forked from Minki/linux
c6401af669
This removes comment tags intended for emacs configuration from 67 files in the Media API DocBook. Such comments are not really helpful and violate the coding style rules. Signed-off-by: Sylwester Nawrocki <snjw23@gmail.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
136 lines
4.0 KiB
XML
136 lines
4.0 KiB
XML
<refentry id="vidioc-g-priority">
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<refmeta>
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<refentrytitle>ioctl VIDIOC_G_PRIORITY, VIDIOC_S_PRIORITY</refentrytitle>
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&manvol;
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</refmeta>
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<refnamediv>
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<refname>VIDIOC_G_PRIORITY</refname>
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<refname>VIDIOC_S_PRIORITY</refname>
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<refpurpose>Query or request the access priority associated with a
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file descriptor</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcprototype>
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<funcdef>int <function>ioctl</function></funcdef>
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<paramdef>int <parameter>fd</parameter></paramdef>
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<paramdef>int <parameter>request</parameter></paramdef>
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<paramdef>enum v4l2_priority *<parameter>argp</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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<funcsynopsis>
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<funcprototype>
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<funcdef>int <function>ioctl</function></funcdef>
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<paramdef>int <parameter>fd</parameter></paramdef>
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<paramdef>int <parameter>request</parameter></paramdef>
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<paramdef>const enum v4l2_priority *<parameter>argp</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Arguments</title>
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<variablelist>
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<varlistentry>
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<term><parameter>fd</parameter></term>
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<listitem>
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<para>&fd;</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>request</parameter></term>
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<listitem>
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<para>VIDIOC_G_PRIORITY, VIDIOC_S_PRIORITY</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>argp</parameter></term>
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<listitem>
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<para>Pointer to an enum v4l2_priority type.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Description</title>
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<para>To query the current access priority
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applications call the <constant>VIDIOC_G_PRIORITY</constant> ioctl
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with a pointer to an enum v4l2_priority variable where the driver stores
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the current priority.</para>
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<para>To request an access priority applications store the
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desired priority in an enum v4l2_priority variable and call
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<constant>VIDIOC_S_PRIORITY</constant> ioctl with a pointer to this
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variable.</para>
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<table frame="none" pgwide="1" id="v4l2-priority">
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<title>enum v4l2_priority</title>
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<tgroup cols="3">
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&cs-def;
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<tbody valign="top">
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<row>
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<entry><constant>V4L2_PRIORITY_UNSET</constant></entry>
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<entry>0</entry>
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<entry></entry>
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</row>
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<row>
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<entry><constant>V4L2_PRIORITY_BACKGROUND</constant></entry>
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<entry>1</entry>
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<entry>Lowest priority, usually applications running in
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background, for example monitoring VBI transmissions. A proxy
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application running in user space will be necessary if multiple
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applications want to read from a device at this priority.</entry>
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</row>
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<row>
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<entry><constant>V4L2_PRIORITY_INTERACTIVE</constant></entry>
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<entry>2</entry>
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<entry></entry>
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</row>
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<row>
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<entry><constant>V4L2_PRIORITY_DEFAULT</constant></entry>
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<entry>2</entry>
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<entry>Medium priority, usually applications started and
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interactively controlled by the user. For example TV viewers, Teletext
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browsers, or just "panel" applications to change the channel or video
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controls. This is the default priority unless an application requests
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another.</entry>
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</row>
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<row>
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<entry><constant>V4L2_PRIORITY_RECORD</constant></entry>
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<entry>3</entry>
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<entry>Highest priority. Only one file descriptor can have
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this priority, it blocks any other fd from changing device properties.
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Usually applications which must not be interrupted, like video
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recording.</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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</refsect1>
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<refsect1>
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&return-value;
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<variablelist>
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<varlistentry>
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<term><errorcode>EINVAL</errorcode></term>
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<listitem>
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<para>The requested priority value is invalid.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><errorcode>EBUSY</errorcode></term>
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<listitem>
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<para>Another application already requested higher
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priority.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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</refentry>
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