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authorLinus Torvalds <torvalds@linux-foundation.org>2011-07-30 00:08:53 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-07-30 00:08:53 -0700
commit664a41b8a91bf78a01a751e15175e0008977685a (patch)
treed9dc15c83400ad2dfb430ff27ae3e7fdc9395856 /Documentation/DocBook/media/v4l/vidioc-g-priority.xml
parent983236b5741e557451f3ed4ec5ebf1f62a5b2c15 (diff)
parentee2ce3a0b43d14d792d34cf88e7bc2091096744b (diff)
Merge branch 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-2.6
* 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-2.6: (430 commits) [media] ir-mce_kbd-decoder: include module.h for its facilities [media] ov5642: include module.h for its facilities [media] em28xx: Fix DVB-C maxsize for em2884 [media] tda18271c2dd: Fix saw filter configuration for DVB-C @6MHz [media] v4l: mt9v032: Fix Bayer pattern [media] V4L: mt9m111: rewrite set_pixfmt [media] V4L: mt9m111: fix missing return value check mt9m111_reg_clear [media] V4L: initial driver for ov5642 CMOS sensor [media] V4L: sh_mobile_ceu_camera: fix Oops when USERPTR mapping fails [media] V4L: soc-camera: remove soc-camera bus and devices on it [media] V4L: soc-camera: un-export the soc-camera bus [media] V4L: sh_mobile_csi2: switch away from using the soc-camera bus notifier [media] V4L: add media bus configuration subdev operations [media] V4L: soc-camera: group struct field initialisations together [media] V4L: soc-camera: remove now unused soc-camera specific PM hooks [media] V4L: pxa-camera: switch to using standard PM hooks [media] NetUP Dual DVB-T/C CI RF: force card hardware revision by module param [media] Don't OOPS if videobuf_dvb_get_frontend return NULL [media] NetUP Dual DVB-T/C CI RF: load firmware according card revision [media] omap3isp: Support configurable HS/VS polarities ... Fix up conflicts: - arch/arm/mach-omap2/board-rx51-peripherals.c: cleanup regulator supply definitions in mach-omap2 vs OMAP3: RX-51: define vdds_csib regulator supply - drivers/staging/tm6000/tm6000-alsa.c (trivial)
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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.</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:
+-->