Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!unmvax!bbx!bbxsda!scott
From: scott@bbxsda.UUCP (Scott Amspoker)
Newsgroups: comp.lang.c
Subject: Re: Port Access
Message-ID: <519@bbxsda.UUCP>
Date: 8 Jan 90 16:25:41 GMT
References: <12720@cbnews.ATT.COM> <504@bbxsda.UUCP> <322@mtndew.UUCP>
Reply-To: scott@bbxsda.UUCP (Scott Amspoker)
Distribution: usa
Organization: Basis International,  Albuquerque, NM
Lines: 23

>Scott Amspoker replies:
>> I would be very surprised if UNIX system allowed a user process
>> to access ports directly.
>
>Surprise!
>
>General-purpose access to I/O ports is not supported, but there
>is limited access to display-related ports.
>[...]
>a handful of what are referred to as "VP/ix reserved ioctls", and
>two are...

Well, the 386 CPU does provide an I/O port bit map which allows user-mode
access to selected I/O ports.  This is quite unusual and is inconsistent with
the UNIX model.  However, I consider VP/ix to be a DOS environment rather
than a UNIX one even though it runs under Xenix.  I would be curious to
know what the original poster was trying to do.

-- 
Scott Amspoker
Basis International, Albuquerque, NM
(505) 345-5232
unmvax.cs.unm.edu!bbx!bbxsda!scott