linux-kernel - Re: [PATCH] ata: Don't use NO_IRQ in pata_of

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Message-ID: <1323112754.7213.49.camel@dabdike.int.hansenpartnership.com>
Date:	Mon, 05 Dec 2011 13:19:14 -0600
From:	James Bottomley <James.Bottomley@...senPartnership.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Dave Martin <dave.martin@...aro.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Anton Vorontsov <cbouatmailru@...il.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Andrew Morton <akpm@...ux-foundation.org>,
	devicetree-discuss@...ts.ozlabs.org,
	LKML <linux-kernel@...r.kernel.org>, linux-ide@...r.kernel.org,
	Randy Dunlap <rdunlap@...otime.net>,
	linux-next@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Jeff Garzik <jgarzik@...hat.com>,
	Pawel Moll <pawel.moll@....com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ata: Don't use NO_IRQ in pata_of_platform driver

On Mon, 2011-12-05 at 18:45 +0000, Alan Cox wrote:
> > But as you illustrated, there is a large number of drivers that already 
> > assume no IRQ is < 0, even if they don't use any IRQ #0 themselves.  
> > That is a much bigger problem to fix.
> 
> And a much larger number assuming the reverse is true which are hiding
> potential bugs on ARM.
> 
> Looking at the serial stuff the best checks appear to be looking at
> "irq", "-1" and NO_IRQ.
> 
> For migration stuff that's doing broken things like
> 
> 	if (irq < 0)
> 
> can be changed to
> 
> 	if (irq <= 0)
> 
> and that can be done before NO_IRQ itself is nailed on ARM and PA-RISC.

To be honest, we don't care very much.  Parisc interrupts are cascading
and mostly software assigned (except our EIEM which we keep internal).
We use a base offset at 16 or 64 (depending on GSC presence or not) so
IRQs 0-15 aren't legal on parisc either (we frob some of the hard coded
ISA interrupts on the WAX eisa bus).

We use NO_IRQ as an IRQ assignment error return and that's about it (and
that error shouldn't ever really occur).

James


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