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- <refentry id="vidioc-expbuf">
- <refmeta>
- <refentrytitle>ioctl VIDIOC_EXPBUF</refentrytitle>
- &manvol;
- </refmeta>
- <refnamediv>
- <refname>VIDIOC_EXPBUF</refname>
- <refpurpose>Export a buffer as a DMABUF 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>struct v4l2_exportbuffer *<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_EXPBUF</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 an extension to the <link linkend="mmap">memory
- mapping</link> I/O method, therefore it is available only for
- <constant>V4L2_MEMORY_MMAP</constant> buffers. It can be used to export a
- buffer as a DMABUF file at any time after buffers have been allocated with the
- &VIDIOC-REQBUFS; ioctl.</para>
- <para> To export a buffer, applications fill &v4l2-exportbuffer;. The
- <structfield>type</structfield> field is set to the same buffer type as was
- previously used with &v4l2-requestbuffers; <structfield>type</structfield>.
- Applications must also set the <structfield>index</structfield> field. Valid
- index numbers range from zero to the number of buffers allocated with
- &VIDIOC-REQBUFS; (&v4l2-requestbuffers; <structfield>count</structfield>)
- minus one. For the multi-planar API, applications set the <structfield>plane</structfield>
- field to the index of the plane to be exported. Valid planes
- range from zero to the maximal number of valid planes for the currently active
- format. For the single-planar API, applications must set <structfield>plane</structfield>
- to zero. Additional flags may be posted in the <structfield>flags</structfield>
- field. Refer to a manual for open() for details.
- Currently only O_CLOEXEC, O_RDONLY, O_WRONLY, and O_RDWR are supported. All
- other fields must be set to zero.
- In the case of multi-planar API, every plane is exported separately using
- multiple <constant>VIDIOC_EXPBUF</constant> calls.</para>
- <para>After calling <constant>VIDIOC_EXPBUF</constant> the <structfield>fd</structfield>
- field will be set by a driver. This is a DMABUF file
- descriptor. The application may pass it to other DMABUF-aware devices. Refer to
- <link linkend="dmabuf">DMABUF importing</link> for details about importing
- DMABUF files into V4L2 nodes. It is recommended to close a DMABUF file when it
- is no longer used to allow the associated memory to be reclaimed.</para>
- </refsect1>
- <refsect1>
- <title>Examples</title>
- <example>
- <title>Exporting a buffer.</title>
- <programlisting>
- int buffer_export(int v4lfd, &v4l2-buf-type; bt, int index, int *dmafd)
- {
- &v4l2-exportbuffer; expbuf;
- memset(&expbuf, 0, sizeof(expbuf));
- expbuf.type = bt;
- expbuf.index = index;
- if (ioctl(v4lfd, &VIDIOC-EXPBUF;, &expbuf) == -1) {
- perror("VIDIOC_EXPBUF");
- return -1;
- }
- *dmafd = expbuf.fd;
- return 0;
- }
- </programlisting>
- </example>
- <example>
- <title>Exporting a buffer using the multi-planar API.</title>
- <programlisting>
- int buffer_export_mp(int v4lfd, &v4l2-buf-type; bt, int index,
- int dmafd[], int n_planes)
- {
- int i;
- for (i = 0; i < n_planes; ++i) {
- &v4l2-exportbuffer; expbuf;
- memset(&expbuf, 0, sizeof(expbuf));
- expbuf.type = bt;
- expbuf.index = index;
- expbuf.plane = i;
- if (ioctl(v4lfd, &VIDIOC-EXPBUF;, &expbuf) == -1) {
- perror("VIDIOC_EXPBUF");
- while (i)
- close(dmafd[--i]);
- return -1;
- }
- dmafd[i] = expbuf.fd;
- }
- return 0;
- }
- </programlisting>
- </example>
- <table pgwide="1" frame="none" id="v4l2-exportbuffer">
- <title>struct <structname>v4l2_exportbuffer</structname></title>
- <tgroup cols="3">
- &cs-str;
- <tbody valign="top">
- <row>
- <entry>__u32</entry>
- <entry><structfield>type</structfield></entry>
- <entry>Type of the buffer, same as &v4l2-format;
- <structfield>type</structfield> or &v4l2-requestbuffers;
- <structfield>type</structfield>, set by the application. See <xref
- linkend="v4l2-buf-type" /></entry>
- </row>
- <row>
- <entry>__u32</entry>
- <entry><structfield>index</structfield></entry>
- <entry>Number of the buffer, set by the application. This field is
- only used for <link linkend="mmap">memory mapping</link> I/O and can range from
- zero to the number of buffers allocated with the &VIDIOC-REQBUFS; and/or
- &VIDIOC-CREATE-BUFS; ioctls. </entry>
- </row>
- <row>
- <entry>__u32</entry>
- <entry><structfield>plane</structfield></entry>
- <entry>Index of the plane to be exported when using the
- multi-planar API. Otherwise this value must be set to zero. </entry>
- </row>
- <row>
- <entry>__u32</entry>
- <entry><structfield>flags</structfield></entry>
- <entry>Flags for the newly created file, currently only
- <constant>O_CLOEXEC</constant>, <constant>O_RDONLY</constant>, <constant>O_WRONLY</constant>,
- and <constant>O_RDWR</constant> are supported, refer to the manual
- of open() for more details.</entry>
- </row>
- <row>
- <entry>__s32</entry>
- <entry><structfield>fd</structfield></entry>
- <entry>The DMABUF file descriptor associated with a buffer. Set by
- the driver.</entry>
- </row>
- <row>
- <entry>__u32</entry>
- <entry><structfield>reserved[11]</structfield></entry>
- <entry>Reserved field for future use. Drivers and applications must
- set the array to zero.</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
- </refsect1>
- <refsect1>
- &return-value;
- <variablelist>
- <varlistentry>
- <term><errorcode>EINVAL</errorcode></term>
- <listitem>
- <para>A queue is not in MMAP mode or DMABUF exporting is not
- supported or <structfield>flags</structfield> or <structfield>type</structfield>
- or <structfield>index</structfield> or <structfield>plane</structfield> fields
- are invalid.</para>
- </listitem>
- </varlistentry>
- </variablelist>
- </refsect1>
- </refentry>
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