linux-kernel - Re: [PATCH] of/irq: lookup 'interrupts-extended' property first

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Date:	Wed, 6 Aug 2014 14:50:47 -0700
From:	Tim Bird <tbird20d@...il.com>
To:	Brian Norris <computersforpeace@...il.com>
Cc:	Rob Herring <robherring2@...il.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] of/irq: lookup 'interrupts-extended' property first

On Wed, Aug 6, 2014 at 1:12 PM, Brian Norris
<computersforpeace@...il.com> wrote:
> On Wed, Aug 06, 2014 at 01:42:08PM -0500, Rob Herring wrote:
>> On Wed, Aug 6, 2014 at 11:54 AM, Brian Norris <computersforpeace@...il.com> wrote:
>> > On Thu, Jul 31, 2014 at 11:00:01AM -0700, Florian Fainelli wrote:
>> > I think it is important that a device tree provide some flexibility on
>> > kernel versions. We only invented 'interrupts-extended' in Linux 3.13,
>> > so it's easy to have device trees that could work only on 3.13+.
>> >
>> > Typically, we might say that new features require new kernels, but this
>> > is a very basic piece of the DT infrastructure. In our case, we have
>> > hardware whose basic features can be supported by a single interrupt
>> > parent, and so we used the 'interrupts' property pre-3.13. But when we
>> > want to add some power management features, there's an additional
>> > interrupt parent. Under the current DT binding, we have to switch over
>> > to using 'interrupts-extended' exclusively, and thus we must have a
>> > completely new DTB for >=3.13, and this DTB no longer works with the old
>> > kernels.
>>
>> "Must have" to enable the new features?
>
> Yes. The new feature requires an additional interrupt parent, and so it
> requires interrupts-extended.

Hold on there.  What about interrupt-map?  That was the traditional DT
feature for
supporting multi-parented interrupts.  Why couldn't the feature have been added
using that instead of interrupts-extended?

I know interrupts-extended is preferred, but has interrupt-map support been
removed from recent kernels?  I'm a bit confused.

 -- Tim Bird
Senior Software Engineer, Sony Mobile
Architecture Group Chair, CE Workgroup, Linux Foundation
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