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

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Message-ID: <CACRpkdYcuSpfZ0=UFUOx_-5kaAtCA4=AyXmSMbfrcqjf0r_xmQ@mail.gmail.com>
Date:   Mon, 10 Sep 2018 09:25:10 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Grygorii Strashko <grygorii.strashko@...com>
Cc:     Keerthy <j-keerthy@...com>, "Andrew F. Davis" <afd@...com>,
        "Nori, Sekhar" <nsekhar@...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>
Subject: Re: [PATCH 2/5] gpio: davinci: Use dev name for label and automatic
 base selection

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.

Yours,
Linus Walleij