mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson
synced 2025-10-31 12:39:23 +00:00
8e080c2e6c
The V4L and DVB API's are there for a long time. however, up to now, no efforts were done to merge them to kernel DocBook. This patch adds the current versions of the specs as an unique compendium. Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
145 lines
4.1 KiB
XML
145 lines
4.1 KiB
XML
<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:
|
|
-->
|