linux-kernel - Re: [PATCH] gpiolib: Avoid side effects in gpio_is

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Message-ID: <CACRpkdbqq1=8SeN18V_iyFQQ00bd8Eia5okB1v3f=nZQOnSiTA@mail.gmail.com>
Date:   Mon, 29 May 2023 11:07:56 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Chris Packham <Chris.Packham@...iedtelesis.co.nz>
Cc:     "brgl@...ev.pl" <brgl@...ev.pl>,
        "johan@...nel.org" <johan@...nel.org>,
        "andy.shevchenko@...il.com" <andy.shevchenko@...il.com>,
        "maz@...nel.org" <maz@...nel.org>,
        Ben Brown <Ben.Brown@...iedtelesis.co.nz>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] gpiolib: Avoid side effects in gpio_is_visible()

On Wed, May 17, 2023 at 12:19 AM Chris Packham
<Chris.Packham@...iedtelesis.co.nz> wrote:
> On 17/05/23 01:57, Linus Walleij wrote:
> > On Mon, May 15, 2023 at 12:27 AM Chris Packham
> > <Chris.Packham@...iedtelesis.co.nz> wrote:

> >> The crux of the problem is that the irq_desc is created when it hasn't
> >> been requested.

> > The right solution to me seems to be to not use gpiod_export()
> > and not use sysfs TBH.
>
> That's not really a feasible solution. I'm dealing with application code
> that has been happily using the sysfs interface for many years.

I wonder how many years.

The GPIO sysfs has been deprecated for seven years:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/Documentation/ABI/obsolete/sysfs-gpio?id=fe95046e960b4b76e73dc1486955d93f47276134

My fear is that deprecation is ignored and people still develop stuff
like this ignoring the fact that the ABI is deprecated.

Yours,
Linus Walleij