linux-kernel - Re: [PATCH 1/3 v2] GPIO: gpio-dwapb: Enable platform driver binding to MFD driver

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Date:	Fri, 5 Sep 2014 21:37:36 +0200
From:	Sebastian Andrzej Siewior <sebastian@...akpoint.cc>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Weike Chen <alvin.chen@...el.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	atull <atull@...nsource.altera.com>, linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	Boon Leong Ong <boon.leong.ong@...el.com>,
	Hock Leong Kweh <hock.leong.kweh@...el.com>,
	Darren Hart <dvhart@...ux.intel.com>,
	Mika Westerberg <mika.westerberg@...el.com>,
	Andriy Shevchenko <andriy.shevchenko@...el.com>
Subject: Re: [PATCH 1/3 v2] GPIO: gpio-dwapb: Enable platform driver binding
 to MFD driver

On 2014-09-05 13:50:06 [+0200], Arnd Bergmann wrote:
> On Friday 05 September 2014 07:53:16 Weike Chen wrote:
> >  
> > -	irq_set_chained_handler(irq, dwapb_irq_handler);
> > -	irq_set_handler_data(irq, gpio);
> > +	if (!pp->irq_shared) {
> > +		irq_set_chained_handler(pp->irq, dwapb_irq_handler);
> > +		irq_set_handler_data(pp->irq, gpio);
> > +	} else {
> > +		/*
> > +		 * Request a shared IRQ since where MFD would have devices
> > +		 * using the same irq pin
> > +		 */
> > +		err = devm_request_irq(gpio->dev, pp->irq,
> > +				       dwapb_irq_handler_mfd,
> > +				       IRQF_SHARED, "gpio-dwapb-mfd", gpio);
> > +		if (err) {
> > +			dev_err(gpio->dev, "error requesting IRQ\n");
> > +			irq_domain_remove(gpio->domain);
> > +			gpio->domain = NULL;
> > +			return;
> > +		}
> > +	}
> >
> 
> I think this need some better documentation. Why is it safe to use
> devm_request_irq rather than irq_set_chained_handler here?

Usually it is preferred to use irq_set_chained_handler() for the chained
handler so the handler does not show up in /proc/interrupts.
This requires an exclusive non-shared handler which is not the case on
the intel platform. So they have to use devm_request_irq() instead.

Sebastian
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