Suggestion about implementing events

Hi,

I need to create a class to read/write from a Serial port and I need a
suggestion about implementing events.
I've implemented the observer pattern with an interface more or less
like this:

class ISerialDevEvents
{
  virtual void DataArrived(void) = 0;
}

class SerialDev
{
  public:
    SerialDev(ISerialDevEvents *handler);
    int Open()
    {
      /* Create thread and Run it ( Reading() ) */
    }

  protected:
    ISerialDevEvents _handler;

  private:
    Reading()
    {
      do while (!StopRequest)
      {
        ....
        if (eventHandler != 0)
         _handler->DataArrived(void);
       }
    }
};

class User : public CThreadEventHandler
{
  main()
  {
    SerialDev Dev;
    Dev.Open(this);
  }

  virtual void DataArrived()
  {
    Dev.GetData();
  }
};

But with this method a user class has to implements all virtual
methods of its interface also if it doesn't use it.
What about if, instead of an interface, I made the open() method to
accept a pointer to member function?

template<class R, class T>
Open( R (T::*pmf)() )

If the classes lives in separated threads is it legal?

PS [OT]: Someone knows if the Boost::serial_port is able to manage PIN
like DTR, RTS etc..?

Tnx,
Daniele.