Based on kernel version 4.7.2. Page generated on 2016-08-22 22:45 EST.
1 <refentry id="vidioc-g-priority"> 2 <refmeta> 3 <refentrytitle>ioctl VIDIOC_G_PRIORITY, VIDIOC_S_PRIORITY</refentrytitle> 4 &manvol; 5 </refmeta> 6 7 <refnamediv> 8 <refname>VIDIOC_G_PRIORITY</refname> 9 <refname>VIDIOC_S_PRIORITY</refname> 10 <refpurpose>Query or request the access priority associated with a 11 file descriptor</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>enum v4l2_priority *<parameter>argp</parameter></paramdef> 21 </funcprototype> 22 </funcsynopsis> 23 <funcsynopsis> 24 <funcprototype> 25 <funcdef>int <function>ioctl</function></funcdef> 26 <paramdef>int <parameter>fd</parameter></paramdef> 27 <paramdef>int <parameter>request</parameter></paramdef> 28 <paramdef>const enum v4l2_priority *<parameter>argp</parameter></paramdef> 29 </funcprototype> 30 </funcsynopsis> 31 </refsynopsisdiv> 32 33 <refsect1> 34 <title>Arguments</title> 35 36 <variablelist> 37 <varlistentry> 38 <term><parameter>fd</parameter></term> 39 <listitem> 40 <para>&fd;</para> 41 </listitem> 42 </varlistentry> 43 <varlistentry> 44 <term><parameter>request</parameter></term> 45 <listitem> 46 <para>VIDIOC_G_PRIORITY, VIDIOC_S_PRIORITY</para> 47 </listitem> 48 </varlistentry> 49 <varlistentry> 50 <term><parameter>argp</parameter></term> 51 <listitem> 52 <para>Pointer to an enum v4l2_priority type.</para> 53 </listitem> 54 </varlistentry> 55 </variablelist> 56 </refsect1> 57 58 <refsect1> 59 <title>Description</title> 60 61 <para>To query the current access priority 62 applications call the <constant>VIDIOC_G_PRIORITY</constant> ioctl 63 with a pointer to an enum v4l2_priority variable where the driver stores 64 the current priority.</para> 65 66 <para>To request an access priority applications store the 67 desired priority in an enum v4l2_priority variable and call 68 <constant>VIDIOC_S_PRIORITY</constant> ioctl with a pointer to this 69 variable.</para> 70 71 <table frame="none" pgwide="1" id="v4l2-priority"> 72 <title>enum v4l2_priority</title> 73 <tgroup cols="3"> 74 &cs-def; 75 <tbody valign="top"> 76 <row> 77 <entry><constant>V4L2_PRIORITY_UNSET</constant></entry> 78 <entry>0</entry> 79 <entry></entry> 80 </row> 81 <row> 82 <entry><constant>V4L2_PRIORITY_BACKGROUND</constant></entry> 83 <entry>1</entry> 84 <entry>Lowest priority, usually applications running in 85 background, for example monitoring VBI transmissions. A proxy 86 application running in user space will be necessary if multiple 87 applications want to read from a device at this priority.</entry> 88 </row> 89 <row> 90 <entry><constant>V4L2_PRIORITY_INTERACTIVE</constant></entry> 91 <entry>2</entry> 92 <entry></entry> 93 </row> 94 <row> 95 <entry><constant>V4L2_PRIORITY_DEFAULT</constant></entry> 96 <entry>2</entry> 97 <entry>Medium priority, usually applications started and 98 interactively controlled by the user. For example TV viewers, Teletext 99 browsers, or just "panel" applications to change the channel or video 100 controls. This is the default priority unless an application requests 101 another.</entry> 102 </row> 103 <row> 104 <entry><constant>V4L2_PRIORITY_RECORD</constant></entry> 105 <entry>3</entry> 106 <entry>Highest priority. Only one file descriptor can have 107 this priority, it blocks any other fd from changing device properties. 108 Usually applications which must not be interrupted, like video 109 recording.</entry> 110 </row> 111 </tbody> 112 </tgroup> 113 </table> 114 </refsect1> 115 116 <refsect1> 117 &return-value; 118 119 <variablelist> 120 <varlistentry> 121 <term><errorcode>EINVAL</errorcode></term> 122 <listitem> 123 <para>The requested priority value is invalid.</para> 124 </listitem> 125 </varlistentry> 126 <varlistentry> 127 <term><errorcode>EBUSY</errorcode></term> 128 <listitem> 129 <para>Another application already requested higher 130 priority.</para> 131 </listitem> 132 </varlistentry> 133 </variablelist> 134 </refsect1> 135 </refentry>
