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Based on kernel version 3.16. Page generated on 2014-08-06 21:38 EST.

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
38	value as given to <function>mmap()</function> and returned by the
39	driver in the &v4l2-buffer; <structfield>length</structfield>
40	field 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
51	buffer and frees it, if possible. <!-- ? This function (not freeing)
52	has no impact on I/O in progress, specifically it does not imply
53	&VIDIOC-STREAMOFF; to terminate I/O. Unmapped buffers can still be
54	enqueued, dequeued or queried, they are just not accessible by the
55	application.--></para>
56	  </refsect1>
57	
58	  <refsect1>
59	    <title>Return Value</title>
60	
61	    <para>On success <function>munmap()</function> returns 0, on
62	failure -1 and the <varname>errno</varname> variable is set
63	appropriately:</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
71	mapped yet.</para>
72		</listitem>
73	      </varlistentry>
74	    </variablelist>
75	  </refsect1>
76	</refentry>
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