Documentation/DocBook/media/v4l/func-munmap.xml

   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>