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-<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>
-
- <note>
- <title>Experimental</title>
- <para>This is an <link linkend="experimental"> experimental </link>
- interface and may change in the future.</para>
- </note>
-
- <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>__u32</entry>
- <entry><structfield>memory</structfield></entry>
- <entry>Applications set this field to
-<constant>V4L2_MEMORY_MMAP</constant> or
-<constant>V4L2_MEMORY_USERPTR</constant>. See <xref linkend="v4l2-memory"
-/></entry>
- </row>
- <row>
- <entry>struct&nbsp;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>