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<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 only the
<constant>V4L2_TUNER_CAP_LOW</constant>,
<constant>V4L2_TUNER_CAP_STEREO</constant> and
<constant>V4L2_TUNER_CAP_RDS</constant> flags can be set.</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.</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.</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=
|