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Date: Fri, 06 Jun 2003 13:18:25 -0600 (MDT)
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To: ticso@cicely.de, ticso@cicely12.cicely.de
From: "M. Warner Losh" <imp@bsdimp.com>
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Subject: Re: [PATCH] Tweak re-routing of PCI interrupts
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In message: <20030606191316.GB1290@cicely12.cicely.de>
            Bernd Walter <ticso@cicely12.cicely.de> writes:
: On Fri, Jun 06, 2003 at 12:36:54PM -0600, M. Warner Losh wrote:
: > In message: <XFMail.20030606141331.jhb@FreeBSD.org>
: >             John Baldwin <jhb@FreeBSD.org> writes:
: > : I have a small tweak to the PCI code that re-routes PCI interrupts.
: > : Basically, it does two things, 1) make the comment less ia64-specific
: > : and 2) if the interrupt route returns an invalid IRQ (i.e. 255), then
: > : we don't change the intline.  In other words, if we can't route the
: > : interrupt, we just assume that the firmware knows more than we do and
: > : go with the value it stuck in the register.  1) is a no-brainer, but
: > : I wonder what people think about 2).  Patch below:
: > 
: > I think #2 isn't so good.  #1 is a no-brainer :-)
: > 
: > :  #if ...
: > ...
: > : +               irq = PCIB_ROUTE_INTERRUPT(pcib, dev, cfg->intpin);
: > : +               if (PCI_INTERRUPT_VALID(irq))
: > : +                       cfg->intline = irq;
: > : +               else
: > :  #endif
: > : +                       irq = cfg->intline;
: > : +               resource_list_add(rl, SYS_RES_IRQ, 0, irq, irq, 1);
: > :         }
: > :  }
: > 
: > The part I don't like is that if we can't route an interrupt, we
: > assume that the interrupt that was written there before is good and
: > routed.  This strikes me as an unwise assumption.  Also, we haven't
: 
: Unless you find a reliable way to ask the BIOS how the board is wired,
: whatelse would you do than trust the inline register?

$PIR table does this for PCIBIOS.  Other mechanisms do it for ACPI.
Pre PCIBIOS machines you are SOL.

Warner