From mboxrd@z Thu Jan  1 00:00:00 1970
From: marc.zyngier@arm.com (Marc Zyngier)
Date: Wed, 03 Dec 2014 14:59:00 +0000
Subject: [PATCH 00/16] irqchip: gic: killing gic_arch_extn, slowly
In-Reply-To: <2236572.MdjJGoEARl@wuerfel>
References: <1417539497-20101-1-git-send-email-marc.zyngier@arm.com>
 <2236572.MdjJGoEARl@wuerfel>
Message-ID: <547F2534.6040104@arm.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

Hi Arnd,

On 03/12/14 14:30, Arnd Bergmann wrote:
> On Tuesday 02 December 2014 16:58:01 Marc Zyngier wrote:
>>
>> - This actively *breaks* existing setups. Once you boot a new kernel
>>   with an old DT, suspend/resume *will* be broken. Old kernels on a
>>   new DT won't even boot! You've been warned. This really outline the
>>   necessity of actually describing the HW in device trees...
> 
> I wonder if we should take this as the trigger to come up with a
> better way of handling incompatible binding changes. The machine_desc
> has a .dt_fixup callback that we could use to modify the DT passed
> from a boot loader and warn about it, but no platform does this
> at the moment.
> 
> From what I can tell, the required change to get an old dtb working
> with a new kernel is to add a particular node and flip a few
> interrupt-parent properties, which seems doable as a quirk if
> people agree that it's a good idea.

That's probably the only way to avoid the breakage introduced by this
kind of changes. A few questions though:
- Where do we stop? Eventually, don't we end-up with a full DT in there?
- When do we retire such fixup? Or do we keep them forever?

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...