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To: Luigi Rizzo <luigi@labinfo.iet.unipi.it>
cc: hackers@freebsd.org, multimedia@freebsd.org
Subject: Re: Advice sought on PnP configuration 
In-reply-to: Your message of "Wed, 30 Jul 1997 06:04:33 +0200."
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Date: Wed, 30 Jul 1997 00:01:13 -0700
From: Amancio Hasty <hasty@rah.star-gate.com>
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Hi Luigi,

PCI devices should be probed and attached last for they are they
are the most flexible to configure and can share interrupts.

	Cheers,
	Amancio
>From The Desk Of Luigi Rizzo :
> > Hopefully, with the on-going work in the multimedia group we will
> > make the use of PnP devices a very painless experience.
> 
> I am revising the PnP configuration stuff. I have got to a point
> where it behaves very similarly to the PCI configuration stuff,
> i.e. it relies on the BIOS to set addresses and IRQs correctly,
> and then fetches the parameters from the board and passes them to
> the driver.  No manual configuration required (of course, the OS
> must recognize your card, but that's another problem and is common
> with PCI stuff -- within some time, a reasonable database of card
> IDs can be compiled to have things working for a wide range of
> boards).
> 
> HOWEVER: this relies on the PnP (or PCI for what matters) BIOS to
> work correctly (which might be false, see at the end of the message).
> 
> In order to configure cards correctly, the bios should know which
> IRQs and which I/O address ranges are used by plain isa devices.
> The former can be told to some bioses, the latter I have never seen
> how to do on my systems. This is not a big deal with PCI devices
> since they usually map addresses in the high range of iospace, but
> a serious problem with PnP ISA devices where iospace is tight and
> shared with non PnP devices.
> 
> Since we cannot trust the BIOS (because it does not have enough
> info) the only way to do autoconfiguration reliably in FreeBSD is
> the following:
> 
> 1 probe & attach pci devices
> 2 disable all pnp devices, so that they are not recognized by isa probes;
> 3 probe & attach plain isa devices;
> 4 configure PnP devices, using info derived from the isa configuration
>   process to determine which address ranges and irqs are busy;
> 5 activate PnP devices;
> 6 finally, probe and attach PnP devices.
> 
> Any comments on the above ? Right now I am doing steps in the order 1,
> 5, 6, 3 (2 and 4 are not necessary if the bios works), but it can
> fail in some cases for the reasons stated above.
> 
> 	Cheers
> 	Luigi