Three primary steps are required to open the input device:

   *  Create a message port using CreatePort(). Reply messages from the
      device must be directed to a message port.

   *  Create an I/O request structure of type IOStdReq or timerequest. The
      I/O request created by the CreateExtIO() function will be used to
      pass commands and data to the input device.

   *  Open the Input device.  Call OpenDevice(), passing the I/O request.

   struct MsgPort  *InputMP;   /* Message port pointer */
   struct IOStdReq *InputIO;   /* I/O request pointer */

   if (InputMP=CreatePort(0,0) )
       if (InputIO=(struct IOStdReq *)
                    CreateExtIO(InputMP,sizeof(struct IOStdReq)) )
           if (OpenDevice("input.device",0L,(struct IORequest *)InputIO,0))
               printf("input.device did not open\n");

The above code will work for all the input device commands except for the
ones which require a time specification.  For those, the code would look
like this:

   #include <devices/timer.h>

   struct MsgPort  *InputMP;      /* Message port pointer */
   struct timerequest *InputIO;   /* I/O request pointer */

   if (InputMP=CreatePort(0,0) )
       if (InputIO=(struct timerequest *)
                    CreateExtIO(InputMP,sizeof(struct timerequest)) )
           if (OpenDevice("input.device",0L,(struct IORequest *)InputIO,0))
               printf("input.device did not open\n");