linux-kernel - Re: [PATCH 0/2] change "client->irq >= 0" to "client->irq

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Date:	Wed, 03 Jun 2015 19:13:45 +0200
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Octavian Purdila <octavian.purdila@...el.com>
CC:	Linus Walleij <linus.walleij@...aro.org>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Jonathan Cameron <jic23@...nel.org>,
	Hartmut Knaack <knaack.h@....de>,
	Peter Meerwald <pmeerw@...erw.net>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	linux-iio@...r.kernel.org, rtc-linux@...glegroups.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] change "client->irq >= 0" to "client->irq > 0"

On 06/03/2015 01:02 PM, Alexandre Belloni wrote:
> On 03/06/2015 at 00:34:11 +0300, Octavian Purdila wrote :
>> This fixes an issue introduces by commit dab472eb931b ("i2c / ACPI:
>> Use 0 to indicate that device does not have interrupt assigned") where
>> drivers will try to request IRQ 0 when no GpioInt is defined in ACPI.
>>
>> The same issue occurs when the device is instantiated via device tree
>> with no IRQ, or from the i2c sysfs interface, even before the patch
>> above.
>>
>> Linus, since the commit above was already merged in the GPIO tree,
>> should these fixes be merged also via the GPIO tree (with ACKs from
>> the others subsystem maintainers)?
>>
>
> Side question, has it been considered that IRQ 0 is valid on some
> platform and that means i2c devices will not be able to be wired to that
> IRQ anymore? Though, I don't think there are any existing design that
> does so.

If IRQ 0 is valid, that's a bug. IRQ 0 has been an invalid IRQ number in the 
global IRQ namespace for a while now. Though architectures are allowed to 
have a valid IRQ 0, but it may only be used inside the architecture code 
itself and must not be used for IRQs that are potentially be used by drivers.

- Lars

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