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Commit 55093284 authored by Guennadi Liakhovetski's avatar Guennadi Liakhovetski Committed by Mauro Carvalho Chehab
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[media] V4L: document the new VIDIOC_CREATE_BUFS and VIDIOC_PREPARE_BUF ioctl()s 

[mchehab@redhat.com: remove emacs format crap at the end of the new files]
Signed-off-by: default avatarGuennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@redhat.com>
parent 21db3e07
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Documentation/DocBook/media/v4l/compat.xml
View file @ 55093284
......@@ -2486,6 +2486,9 @@ ioctls.</para>
<listitem>
<para>Flash API. <xref linkend="flash-controls" /></para>
</listitem>
<listitem>
<para>&VIDIOC-CREATE-BUFS; and &VIDIOC-PREPARE-BUF; ioctls.</para>
</listitem>
</itemizedlist>
</section>
......
Documentation/DocBook/media/v4l/io.xml
View file @ 55093284
......@@ -927,6 +927,33 @@ ioctl is called.</entry>
Applications set or clear this flag before calling the
<constant>VIDIOC_QBUF</constant> ioctl.</entry>
</row>
<row>
<entry><constant>V4L2_BUF_FLAG_PREPARED</constant></entry>
<entry>0x0400</entry>
<entry>The buffer has been prepared for I/O and can be queued by the
application. Drivers set or clear this flag when the
<link linkend="vidioc-querybuf">VIDIOC_QUERYBUF</link>, <link
linkend="vidioc-qbuf">VIDIOC_PREPARE_BUF</link>, <link
linkend="vidioc-qbuf">VIDIOC_QBUF</link> or <link
linkend="vidioc-qbuf">VIDIOC_DQBUF</link> ioctl is called.</entry>
</row>
<row>
<entry><constant>V4L2_BUF_FLAG_NO_CACHE_INVALIDATE</constant></entry>
<entry>0x0400</entry>
<entry>Caches do not have to be invalidated for this buffer.
Typically applications shall use this flag if the data captured in the buffer
is not going to be touched by the CPU, instead the buffer will, probably, be
passed on to a DMA-capable hardware unit for further processing or output.
</entry>
</row>
<row>
<entry><constant>V4L2_BUF_FLAG_NO_CACHE_CLEAN</constant></entry>
<entry>0x0800</entry>
<entry>Caches do not have to be cleaned for this buffer.
Typically applications shall use this flag for output buffers if the data
in this buffer has not been created by the CPU but by some DMA-capable unit,
in which case caches have not been used.</entry>
</row>
</tbody>
</tgroup>
</table>
......
Documentation/DocBook/media/v4l/v4l2.xml
View file @ 55093284
......@@ -469,6 +469,7 @@ and discussions on the V4L mailing list.</revremark>
&sub-close;
&sub-ioctl;
<!-- All ioctls go here. -->
&sub-create-bufs;
&sub-cropcap;
&sub-dbg-g-chip-ident;
&sub-dbg-g-register;
......@@ -511,6 +512,7 @@ and discussions on the V4L mailing list.</revremark>
&sub-queryctrl;
&sub-query-dv-preset;
&sub-querystd;
&sub-prepare-buf;
&sub-reqbufs;
&sub-s-hw-freq-seek;
&sub-streamon;
......
Documentation/DocBook/media/v4l/vidioc-create-bufs.xml 0 → 100644
View file @ 55093284
<refentry id="vidioc-create-bufs">
<refmeta>
<refentrytitle>ioctl VIDIOC_CREATE_BUFS</refentrytitle>
&manvol;
</refmeta>
<refnamediv>
<refname>VIDIOC_CREATE_BUFS</refname>
<refpurpose>Create buffers for Memory Mapped or User Pointer I/O</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcprototype>
<funcdef>int <function>ioctl</function></funcdef>
<paramdef>int <parameter>fd</parameter></paramdef>
<paramdef>int <parameter>request</parameter></paramdef>
<paramdef>struct v4l2_create_buffers *<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_CREATE_BUFS</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>argp</parameter></term>
<listitem>
<para></para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>This ioctl is used to create buffers for <link linkend="mmap">memory
mapped</link> or <link linkend="userp">user pointer</link>
I/O. It can be used as an alternative or in addition to the
<constant>VIDIOC_REQBUFS</constant> ioctl, when a tighter control over buffers
is required. This ioctl can be called multiple times to create buffers of
different sizes.</para>
<para>To allocate device buffers applications initialize relevant fields of
the <structname>v4l2_create_buffers</structname> structure. They set the
<structfield>type</structfield> field in the
<structname>v4l2_format</structname> structure, embedded in this
structure, to the respective stream or buffer type.
<structfield>count</structfield> must be set to the number of required buffers.
<structfield>memory</structfield> specifies the required I/O method. The
<structfield>format</structfield> field shall typically be filled in using
either the <constant>VIDIOC_TRY_FMT</constant> or
<constant>VIDIOC_G_FMT</constant> ioctl(). Additionally, applications can adjust
<structfield>sizeimage</structfield> fields to fit their specific needs. The
<structfield>reserved</structfield> array must be zeroed.</para>
<para>When the ioctl is called with a pointer to this structure the driver
will attempt to allocate up to the requested number of buffers and store the
actual number allocated and the starting index in the
<structfield>count</structfield> and the <structfield>index</structfield> fields
respectively. On return <structfield>count</structfield> can be smaller than
the number requested. The driver may also increase buffer sizes if required,
however, it will not update <structfield>sizeimage</structfield> field values.
The user has to use <constant>VIDIOC_QUERYBUF</constant> to retrieve that
information.</para>
<table pgwide="1" frame="none" id="v4l2-create-buffers">
<title>struct <structname>v4l2_create_buffers</structname></title>
<tgroup cols="3">
&cs-str;
<tbody valign="top">
<row>
<entry>__u32</entry>
<entry><structfield>index</structfield></entry>
<entry>The starting buffer index, returned by the driver.</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>count</structfield></entry>
<entry>The number of buffers requested or granted.</entry>
</row>
<row>
<entry>&v4l2-memory;</entry>
<entry><structfield>memory</structfield></entry>
<entry>Applications set this field to
<constant>V4L2_MEMORY_MMAP</constant> or
<constant>V4L2_MEMORY_USERPTR</constant>.</entry>
</row>
<row>
<entry>&v4l2-format;</entry>
<entry><structfield>format</structfield></entry>
<entry>Filled in by the application, preserved by the driver.</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>reserved</structfield>[8]</entry>
<entry>A place holder for future extensions.</entry>
</row>
</tbody>
</tgroup>
</table>
</refsect1>
<refsect1>
&return-value;
<variablelist>
<varlistentry>
<term><errorcode>ENOMEM</errorcode></term>
<listitem>
<para>No memory to allocate buffers for <link linkend="mmap">memory
mapped</link> I/O.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><errorcode>EINVAL</errorcode></term>
<listitem>
<para>The buffer type (<structfield>type</structfield> field) or the
requested I/O method (<structfield>memory</structfield>) is not
supported.</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
</refentry>
Documentation/DocBook/media/v4l/vidioc-prepare-buf.xml 0 → 100644
View file @ 55093284
<refentry id="vidioc-prepare-buf">
<refmeta>
<refentrytitle>ioctl VIDIOC_PREPARE_BUF</refentrytitle>
&manvol;
</refmeta>
<refnamediv>
<refname>VIDIOC_PREPARE_BUF</refname>
<refpurpose>Prepare a buffer for I/O</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcprototype>
<funcdef>int <function>ioctl</function></funcdef>
<paramdef>int <parameter>fd</parameter></paramdef>
<paramdef>int <parameter>request</parameter></paramdef>
<paramdef>struct v4l2_buffer *<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_PREPARE_BUF</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>argp</parameter></term>
<listitem>
<para></para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>Applications can optionally call the
<constant>VIDIOC_PREPARE_BUF</constant> ioctl to pass ownership of the buffer
to the driver before actually enqueuing it, using the
<constant>VIDIOC_QBUF</constant> ioctl, and to prepare it for future I/O.
Such preparations may include cache invalidation or cleaning. Performing them
in advance saves time during the actual I/O. In case such cache operations are
not required, the application can use one of
<constant>V4L2_BUF_FLAG_NO_CACHE_INVALIDATE</constant> and
<constant>V4L2_BUF_FLAG_NO_CACHE_CLEAN</constant> flags to skip the respective
step.</para>
<para>The <structname>v4l2_buffer</structname> structure is
specified in <xref linkend="buffer" />.</para>
</refsect1>
<refsect1>
&return-value;
<variablelist>
<varlistentry>
<term><errorcode>EBUSY</errorcode></term>
<listitem>
<para>File I/O is in progress.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><errorcode>EINVAL</errorcode></term>
<listitem>
<para>The buffer <structfield>type</structfield> is not
supported, or the <structfield>index</structfield> is out of bounds,
or no buffers have been allocated yet, or the
<structfield>userptr</structfield> or
<structfield>length</structfield> are invalid.</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
</refentry>
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