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Subject: Re: [PATCH 2/5] gpio: davinci: Use dev name for label and automatic
 base selection
To:     Linus Walleij <linus.walleij@linaro.org>,
        Grygorii Strashko <grygorii.strashko@ti.com>
CC:     Keerthy <j-keerthy@ti.com>, "Andrew F. Davis" <afd@ti.com>,
        Kevin Hilman <khilman@kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        David Lechner <david@lechnology.com>,
        Adam Ford <aford173@gmail.com>,
        Bartosz Golaszewski <bgolaszewski@baylibre.com>
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 <CACRpkdYvNeKyfRf5Et5zC4=hcu9cfDubftRFRHtrKLN-5Snd1Q@mail.gmail.com>
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From:   Sekhar Nori <nsekhar@ti.com>
Message-ID: <b1f74d63-c9e8-2a7f-bd13-8f5fff27fc22@ti.com>
Date:   Mon, 10 Sep 2018 13:07:19 +0530
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On Monday 10 September 2018 12:55 PM, Linus Walleij wrote:
> On Sat, Sep 8, 2018 at 9:41 PM Grygorii Strashko
> <grygorii.strashko@ti.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