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Subject: Re: [PATCH 4/5] Centralise NO_IRQ definition
From: David Woodhouse <dwmw2@infradead.org>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Paul Mackerras <paulus@samba.org>, Ingo Molnar <mingo@elte.hu>,
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Date: Tue, 22 Nov 2005 11:13:11 +0000
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On Mon, 2005-11-21 at 22:20 +0000, Alan Cox wrote:
> > Yes, G5 powermacs have the SATA controller on irq 0.  So if we can't
> > use irq 0, I can't get to my hard disk. :)  Other powermacs also use
> > irq 0 for various things, as do embedded PPC machines.
> 
> G5 powermacs have the SATA controller on physical IRQ value 0. Linux IRQ
> values don't need to exactly map. One of the x86 ports handles 'real IRQ
> 0' exactly this way. Its a cookie. Sure would benefit from a function
> for turning an IRQ into a description as a cleanup.

Remapping in that way sounds like a half-arsed hack to work around the
problem which Matthew is trying to fix properly by using NO_IRQ == -1.

Yes, there are drivers which are currently broken and assume irq 0 is
'no irq'. They are broken. Let's just fix them and not continue the
brain-damage.

-- 
dwmw2