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Date: Sun, 14 Jun 2009 21:36:53 +0200
From: Wolfgang Grandegger <wg@grandegger.com>
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To: "Hans J. Koch" <hjk@linutronix.de>
Subject: Re: [PATCH 2/2] uio: add an of_genirq driver
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Cc: devicetree-discuss@ozlabs.org, Greg KH <gregkh@suse.de>,
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Hans J. Koch wrote:
> On Sun, Jun 14, 2009 at 09:05:33PM +0200, Wolfram Sang wrote:
>>> Anyway, 0 is a valid IRQ number, so it cannot be used as "no irq".
>> May I point you to this thread?
>>
>> http://lkml.org/lkml/2005/11/21/221
> 
> Linus is just plain wrong in this 4 year old mail.

See also this related thread.

http://groups.google.com/group/rtc-linux/browse_thread/thread/9816648d5a8a1c9e/9968968188b5ab5a?lnk=gst&q=rx8025#9968968188b5ab5a

> 
>> (The issue comes up once in a while as some archs still use NO_IRQ, some with
>> 0 some with -1)
>>
>>>> 	if (uioinfo->irq == NO_IRQ)
>>>> 		uioinfo->irq = UIO_IRQ_NONE;
>>> Sorry for my ignorance, but what is NO_IRQ? If I do

It's 0 on PowerPC but ARM seems still to use -1.

http://lxr.linux.no/linux+v2.6.30/arch/powerpc/include/asm/irq.h#L29

For x86 it's not defined at all. But as this code is for the PowerPC,
where using NO_IRQ seems still to be OK.

Wolfgang.