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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 <unistd.h>
16#include <sys/mman.h></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.</para>
41 </listitem>
42 </varlistentry>
43 </variablelist>
44 </refsect1>
45
46 <refsect1>
47 <title>Description</title>
48
49 <para>Unmaps a previously with the &func-mmap; function mapped
50buffer and frees it, if possible. <!-- ? This function (not freeing)
51has no impact on I/O in progress, specifically it does not imply
52&VIDIOC-STREAMOFF; to terminate I/O. Unmapped buffers can still be
53enqueued, dequeued or queried, they are just not accessible by the
54application.--></para>
55 </refsect1>
56
57 <refsect1>
58 <title>Return Value</title>
59
60 <para>On success <function>munmap()</function> returns 0, on
61failure -1 and the <varname>errno</varname> variable is set
62appropriately:</para>
63
64 <variablelist>
65 <varlistentry>
66 <term><errorcode>EINVAL</errorcode></term>
67 <listitem>
68 <para>The <parameter>start</parameter> or
69<parameter>length</parameter> is incorrect, or no buffers have been
70mapped yet.</para>
71 </listitem>
72 </varlistentry>
73 </variablelist>
74 </refsect1>
75</refentry>
76
77<!--
78Local Variables:
79mode: sgml
80sgml-parent-document: "v4l2.sgml"
81indent-tabs-mode: nil
82End:
83-->