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Date:      Thu, 22 Feb 1996 11:04:00 -0700 (MST)
From:      Terry Lambert <terry@lambert.org>
To:        koshy@india.hp.com (A JOSEPH KOSHY)
Cc:        freebsd-hackers@freebsd.org
Subject:   Re: ISA device irq/mem auto-configuration
Message-ID:  <199602221804.LAA21281@phaeton.artisoft.com>
In-Reply-To: <199602210718.AA255777134@fakir.india.hp.com> from "A JOSEPH KOSHY" at Feb 21, 96 12:48:53 pm

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> This is a basic question about how we handle boards whose IRQ, I/O and
> memory ranges can be autodetected at boot time.  
> 
> Consider a network card : If the kernel has been configured for say, 
> IRQ 5 but the actual board was detected at IRQ 11, whats the right thing to 
> do? We could :
> 
> (a) Ignore the board : this can be pretty frustrating to the user.

If you can't probe it, you can't *not* ignore the board...

> (b) Print out some informative message : stating something like 
>     "board setup for IRQ XX but kernel was configured for YY" and leave
>     it at that.  

If you could actually tell what it was configured for...


> (c) Take in the new IRQ setting somehow and do the right thing.
> 
> Option (C) seems to me to be the right thing from the users point of
> view; I don't know enough of the FreeBSD kernel to tell if it is feasible.

There is work on PnP device management.  I think this falls into the
category of space assignment.  It's probably not possible to safely
relocate the board -- you might have a non-PnP OS on the machine.


> I have seen in some places "-1" being used as a kind of "wildcard" address
> in some drivers.  Is this a convention?

It's a convention to indicate that it is detected by the probe.

> Can anyone point me to further reading?   Have I missed something?

Only "how do you know the board is at IRQ 11 when the probe code
has to assume the interrupt for the probe to work?".  8-).


					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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