Documentation/DocBook/media/v4l/vidioc-enum-freq-bands.xml

   1 <refentry id="vidioc-enum-freq-bands">
   2   <refmeta>
   3     <refentrytitle>ioctl VIDIOC_ENUM_FREQ_BANDS</refentrytitle>
   4     &manvol;
   5   </refmeta>
   6
   7   <refnamediv>
   8     <refname>VIDIOC_ENUM_FREQ_BANDS</refname>
   9     <refpurpose>Enumerate supported frequency bands</refpurpose>
  10   </refnamediv>
  11
  12   <refsynopsisdiv>
  13     <funcsynopsis>
  14       <funcprototype>
  15         <funcdef>int <function>ioctl</function></funcdef>
  16         <paramdef>int <parameter>fd</parameter></paramdef>
  17         <paramdef>int <parameter>request</parameter></paramdef>
  18         <paramdef>struct v4l2_frequency_band
  19 *<parameter>argp</parameter></paramdef>
  20       </funcprototype>
  21     </funcsynopsis>
  22   </refsynopsisdiv>
  23
  24   <refsect1>
  25     <title>Arguments</title>
  26
  27     <variablelist>
  28       <varlistentry>
  29         <term><parameter>fd</parameter></term>
  30         <listitem>
  31           <para>&fd;</para>
  32         </listitem>
  33       </varlistentry>
  34       <varlistentry>
  35         <term><parameter>request</parameter></term>
  36         <listitem>
  37           <para>VIDIOC_ENUM_FREQ_BANDS</para>
  38         </listitem>
  39       </varlistentry>
  40       <varlistentry>
  41         <term><parameter>argp</parameter></term>
  42         <listitem>
  43           <para></para>
  44         </listitem>
  45       </varlistentry>
  46     </variablelist>
  47   </refsect1>
  48
  49   <refsect1>
  50     <title>Description</title>
  51
  52     <para>Enumerates the frequency bands that a tuner or modulator supports.
  53 To do this applications initialize the <structfield>tuner</structfield>,
  54 <structfield>type</structfield> and <structfield>index</structfield> fields,
  55 and zero out the <structfield>reserved</structfield> array of a &v4l2-frequency-band; and
  56 call the <constant>VIDIOC_ENUM_FREQ_BANDS</constant> ioctl with a pointer
  57 to this structure.</para>
  58
  59     <para>This ioctl is supported if the <constant>V4L2_TUNER_CAP_FREQ_BANDS</constant> capability
  60     of the corresponding tuner/modulator is set.</para>
  61
  62     <table pgwide="1" frame="none" id="v4l2-frequency-band">
  63       <title>struct <structname>v4l2_frequency_band</structname></title>
  64       <tgroup cols="3">
  65         &cs-str;
  66         <tbody valign="top">
  67           <row>
  68             <entry>__u32</entry>
  69             <entry><structfield>tuner</structfield></entry>
  70             <entry>The tuner or modulator index number. This is the
  71 same value as in the &v4l2-input; <structfield>tuner</structfield>
  72 field and the &v4l2-tuner; <structfield>index</structfield> field, or
  73 the &v4l2-output; <structfield>modulator</structfield> field and the
  74 &v4l2-modulator; <structfield>index</structfield> field.</entry>
  75           </row>
  76           <row>
  77             <entry>__u32</entry>
  78             <entry><structfield>type</structfield></entry>
  79             <entry>The tuner type. This is the same value as in the
  80 &v4l2-tuner; <structfield>type</structfield> field. The type must be set
  81 to <constant>V4L2_TUNER_RADIO</constant> for <filename>/dev/radioX</filename>
  82 device nodes, and to <constant>V4L2_TUNER_ANALOG_TV</constant>
  83 for all others. Set this field to <constant>V4L2_TUNER_RADIO</constant> for
  84 modulators (currently only radio modulators are supported).
  85 See <xref linkend="v4l2-tuner-type" /></entry>
  86           </row>
  87           <row>
  88             <entry>__u32</entry>
  89             <entry><structfield>index</structfield></entry>
  90             <entry>Identifies the frequency band, set by the application.</entry>
  91           </row>
  92           <row>
  93             <entry>__u32</entry>
  94             <entry><structfield>capability</structfield></entry>
  95             <entry spanname="hspan">The tuner/modulator capability flags for
  96 this frequency band, see <xref linkend="tuner-capability" />. The <constant>V4L2_TUNER_CAP_LOW</constant>
  97 or <constant>V4L2_TUNER_CAP_1HZ</constant> capability must be the same for all frequency bands of the selected tuner/modulator.
  98 So either all bands have that capability set, or none of them have that capability.</entry>
  99           </row>
 100           <row>
 101             <entry>__u32</entry>
 102             <entry><structfield>rangelow</structfield></entry>
 103             <entry spanname="hspan">The lowest tunable frequency in
 104 units of 62.5 kHz, or if the <structfield>capability</structfield>
 105 flag <constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
 106 Hz, for this frequency band. A 1 Hz unit is used when the <structfield>capability</structfield> flag
 107 <constant>V4L2_TUNER_CAP_1HZ</constant> is set.</entry>
 108           </row>
 109           <row>
 110             <entry>__u32</entry>
 111             <entry><structfield>rangehigh</structfield></entry>
 112             <entry spanname="hspan">The highest tunable frequency in
 113 units of 62.5 kHz, or if the <structfield>capability</structfield>
 114 flag <constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
 115 Hz, for this frequency band. A 1 Hz unit is used when the <structfield>capability</structfield> flag
 116 <constant>V4L2_TUNER_CAP_1HZ</constant> is set.</entry>
 117           </row>
 118           <row>
 119             <entry>__u32</entry>
 120             <entry><structfield>modulation</structfield></entry>
 121             <entry spanname="hspan">The supported modulation systems of this frequency band.
 122             See <xref linkend="band-modulation" />. Note that currently only one
 123             modulation system per frequency band is supported. More work will need to
 124             be done if multiple modulation systems are possible. Contact the
 125             linux-media mailing list (&v4l-ml;) if you need that functionality.</entry>
 126           </row>
 127           <row>
 128             <entry>__u32</entry>
 129             <entry><structfield>reserved</structfield>[9]</entry>
 130             <entry>Reserved for future extensions. Applications and drivers
 131             must set the array to zero.</entry>
 132           </row>
 133         </tbody>
 134       </tgroup>
 135     </table>
 136
 137     <table pgwide="1" frame="none" id="band-modulation">
 138       <title>Band Modulation Systems</title>
 139       <tgroup cols="3">
 140         &cs-def;
 141         <tbody valign="top">
 142           <row>
 143             <entry><constant>V4L2_BAND_MODULATION_VSB</constant></entry>
 144             <entry>0x02</entry>
 145             <entry>Vestigial Sideband modulation, used for analog TV.</entry>
 146           </row>
 147           <row>
 148             <entry><constant>V4L2_BAND_MODULATION_FM</constant></entry>
 149             <entry>0x04</entry>
 150             <entry>Frequency Modulation, commonly used for analog radio.</entry>
 151           </row>
 152           <row>
 153             <entry><constant>V4L2_BAND_MODULATION_AM</constant></entry>
 154             <entry>0x08</entry>
 155             <entry>Amplitude Modulation, commonly used for analog radio.</entry>
 156           </row>
 157         </tbody>
 158       </tgroup>
 159     </table>
 160   </refsect1>
 161
 162   <refsect1>
 163     &return-value;
 164
 165     <variablelist>
 166       <varlistentry>
 167         <term><errorcode>EINVAL</errorcode></term>
 168         <listitem>
 169           <para>The <structfield>tuner</structfield> or <structfield>index</structfield>
 170 is out of bounds or the <structfield>type</structfield> field is wrong.</para>
 171         </listitem>
 172       </varlistentry>
 173     </variablelist>
 174   </refsect1>
 175 </refentry>