131 lines
3.6 KiB
XML
131 lines
3.6 KiB
XML
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<refentry id="vidioc-g-ctrl">
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<refmeta>
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<refentrytitle>ioctl VIDIOC_G_CTRL, VIDIOC_S_CTRL</refentrytitle>
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&manvol;
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</refmeta>
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<refnamediv>
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<refname>VIDIOC_G_CTRL</refname>
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<refname>VIDIOC_S_CTRL</refname>
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<refpurpose>Get or set the value of a control</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_control
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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_CTRL, VIDIOC_S_CTRL</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 value of a control applications
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initialize the <structfield>id</structfield> field of a struct
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<structname>v4l2_control</structname> and call the
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<constant>VIDIOC_G_CTRL</constant> ioctl with a pointer to this
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structure. To change the value of a control applications initialize
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the <structfield>id</structfield> and <structfield>value</structfield>
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fields of a struct <structname>v4l2_control</structname> and call the
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<constant>VIDIOC_S_CTRL</constant> ioctl.</para>
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<para>When the <structfield>id</structfield> is invalid drivers
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return an &EINVAL;. When the <structfield>value</structfield> is out
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of bounds drivers can choose to take the closest valid value or return
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an &ERANGE;, whatever seems more appropriate. However,
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<constant>VIDIOC_S_CTRL</constant> is a write-only ioctl, it does not
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return the actual new value.</para>
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<para>These ioctls work only with user controls. For other
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control classes the &VIDIOC-G-EXT-CTRLS;, &VIDIOC-S-EXT-CTRLS; or
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&VIDIOC-TRY-EXT-CTRLS; must be used.</para>
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<table pgwide="1" frame="none" id="v4l2-control">
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<title>struct <structname>v4l2_control</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>id</structfield></entry>
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<entry>Identifies the control, set by the
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application.</entry>
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</row>
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<row>
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<entry>__s32</entry>
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<entry><structfield>value</structfield></entry>
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<entry>New value or current value.</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 &v4l2-control; <structfield>id</structfield> is
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invalid.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><errorcode>ERANGE</errorcode></term>
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<listitem>
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<para>The &v4l2-control; <structfield>value</structfield>
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is out of bounds.</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>The control is temporarily not changeable, possibly
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because another applications took over control of the device function
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this control belongs to.</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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<!--
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Local Variables:
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mode: sgml
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sgml-parent-document: "v4l2.sgml"
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indent-tabs-mode: nil
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End:
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-->
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