1<refentry id="func-munmap">
2  <refmeta>
3    <refentrytitle>V4L2 munmap()</refentrytitle>
4    &manvol;
5  </refmeta>
6
7  <refnamediv>
8    <refname>v4l2-munmap</refname>
9    <refpurpose>Unmap device memory</refpurpose>
10  </refnamediv>
11
12  <refsynopsisdiv>
13    <funcsynopsis>
14      <funcsynopsisinfo>
15#include &lt;unistd.h&gt;
16#include &lt;sys/mman.h&gt;</funcsynopsisinfo>
17      <funcprototype>
18	<funcdef>int <function>munmap</function></funcdef>
19	<paramdef>void *<parameter>start</parameter></paramdef>
20	<paramdef>size_t <parameter>length</parameter></paramdef>
21      </funcprototype>
22    </funcsynopsis>
23  </refsynopsisdiv>
24  <refsect1>
25    <title>Arguments</title>
26    <variablelist>
27      <varlistentry>
28	<term><parameter>start</parameter></term>
29	<listitem>
30	  <para>Address of the mapped buffer as returned by the
31&func-mmap; function.</para>
32	</listitem>
33      </varlistentry>
34      <varlistentry>
35	<term><parameter>length</parameter></term>
36	<listitem>
37	  <para>Length of the mapped buffer. This must be the same
38value as given to <function>mmap()</function> and returned by the
39driver in the &v4l2-buffer; <structfield>length</structfield>
40field for the single-planar API and in the &v4l2-plane;
41<structfield>length</structfield> field for the multi-planar API.</para>
42	</listitem>
43      </varlistentry>
44    </variablelist>
45  </refsect1>
46
47  <refsect1>
48    <title>Description</title>
49
50    <para>Unmaps a previously with the &func-mmap; function mapped
51buffer and frees it, if possible. <!-- ? This function (not freeing)
52has no impact on I/O in progress, specifically it does not imply
53&VIDIOC-STREAMOFF; to terminate I/O. Unmapped buffers can still be
54enqueued, dequeued or queried, they are just not accessible by the
55application.--></para>
56  </refsect1>
57
58  <refsect1>
59    <title>Return Value</title>
60
61    <para>On success <function>munmap()</function> returns 0, on
62failure -1 and the <varname>errno</varname> variable is set
63appropriately:</para>
64
65    <variablelist>
66      <varlistentry>
67	<term><errorcode>EINVAL</errorcode></term>
68	<listitem>
69	  <para>The <parameter>start</parameter> or
70<parameter>length</parameter> is incorrect, or no buffers have been
71mapped yet.</para>
72	</listitem>
73      </varlistentry>
74    </variablelist>
75  </refsect1>
76</refentry>
77