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To: obrien@FreeBSD.ORG
Subject: Re: removal of kvtop() on i386 
Cc: arch@FreeBSD.ORG
In-reply-to: Your message of "Tue, 18 Jul 2000 18:45:00 PDT."
		<20000718184500.E15761@dragon.nuxi.com> 
References: <20000718184500.E15761@dragon.nuxi.com>  <20000717155552.A19233@cichlids.cichlids.com> <200007171828.LAA10544@mass.osd.bsdi.com> 
Date: Tue, 18 Jul 2000 21:13:04 -0600
From: Warner Losh <imp@village.org>
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In message <20000718184500.E15761@dragon.nuxi.com> "David O'Brien" writes:
: I have to agree with Mike.  Please do not dirty the Alpha code with
: obsoleted interfaces.  The Alpha is a lot cleaner than our i386 code.

Yes.  Although the old pccard interface uses kvtop, it does so in a
very bad way.  It should bus_alloc_resource followed by a
rman_get_vmaddr() for the stuff it does.  It can't[*] use the DMA
routines, because there's no DMA.  Just the need to know where the
device lives in bus space (so it can tell the device) and where it
lives in virtual space (so it can access it).  If one was really
ambitious, one would convert the current direct access (via char *foo
= vmaddr; *foo = blah;) with busspace (bus_read_1(...)).  However,
since that code is on its glide path to retirement, that might be too
much work that would be better spend on other things.

If the ed driver (or any other network driver) needs to access the
memory directly, it should use the busspace routines to do it.

In fact, since many of our network drivers don't use the busdma
routines, it is very hard to get FreeBSD to run on an intel with > 4G
of RAM (processors since the PPro have supported 36 or more address
lines).  kvtop is one of the things that is holding us back from doing 
that easily.

Warner


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