From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>
Subject: Re: [PATCH V2 5/5] ARM: remove #gpio-ranges-cells property
Date: Tue, 16 Jul 2013 17:30:23 -0600
Message-ID: <51E5D78F.8060400@wwwdotorg.org>
References: <1373913629-32179-1-git-send-email-swarren@wwwdotorg.org>
 <1373913629-32179-5-git-send-email-swarren@wwwdotorg.org>
 <51E44ED9.9020807@gmail.com> <51E47F85.4050905@wwwdotorg.org>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org>
In-Reply-To: <51E47F85.4050905-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>
List-Unsubscribe: <https://lists.ozlabs.org/options/devicetree-discuss>,
 <mailto:devicetree-discuss-request-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org?subject=unsubscribe>
List-Archive: <http://lists.ozlabs.org/pipermail/devicetree-discuss/>
List-Post: <mailto:devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org>
List-Help: <mailto:devicetree-discuss-request-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org?subject=help>
List-Subscribe: <https://lists.ozlabs.org/listinfo/devicetree-discuss>,
 <mailto:devicetree-discuss-request-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org?subject=subscribe>
Errors-To: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org
Sender: "devicetree-discuss"
 <devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org>
To: Rob Herring <robherring2-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>, Shiraz Hashim <shiraz.hashim-qxv4g6HH51o@public.gmane.org>, Rob Herring <rob.herring-bsGFqQB8/DxBDgjK7y7TUQ@public.gmane.org>, linux-gpio-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Haojian Zhuang <haojian.zhuang-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>, Jingchang Lu <b35083-KZfg59tc24xl57MIdRCFDg@public.gmane.org>, devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
List-Id: devicetree@vger.kernel.org

On 07/15/2013 05:02 PM, Stephen Warren wrote:
> On 07/15/2013 01:34 PM, Rob Herring wrote:
>> On 07/15/2013 01:40 PM, Stephen Warren wrote:
>>> From: Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
>>>
>>> This property is no longer required by the GPIO binding. Remove it.
>>
>> Won't this break compatibility with older kernel? It is one thing to
>> deprecate, but removal is another. If the relevant maintainers don't
>> care, then I guess it is fine.
> 
> Yes.
> 
> I had originally hoped this could sneak in late for 3.11, but I suppose
> it's too late now. vf610.dtsi is a new file in 3.11 so has no legacy to
> protect.
> 
> Admittedly, the #gpio-cells property was added into the SPEAr files in 3.10.

One more thought here:

I know DT bindings are supposed to evolve so that a new kernel will
support arbitrary old DTs. I'll call that backwards-compatibility for
the DT parsing code.

However, this situation is the reverse; this patch would prevent a new
DT running on an older kernel. I'll call that forwards-compatibility.
I'm not sure if the intent is to support this or not? It's certainly the
first I explicitly thought about compatibility in this direction...