linux-kernel - Re: [PATCH] gpio: zynq: Setup chip->base based on alias ID

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Date:   Wed, 2 May 2018 15:01:24 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Michal Simek <michal.simek@...inx.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Michal Simek <monstr@...str.eu>,
        Steffen Trumtrar <s.trumtrar@...gutronix.de>,
        Peter Crosthwaite <peter.crosthwaite@...inx.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Rob Herring <robherring2@...il.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] gpio: zynq: Setup chip->base based on alias ID

On Wed, May 2, 2018 at 12:15 PM, Michal Simek <michal.simek@...inx.com> wrote:
> On 2.5.2018 12:10, Linus Walleij wrote:
>> On Thu, Apr 26, 2018 at 3:35 PM, Michal Simek <michal.simek@...inx.com> wrote:

>>> Yes, it is about legacy application which I have seen recently and there
>>> is no source code for application calls it because board vendor doesn't
>>> provide it.
>>>
>>> You are right that -1 was used from the beginning in mainline but
>>> unfortunately this driver was in vendor tree for a while and it uses 0
>>> there.
>>>
>>> In upstreaming this was changed to -1 but customers have a lot of code
>>> which developed against vendor tree and they want to use
>>> latest&greatest. And without this they are not able to run that
>>> applications.
>>>
>>> I found that this logic is already in 5 drivers in mainline that's why I
>>> send this patch to be +1.
>>
>> I see.
>>
>> Sadly comaptibility with out-of-tree driver code is none of our
>> (community) business.
>>
>> We do pay a lot of effort not to break the ABI to userspace, but
>> it needs to be an ABI coming from the mainline kernel, not from
>> a vendor tree.
>>
>> So to the mainline kernel this is no regression.
>
> I understand your statement. On the other hand it is feature which was
> permitted in past for some drivers and this is +1.

But was it permitted because of breaking out of tree code?

I know people have done questionable things in the past, but
two wrongs does not make one right.

Yours,
Linus Walleij