linux-kernel - Re: [PATCH] RFC: interrupt consistency check for OF GPIO IRQs

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Date:	Thu, 12 Sep 2013 17:57:00 +0200
From:	Alexander Holler <holler@...oftware.de>
To:	Stephen Warren <swarren@...dotorg.org>
CC:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>,
	Linus Walleij <linus.walleij@...aro.org>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Grant Likely <grant.likely@...aro.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Linux-OMAP <linux-omap@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Enric Balletbo i Serra <eballetbo@...il.com>,
	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>,
	Santosh Shilimkar <santosh.shilimkar@...com>,
	Kevin Hilman <khilman@...aro.org>,
	Balaji T K <balajitk@...com>,
	Tony Lindgren <tony@...mide.com>,
	Jon Hunter <jgchunter@...il.com>
Subject: Re: [PATCH] RFC: interrupt consistency check for OF GPIO IRQs

Am 12.09.2013 17:19, schrieb Stephen Warren:
>
> IRQs, DMA channels, and GPIOs are all different things. Their bindings
> are defined independently. While it's good to define new types of
> bindings consistently with other bindings, this hasn't always happened,
> so you can make zero assumptions about the IRQ bindings by reading the
> documentation for any other kind of binding.
>
> Multiple interrupts are defined as follows:
>
> 	// Optional; otherwise inherited from parent/grand-parent/...
> 	interrupt-parent = <&gpio6>;
> 	// Must be in a fixed order, unless binding defines that the
> 	// optional interrupt-names property is to be used.
> 	interrupts = <1 IRQF_TRIGGER_HIGH> <2 IRQF_TRIGGER_LOW>;
> 	// Optional; binding for device defines whether it must
> 	// be present
> 	interrupt-names = "foo", "bar";
>
> If you need multiple interrupts, each with a different parent, you need
> to use an interrupt-map property (Google it for a more complete
> explanation I guess). Unlike "interrupts", "interrupt-map" has a phandle
> in each entry, and hence each entry can refer to a different IRQ
> controller. You end up defining a dummy interrupt controller node (which
> may be the leaf node with multiple IRQ outputs, which then points at
> itself as the interrupt parent), pointing the leaf node's
> interrupt-parent at that node, and then having interrupt-map "demux" the
> N interrupt outputs to the various interrupt controllers.
> --
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>

What a mess. I assume that is the price that bindings don't have to change.

Thanks for clarifying that,

Alexander Holler
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