RE: RFC Proposal to enable MSI support in Linux kernel

Nguyen, Tom L (tom.l.nguyen@intel.com)
Thu, 29 May 2003 11:12:18 -0700


I am working on an updated patch to 2.5.70 to incorporate the comments from you and Jeff Garzik. Regarding the variable renaming of irq, I am open to any suggestions. Please make a recommendation and I will incorporate it into the next update. Regarding platform_legacy_irq, I have not seen an edge-triggered interrupt failure caused by platform_legacy_irq.

CPU0 CPU1
0: 380044 0 IO-APIC-edge timer
1: 590 0 IO-APIC-edge i8042
2: 0 0 XT-PIC cascade
12: 715 0 IO-APIC-edge i8042
14: 7902 0 IO-APIC-edge ide0
15: 2 0 IO-APIC-edge ide1
169: 0 0 IO-APIC-level uhci-hcd
185: 0 0 IO-APIC-level uhci-hcd
193: 84 0 IO-APIC-level aic79xx
201: 30 0 IO-APIC-level aic79xx
225: 16 0 IO-APIC-level aic7xxx
233: 16 0 IO-APIC-level aic7xxx
NMI: 0 0
LOC: 379962 380218
ERR: 0
MIS: 0

Thanks,
Tom

-----Original Message-----
From: Zwane Mwaikambo [mailto:zwane@linuxpower.ca]
Sent: Wednesday, May 28, 2003 4:06 PM
To: Jeff Garzik
Cc: Nguyen, Tom L; Nakajima, Jun; linux-kernel@vger.kernel.org; Saxena,
Sunil; Mallick, Asit K; Carbonari, Steven
Subject: Re: RFC Proposal to enable MSI support in Linux kernel

On Wed, 28 May 2003, Jeff Garzik wrote:

> > +#ifdef CONFIG_PCI_USE_VECTOR
> > + for (i = 0; i < (NR_VECTORS - FIRST_EXTERNAL_VECTOR); i++) {
> > +#else
> > for (i = 0; i < NR_IRQS; i++) {
> > +#endif
>
> This ifdef isn't necessary. ifdef in a header somewhere. For example,
> make NR_IRQS (or some other constant, if changing NR_IRQS definition
> isn't ok) condition on the CONFIG_xxx options.

Actually we can simply use;

for (i = 0; i < (NR_VECTORS - FIRST_EXTERNAL_VECTOR); i++) {
vector = ...
if (i >= NR_IRQS)
break;
...
set_intr_gate(vector, interrupt[i]);
}

> split into two functions, maybe? (due to the ifdef) Your call, it's
> mainly a programmer preference.

I agree.

> A bigger question though: if platform_legacy_irq() returns zero, will
> the handler _ever_ be edge-triggered?

Good question, i wouldn't think so, that would collapse that section into
two lines.

> As I see more and more of these ifdefs, I wonder if they couldn't be
> hidden inside wrappers?

Yes some of them are a bit easy to botch up later on.. like the following
excerpt.

> > +#ifdef CONFIG_PCI_USE_VECTOR
> > + if (!platform_legacy_irq(irq))
> > + entry->irq = IO_APIC_VECTOR(irq);
> > + else
> > +#endif
> > entry->irq = irq;
> > continue;

Thanks,
Zwane

-- 
function.linuxpower.ca
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