Date: Sat, 30 May 1998 12:00:16 +0100 (BST) From: Doug Rabson <dfr@nlsystems.com> To: Matt Thomas <matt@3am-software.com> Cc: current@FreeBSD.ORG Subject: Re: FreeBSD/alpha status report (2) Message-ID: <Pine.BSF.3.95q.980530115823.15699a-100000@herring.nlsystems.com> In-Reply-To: <199805301053.GAA05668@tecumseh.altavista-software.com>
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On Sat, 30 May 1998, Matt Thomas wrote: > At 03:16 AM 5/30/98 , Doug Rabson wrote: > > >I am not saying that there won't be a <machine/bus.h>. I am saying that I > >don't think that all the chipset implementations need to implement it. If > >I do a bus_space interface, I expect that it will be something like > >i386/include/bus.h. It is possible that TurboChannel and TurboLaser boxes > >with multiple PCI busses might provide their own implementation rather > >than the generic one. > > That's misguided. The point of the bus_space and bus_dma is to hide > the mechanics of the underlying bus from the driver. Even if the bus > is simple, the point is to abstract it (so you would have a simple > abstraction). As an example, I recently moved the DEC FDDI driver > to bus_dma (it already used in bus_space) which allowed me to get it > running under NetBSD/pmax but only fixing coherency bugs. This means > this drivers is known to work on 3 difference architectures and 3 > different buses. This would be almost impossible without bus_space > and bus_dma. In a week or two, I should be able to confirm it works > under NetBSD/arm32. Why is it misguided? Drivers which use bus_space will see the same set of functions. Alpha chipsets for modern cpus with dense i/o space will use the trivial implementation of bus_space. Legacy drivers which use inb etc (we have quite a few) will work. -- Doug Rabson Mail: dfr@nlsystems.com Nonlinear Systems Ltd. Phone: +44 181 951 1891 Fax: +44 181 381 1039 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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