title: Enable wake-up from sleep mode through GPIO signal
body: <p>I need to wake up my BeagleBone device, running Angstrom OS, from sleep mode through GPIO signal.</p>
  
  <p>I read that using <code>/sys/class/gpio/gpioXX/power/wakeup</code> is the way to do. The problem is that there isn't any "wakeup" file under power directory. So, how I should proceed to activate it? Is there any solution without recompiling kernel?</p>
  
  <p>I can read fine from GPIO value, so GPIO sysfs is working.</p>