linux-kernel - Re: [PATCH 0/3] i2c: mux: don't access GPIOLIB internal structures

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Message-ID: <CAMRc=MdxF-0TE2uTOCQU8XJdgtQf_8t_yZPd2+xbF6_0WUmSGA@mail.gmail.com>
Date:   Fri, 13 Oct 2023 08:50:37 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Linus Walleij <linus.walleij@...aro.org>,
        Andy Shevchenko <andy@...nel.org>,
        Peter Korsgaard <peter.korsgaard@...co.com>,
        Peter Rosin <peda@...ntia.se>
Cc:     linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-i2c@...r.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH 0/3] i2c: mux: don't access GPIOLIB internal structures

On Wed, Oct 11, 2023 at 3:02 PM Bartosz Golaszewski <brgl@...ev.pl> wrote:
>
> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
>
> The backstory for this short series is that we are identyfing and
> removing all unauthorized uses of GPIOLIB structures across the kernel.
>
> For example: there are many users that access struct gpio_chip when the
> only user allowed to safely do this is the provider of that chip.
>
> We are very close to removing gpiochip_find(). Another function that
> poses a similar problem is gpiod_to_chip() which also returns the
> address of the underlying gpio_chip without assuring that it will not go
> away e.g. due to a hot-unplug event or a device unbind.
>
> We'll need to replace it with gpiod_to_gpio_device() across the entire
> tree. Let's start by actually providing it and adding the first user:
> the i2c-mux-gpio driver which dereferences the otherwise opaque struct
> gpio_desc.
>
> Let's also add a helper that allows to retrieve the address of the
> struct device backing the GPIO device as this is another valid use-case.
>
> Finally, let's un-include the GPIO private header and fix the code to
> access the device in a safe way.
>
> As the change is pretty minor, it would be best if patch 3/3 could be
> acked by the I2C mux maintainers and went through the GPIO tree.
> Otherwise, I can apply patches 1 and 2 and provide an immutable branch.
>
> Bartosz Golaszewski (3):
>   gpiolib: provide gpio_device_to_device()
>   gpiolib: provide gpiod_to_gpio_device()
>   i2c: mux: gpio: don't fiddle with GPIOLIB internals
>
>  drivers/gpio/gpiolib.c           | 38 ++++++++++++++++++++++++++++++++
>  drivers/i2c/muxes/i2c-mux-gpio.c | 12 +++++-----
>  include/linux/gpio/driver.h      |  3 +++
>  3 files changed, 47 insertions(+), 6 deletions(-)
>
> --
> 2.39.2
>

Queued for v6.7.

Bart