mirror of https://gitee.com/openkylin/linux.git
185 lines
6.4 KiB
XML
185 lines
6.4 KiB
XML
<refentry id="vidioc-s-hw-freq-seek">
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<refmeta>
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<refentrytitle>ioctl VIDIOC_S_HW_FREQ_SEEK</refentrytitle>
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&manvol;
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</refmeta>
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<refnamediv>
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<refname>VIDIOC_S_HW_FREQ_SEEK</refname>
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<refpurpose>Perform a hardware frequency seek</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_hw_freq_seek
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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_S_HW_FREQ_SEEK</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>Start a hardware frequency seek from the current frequency.
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To do this applications initialize the <structfield>tuner</structfield>,
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<structfield>type</structfield>, <structfield>seek_upward</structfield>,
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<structfield>wrap_around</structfield>, <structfield>spacing</structfield>,
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<structfield>rangelow</structfield> and <structfield>rangehigh</structfield>
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fields, and zero out the <structfield>reserved</structfield> array of a
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&v4l2-hw-freq-seek; and call the <constant>VIDIOC_S_HW_FREQ_SEEK</constant>
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ioctl with a pointer to this structure.</para>
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<para>The <structfield>rangelow</structfield> and
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<structfield>rangehigh</structfield> fields can be set to a non-zero value to
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tell the driver to search a specific band. If the &v4l2-tuner;
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<structfield>capability</structfield> field has the
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<constant>V4L2_TUNER_CAP_HWSEEK_PROG_LIM</constant> flag set, these values
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must fall within one of the bands returned by &VIDIOC-ENUM-FREQ-BANDS;. If
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the <constant>V4L2_TUNER_CAP_HWSEEK_PROG_LIM</constant> flag is not set,
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then these values must exactly match those of one of the bands returned by
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&VIDIOC-ENUM-FREQ-BANDS;. If the current frequency of the tuner does not fall
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within the selected band it will be clamped to fit in the band before the
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seek is started.</para>
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<para>If an error is returned, then the original frequency will
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be restored.</para>
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<para>This ioctl is supported if the <constant>V4L2_CAP_HW_FREQ_SEEK</constant> capability is set.</para>
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<para>If this ioctl is called from a non-blocking filehandle, then &EAGAIN; is
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returned and no seek takes place.</para>
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<table pgwide="1" frame="none" id="v4l2-hw-freq-seek">
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<title>struct <structname>v4l2_hw_freq_seek</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 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.</entry>
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</row>
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<row>
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<entry>__u32</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. See <xref
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linkend="v4l2-tuner-type" /></entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>seek_upward</structfield></entry>
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<entry>If non-zero, seek upward from the current frequency, else seek downward.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>wrap_around</structfield></entry>
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<entry>If non-zero, wrap around when at the end of the frequency range, else stop seeking.
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The &v4l2-tuner; <structfield>capability</structfield> field will tell you what the
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hardware supports.
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</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>spacing</structfield></entry>
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<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>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>rangelow</structfield></entry>
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<entry>If non-zero, the lowest tunable frequency of the band to
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search in units of 62.5 kHz, or if the &v4l2-tuner;
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<structfield>capability</structfield> field has the
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<constant>V4L2_TUNER_CAP_LOW</constant> flag set, in units of 62.5 Hz.
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If <structfield>rangelow</structfield> is zero a reasonable default value
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is used.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>rangehigh</structfield></entry>
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<entry>If non-zero, the highest tunable frequency of the band to
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search in units of 62.5 kHz, or if the &v4l2-tuner;
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<structfield>capability</structfield> field has the
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<constant>V4L2_TUNER_CAP_LOW</constant> flag set, in units of 62.5 Hz.
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If <structfield>rangehigh</structfield> is zero a reasonable default value
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is used.</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>[5]</entry>
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<entry>Reserved for future extensions. Applications
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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, the <structfield>wrap_around</structfield> value is not supported or
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one of the values in the <structfield>type</structfield>,
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<structfield>rangelow</structfield> or <structfield>rangehigh</structfield>
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fields is wrong.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><errorcode>EAGAIN</errorcode></term>
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<listitem>
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<para>Attempted to call <constant>VIDIOC_S_HW_FREQ_SEEK</constant>
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with the filehandle in non-blocking mode.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><errorcode>ENODATA</errorcode></term>
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<listitem>
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<para>The hardware seek found no channels.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><errorcode>EBUSY</errorcode></term>
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<listitem>
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<para>Another hardware seek is already in progress.</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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