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

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Message-ID: <alpine.LFD.2.02.1112061408000.2357@xanadu.home>
Date:	Tue, 6 Dec 2011 14:11:42 -0500 (EST)
From:	Nicolas Pitre <nicolas.pitre@...aro.org>
To:	Dave Martin <dave.martin@...aro.org>
cc:	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>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	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 Tue, 6 Dec 2011, Dave Martin wrote:

> On Mon, Dec 05, 2011 at 02:49:01PM -0500, Nicolas Pitre wrote:
> 
> > No need to convert everything.
> > 
> > First move is to make irq=0 meaning no IRQ.  That means making things 
> > like:
> > 
> > 	if (irq < 0)
> > 	if (irq >= 0)
> > 
> > into
> > 
> > 	if (irq <= 0)
> > 	if (irq > 0)
> > 
> > And replace NO_IRQ with 0.
> >
> > That change shouldn't break anything, except those drivers which are 1) 
> > being passed an actual IRQ #0 and 2) testing for no IRQ.  I suspect that 
> > those conditions aren't very common together.
> 
> To clarify, you're suggesting that the meanings of all other IRQ values
> would not change initially?

Initially, or even ever.

> (i.e., we remap HW irq 0, if there is one,
> to some other random number but have a 1:1 mapping for everything else).

Exact.

> That could make sense as an approach.

You might notice that a true IRQ #0 passed to generic drivers is not 
really frequent.


Nicolas
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