title: An example of using request_region and release_region
body: <p>I read about I/O ports and communicating with the hardware, I want to gain access to an I/O port to see a live example of the various functions. I don't understand what the first argument (<code>unsigned long start</code>) of <code>request_region</code> is.</p>
  <p><strong>I'd like someone to show me a very simple use of these functions.</strong></p>
  <pre class="lang-c prettyprint-override"><code>struct resource *request_region(unsigned long start, unsigned long n, const char *name);
  void release_region(unsigned long first, unsigned long n);
  </code></pre>
  <p><strong>Also, where can we see a list of I/O ports? I guess it might be in <code>/proc/ioports</code>?</strong></p>