linux-kernel - Re: [PATCH] sparse_irq aka dyn

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Date:	Mon, 17 Nov 2008 15:25:33 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Yinghai Lu <yinghai@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>, mingo@...e.hu,
	tglx@...utronix.de, linux-kernel@...r.kernel.org, travis@....com
Subject: Re: [PATCH] sparse_irq aka dyn_irq v13

On Sun, 2008-11-16 at 15:59 -0800, H. Peter Anvin wrote:
> 
> No, I think the whole notion of a static *numeric* identifier for an IRQ
> when it's something like MSI-X is simply pointless.  I think we should
> assign IRQ numbers beyond the legacy range dynamically.

Yup, exactly. Which is what we do on other platforms :-)

I think there is some value in getting rid of the irq_desc static array,
and to a certain extend having the ability to have irq_desc's be per-cpu
allocated but I think that patch tries to mix up way too many different
things, including a dubious attempt at tying the interrupt subsystem
into a specific implementation choice of x86 platforms for numbering.

Linux interrupts should just be a dynamically allocated number space,
with an exception for the 16 first ones (0 = illegal, 1...15 = legacy)
and that should be -separate- from the actual HW number of one on a
given PIC. In fact, powerpc handles multiple HW interrupt domain numbers
just fine that way which is very useful for embedded platforms with
funky cascaded PIC setups..

Ben.

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