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From: Grant Likely <grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org>
To: "Uwe Kleine-König"
	<u.kleine-koenig-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
Cc: dbrownell-Rn4VEauK+AKRv+LV9MX5uipxlwaOVQ5f@public.gmane.org,
	mm-commits-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Greg Kroah-Hartman <greg-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org>,
	daniel-rDUAYElUppE@public.gmane.org,
	spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org,
	akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org,
	David Vrabel <dvrabel-2sJRl1BP9u0AvxtiuMwx3w@public.gmane.org>
Subject: Re: + spi-imx-correct-check-for-platform_get_irq-failing.patch added to -mm tree
Date: Wed, 9 Dec 2009 10:23:48 -0700	[thread overview]
Message-ID: <fa686aa40912090923v3a694fb6l18cb0d97cb1cdf9b@mail.gmail.com> (raw)
In-Reply-To: <20091209153241.GB1389-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>

2009/12/9 Uwe Kleine-König <u.kleine-koenig-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>:
> On Wed, Dec 09, 2009 at 08:08:19AM -0700, Grant Likely wrote:
>> >> This changes the old behaviour.  Is that what you intended?  '<= 0' perhaps?
>> > Yes, the old check was wrong.  What if the irq to use is 0?  I thought
>> > the commit log to be understandable.  platform_get_irq returns -ENXIO on
>> > error and an irq number on success.  So 0 has to be interpreted as valid
>> > irq, not an error.
>>
>> 0 is not a valid IRQ
> Hmm, on my x86 I have:
>
>        $ grep '\<0:' /proc/interrupts
>           0:      24330   IO-APIC-edge      timer
>
> arm/davinci starts at 0, too.  As does arm/ns9xxx.  arm/pxa seems to
> start at 1.  realview starts at 1, too.  So four out of five make are
> wrong?  Seems like a big area for cleanup.

As discussed on IRC, regardless of some of the core & arch use cases.
As far as drivers are concerned, 0 is not a valid IRQ.  Linus'
comments here were referenced: http://lkml.org/lkml/2005/11/21/221

The return of -ENXIO was added in commit 305b3228, and it is
definitely in the workaround category.  Damn.  And a quick grep show a
lot of broken drivers because of it.  (variations on the common 'if
(!irq)' pattern abound as well as a large number of the variant 'if
(irq < 0)').

Well.  Though I don't like it, I will take the patch as testing for <=
0 instead of < 0.  At least that doesn't create new situations of 0
being used as a valid IRQ.

g.

-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.

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  parent reply	other threads:[~2009-12-09 17:23 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <200912082330.nB8NU4IO016215@imap1.linux-foundation.org>
     [not found] ` <fa686aa40912081638m734e97c3r2c3f412898d293b@mail.gmail.com>
     [not found]   ` <20091209074533.GB8136@pengutronix.de>
     [not found]     ` <20091209074533.GB8136-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
2009-12-09 15:08       ` + spi-imx-correct-check-for-platform_get_irq-failing.patch added to -mm tree Grant Likely
     [not found]         ` <fa686aa40912090708g45879802l6cea7b401b1434e3-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2009-12-09 15:32           ` Uwe Kleine-König
     [not found]             ` <20091209153241.GB1389-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
2009-12-09 17:23               ` Grant Likely [this message]
2009-12-09 17:55             ` Uwe Kleine-König
2009-12-09 18:00               ` Grant Likely

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