Q39973: Accessing I/O Ports under OS/2 Protected Mode

Article: Q39973
Product(s): See article
Version(s): 5.10
Operating System(s): OS/2
Keyword(s): ENDUSER | COM1 COM2 serial communication | mspl13_c
Last Modified: 5-JAN-1989

Problem:

I am trying to use the inp(), inpw(), outp(), and outpw() routines in
the Microsoft C Version 5.10 run-time library. Every time I run my
program I get the following message:

   SYS1943: A program caused a protection violation.

Response:

To read from or write to ports under OS/2 protected mode you must have
a .DEF module-definition file that gives IOPL (input/output privilege)
to the _IOSEG segment. Also, if the intrinsic (/Oi) switch is used
during compilation, the segments that contain the port functions must
be given IOPL. You can check the .MAP file for the associated segment
name or compile with the /NT switch to manually name the segment.

The following must be in your .DEF file if /Oi was not used:

SEGMENTS
    _IOSEG CLASS 'IOSEG_CODE' IOPL

If /Oi was used, the following must be in your .DEF file:

SEGMENTS
    (segment name) IOPL

Note: Segments that have IOPL cannot make system calls. If you do,
you will generate a GP fault, a general protection violation. This
behavior is discussed on Page 239 of Letwin's "Inside OS/2."

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1986-2002.