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<refentry id="func-munmap">
<refmeta>
<refentrytitle>V4L2 munmap()</refentrytitle>
&manvol;
</refmeta>
<refnamediv>
<refname>v4l2-munmap</refname>
<refpurpose>Unmap device memory</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>
#include <unistd.h>
#include <sys/mman.h></funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>munmap</function></funcdef>
<paramdef>void *<parameter>start</parameter></paramdef>
<paramdef>size_t <parameter>length</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>start</parameter></term>
<listitem>
<para>Address of the mapped buffer as returned by the
&func-mmap; function.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>length</parameter></term>
<listitem>
<para>Length of the mapped buffer. This must be the same
value as given to <function>mmap()</function> and returned by the
driver in the &v4l2-buffer; <structfield>length</structfield>
field for the single-planar API and in the &v4l2-plane;
<structfield>length</structfield> field for the multi-planar API.</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>Unmaps a previously with the &func-mmap; function mapped
buffer and frees it, if possible. <!-- ? This function (not freeing)
has no impact on I/O in progress, specifically it does not imply
&VIDIOC-STREAMOFF; to terminate I/O. Unmapped buffers can still be
enqueued, dequeued or queried, they are just not accessible by the
application.--></para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>On success <function>munmap()</function> returns 0, on
failure -1 and the <varname>errno</varname> variable is set
appropriately:</para>
<variablelist>
<varlistentry>
<term><errorcode>EINVAL</errorcode></term>
<listitem>
<para>The <parameter>start</parameter> or
<parameter>length</parameter> is incorrect, or no buffers have been
mapped yet.</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
</refentry>
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