linux-kernel - Re: [PATCH 0/3] GPIO support for BRCMSTB

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Message-ID: <CACRpkdY_-zq-1srBC213MK_RoVvPsfTpRTQyx-4yRvCOV5JdxQ@mail.gmail.com>
Date:	Tue, 2 Jun 2015 11:05:21 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Gregory Fong <gregory.0xf0@...il.com>
Cc:	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	Alexandre Courbot <gnurou@...il.com>,
	bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>,
	Brian Norris <computersforpeace@...il.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Florian Fainelli <f.fainelli@...il.com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Mark Rutland <mark.rutland@....com>,
	Pawel Moll <pawel.moll@....com>,
	Rob Herring <robh+dt@...nel.org>,
	Russell King <linux@....linux.org.uk>
Subject: Re: [PATCH 0/3] GPIO support for BRCMSTB

On Wed, May 27, 2015 at 5:26 AM, Gregory Fong <gregory.0xf0@...il.com> wrote:

> I've now actually attempted to use the gpiolib irqchip code.  This
> driver can't directly use gpiochip_irqchip_add() because of the
> multiple gpiochip : one irqchip map.  At first, I thought it might be
> possible to simply add a new argument (or break things into a helper
> function) to allow setting the associated IRQ domain, but then I can't
> use the generic map and unmap functions which expect the irq_domain
> host_data member to be struct gpiochip *, which makes no sense in this
> case.  That puts me right back to implementing a special version of
> the map and unmap function.

I see.

I wonder if it is better to use one device per bank, and then set
IRQF_SHARED when you issue request_irq(), and have the
IRQ handler return IRQ_NONE if the IRQ comes from this
bank, or IRQ_HANDLED if it has handled an IRQ from its own
space.

This way multiple banks can share a single interrupt line.

Yours,
Linus Walleij
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