Serial port configuration

[hreba <hreba@terra.com.br>]

The problem
-----------
I am trying to communicate with an Arduino using 
GNAT.Serial_Communications, which I will abbreviate as "Serial". The 
"Set" procedure isn't detailed enough, I need "fcntl", "tcgetattr" and 
"tcsetattr" which are private in Serial. To call them, I need the file 
descriptor which is a private component of the type "Port".

The Idea
--------
1. Create a new package "SerAux"
2. declare "fcntl", "tcgetattr" and "tcsetattr" the same way as in
    "Serial", but public
3. define a new type "Port" the same way as in "Serial", but public,
    and do the conversion somehow.

The obstacles
-------------
Creating the new Port requires to override its methods "Read" and 
"Write", but even doing that the same way as in "Serial" gets me a lot 
of error messages. The SerAux.adb begins like this (reproduced from 
original line # 4 on):

--------------------------------------------------------------
...
package body SerAux is

    type Port_Data is new int;
    type Port_Data_Access is access Port_Data;
    type Port is new Ada.Streams.Root_Stream_Type with record
       H : Port_Data_Access;
    end record;


    overriding procedure Read
      (--Port   : in out Serial_Port;
       Port   : in out Port;
       Buffer : out Ada.Streams.Stream_Element_Array;
       Last   : out Ada.Streams.Stream_Element_Offset)
    is
    begin
       Read (Serial.Serial_Port(Port), Buffer, Last);
    end Read;

    ...
----------------------------------------------------------------

The error messages for this fragment are:

seraux.adb:8:09: type must be declared abstract or "Read" overridden
seraux.adb:8:09: "Read" has been inherited at line 8
seraux.adb:8:09: "Read" has been inherited from subprogram at 
a-stream.ads:54
seraux.adb:13:15: subprogram "Read" is not overriding
seraux.adb:15:23: formal parameter "Port" cannot be used before end of 
specification
seraux.adb:20:07: warning: possible infinite recursion
seraux.adb:20:07: warning: Storage_Error may be raised at run time
...
-----------------------------------------------------------------

The questions
-------------
1. Why is all that an error here and not in "Serial"?
2. Am I on the right way or would you solve the problem completely 
different?

Please consider that I am a beginner.

--
hreba