfield>
 flag <constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
 Hz. If multiple frequency bands are supported, then
 <structfield>rangehigh</structfield> is the highest frequency
 of all the frequency bands.</entry>
 	  </row>
 	  <row>
 	    <entry>__u32</entry>
 	    <entry><structfield>rxsubchans</structfield></entry>
 	    <entry spanname="hspan"><para>Some tuners or audio
 decoders can determine the received audio subprograms by analyzing
 audio carriers, pilot tones or other indicators. To pass this
 information drivers set flags defined in <xref
 		  linkend="tuner-rxsubchans" /> in this field. For
 example:</para></entry>
 	  </row>
 	  <row>
 	    <entry></entry>
 	    <entry></entry>
 	    <entry><constant>V4L2_TUNER_SUB_MONO</constant></entry>
 	    <entry>receiving mono audio</entry>
 	  </row>
 	  <row>
 	    <entry></entry>
 	    <entry></entry>
 	    <entry><constant>STEREO | SAP</constant></entry>
 	    <entry>receiving stereo audio and a secondary audio
 program</entry>
 	  </row>
 	  <row>
 	    <entry></entry>
 	    <entry></entry>
 	    <entry><constant>MONO | STEREO</constant></entry>
 	    <entry>receiving mono or stereo audio, the hardware cannot
 distinguish</entry>
 	  </row>
 	  <row>
 	    <entry></entry>
 	    <entry></entry>
 	    <entry><constant>LANG1 | LANG2</constant></entry>
 	    <entry>receiving bilingual audio</entry>
 	  </row>
 	  <row>
 	    <entry></entry>
 	    <entry></entry>
 	    <entry><constant>MONO | STEREO | LANG1 | LANG2</constant></entry>
 	    <entry>receiving mono, stereo or bilingual
 audio</entry>
 	  </row>
 	  <row>
 	    <entry></entry>
 	    <entry></entry>
 	    <entry spanname="hspan"><para>When the
 <constant>V4L2_TUNER_CAP_STEREO</constant>,
 <constant>_LANG1</constant>, <constant>_LANG2</constant> or
 <constant>_SAP</constant> flag is cleared in the
 <structfield>capability</structfield> field, the corresponding
 <constant>V4L2_TUNER_SUB_</constant> flag must not be set
 here.</para><para>This field is valid only if this is the tuner of the
 current video input, or when the structure refers to a radio
 tuner.</para></entry>
 	  </row>
 	  <row>
 	    <entry>__u32</entry>
 	    <entry><structfield>audmode</structfield></entry>
 	    <entry spanname="hspan"><para>The selected audio mode, see
 <xref linkend="tuner-audmode" /> for valid values. The audio mode does
 not affect audio subprogram detection, and like a <link
 linkend="control">control</link> it does not automatically change
 unless the requested mode is invalid or unsupported. See <xref
 		  linkend="tuner-matrix" /> for possible results when
 the selected and received audio programs do not
 match.</para><para>Currently this is the only field of struct
 <structname>v4l2_tuner</structname> applications can
 change.</para></entry>
 	  </row>
 	  <row>
 	    <entry>__u32</entry>
 	    <entry><structfield>signal</structfield></entry>
 	    <entry spanname="hspan">The signal strength if known, ranging
 from 0 to 65535. Higher values indicate a better signal.</entry>
 	  </row>
 	  <row>
 	    <entry>__s32</entry>
 	    <entry><structfield>afc</structfield></entry>
 	    <entry spanname="hspan">Automatic frequency control: When the
 <structfield>afc</structfield> value is negative, the frequency is too
 low, when positive too high.<!-- FIXME need example what to do when it never
 settles at zero, &ie; range is what? --></entry>
 	  </row>
 	  <row>
 	    <entry>__u32</entry>
 	    <entry><structfield>reserved</structfield>[4]</entry>
 	    <entry spanname="hspan">Reserved for future extensions. Drivers and
 applications must set the array to zero.</entry>
 	  </row>
 	</tbody>
       </tgroup>
     </table>

     <table pgwide="1" frame="none" id="v4l2-tuner-type">
       <title>enum v4l2_tuner_type</title>
       <tgroup cols="3">
 	&cs-def;
 	<tbody valign="top">
 	  <row>
 	    <entry><constant>V4L2_TUNER_RADIO</constant></entry>
 	    <entry>1</entry>
 	    <entry></entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_TUNER_ANALOG_TV</constant></entry>
 	    <entry>2</entry>
 	    <entry></entry>
 	  </row>
 	</tbody>
       </tgroup>
     </table>

     <table pgwide="1" frame="none" id="tuner-capability">
       <title>Tuner and Modulator Capability Flags</title>
       <tgroup cols="3">
 	&cs-def;
 	<tbody valign="top">
 	  <row>
 	    <entry><constant>V4L2_TUNER_CAP_LOW</constant></entry>
 	    <entry>0x0001</entry>
 	    <entry>When set, tuning frequencies are expressed in units of
 62.5&nbsp;Hz, otherwise in units of 62.5&nbsp;kHz.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_TUNER_CAP_NORM</constant></entry>
 	    <entry>0x0002</entry>
 	    <entry>This is a multi-standard tuner; the video standard
 can or must be switched. (B/G PAL tuners for example are typically not
       considered multi-standard because the video standard is automatically
       determined from the frequency band.) The set of supported video
       standards is available from the &v4l2-input; pointing to this tuner,
       see the description of ioctl &VIDIOC-ENUMINPUT; for details. Only
       <constant>V4L2_TUNER_ANALOG_TV</constant> tuners can have this capability.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_TUNER_CAP_HWSEEK_BOUNDED</constant></entry>
 	    <entry>0x0004</entry>
 	    <entry>If set, then this tuner supports the hardware seek functionality
 	    where the seek stops when it reaches the end of the frequency range.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_TUNER_CAP_HWSEEK_WRAP</constant></entry>
 	    <entry>0x0008</entry>
 	    <entry>If set, then this tuner supports the hardware seek functionality
 	    where the seek wraps around when it reaches the end of the frequency range.</entry>
 	  </row>
 	  <row>
 	<entry><constant>V4L2_TUNER_CAP_STEREO</constant></entry>
 	<entry>0x0010</entry>
 	<entry>Stereo audio reception is supported.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_TUNER_CAP_LANG1</constant></entry>
 	    <entry>0x0040</entry>
 	    <entry>Reception of the primary language of a bilingual
 audio program is supported. Bilingual audio is a feature of
 two-channel systems, transmitting the primary language monaural on the
 main audio carrier and a secondary language monaural on a second
 carrier. Only
       <constant>V4L2_TUNER_ANALOG_TV</constant> tuners can have this capability.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_TUNER_CAP_LANG2</constant></entry>
 	    <entry>0x0020</entry>
 	    <entry>Reception of the secondary language of a bilingual
 audio program is supported. Only
       <constant>V4L2_TUNER_ANALOG_TV</constant> tuners can have this capability.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_TUNER_CAP_SAP</constant></entry>
 	    <entry>0x0020</entry>
 	    <entry><para>Reception of a secondary audio program is
 supported. This is a feature of the BTSC system which accompanies the
 NTSC video standard. Two audio carriers are available for mono or
 stereo transmissions of a primary language, and an independent third
 carrier for a monaural secondary language. Only
       <constant>V4L2_TUNER_ANALOG_TV</constant> tuners can have this capability.</para><para>Note the
 <constant>V4L2_TUNER_CAP_LANG2</constant> and
 <constant>V4L2_TUNER_CAP_SAP</constant> flags are synonyms.
 <constant>V4L2_TUNER_CAP_SAP</constant> applies when the tuner
 supports the <constant>V4L2_STD_NTSC_M</constant> video
 standard.</para><!-- FIXME what if PAL+NTSC and Bi but not SAP? --></entry>
 	  </row>
 	  <row>
 	<entry><constant>V4L2_TUNER_CAP_RDS</constant></entry>
 	<entry>0x0080</entry>
 	<entry>RDS capture is supported. This capability is only valid for
 radio tuners.</entry>
 	  </row>
 	  <row>
 	<entry><constant>V4L2_TUNER_CAP_RDS_BLOCK_IO</constant></entry>
 	<entry>0x0100</entry>
 	<entry>The RDS data is passed as unparsed RDS blocks.</entry>
 	  </row>
 	  <row>
 	<entry><constant>V4L2_TUNER_CAP_RDS_CONTROLS</constant></entry>
 	<entry>0x0200</entry>
 	<entry>The RDS data is parsed by the hardware and set via controls.</entry>
 	  </row>
 	  <row>
 	<entry><constant>V4L2_TUNER_CAP_FREQ_BANDS</constant></entry>
 	<entry>0x0400</entry>
 	<entry>The &VIDIOC-ENUM-FREQ-BANDS; ioctl can be used to enumerate
 	the available frequency bands.</entry>
 	  </row>
 	</tbody>
       </tgroup>
     </table>

     <table pgwide="1" frame="none" id="tuner-rxsubchans">
       <title>Tuner Audio Reception Flags</title>
       <tgroup cols="3">
 	&cs-def;
 	<tbody valign="top">
 	  <row>
 	    <entry><constant>V4L2_TUNER_SUB_MONO</constant></entry>
 	    <entry>0x0001</entry>
 	    <entry>The tuner receives a mono audio signal.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_TUNER_SUB_STEREO</constant></entry>
 	    <entry>0x0002</entry>
 	    <entry>The tuner receives a stereo audio signal.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_TUNER_SUB_LANG1</constant></entry>
 	    <entry>0x0008</entry>
 	    <entry>The tuner receives the primary language of a
 bilingual audio signal. Drivers must clear this flag when the current
 video standard is <constant>V4L2_STD_NTSC_M</constant>.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_TUNER_SUB_LANG2</constant></entry>
 	    <entry>0x0004</entry>
 	    <entry>The tuner receives the secondary language of a
 bilingual audio signal (or a second audio program).</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_TUNER_SUB_SAP</constant></entry>
 	    <entry>0x0004</entry>
 	    <entry>The tuner receives a Second Audio Program. Note the
 <constant>V4L2_TUNER_SUB_LANG2</constant> and
 <constant>V4L2_TUNER_SUB_SAP</constant> flags are synonyms. The
 <constant>V4L2_TUNER_SUB_SAP</constant> flag applies when the
 current video standard is <constant>V4L2_STD_NTSC_M</constant>.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_TUNER_SUB_RDS</constant></entry>
 	    <entry>0x0010</entry>
 	    <entry>The tuner receives an RDS channel.</entry>
 	  </row>
 	</tbody>
       </tgroup>
     </table>

     <table pgwide="1" frame="none" id="tuner-audmode">
       <title>Tuner Audio Modes</title>
       <tgroup cols="3">
 	&cs-def;
 	<tbody valign="top">
 	  <row>
 	    <entry><constant>V4L2_TUNER_MODE_MONO</constant></entry>
 	    <entry>0</entry>
 	    <entry>Play mono audio. When the tuner receives a stereo
 signal this a down-mix of the left and right channel. When the tuner
 receives a bilingual or SAP signal this mode selects the primary
 language.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_TUNER_MODE_STEREO</constant></entry>
 	    <entry>1</entry>
 	    <entry><para>Play stereo audio. When the tuner receives
 bilingual audio it may play different languages on the left and right
 channel or the primary language is played on both channels.</para><para>Playing
 different languages in this mode is
 deprecated. New drivers should do this only in
 <constant>MODE_LANG1_LANG2</constant>.</para><para>When the tuner
 receives no stereo signal or does not support stereo reception the
 driver shall fall back to <constant>MODE_MONO</constant>.</para></entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_TUNER_MODE_LANG1</constant></entry>
 	    <entry>3</entry>
 	    <entry>Play the primary language, mono or stereo. Only
 <constant>V4L2_TUNER_ANALOG_TV</constant> tuners support this
 mode.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_TUNER_MODE_LANG2</constant></entry>
 	    <entry>2</entry>
 	    <entry>Play the secondary language, mono. When the tuner
 receives no bilingual audio or SAP, or their reception is not
 supported the driver shall fall back to mono or stereo mode. Only
 <constant>V4L2_TUNER_ANALOG_TV</constant> tuners support this
 mode.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_TUNER_MODE_SAP</constant></entry>
 	    <entry>2</entry>
 	    <entry>Play the Second Audio Program. When the tuner
 receives no bilingual audio or SAP, or their reception is not
 supported the driver shall fall back to mono or stereo mode. Only
 <constant>V4L2_TUNER_ANALOG_TV</constant> tuners support this mode.
 Note the <constant>V4L2_TUNER_MODE_LANG2</constant> and
 <constant>V4L2_TUNER_MODE_SAP</constant> are synonyms.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_TUNER_MODE_LANG1_LANG2</constant></entry>
 	    <entry>4</entry>
 	    <entry>Play the primary language on the left channel, the
 secondary language on the right channel. When the tuner receives no
 bilingual audio or SAP, it shall fall back to
 <constant>MODE_LANG1</constant> or <constant>MODE_MONO</constant>.
 Only <constant>V4L2_TUNER_ANALOG_TV</constant> tuners support this
 mode.</entry>
 	  </row>
 	</tbody>
       </tgroup>
     </table>

     <table pgwide="1" frame="all" id="tuner-matrix">
       <title>Tuner Audio Matrix</title>
       <tgroup cols="6" align="center">
 	<colspec align="left" />
 	<colspec colname="c2" colwidth="1*" />
 	<colspec colwidth="1*" />
 	<colspec colwidth="1*" />
 	<colspec colnum="6" colname="c6" colwidth="1*" />
 	<spanspec namest="c2" nameend="c6" spanname="hspan" align="center" />
 	<thead>
 	  <row>
 	    <entry></entry>
 	    <entry spanname="hspan">Selected
 <constant>V4L2_TUNER_MODE_</constant></entry>
 	  </row>
 	  <row>
 	    <entry>Received <constant>V4L2_TUNER_SUB_</constant></entry>
 	    <entry><constant>MONO</constant></entry>
 	    <entry><constant>STEREO</constant></entry>
 	    <entry><constant>LANG1</constant></entry>
 	    <entry><constant>LANG2 = SAP</constant></entry>
 	    <entry><constant>LANG1_LANG2</constant><footnote><para>This
 mode has been added in Linux 2.6.17 and may not be supported by older
 drivers.</para></footnote></entry>
 	  </row>
 	</thead>
 	<tbody valign="top">
 	  <row>
 	    <entry><constant>MONO</constant></entry>
 	    <entry>Mono</entry>
 	    <entry>Mono/Mono</entry>
 	    <entry>Mono</entry>
 	    <entry>Mono</entry>
 	    <entry>Mono/Mono</entry>
 	  </row>
 	  <row>
 	    <entry><constant>MONO | SAP</constant></entry>
 	    <entry>Mono</entry>
 	    <entry>Mono/Mono</entry>
 	    <entry>Mono</entry>
 	    <entry>SAP</entry>
 	    <entry>Mono/SAP (preferred) or Mono/Mono</entry>
 	  </row>
 	  <row>
 	    <entry><constant>STEREO</constant></entry>
 	    <entry>L+R</entry>
 	    <entry>L/R</entry>
 	    <entry>Stereo L/R (preferred) or Mono L+R</entry>
 	    <entry>Stereo L/R (preferred) or Mono L+R</entry>
 	    <entry>L/R (preferred) or L+R/L+R</entry>
 	  </row>
 	  <row>
 	    <entry><constant>STEREO | SAP</constant></entry>
 	    <entry>L+R</entry>
 	    <entry>L/R</entry>
 	    <entry>Stereo L/R (preferred) or Mono L+R</entry>
 	    <entry>SAP</entry>
 	    <entry>L+R/SAP (preferred) or L/R or L+R/L+R</entry>
 	  </row>
 	  <row>
 	    <entry><constant>LANG1 | LANG2</constant></entry>
 	    <entry>Language&nbsp;1</entry>
 	    <entry>Lang1/Lang2 (deprecated<footnote><para>Playback of
 both languages in <constant>MODE_STEREO</constant> is deprecated. In
 the future drivers should produce only the primary language in this
 mode. Applications should request
 <constant>MODE_LANG1_LANG2</constant> to record both languages or a
 stereo signal.</para></footnote>) or
 Lang1/Lang1</entry>
 	    <entry>Language&nbsp;1</entry>
 	    <entry>Language&nbsp;2</entry>
 	    <entry>Lang1/Lang2 (preferred) or Lang1/Lang1</entry>
 	  </row>
 	</tbody>
       </tgroup>
     </table>
   </refsect1>

   <refsect1>
     &return-value;

     <variablelist>
       <varlistentry>
 	<term><errorcode>EINVAL</errorcode></term>
 	<listitem>
 	  <para>The &v4l2-tuner; <structfield>index</structfield> is
 out of bounds.</para>
 	</listitem>
       </varlistentry>
     </variablelist>
   </refsect1>
 </refentry>
	<refentry id="vidioc-g-tuner">
	<refmeta>
	<refentrytitle>ioctl VIDIOC_G_TUNER, VIDIOC_S_TUNER</refentrytitle>
	&manvol;
	</refmeta>

	<refnamediv>
	<refname>VIDIOC_G_TUNER</refname>
	<refname>VIDIOC_S_TUNER</refname>
	<refpurpose>Get or set tuner attributes</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_tuner
	*<parameter>argp</parameter></paramdef>
	</funcprototype>
	</funcsynopsis>
	<funcsynopsis>
	<funcprototype>
	<funcdef>int <function>ioctl</function></funcdef>
	<paramdef>int <parameter>fd</parameter></paramdef>
	<paramdef>int <parameter>request</parameter></paramdef>
	<paramdef>const struct v4l2_tuner
	*<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_TUNER, VIDIOC_S_TUNER</para>
	</listitem>
	</varlistentry>
	<varlistentry>
	<term><parameter>argp</parameter></term>
	<listitem>
	<para></para>
	</listitem>
	</varlistentry>
	</variablelist>
	</refsect1>

	<refsect1>
	<title>Description</title>

	<para>To query the attributes of a tuner applications initialize the
	<structfield>index</structfield> field and zero out the
	<structfield>reserved</structfield> array of a &v4l2-tuner; and call the
	<constant>VIDIOC_G_TUNER</constant> ioctl with a pointer to this
	structure. Drivers fill the rest of the structure or return an
	&EINVAL; when the index is out of bounds. To enumerate all tuners
	applications shall begin at index zero, incrementing by one until the
	driver returns <errorcode>EINVAL</errorcode>.</para>

	<para>Tuners have two writable properties, the audio mode and
	the radio frequency. To change the audio mode, applications initialize
	the <structfield>index</structfield>,
	<structfield>audmode</structfield> and
	<structfield>reserved</structfield> fields and call the
	<constant>VIDIOC_S_TUNER</constant> ioctl. This will
	<emphasis>not</emphasis> change the current tuner, which is determined
	by the current video input. Drivers may choose a different audio mode
	if the requested mode is invalid or unsupported. Since this is a
	<!-- FIXME -->write-only ioctl, it does not return the actually
	selected audio mode.</para>

	<para>To change the radio frequency the &VIDIOC-S-FREQUENCY; ioctl
	is available.</para>

	<table pgwide="1" frame="none" id="v4l2-tuner">
	<title>struct <structname>v4l2_tuner</structname></title>
	<tgroup cols="3">
	<colspec colname="c1" colwidth="1*" />
	<colspec colname="c2" colwidth="1*" />
	<colspec colname="c3" colwidth="1*" />
	<colspec colname="c4" colwidth="1*" />
	<spanspec spanname="hspan" namest="c3" nameend="c4" />
	<tbody valign="top">
	<row>
	<entry>__u32</entry>
	<entry><structfield>index</structfield></entry>
	<entry spanname="hspan">Identifies the tuner, set by the
	application.</entry>
	</row>
	<row>
	<entry>__u8</entry>
	<entry><structfield>name</structfield>[32]</entry>
	<entry spanname="hspan"><para>Name of the tuner, a
	NUL-terminated ASCII string. This information is intended for the
	user.<!-- FIXME Video inputs already have a name, the purpose of this
	field is not quite clear.--></para></entry>
	</row>
	<row>
	<entry>__u32</entry>
	<entry><structfield>type</structfield></entry>
	<entry spanname="hspan">Type of the tuner, see <xref
	linkend="v4l2-tuner-type" />.</entry>
	</row>
	<row>
	<entry>__u32</entry>
	<entry><structfield>capability</structfield></entry>
	<entry spanname="hspan"><para>Tuner capability flags, see
	<xref linkend="tuner-capability" />. Audio flags indicate the ability
	to decode audio subprograms. They will <emphasis>not</emphasis>
	change, for example with the current video standard.</para><para>When
	the structure refers to a radio tuner the
	<constant>V4L2_TUNER_CAP_LANG1</constant>,
	<constant>V4L2_TUNER_CAP_LANG2</constant> and
	<constant>V4L2_TUNER_CAP_NORM</constant> flags can't be used.</para>
	<para>If multiple frequency bands are supported, then
	<structfield>capability</structfield> is the union of all
	<structfield>capability</structfield> fields of each &v4l2-frequency-band;.
	</para></entry>
	</row>
	<row>
	<entry>__u32</entry>
	<entry><structfield>rangelow</structfield></entry>
	<entry spanname="hspan">The lowest tunable frequency in
	units of 62.5 kHz, or if the <structfield>capability</structfield>
	flag <constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
	Hz. If multiple frequency bands are supported, then
	<structfield>rangelow</structfield> is the lowest frequency
	of all the frequency bands.</entry>
	</row>
	<row>
	<entry>__u32</entry>
	<entry><structfield>rangehigh</structfield></entry>
	<entry spanname="hspan">The highest tunable frequency in
	units of 62.5 kHz, or if the <structfield>capability</structfield>
	flag <constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
	Hz. If multiple frequency bands are supported, then
	<structfield>rangehigh</structfield> is the highest frequency
	of all the frequency bands.</entry>
	</row>
	<row>
	<entry>__u32</entry>
	<entry><structfield>rxsubchans</structfield></entry>
	<entry spanname="hspan"><para>Some tuners or audio
	decoders can determine the received audio subprograms by analyzing
	audio carriers, pilot tones or other indicators. To pass this
	information drivers set flags defined in <xref
	linkend="tuner-rxsubchans" /> in this field. For
	example:</para></entry>
	</row>
	<row>
	<entry></entry>
	<entry></entry>
	<entry><constant>V4L2_TUNER_SUB_MONO</constant></entry>
	<entry>receiving mono audio</entry>
	</row>
	<row>
	<entry></entry>
	<entry></entry>
	<entry><constant>STEREO \| SAP</constant></entry>
	<entry>receiving stereo audio and a secondary audio
	program</entry>
	</row>
	<row>
	<entry></entry>
	<entry></entry>
	<entry><constant>MONO \| STEREO</constant></entry>
	<entry>receiving mono or stereo audio, the hardware cannot
	distinguish</entry>
	</row>
	<row>
	<entry></entry>
	<entry></entry>
	<entry><constant>LANG1 \| LANG2</constant></entry>
	<entry>receiving bilingual audio</entry>
	</row>
	<row>
	<entry></entry>
	<entry></entry>
	<entry><constant>MONO \| STEREO \| LANG1 \| LANG2</constant></entry>
	<entry>receiving mono, stereo or bilingual
	audio</entry>
	</row>
	<row>
	<entry></entry>
	<entry></entry>
	<entry spanname="hspan"><para>When the
	<constant>V4L2_TUNER_CAP_STEREO</constant>,
	<constant>_LANG1</constant>, <constant>_LANG2</constant> or
	<constant>_SAP</constant> flag is cleared in the
	<structfield>capability</structfield> field, the corresponding
	<constant>V4L2_TUNER_SUB_</constant> flag must not be set
	here.</para><para>This field is valid only if this is the tuner of the
	current video input, or when the structure refers to a radio
	tuner.</para></entry>
	</row>
	<row>
	<entry>__u32</entry>
	<entry><structfield>audmode</structfield></entry>
	<entry spanname="hspan"><para>The selected audio mode, see
	<xref linkend="tuner-audmode" /> for valid values. The audio mode does
	not affect audio subprogram detection, and like a <link
	linkend="control">control</link> it does not automatically change
	unless the requested mode is invalid or unsupported. See <xref
	linkend="tuner-matrix" /> for possible results when
	the selected and received audio programs do not
	match.</para><para>Currently this is the only field of struct
	<structname>v4l2_tuner</structname> applications can
	change.</para></entry>
	</row>
	<row>
	<entry>__u32</entry>
	<entry><structfield>signal</structfield></entry>
	<entry spanname="hspan">The signal strength if known, ranging
	from 0 to 65535. Higher values indicate a better signal.</entry>
	</row>
	<row>
	<entry>__s32</entry>
	<entry><structfield>afc</structfield></entry>
	<entry spanname="hspan">Automatic frequency control: When the
	<structfield>afc</structfield> value is negative, the frequency is too
	low, when positive too high.<!-- FIXME need example what to do when it never
	settles at zero, &ie; range is what? --></entry>
	</row>
	<row>
	<entry>__u32</entry>
	<entry><structfield>reserved</structfield>[4]</entry>
	<entry spanname="hspan">Reserved for future extensions. Drivers and
	applications must set the array to zero.</entry>
	</row>
	</tbody>
	</tgroup>
	</table>

	<table pgwide="1" frame="none" id="v4l2-tuner-type">
	<title>enum v4l2_tuner_type</title>
	<tgroup cols="3">
	&cs-def;
	<tbody valign="top">
	<row>
	<entry><constant>V4L2_TUNER_RADIO</constant></entry>
	<entry>1</entry>
	<entry></entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_ANALOG_TV</constant></entry>
	<entry>2</entry>
	<entry></entry>
	</row>
	</tbody>
	</tgroup>
	</table>

	<table pgwide="1" frame="none" id="tuner-capability">
	<title>Tuner and Modulator Capability Flags</title>
	<tgroup cols="3">
	&cs-def;
	<tbody valign="top">
	<row>
	<entry><constant>V4L2_TUNER_CAP_LOW</constant></entry>
	<entry>0x0001</entry>
	<entry>When set, tuning frequencies are expressed in units of
	62.5 Hz, otherwise in units of 62.5 kHz.</entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_CAP_NORM</constant></entry>
	<entry>0x0002</entry>
	<entry>This is a multi-standard tuner; the video standard
	can or must be switched. (B/G PAL tuners for example are typically not
	considered multi-standard because the video standard is automatically
	determined from the frequency band.) The set of supported video
	standards is available from the &v4l2-input; pointing to this tuner,
	see the description of ioctl &VIDIOC-ENUMINPUT; for details. Only
	<constant>V4L2_TUNER_ANALOG_TV</constant> tuners can have this capability.</entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_CAP_HWSEEK_BOUNDED</constant></entry>
	<entry>0x0004</entry>
	<entry>If set, then this tuner supports the hardware seek functionality
	where the seek stops when it reaches the end of the frequency range.</entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_CAP_HWSEEK_WRAP</constant></entry>
	<entry>0x0008</entry>
	<entry>If set, then this tuner supports the hardware seek functionality
	where the seek wraps around when it reaches the end of the frequency range.</entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_CAP_STEREO</constant></entry>
	<entry>0x0010</entry>
	<entry>Stereo audio reception is supported.</entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_CAP_LANG1</constant></entry>
	<entry>0x0040</entry>
	<entry>Reception of the primary language of a bilingual
	audio program is supported. Bilingual audio is a feature of
	two-channel systems, transmitting the primary language monaural on the
	main audio carrier and a secondary language monaural on a second
	carrier. Only
	<constant>V4L2_TUNER_ANALOG_TV</constant> tuners can have this capability.</entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_CAP_LANG2</constant></entry>
	<entry>0x0020</entry>
	<entry>Reception of the secondary language of a bilingual
	audio program is supported. Only
	<constant>V4L2_TUNER_ANALOG_TV</constant> tuners can have this capability.</entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_CAP_SAP</constant></entry>
	<entry>0x0020</entry>
	<entry><para>Reception of a secondary audio program is
	supported. This is a feature of the BTSC system which accompanies the
	NTSC video standard. Two audio carriers are available for mono or
	stereo transmissions of a primary language, and an independent third
	carrier for a monaural secondary language. Only
	<constant>V4L2_TUNER_ANALOG_TV</constant> tuners can have this capability.</para><para>Note the
	<constant>V4L2_TUNER_CAP_LANG2</constant> and
	<constant>V4L2_TUNER_CAP_SAP</constant> flags are synonyms.
	<constant>V4L2_TUNER_CAP_SAP</constant> applies when the tuner
	supports the <constant>V4L2_STD_NTSC_M</constant> video
	standard.</para><!-- FIXME what if PAL+NTSC and Bi but not SAP? --></entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_CAP_RDS</constant></entry>
	<entry>0x0080</entry>
	<entry>RDS capture is supported. This capability is only valid for
	radio tuners.</entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_CAP_RDS_BLOCK_IO</constant></entry>
	<entry>0x0100</entry>
	<entry>The RDS data is passed as unparsed RDS blocks.</entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_CAP_RDS_CONTROLS</constant></entry>
	<entry>0x0200</entry>
	<entry>The RDS data is parsed by the hardware and set via controls.</entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_CAP_FREQ_BANDS</constant></entry>
	<entry>0x0400</entry>
	<entry>The &VIDIOC-ENUM-FREQ-BANDS; ioctl can be used to enumerate
	the available frequency bands.</entry>
	</row>
	</tbody>
	</tgroup>
	</table>

	<table pgwide="1" frame="none" id="tuner-rxsubchans">
	<title>Tuner Audio Reception Flags</title>
	<tgroup cols="3">
	&cs-def;
	<tbody valign="top">
	<row>
	<entry><constant>V4L2_TUNER_SUB_MONO</constant></entry>
	<entry>0x0001</entry>
	<entry>The tuner receives a mono audio signal.</entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_SUB_STEREO</constant></entry>
	<entry>0x0002</entry>
	<entry>The tuner receives a stereo audio signal.</entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_SUB_LANG1</constant></entry>
	<entry>0x0008</entry>
	<entry>The tuner receives the primary language of a
	bilingual audio signal. Drivers must clear this flag when the current
	video standard is <constant>V4L2_STD_NTSC_M</constant>.</entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_SUB_LANG2</constant></entry>
	<entry>0x0004</entry>
	<entry>The tuner receives the secondary language of a
	bilingual audio signal (or a second audio program).</entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_SUB_SAP</constant></entry>
	<entry>0x0004</entry>
	<entry>The tuner receives a Second Audio Program. Note the
	<constant>V4L2_TUNER_SUB_LANG2</constant> and
	<constant>V4L2_TUNER_SUB_SAP</constant> flags are synonyms. The
	<constant>V4L2_TUNER_SUB_SAP</constant> flag applies when the
	current video standard is <constant>V4L2_STD_NTSC_M</constant>.</entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_SUB_RDS</constant></entry>
	<entry>0x0010</entry>
	<entry>The tuner receives an RDS channel.</entry>
	</row>
	</tbody>
	</tgroup>
	</table>

	<table pgwide="1" frame="none" id="tuner-audmode">
	<title>Tuner Audio Modes</title>
	<tgroup cols="3">
	&cs-def;
	<tbody valign="top">
	<row>
	<entry><constant>V4L2_TUNER_MODE_MONO</constant></entry>
	<entry>0</entry>
	<entry>Play mono audio. When the tuner receives a stereo
	signal this a down-mix of the left and right channel. When the tuner
	receives a bilingual or SAP signal this mode selects the primary
	language.</entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_MODE_STEREO</constant></entry>
	<entry>1</entry>
	<entry><para>Play stereo audio. When the tuner receives
	bilingual audio it may play different languages on the left and right
	channel or the primary language is played on both channels.</para><para>Playing
	different languages in this mode is
	deprecated. New drivers should do this only in
	<constant>MODE_LANG1_LANG2</constant>.</para><para>When the tuner
	receives no stereo signal or does not support stereo reception the
	driver shall fall back to <constant>MODE_MONO</constant>.</para></entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_MODE_LANG1</constant></entry>
	<entry>3</entry>
	<entry>Play the primary language, mono or stereo. Only
	<constant>V4L2_TUNER_ANALOG_TV</constant> tuners support this
	mode.</entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_MODE_LANG2</constant></entry>
	<entry>2</entry>
	<entry>Play the secondary language, mono. When the tuner
	receives no bilingual audio or SAP, or their reception is not
	supported the driver shall fall back to mono or stereo mode. Only
	<constant>V4L2_TUNER_ANALOG_TV</constant> tuners support this
	mode.</entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_MODE_SAP</constant></entry>
	<entry>2</entry>
	<entry>Play the Second Audio Program. When the tuner
	receives no bilingual audio or SAP, or their reception is not
	supported the driver shall fall back to mono or stereo mode. Only
	<constant>V4L2_TUNER_ANALOG_TV</constant> tuners support this mode.
	Note the <constant>V4L2_TUNER_MODE_LANG2</constant> and
	<constant>V4L2_TUNER_MODE_SAP</constant> are synonyms.</entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_MODE_LANG1_LANG2</constant></entry>
	<entry>4</entry>
	<entry>Play the primary language on the left channel, the
	secondary language on the right channel. When the tuner receives no
	bilingual audio or SAP, it shall fall back to
	<constant>MODE_LANG1</constant> or <constant>MODE_MONO</constant>.
	Only <constant>V4L2_TUNER_ANALOG_TV</constant> tuners support this
	mode.</entry>
	</row>
	</tbody>
	</tgroup>
	</table>

	<table pgwide="1" frame="all" id="tuner-matrix">
	<title>Tuner Audio Matrix</title>
	<tgroup cols="6" align="center">
	<colspec align="left" />
	<colspec colname="c2" colwidth="1*" />
	<colspec colwidth="1*" />
	<colspec colwidth="1*" />
	<colspec colnum="6" colname="c6" colwidth="1*" />
	<spanspec namest="c2" nameend="c6" spanname="hspan" align="center" />
	<thead>
	<row>
	<entry></entry>
	<entry spanname="hspan">Selected
	<constant>V4L2_TUNER_MODE_</constant></entry>
	</row>
	<row>
	<entry>Received <constant>V4L2_TUNER_SUB_</constant></entry>
	<entry><constant>MONO</constant></entry>
	<entry><constant>STEREO</constant></entry>
	<entry><constant>LANG1</constant></entry>
	<entry><constant>LANG2 = SAP</constant></entry>
	<entry><constant>LANG1_LANG2</constant><footnote><para>This
	mode has been added in Linux 2.6.17 and may not be supported by older
	drivers.</para></footnote></entry>
	</row>
	</thead>
	<tbody valign="top">
	<row>
	<entry><constant>MONO</constant></entry>
	<entry>Mono</entry>
	<entry>Mono/Mono</entry>
	<entry>Mono</entry>
	<entry>Mono</entry>
	<entry>Mono/Mono</entry>
	</row>
	<row>
	<entry><constant>MONO \| SAP</constant></entry>
	<entry>Mono</entry>
	<entry>Mono/Mono</entry>
	<entry>Mono</entry>
	<entry>SAP</entry>
	<entry>Mono/SAP (preferred) or Mono/Mono</entry>
	</row>
	<row>
	<entry><constant>STEREO</constant></entry>
	<entry>L+R</entry>
	<entry>L/R</entry>
	<entry>Stereo L/R (preferred) or Mono L+R</entry>
	<entry>Stereo L/R (preferred) or Mono L+R</entry>
	<entry>L/R (preferred) or L+R/L+R</entry>
	</row>
	<row>
	<entry><constant>STEREO \| SAP</constant></entry>
	<entry>L+R</entry>
	<entry>L/R</entry>
	<entry>Stereo L/R (preferred) or Mono L+R</entry>
	<entry>SAP</entry>
	<entry>L+R/SAP (preferred) or L/R or L+R/L+R</entry>
	</row>
	<row>
	<entry><constant>LANG1 \| LANG2</constant></entry>
	<entry>Language 1</entry>
	<entry>Lang1/Lang2 (deprecated<footnote><para>Playback of
	both languages in <constant>MODE_STEREO</constant> is deprecated. In
	the future drivers should produce only the primary language in this
	mode. Applications should request
	<constant>MODE_LANG1_LANG2</constant> to record both languages or a
	stereo signal.</para></footnote>) or
	Lang1/Lang1</entry>
	<entry>Language 1</entry>
	<entry>Language 2</entry>
	<entry>Lang1/Lang2 (preferred) or Lang1/Lang1</entry>
	</row>
	</tbody>
	</tgroup>
	</table>
	</refsect1>

	<refsect1>
	&return-value;

	<variablelist>
	<varlistentry>
	<term><errorcode>EINVAL</errorcode></term>
	<listitem>
	<para>The &v4l2-tuner; <structfield>index</structfield> is
	out of bounds.</para>
	</listitem>
	</varlistentry>
	</variablelist>
	</refsect1>
	</refentry>