From owner-freebsd-hackers  Wed Feb 12 09:25:32 1997
Return-Path: <owner-hackers>
Received: (from root@localhost)
          by freefall.freebsd.org (8.8.5/8.8.5) id JAA12383
          for hackers-outgoing; Wed, 12 Feb 1997 09:25:32 -0800 (PST)
Received: from phaeton.artisoft.com (phaeton.Artisoft.COM [198.17.250.211])
          by freefall.freebsd.org (8.8.5/8.8.5) with SMTP id JAA12376
          for <freebsd-hackers@freebsd.org>; Wed, 12 Feb 1997 09:25:24 -0800 (PST)
Received: (from terry@localhost) by phaeton.artisoft.com (8.6.11/8.6.9) id KAA00730; Wed, 12 Feb 1997 10:19:44 -0700
From: Terry Lambert <terry@lambert.org>
Message-Id: <199702121719.KAA00730@phaeton.artisoft.com>
Subject: Re: Raw I/O Question
To: bde@zeta.org.au (Bruce Evans)
Date: Wed, 12 Feb 1997 10:19:44 -0700 (MST)
Cc: julian@whistle.com, terry@lambert.org, freebsd-hackers@freebsd.org,
        Shimon@i-Connect.Net
In-Reply-To: <199702120822.TAA06992@godzilla.zeta.org.au> from "Bruce Evans" at Feb 12, 97 07:22:17 pm
X-Mailer: ELM [version 2.4 PL24]
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: owner-hackers@freebsd.org
X-Loop: FreeBSD.org
Precedence: bulk

> >it then calls the strategy routine for the device
> >which gets the kv region, 
> >and extracts the phyical addresses again and 
> >sets up the DMA
> >and then waits
> >
> >DMA is directly into the users pages..
> 
> Only for devices and device drivers that support and use DMA.

And are not limited to 24 bit ISA I/O when the physical memory
target of the DMA is not above 16M.  These will be bounced and
then copied to the users pages.


					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.