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From: grt@twitch.UUCP ( G.R.Tomasevich)
Newsgroups: net.unix-wizards
Subject: phys(2) and accessing physical memory
Message-ID: <264@twitch.UUCP>
Date: Fri, 20-Dec-85 15:23:46 EST
Article-I.D.: twitch.264
Posted: Fri Dec 20 15:23:46 1985
Date-Received: Mon, 23-Dec-85 04:16:28 EST
References: <270@moncskermit.oz> <177@daab.UUCP> <612@unisoft.UUCP> <135@hadron.UUCP>
Organization: AT&T Bell Labs, Holmdel
Lines: 15

> >addresses from user processes. This is a Uniplus   'feature', not a System
> >V 'feature'. Don't expect to see it in a port done by someone other than
> >Unisoft.

It would be nice for phys() to become permanent.  My suggestion about reading
from /dev/mem and calculating the address is trivial only if the physical
address space is commensurate with the number of address bits in the DMA
device, such as 18 bits for PDP-11/45 and DR11W or LSI-11/23 and DRV11B,
both of which we have done.  If you need to access something like a Unibus
map, for example, it would be a pain from user space.  I am not sure one
could even cook up a way to grab some Unibus map registers without some kind
of 'driver'.
-- 
	George Tomasevich, ihnp4!twitch!grt
	AT&T Bell Laboratories, Holmdel, NJ