title: device file open failed in linux system
body: <p>I am working in omap4 based system. It has 4 UART port so kernel makes:</p>
  
  <pre><code>/dev/ttyO0
  /dev/ttyO1
  /dev/ttyO2
  /dev/ttyO3
  </code></pre>
  
  <p>When I open from user space:</p>
  
  <pre><code>fd = open("/dev/ttyO1",O_RDONLY)
  </code></pre>
  
  <p>it succesfully open and i can peform read and write with that.</p>
  
  <p>But when I open:</p>
  
  <pre><code>fd = open("/dev/ttyO3",O_RDONLY)
  </code></pre>
  
  <p>Its failed.</p>
  
  <p>I am able to see <code>/dev/ttyO3</code> node in my system still why i am not able to open it? Any idea?</p>