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From:   Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Date:   Wed, 11 Oct 2023 17:39:29 +0200
Message-ID: <CACMJSetxih3kwAVDpQNm_fApgdkOv-XfErqC8+hi7Nac4J+ZOg@mail.gmail.com>
Subject: Re: [PATCH 2/3] gpiolib: provide gpiod_to_gpio_device()
To:     Andy Shevchenko <andy.shevchenko@gmail.com>
Cc:     Bartosz Golaszewski <brgl@bgdev.pl>,
        Linus Walleij <linus.walleij@linaro.org>,
        Andy Shevchenko <andy@kernel.org>,
        Peter Korsgaard <peter.korsgaard@barco.com>,
        Peter Rosin <peda@axentia.se>, linux-gpio@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org
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On Wed, 11 Oct 2023 at 17:23, Andy Shevchenko <andy.shevchenko@gmail.com> w=
rote:
>
> On Wed, Oct 11, 2023 at 4:02=E2=80=AFPM Bartosz Golaszewski <brgl@bgdev.p=
l> wrote:
> >
> > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> >
> > Accessing struct gpio_chip backing a GPIO device is only allowed for th=
e
> > actual providers of that chip.
> >
> > Similarly to how we introduced gpio_device_find() in order to replace
> > the abused gpiochip_find(), let's introduce a counterpart to
> > gpiod_to_chip() that returns a reference to the GPIO device owning the
> > descriptor. This is done in order to later remove gpiod_to_chip()
> > entirely.
>
> My concern with this API is the following scenario:
> 1. One driver requests the GPIO descriptor.
> 2. Another driver does take an arbitrary number, converts to a
> descriptor and calls for this API.
>
> Is there any (potential) problem?

YES! And I have it already on my TODO list! But it's great to know I'm
not the only one seeing it.

Basically we need to

The end-goal should be to make gpio_to_desc() an internal GPIOLIB
symbol. There are still around 10 users outside drivers/gpio/ that
will need to be addressed in one way or another. Preferably by being
converted to using descriptors.

Bart

>
> --
> With Best Regards,
> Andy Shevchenko