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Diffstat (limited to 'kernel/Documentation/DocBook/media/v4l/vidioc-g-priority.xml')
| -rw-r--r-- | kernel/Documentation/DocBook/media/v4l/vidioc-g-priority.xml | 135 |
1 files changed, 135 insertions, 0 deletions
diff --git a/kernel/Documentation/DocBook/media/v4l/vidioc-g-priority.xml b/kernel/Documentation/DocBook/media/v4l/vidioc-g-priority.xml new file mode 100644 index 000000000..6a81b4fe9 --- /dev/null +++ b/kernel/Documentation/DocBook/media/v4l/vidioc-g-priority.xml @@ -0,0 +1,135 @@ +<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> |