141 lines
4.6 KiB
XML
141 lines
4.6 KiB
XML
<refentry id="vidioc-g-frequency">
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<refmeta>
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<refentrytitle>ioctl VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY</refentrytitle>
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&manvol;
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</refmeta>
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<refnamediv>
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<refname>VIDIOC_G_FREQUENCY</refname>
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<refname>VIDIOC_S_FREQUENCY</refname>
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<refpurpose>Get or set tuner or modulator radio
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frequency</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcprototype>
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<funcdef>int <function>ioctl</function></funcdef>
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<paramdef>int <parameter>fd</parameter></paramdef>
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<paramdef>int <parameter>request</parameter></paramdef>
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<paramdef>struct v4l2_frequency
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*<parameter>argp</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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<funcsynopsis>
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<funcprototype>
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<funcdef>int <function>ioctl</function></funcdef>
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<paramdef>int <parameter>fd</parameter></paramdef>
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<paramdef>int <parameter>request</parameter></paramdef>
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<paramdef>const struct v4l2_frequency
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*<parameter>argp</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Arguments</title>
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<variablelist>
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<varlistentry>
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<term><parameter>fd</parameter></term>
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<listitem>
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<para>&fd;</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>request</parameter></term>
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<listitem>
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<para>VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>argp</parameter></term>
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<listitem>
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<para></para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Description</title>
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<para>To get the current tuner or modulator radio frequency
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applications set the <structfield>tuner</structfield> field of a
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&v4l2-frequency; to the respective tuner or modulator number (only
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input devices have tuners, only output devices have modulators), zero
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out the <structfield>reserved</structfield> array and
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call the <constant>VIDIOC_G_FREQUENCY</constant> ioctl with a pointer
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to this structure. The driver stores the current frequency in the
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<structfield>frequency</structfield> field.</para>
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<para>To change the current tuner or modulator radio frequency
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applications initialize the <structfield>tuner</structfield>,
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<structfield>type</structfield> and
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<structfield>frequency</structfield> fields, and the
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<structfield>reserved</structfield> array of a &v4l2-frequency; and
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call the <constant>VIDIOC_S_FREQUENCY</constant> ioctl with a pointer
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to this structure. When the requested frequency is not possible the
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driver assumes the closest possible value. However
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<constant>VIDIOC_S_FREQUENCY</constant> is a write-only ioctl, it does
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not return the actual new frequency.</para>
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<table pgwide="1" frame="none" id="v4l2-frequency">
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<title>struct <structname>v4l2_frequency</structname></title>
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<tgroup cols="3">
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&cs-str;
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<tbody valign="top">
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<row>
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<entry>__u32</entry>
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<entry><structfield>tuner</structfield></entry>
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<entry>The tuner or modulator index number. This is the
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same value as in the &v4l2-input; <structfield>tuner</structfield>
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field and the &v4l2-tuner; <structfield>index</structfield> field, or
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the &v4l2-output; <structfield>modulator</structfield> field and the
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&v4l2-modulator; <structfield>index</structfield> field.</entry>
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</row>
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<row>
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<entry>&v4l2-tuner-type;</entry>
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<entry><structfield>type</structfield></entry>
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<entry>The tuner type. This is the same value as in the
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&v4l2-tuner; <structfield>type</structfield> field. The type must be set
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to <constant>V4L2_TUNER_RADIO</constant> for <filename>/dev/radioX</filename>
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device nodes, and to <constant>V4L2_TUNER_ANALOG_TV</constant>
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for all others. The field is not applicable to modulators, &ie; ignored
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by drivers.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>frequency</structfield></entry>
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<entry>Tuning frequency in units of 62.5 kHz, or if the
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&v4l2-tuner; or &v4l2-modulator; <structfield>capabilities</structfield> flag
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<constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
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Hz.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>reserved</structfield>[8]</entry>
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<entry>Reserved for future extensions. Drivers and
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applications must set the array to zero.</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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</refsect1>
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<refsect1>
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&return-value;
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<variablelist>
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<varlistentry>
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<term><errorcode>EINVAL</errorcode></term>
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<listitem>
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<para>The <structfield>tuner</structfield> index is out of
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bounds or the value in the <structfield>type</structfield> field is
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wrong.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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</refentry>
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