Re: can someone explain...[ PCI interrupts]

From: Julian Elischer <julian_at_elischer.org>
Date: Tue, 06 Dec 2005 15:59:34 -0800
Jack Vogel wrote:

>On 12/6/05, Julian Elischer <julian_at_elischer.org> wrote:
>  
>
>>In short words for the likes of me,
>>Can someone give a quicj roundup on PCI routing in 4.x and -current.
>>
>>Specifically:
>>
>>How much is set up by the BIOS and how much is set up by the OS (4.x and
>>-current).
>>
>>How much of my fondly held knowledge of the old hardware PICS (where
>>an interrupt corresponded to an interrupt line) is now out of date?
>>
>>In this world of multiple PCI to PCI bridges, how much latitude doe the
>>OS have in
>>deciding where an interrupt turns up?
>>(in 4.x and -current)
>>
>>An example is my Dell PE2850 (on 4.x), in which my 4 port ethernet card
>>seems to
>>be assigned irqs 10,14,14,2 in that order sometimes and 16,17,17,2 at
>>others.
>>
>>Who is making those decisions? Is it the BIOS and 4.x is just playing along?
>>
>>Assuming the much maligned "boot interrupt" comes in on irq2, does the OS
>>have the oportunity to put my 4th port somewhere else? On 4.x it collides
>>with one of my ether ports but in -current it doesn't
>>
>>Linux and -current on teh same box a;;ocate way different irqs, and
>>they agree about it.. i.e. Linux and -current assign my 4 port card IRQs
>>18,19,19,16.
>>
>>Do they agree becasue something else has decided it (the bios again?) or
>>becasue they
>>use the same algorythm to work it out..
>>
>>Also, if the "boot interrupt" was previously set to 2, is that likely to
>>have changed in -current?
>>Am I now going to get clobbered on IRQ16?  If yes, is this something
>>that teh BIOS writers
>>decided, or something that the Motherboard designers decided?
>>    
>>
>
>The canonical method for getting this kind of information now (and at
>least current Linux kernels do this unless forced not to) is via ACPI...
>And indirectly that really means how the BIOS sets up its tables.
>
>I'm still coming up to speed on the current FreeBSD kernel, but I
>would hope it does the same :)
>  
>

so, for your next trick can you explain acpi and the "boot interrupt" :-)
p.s. got info on the dewey beach card yet? ;-)  (That's what's causing 
me this pain :-)


>Cheers,
>
>Jack
>  
>
Received on Tue Dec 06 2005 - 22:59:36 UTC

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