From: Travis Hassloch <travis@evtech.com>
Message-Id: <9512081926.AA20961@borneo>
Subject: I/O maps and user-level device drivers
To: port-i386@netbsd.org, tech-kern@netbsd.org
Date: Fri, 8 Dec 1995 13:26:17 -0600 (CST)
Content-Type: text
Sender: owner-port-i386@NetBSD.ORG
Precedence: list

I remember reading something in the Intel uprocessor book about tasks
having a "I/O map" that could allow access to certain areas of I/O space.
I don't remember how fine a granularity this map had (per-word?) but it
got me thinking.

How could one allow (in an aethetically pleasing way) the Unix kernel to
start a particular process with (or allow it to get) a particular I/O
privilege map or a fixed virtual-to-physical mapping (to grab memory-mapped
I/O space)?  Would an a.out field and [e]uid-check be appropriate?

I _think_ Linux may have some kind of mechanism to this effect, since I
vaguely recall some kind of way that they allow procs to access video
memory directly, but I could be wrong.  Unfortunately, I'm so far out
of the Linux loop I wouldn't know where to start looking.

This note sent to both i386 and kern groups.
-- 
travis@evtech.com | The computer is your friend | P=NP if N=1
``My life is spent in one long effort to escape from the commonplaces of
  existence.'' -- Sir A.C. Doyle, "The Red-Headed League"          fnord