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+<refentry id="vidioc-g-priority">
+ <refmeta>
+ <refentrytitle>ioctl VIDIOC_G_PRIORITY, VIDIOC_S_PRIORITY</refentrytitle>
+ &manvol;
+ </refmeta>
+
+ <refnamediv>
+ <refname>VIDIOC_G_PRIORITY</refname>
+ <refname>VIDIOC_S_PRIORITY</refname>
+ <refpurpose>Query or request the access priority associated with a
+file descriptor</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcprototype>
+ <funcdef>int <function>ioctl</function></funcdef>
+ <paramdef>int <parameter>fd</parameter></paramdef>
+ <paramdef>int <parameter>request</parameter></paramdef>
+ <paramdef>enum v4l2_priority *<parameter>argp</parameter></paramdef>
+ </funcprototype>
+ </funcsynopsis>
+ <funcsynopsis>
+ <funcprototype>
+ <funcdef>int <function>ioctl</function></funcdef>
+ <paramdef>int <parameter>fd</parameter></paramdef>
+ <paramdef>int <parameter>request</parameter></paramdef>
+ <paramdef>const enum v4l2_priority *<parameter>argp</parameter></paramdef>
+ </funcprototype>
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Arguments</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><parameter>fd</parameter></term>
+ <listitem>
+ <para>&fd;</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><parameter>request</parameter></term>
+ <listitem>
+ <para>VIDIOC_G_PRIORITY, VIDIOC_S_PRIORITY</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><parameter>argp</parameter></term>
+ <listitem>
+ <para>Pointer to an enum v4l2_priority type.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para>To query the current access priority
+applications call the <constant>VIDIOC_G_PRIORITY</constant> ioctl
+with a pointer to an enum v4l2_priority variable where the driver stores
+the current priority.</para>
+
+ <para>To request an access priority applications store the
+desired priority in an enum v4l2_priority variable and call
+<constant>VIDIOC_S_PRIORITY</constant> ioctl with a pointer to this
+variable.</para>
+
+ <table frame="none" pgwide="1" id="v4l2-priority">
+ <title>enum v4l2_priority</title>
+ <tgroup cols="3">
+ &cs-def;
+ <tbody valign="top">
+ <row>
+ <entry><constant>V4L2_PRIORITY_UNSET</constant></entry>
+ <entry>0</entry>
+ <entry></entry>
+ </row>
+ <row>
+ <entry><constant>V4L2_PRIORITY_BACKGROUND</constant></entry>
+ <entry>1</entry>
+ <entry>Lowest priority, usually applications running in
+background, for example monitoring VBI transmissions. A proxy
+application running in user space will be necessary if multiple
+applications want to read from a device at this priority.</entry>
+ </row>
+ <row>
+ <entry><constant>V4L2_PRIORITY_INTERACTIVE</constant></entry>
+ <entry>2</entry>
+ <entry></entry>
+ </row>
+ <row>
+ <entry><constant>V4L2_PRIORITY_DEFAULT</constant></entry>
+ <entry>2</entry>
+ <entry>Medium priority, usually applications started and
+interactively controlled by the user. For example TV viewers, Teletext
+browsers, or just "panel" applications to change the channel or video
+controls. This is the default priority unless an application requests
+another.</entry>
+ </row>
+ <row>
+ <entry><constant>V4L2_PRIORITY_RECORD</constant></entry>
+ <entry>3</entry>
+ <entry>Highest priority. Only one file descriptor can have
+this priority, it blocks any other fd from changing device properties.
+Usually applications which must not be interrupted, like video
+recording.</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+ </refsect1>
+
+ <refsect1>
+ &return-value;
+
+ <variablelist>
+ <varlistentry>
+ <term><errorcode>EINVAL</errorcode></term>
+ <listitem>
+ <para>The requested priority value is invalid, or the
+driver does not support access priorities.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><errorcode>EBUSY</errorcode></term>
+ <listitem>
+ <para>Another application already requested higher
+priority.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+</refentry>
+
+<!--
+Local Variables:
+mode: sgml
+sgml-parent-document: "v4l2.sgml"
+indent-tabs-mode: nil
+End:
+-->