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

   1 <refentry id="vidioc-s-hw-freq-seek">
   2   <refmeta>
   3     <refentrytitle>ioctl VIDIOC_S_HW_FREQ_SEEK</refentrytitle>
   4     &manvol;
   5   </refmeta>
   6
   7   <refnamediv>
   8     <refname>VIDIOC_S_HW_FREQ_SEEK</refname>
   9     <refpurpose>Perform a hardware frequency seek</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_hw_freq_seek
  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_S_HW_FREQ_SEEK</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>Start a hardware frequency seek from the current frequency.
  53 To do this applications initialize the <structfield>tuner</structfield>,
  54 <structfield>type</structfield>, <structfield>seek_upward</structfield>,
  55 <structfield>wrap_around</structfield>, <structfield>spacing</structfield>,
  56 <structfield>rangelow</structfield> and <structfield>rangehigh</structfield>
  57 fields, and zero out the <structfield>reserved</structfield> array of a
  58 &v4l2-hw-freq-seek; and call the <constant>VIDIOC_S_HW_FREQ_SEEK</constant>
  59 ioctl with a pointer to this structure.</para>
  60
  61     <para>The <structfield>rangelow</structfield> and
  62 <structfield>rangehigh</structfield> fields can be set to a non-zero value to
  63 tell the driver to search a specific band. If the &v4l2-tuner;
  64 <structfield>capability</structfield> field has the
  65 <constant>V4L2_TUNER_CAP_HWSEEK_PROG_LIM</constant> flag set, these values
  66 must fall within one of the bands returned by &VIDIOC-ENUM-FREQ-BANDS;. If
  67 the <constant>V4L2_TUNER_CAP_HWSEEK_PROG_LIM</constant> flag is not set,
  68 then these values must exactly match those of one of the bands returned by
  69 &VIDIOC-ENUM-FREQ-BANDS;. If the current frequency of the tuner does not fall
  70 within the selected band it will be clamped to fit in the band before the
  71 seek is started.</para>
  72
  73     <para>If an error is returned, then the original frequency will
  74     be restored.</para>
  75
  76     <para>This ioctl is supported if the <constant>V4L2_CAP_HW_FREQ_SEEK</constant> capability is set.</para>
  77
  78     <para>If this ioctl is called from a non-blocking filehandle, then &EAGAIN; is
  79     returned and no seek takes place.</para>
  80
  81     <table pgwide="1" frame="none" id="v4l2-hw-freq-seek">
  82       <title>struct <structname>v4l2_hw_freq_seek</structname></title>
  83       <tgroup cols="3">
  84         &cs-str;
  85         <tbody valign="top">
  86           <row>
  87             <entry>__u32</entry>
  88             <entry><structfield>tuner</structfield></entry>
  89             <entry>The tuner index number. This is the
  90 same value as in the &v4l2-input; <structfield>tuner</structfield>
  91 field and the &v4l2-tuner; <structfield>index</structfield> field.</entry>
  92           </row>
  93           <row>
  94             <entry>__u32</entry>
  95             <entry><structfield>type</structfield></entry>
  96             <entry>The tuner type. This is the same value as in the
  97 &v4l2-tuner; <structfield>type</structfield> field. See <xref
  98             linkend="v4l2-tuner-type" /></entry>
  99           </row>
 100           <row>
 101             <entry>__u32</entry>
 102             <entry><structfield>seek_upward</structfield></entry>
 103             <entry>If non-zero, seek upward from the current frequency, else seek downward.</entry>
 104           </row>
 105           <row>
 106             <entry>__u32</entry>
 107             <entry><structfield>wrap_around</structfield></entry>
 108             <entry>If non-zero, wrap around when at the end of the frequency range, else stop seeking.
 109             The &v4l2-tuner; <structfield>capability</structfield> field will tell you what the
 110             hardware supports.
 111             </entry>
 112           </row>
 113           <row>
 114             <entry>__u32</entry>
 115             <entry><structfield>spacing</structfield></entry>
 116             <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>
 117           </row>
 118           <row>
 119             <entry>__u32</entry>
 120             <entry><structfield>rangelow</structfield></entry>
 121             <entry>If non-zero, the lowest tunable frequency of the band to
 122 search in units of 62.5 kHz, or if the &v4l2-tuner;
 123 <structfield>capability</structfield> field has the
 124 <constant>V4L2_TUNER_CAP_LOW</constant> flag set, in units of 62.5 Hz.
 125 If <structfield>rangelow</structfield> is zero a reasonable default value
 126 is used.</entry>
 127           </row>
 128           <row>
 129             <entry>__u32</entry>
 130             <entry><structfield>rangehigh</structfield></entry>
 131             <entry>If non-zero, the highest tunable frequency of the band to
 132 search in units of 62.5 kHz, or if the &v4l2-tuner;
 133 <structfield>capability</structfield> field has the
 134 <constant>V4L2_TUNER_CAP_LOW</constant> flag set, in units of 62.5 Hz.
 135 If <structfield>rangehigh</structfield> is zero a reasonable default value
 136 is used.</entry>
 137           </row>
 138           <row>
 139             <entry>__u32</entry>
 140             <entry><structfield>reserved</structfield>[5]</entry>
 141             <entry>Reserved for future extensions. Applications
 142             must set the array to zero.</entry>
 143           </row>
 144         </tbody>
 145       </tgroup>
 146     </table>
 147   </refsect1>
 148
 149   <refsect1>
 150     &return-value;
 151
 152     <variablelist>
 153       <varlistentry>
 154         <term><errorcode>EINVAL</errorcode></term>
 155         <listitem>
 156           <para>The <structfield>tuner</structfield> index is out of
 157 bounds, the <structfield>wrap_around</structfield> value is not supported or
 158 one of the values in the <structfield>type</structfield>,
 159 <structfield>rangelow</structfield> or <structfield>rangehigh</structfield>
 160 fields is wrong.</para>
 161         </listitem>
 162       </varlistentry>
 163       <varlistentry>
 164         <term><errorcode>EAGAIN</errorcode></term>
 165         <listitem>
 166           <para>Attempted to call <constant>VIDIOC_S_HW_FREQ_SEEK</constant>
 167           with the filehandle in non-blocking mode.</para>
 168         </listitem>
 169       </varlistentry>
 170       <varlistentry>
 171         <term><errorcode>ENODATA</errorcode></term>
 172         <listitem>
 173           <para>The hardware seek found no channels.</para>
 174         </listitem>
 175       </varlistentry>
 176       <varlistentry>
 177         <term><errorcode>EBUSY</errorcode></term>
 178         <listitem>
 179           <para>Another hardware seek is already in progress.</para>
 180         </listitem>
 181       </varlistentry>
 182     </variablelist>
 183   </refsect1>
 184 </refentry>