Based on kernel version 4.7.2. Page generated on 2016-08-22 22:45 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 <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 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>
