Re: Updated MSI Patches

Greg KH
2003-08-12T05:53:02Z

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