From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 22 May 2001 17:35:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 22 May 2001 17:35:17 -0400 Received: from geos.coastside.net ([207.213.212.4]:48575 "EHLO geos.coastside.net") by vger.kernel.org with ESMTP id ; Tue, 22 May 2001 17:35:12 -0400 Mime-Version: 1.0 Message-Id: In-Reply-To: In-Reply-To: Date: Tue, 22 May 2001 14:34:35 -0700 To: Alan Cox From: Jonathan Lundell Subject: Re: alpha iommu fixes Cc: rth@twiddle.net (Richard Henderson), andrea@suse.de (Andrea Arcangeli), ink@jurassic.park.msu.ru (Ivan Kokshaysky), linux-kernel@vger.kernel.org, davem@redhat.com (David S. Miller) Content-Type: text/plain; charset="us-ascii" ; format="flowed" Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org At 10:24 PM +0100 2001-05-22, Alan Cox wrote: > > On the main board, and not just the old ones. These days it's >> typically in the chipset's south bridge. "Third-party DMA" is >> sometimes called "fly-by DMA". The ISA card is a slave, as is memory, >> and the DMA chip reads from one ands writes to the other. > >There is also another mode which will give the Alpha kittens I suspect. A >few PCI cards do SB emulation by snooping the PCI bus. So the kernel writes >to the ISA DMA controller which does a pointless ISA transfer and the PCI >card sniffs the DMA controller setup (as it goes to pci, then when nobody >claims it on to the isa bridge) then does bus mastering DMA of its own to fake >the ISA dma That's sick. -- /Jonathan Lundell.