linux-kernel - Re: [PATCH 2/5] gpio: davinci: Use dev name for label and automatic base selection

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Date:   Mon, 10 Sep 2018 12:03:21 -0500
From:   David Lechner <david@...hnology.com>
To:     Sekhar Nori <nsekhar@...com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Grygorii Strashko <grygorii.strashko@...com>
Cc:     Keerthy <j-keerthy@...com>, "Andrew F. Davis" <afd@...com>,
        Kevin Hilman <khilman@...nel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Adam Ford <aford173@...il.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH 2/5] gpio: davinci: Use dev name for label and automatic
 base selection

On 09/10/2018 02:37 AM, Sekhar Nori wrote:
> On Monday 10 September 2018 12:55 PM, Linus Walleij wrote:
>> On Sat, Sep 8, 2018 at 9:41 PM Grygorii Strashko
>> <grygorii.strashko@...com> wrote:
>>> On 09/06/2018 09:16 AM, Keerthy wrote:
>>
>>>> Okay now its numbered differently:
>>>>
>>>> cat /sys/class/gpio/gpiochip340/ngpio
>>>> 144
>>>>
>>>> cat /sys/class/gpio/gpiochip272/ngpio
>>>> 68
>> (...)
>>
>> So:
>>
>>>>> Are there applications that rely on the sysfs ABI on DaVinci?
>>>>>
>>>>> In that case base needs to be prerseved.
>>>
>>> Not only base, but label also - /sys/class/gpio/gpiochip0/label, as this is
>>> the way to find proper GPIO chip in sysfs using legacy GPIO ABI.
>>>
>>> Linus, this platform is old and most of the users do not use new ABI (chardev),
>>> so we could try change this, but need to be prepared for regressions reports.
>>
>> So what I'm trying to ask you guys is if there are applications that you
>> are aware of that use the old ABI, and who will upgrade their
>> kernels and be upset.
>>
>> We must not break userspace, but as you know if a tree falls in the
>> forest and nobody is there to hear it, it doesn't make a sound.
>>
>> If you're not aware of any such applications I guess we should try
>> changing this.
> 
> Personally I am not really aware of any application which relies on the
> ABI. I may have some scripts, but I can adjust them. I am also copying
> some frequent users of DaVinci in mainline for any comments from them.
> 
> Thanks,
> Sekhar
> 

It won't break anything that I am aware of.