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Date:      Thu, 15 Jun 2000 15:46:52 -0700
From:      Mike Smith <msmith@freebsd.org>
To:        Terry Lambert <tlambert@primenet.com>
Cc:        msmith@FreeBSD.ORG (Mike Smith), arch@FreeBSD.ORG
Subject:   Re: cvs commit: src/sys/pci pci.c pcisupport.c pcivar.h 
Message-ID:  <200006152246.PAA00823@mass.osd.bsdi.com>
In-Reply-To: Your message of "Thu, 15 Jun 2000 22:00:42 -0000." <200006152200.PAA12388@usr08.primenet.com> 

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> > > The PCI issue is unique, in that PCI devices can be identified by
> > > a generic routine.
> > 
> > This is nonsense, and it basically removes the justification for 
> > everything else that you've said here. 8)
> > 
> > The real situation is, in fact, just the opposite; there are *very* few 
> > devices for which it is not possible to obtain, in a generic fashion, a 
> > uniquifying token.
> 
> PCI cards have a card identification register which is per slot
> relative, and which can be read by a generic routine.  EISA and
> MCA have similar capabilities.
> 
> ISA cards, you have to go grovelling in a per card way with a
> passive probe for most cards; but the routine used to do this is
> _not_ the same for all IS cards, and can not, therefore, be
> written once per bus, but instead must be written once per card.

Not "most cards".  These days, "for old cards only".

> I think it's OK to statically compile in a generic PCI probe that
> then does I/O against a file to identify the driver to load (the
> ID as the left hand side, the driver module information as the
> right hand side, in a data table).
> 
> I _don't_ think it's OK to statically link in all ISA devices, or
> even to load the full driver for each device before deciding to
> discard it because the probe failed to find a device.

I think there are so few ISA devices left that we care about that it's 
fine to load their drivers if and when you give a damn about them, and 
then unload them if you decide they failed to load.  It's so rare an 
event to probe an ISA device that I don't think the difference between 
paging in the probe vs. just loading the entire driver is so trivial that 
it's not worth arguing about.

-- 
\\ Give a man a fish, and you feed him for a day. \\  Mike Smith
\\ Tell him he should learn how to fish himself,  \\  msmith@freebsd.org
\\ and he'll hate you for a lifetime.             \\  msmith@cdrom.com




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