linux-kernel - Re: [PATCH v2] gpio: Add Avionic Design N-bit GPIO expander support

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Message-ID: <20120810084859.GA16550@avionic-0098.mockup.avionic-design.de>
Date:	Fri, 10 Aug 2012 10:48:59 +0200
From:	Thierry Reding <thierry.reding@...onic-design.de>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	Grant Likely <grant.likely@...retlab.ca>,
	Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org,
	devicetree-discuss@...ts.ozlabs.org,
	Linus Walleij <linus.walleij@...ricsson.com>,
	Rob Herring <rob.herring@...xeda.com>,
	Wolfram Sang <w.sang@...gutronix.de>
Subject: Re: [PATCH v2] gpio: Add Avionic Design N-bit GPIO expander support

On Fri, Aug 10, 2012 at 10:41:58AM +0200, Linus Walleij wrote:
> On Fri, Aug 10, 2012 at 10:35 AM, Thierry Reding
> <thierry.reding@...onic-design.de> wrote:
> >> Consult the following article on LWN:
> >> http://lwn.net/Articles/470820/
> >>
> >> Then grep your gitlog and you'll see we got rid of it from ARM.
> >
> > Then why is there still the following in arch/arm/include/asm/irq.h?
> >
> >         /*
> >          * Use this value to indicate lack of interrupt
> >          * capability
> >          */
> >         #ifndef NO_IRQ
> >         #define NO_IRQ  ((unsigned int)(-1))
> >         #endif
> 
> That's a question for Russell but I think it's basically there for
> old platforms, on a "don't use it"-basis. (Maybe a comment could
> be good.)
> 
> As you see non-sparse platforms can redefine NO_IRQS in their
> <mach/irqs.h> file, but in practice things like the VIC and GIC
> drivers have been switched over to using irqdomain which
> in turn does *not* allow IRQ 0 to be used, so most platforms
> are indirectly disallowed to use IRQ 0 anyway. In fact I think
> some of them are just broken now.

In that case it might be better to just drop it altogether and wait
until people with the broken platforms start complaining.

Thierry

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