<?xml version="1.0" encoding="ANSI_X3.4-1968" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968" /><title>mmap() device memory</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="The Userspace I/O HOWTO" /><link rel="up" href="userspace_driver.html" title="Chapter 4. Writing a driver in userspace" /><link rel="prev" href="userspace_driver.html" title="Chapter 4. Writing a driver in userspace" /><link rel="next" href="ch04s03.html" title="Waiting for interrupts" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">mmap() device memory</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="userspace_driver.html">Prev</a> </td><th width="60%" align="center">Chapter 4. Writing a driver in userspace</th><td width="20%" align="right"> <a accesskey="n" href="ch04s03.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="mmap() device memory"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="mmap_device_memory"></a>mmap() device memory</h2></div></div></div><p> After you made sure you've got the right device with the memory mappings you need, all you have to do is to call <code class="function">mmap()</code> to map the device's memory to userspace. </p><p> The parameter <code class="varname">offset</code> of the <code class="function">mmap()</code> call has a special meaning for UIO devices: It is used to select which mapping of your device you want to map. To map the memory of mapping N, you have to use N times the page size as your offset: </p><pre class="programlisting"> offset = N * getpagesize(); </pre><p> N starts from zero, so if you've got only one memory range to map, set <code class="varname">offset = 0</code>. A drawback of this technique is that memory is always mapped beginning with its start address. </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="userspace_driver.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="userspace_driver.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ch04s03.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 4. Writing a driver in userspace </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Waiting for interrupts</td></tr></table></div></body></html>
