🚀 go-pugleaf

Summary on IOPL

1. IOPL'd code has to be 16 bit, can't be 32 bit. So for that matter do device
   drivers. All 2.0 device drivers according to IBM are 16 bits.

2. To run a 16 bit IOPL routine with 32 bit programs, the user needs to make
   the IOPL routines into a DLL. I haven't tried it yet (just using all 16 
   bits), but no doubt I will soon.

3. IBM does have plans to include inp and outp routines in their next release
   of CSET/2.

4. I have managed to get 16 bit versions of inp and outp to run properly using
   the following sample from Barry King, who cribbed it from an issue of OS/2
   Monthly Magazine. - THANKS MUCHO!

   Sample code:

   #include <conio.h>      // for outp()
   int main()
   {
       outp( 0x60, 0xE9 );
       return 0;
   }
 
   The .DEF looks like this:
 
   NAME ....
   DESCRIPTION ....
   PROTMODE
   SEGMENTS  _IOSEG CLASS 'IOSEG_CODE' iopl
 

5. I have NOT managed to get my own assembler routines to run in Ring 2. Any
   further information would be welcome.

5. There is some documentation and users stating that the DosPortAccess 
   routine is necessary to actually perform i/o. I've run my code with and 
   without it and haven't seen a difference.

Thanks to everyone to gave me information. 
Jan