GNAT x86 Port Access

["Jeff C," <nolongersafeto@userealemailsniff.com>]

A few days ago there was a thread about doing x86 IO port access. I
eventually dug out my old laptop and found
a little (very little) package I wrote to do this. It is only setup to do
byte IO on the ports . It WILL NOT WORK under
windows 2000, NT, XP or any OS that limits the instructions that user land
applications can use. I have used
this under windows 98 with success.




with Interfaces;

package PC_IO_Port_Access is

  --------------------------------------------------------------------------
----
  -- 
  -- PROCEDURE/FUNCTION: Inportb
  --
  -- PURPOSE: Performs a byte read of the given IO port address.
  -- 
  -- NOTES:   None
  --
  --------------------------------------------------------------------------
----

  function Inportb (
        Port_Address : in     Interfaces.Unsigned_16 )
    return Interfaces.Unsigned_8;


  --------------------------------------------------------------------------
----
  -- 
  -- PROCEDURE/FUNCTION: Outportb
  --
  -- PURPOSE: Writes the given value to the given port address.
  -- 
  -- NOTES:   None
  --
  --------------------------------------------------------------------------
----

  procedure Outportb (
        Port_Address : in     Interfaces.Unsigned_16;
        Value        : in     Interfaces.Unsigned_8   );

end PC_IO_Port_Access;






with Machine_Code;
use Machine_Code;

package body PC_IO_Port_Access is


  --------------------------------------------------------------------------
----
  -- 
  -- PROCEDURE/FUNCTION: Inportb
  --
  -- PURPOSE: Performs a byte read of the given IO port address.
  -- 
  -- NOTES:   None
  --
  --------------------------------------------------------------------------
----

  function Inportb (
        Port_Address : in     Interfaces.Unsigned_16 )
    return Interfaces.Unsigned_8 is
    Return_Value : Interfaces.Unsigned_8;

  begin

    Asm ("inb %1 %0", -- %%dx %%al",
      Interfaces.Unsigned_8'Asm_Output ("=a", Return_Value),
      Interfaces.Unsigned_16'Asm_Input("d", Port_Address));

    return Return_Value;

  end Inportb;


  --------------------------------------------------------------------------
----
  -- 
  -- PROCEDURE/FUNCTION: Outportb
  --
  -- PURPOSE: Writes the given value to the given port address.
  -- 
  -- NOTES:   None
  --
  -----------------------------------------------------------------------

  procedure Outportb (
        Port_Address : in     Interfaces.Unsigned_16;
        Value        : in     Interfaces.Unsigned_8   ) is
  begin

    Asm (Template => "outb %1 %0", -- %%dx %%al",
      Inputs   => (Interfaces.Unsigned_8'
        Asm_Input ("a", Value),Interfaces.Unsigned_16'Asm_Input("d",
          Port_Address)));

  end OutPortb;


end PC_IO_Port_Access;