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 17:33:49 +0000
From:	"J, KEERTHY" <j-keerthy@...com>
To:	Stephen Warren <swarren@...dotorg.org>
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



> -----Original Message-----
> From: Stephen Warren [mailto:swarren@...dotorg.org]
> Sent: Tuesday, June 18, 2013 10:53 PM
> To: J, KEERTHY
> Cc: linux-omap@...r.kernel.org; broonie@...nel.org;
> ldewangan@...dia.com; sameo@...ux.intel.com; grant.likely@...retlab.ca;
> swarren@...dia.com; linux-kernel@...r.kernel.org; linux-
> doc@...r.kernel.org; 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 11:19 AM, J, KEERTHY wrote:
> >
> >
> >> -----Original Message-----
> >> From: Stephen Warren [mailto:swarren@...dotorg.org]
> >> Sent: Tuesday, June 18, 2013 10:38 PM
> >> To: J, KEERTHY
> >> Cc: linux-omap@...r.kernel.org; broonie@...nel.org;
> >> ldewangan@...dia.com; sameo@...ux.intel.com;
> >> grant.likely@...retlab.ca; swarren@...dia.com;
> >> linux-kernel@...r.kernel.org; linux- doc@...r.kernel.org;
> >> 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 10:54 AM, J, KEERTHY wrote:
> >>> Hi Stephen,
> >>>
> >>>> -----Original Message-----
> >>>> From: Stephen Warren [mailto:swarren@...dotorg.org]
> >>>> Sent: Tuesday, June 18, 2013 9:22 PM
> >>>> To: J, KEERTHY
> >>>> Cc: linux-omap@...r.kernel.org; broonie@...nel.org;
> >>>> ldewangan@...dia.com; sameo@...ux.intel.com;
> >>>> grant.likely@...retlab.ca; swarren@...dia.com;
> >>>> linux-kernel@...r.kernel.org; linux- doc@...r.kernel.org;
> >>>> 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 04:01 AM, J Keerthy wrote:
> >>>>> Check if interrupts property exists and then only request irq.
> >>>>> On some boards INT line might not be connected to a valid irq
> line
> >>>>> on the application processor. Hence keeping a check before
> >>>>> requesting irq.
> >>>>
> >>>> When there is no interrupts property, surely i2c->irq == 0, which
> >>>> is an invalid IRQ, and hence there's no need to check this before
> >>>> copying the value?
> >>>
> >>> The intent here is NOT to request irq with 0 or Invalid IRQ.
> >>
> >> Sure.
> >>
> >>> The board File will not populate the interrupts entry if the INT
> >>> line is not Connected.
> >>
> >> Do you mean the interrupts DT property won't be present if there is
> >> no interrupt. If so, sure.
> >
> > Yes.
> >
> >>
> >>> Hence the patch checks for the 'interrupts' property.
> >>
> >> That shouldn't be necessary; IIRC, the I2C core has already parsed
> >> the interrupts property if there was one, and if there wasn't, it
> has
> >> set
> >> i2c->irq to some invalid value already.
> >>
> >> So, you simply need to check the value in i2c->irq, and don't need
> to
> >> look at the DT at all.
> >
> > Instead of checking the Invalid irq value which most likely can be 0.
> > I am not sure.
> > I am explicitly checking if the interrupts property exists or not.
> >
> > If not present then It throws out a warning. Either there is no Valid
> > INT line connection or the DeviceTree was not populated fully.
> >
> > This additional piece of information is good to have in the driver
> > IMHO. Let me know if this is rational enough to have in the driver.
> 
> No, you should just check the IRQ number.

Hmmm...so something like (!i2c->irq)

> 
> 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.

Regards,
Keerthy



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