Based on kernel version 3.0.4. Page generated on 2011-10-03 22:07 EST.
1 <refentry id="vidioc-g-frequency"> 2 <refmeta> 3 <refentrytitle>ioctl VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY</refentrytitle> 4 &manvol; 5 </refmeta> 6 7 <refnamediv> 8 <refname>VIDIOC_G_FREQUENCY</refname> 9 <refname>VIDIOC_S_FREQUENCY</refname> 10 <refpurpose>Get or set tuner or modulator radio 11 frequency</refpurpose> 12 </refnamediv> 13 14 <refsynopsisdiv> 15 <funcsynopsis> 16 <funcprototype> 17 <funcdef>int <function>ioctl</function></funcdef> 18 <paramdef>int <parameter>fd</parameter></paramdef> 19 <paramdef>int <parameter>request</parameter></paramdef> 20 <paramdef>struct v4l2_frequency 21 *<parameter>argp</parameter></paramdef> 22 </funcprototype> 23 </funcsynopsis> 24 <funcsynopsis> 25 <funcprototype> 26 <funcdef>int <function>ioctl</function></funcdef> 27 <paramdef>int <parameter>fd</parameter></paramdef> 28 <paramdef>int <parameter>request</parameter></paramdef> 29 <paramdef>const struct v4l2_frequency 30 *<parameter>argp</parameter></paramdef> 31 </funcprototype> 32 </funcsynopsis> 33 </refsynopsisdiv> 34 35 <refsect1> 36 <title>Arguments</title> 37 38 <variablelist> 39 <varlistentry> 40 <term><parameter>fd</parameter></term> 41 <listitem> 42 <para>&fd;</para> 43 </listitem> 44 </varlistentry> 45 <varlistentry> 46 <term><parameter>request</parameter></term> 47 <listitem> 48 <para>VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY</para> 49 </listitem> 50 </varlistentry> 51 <varlistentry> 52 <term><parameter>argp</parameter></term> 53 <listitem> 54 <para></para> 55 </listitem> 56 </varlistentry> 57 </variablelist> 58 </refsect1> 59 60 <refsect1> 61 <title>Description</title> 62 63 <para>To get the current tuner or modulator radio frequency 64 applications set the <structfield>tuner</structfield> field of a 65 &v4l2-frequency; to the respective tuner or modulator number (only 66 input devices have tuners, only output devices have modulators), zero 67 out the <structfield>reserved</structfield> array and 68 call the <constant>VIDIOC_G_FREQUENCY</constant> ioctl with a pointer 69 to this structure. The driver stores the current frequency in the 70 <structfield>frequency</structfield> field.</para> 71 72 <para>To change the current tuner or modulator radio frequency 73 applications initialize the <structfield>tuner</structfield>, 74 <structfield>type</structfield> and 75 <structfield>frequency</structfield> fields, and the 76 <structfield>reserved</structfield> array of a &v4l2-frequency; and 77 call the <constant>VIDIOC_S_FREQUENCY</constant> ioctl with a pointer 78 to this structure. When the requested frequency is not possible the 79 driver assumes the closest possible value. However 80 <constant>VIDIOC_S_FREQUENCY</constant> is a write-only ioctl, it does 81 not return the actual new frequency.</para> 82 83 <table pgwide="1" frame="none" id="v4l2-frequency"> 84 <title>struct <structname>v4l2_frequency</structname></title> 85 <tgroup cols="3"> 86 &cs-str; 87 <tbody valign="top"> 88 <row> 89 <entry>__u32</entry> 90 <entry><structfield>tuner</structfield></entry> 91 <entry>The tuner or modulator index number. This is the 92 same value as in the &v4l2-input; <structfield>tuner</structfield> 93 field and the &v4l2-tuner; <structfield>index</structfield> field, or 94 the &v4l2-output; <structfield>modulator</structfield> field and the 95 &v4l2-modulator; <structfield>index</structfield> field.</entry> 96 </row> 97 <row> 98 <entry>&v4l2-tuner-type;</entry> 99 <entry><structfield>type</structfield></entry> 100 <entry>The tuner type. This is the same value as in the 101 &v4l2-tuner; <structfield>type</structfield> field. The field is not 102 applicable to modulators, &ie; ignored by drivers.</entry> 103 </row> 104 <row> 105 <entry>__u32</entry> 106 <entry><structfield>frequency</structfield></entry> 107 <entry>Tuning frequency in units of 62.5 kHz, or if the 108 &v4l2-tuner; or &v4l2-modulator; <structfield>capabilities</structfield> flag 109 <constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5 110 Hz.</entry> 111 </row> 112 <row> 113 <entry>__u32</entry> 114 <entry><structfield>reserved</structfield>[8]</entry> 115 <entry>Reserved for future extensions. Drivers and 116 applications must set the array to zero.</entry> 117 </row> 118 </tbody> 119 </tgroup> 120 </table> 121 </refsect1> 122 123 <refsect1> 124 &return-value; 125 126 <variablelist> 127 <varlistentry> 128 <term><errorcode>EINVAL</errorcode></term> 129 <listitem> 130 <para>The <structfield>tuner</structfield> index is out of 131 bounds or the value in the <structfield>type</structfield> field is 132 wrong.</para> 133 </listitem> 134 </varlistentry> 135 </variablelist> 136 </refsect1> 137 </refentry> 138 139 <!-- 140 Local Variables: 141 mode: sgml 142 sgml-parent-document: "v4l2.sgml" 143 indent-tabs-mode: nil 144 End: 145 -->
