Re: Updated MSI Patches

[Greg KH]

On Mon, Aug 11, 2003 at 09:41:30PM -0400, Zwane Mwaikambo wrote:
> > > I hope there may be a way to determine the number of vectors supported 
> > > by CPU during the run-time. I look at the file ../include/asm-i386/mach-
> > > default/irq_vectors.h, the maximum of vectors (256) is already well 
> > > commented.
> > 
> > Yeah, but that's in reference to APIC interrupt sources, right?  Does
> > that correspond to these "vectors" too?  If so, why not just use the
> > existing NR_IRQS value instead of creating your own?
> 
> There isn't a 1:1 relationship between NR_IRQS and NR_VECTORS we really 
> shouldn't mix them together. NR_IRQS can be much higher than 256 whilst 
> on i386 we're fixed to 256 vectors due to that being the Interrupt 
> Descriptor Table capacity. It is still possible to service more interrupt 
> lines than 256 on SMP however by making IDTs per 'interrupt servicing 
> node'

Ah, so for processors other than i386, NR_VECTORS can be bigger?

I think a nice description is still needed for this value for just this
reason :)

thanks,

greg k-h
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