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Date:      Tue, 13 Jun 2000 16:35:43 +0000 (GMT)
From:      Terry Lambert <tlambert@primenet.com>
To:        mjacob@feral.com
Cc:        arch@FreeBSD.ORG
Subject:   Re: cvs commit: src/sys/pci pci.c pcisupport.c pcivar.h
Message-ID:  <200006131635.JAA08394@usr05.primenet.com>
In-Reply-To: <Pine.BSF.4.05.10006130901170.2214-100000@semuta.feral.com> from "Matthew Jacob" at Jun 13, 2000 09:05:04 AM

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> We discussed this very extensively during SparcStation-1 development. In fact
> early SunOS 4.0.3c prior to release had just something like this (the code
> stayed around for years protected by "DAVE_DOESNT_WANT_THIS_ANY_MORE").
> 
> The consensus eventually was that this was pointless because the ultimate goal
> is to have all possible available drivers sit somewhere and just be loaded if
> the h/w was present.
> 
> Once you get even close to the goal of all self-identifying devices (which is
> pretty darn close now), what's the added advantage of a message that most
> users won't grok and will generate a support call about (I'm talking
> commercial space here)?

Exactly.

The PCI issue is unique, in that PCI devices can be identified by
a generic routine.

For this to be general, we would need the concept of discaradable
vs. non-discardable pages.  ELF format actually handles this rather
well, and Microsoft uses it to advantage in their portable executable
format.

In fact, they have the following useful flags, expected to be applied
to discrete ELF sections:


nonswappable		is the code in the swap path?
initialization		this code only used on module load, and its
			pages can be recovered afterward
relocatable		with appropriate locking, you can move this
			code around to defragment kernel memory,
			since it is accessed by handle

etc.

The same for data sections, of course.

Looking at the PE documentation on the microsoft.com site would not
be a bad idea for people hacking this code; in particular, you can
learn from them, even if you consider them your enemy.


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


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