linux-kernel - Re: [PATCH v2 1/4] MFD: Palmas: Check if interrupts property exists and then only request irq

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Date:	Tue, 18 Jun 2013 13:11:56 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	"J, KEERTHY" <j-keerthy@...com>
CC:	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"broonie@...nel.org" <broonie@...nel.org>,
	"ldewangan@...dia.com" <ldewangan@...dia.com>,
	"sameo@...ux.intel.com" <sameo@...ux.intel.com>,
	"grant.likely@...retlab.ca" <grant.likely@...retlab.ca>,
	"swarren@...dia.com" <swarren@...dia.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"gg@...mlogic.co.uk" <gg@...mlogic.co.uk>
Subject: Re: [PATCH v2 1/4] MFD: Palmas: Check if interrupts property exists
 and then only request irq

On 06/18/2013 11:33 AM, J, KEERTHY wrote:
> Stephen Warren wrote at Tuesday, June 18, 2013 10:53 PM:
...>> No, you should just check the IRQ number.
> 
> Hmmm...so something like (!i2c->irq)

Yes.

>> Consider this:
>>
>> If the device was instantiated from a board file *or* a device tree,
>> i2c->irq is correctly set. Hence, checking that value works in both
>> cases.
>>
>> If you check the interrupts DT property, that will only work if the
>> device was instantiated from device tree, and not if it was
>> instantiated from a board file; the property will never exist in the
>> board file case, and hence you'll never be able to have a board file
>> provide an interrupt.
> 
> The board file approach is getting deprecated for this. I
> Myself removed board file related pdata stuff in one of the patches.
> 
> http://www.mail-archive.com/linux-omap@vger.kernel.org/msg90598.html
> 
> So going the DeviceTree way.

Even if you're 100% sure this driver will only ever work with DT (which
seems like a bad assumption to make no matter what the circumstance),
it'd still be best to detect whether an IRQ was specified in a generic
way. That way, nobody will read this driver, assume the code is generic,
and just copy/paste it without thinking.
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