linux-kernel - Re: [PATCH 2/2] gpio: use a mutex to protect the list of GPIO devices

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Date:   Tue, 28 Nov 2023 18:08:58 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Kent Gibson <warthog618@...il.com>, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH 2/2] gpio: use a mutex to protect the list of GPIO devices

On Mon, Nov 27, 2023 at 08:37:16PM +0100, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> 
> The global list of GPIO devices is never modified or accessed from
> atomic context so it's fine to protect it using a mutex. Add a new
> global lock dedicated to the gpio_devices list and use it whenever
> accessing or modifying it.
> 
> While at it: fold the sysfs registering of existing devices into
> gpiolib.c and make gpio_devices static within its compilation unit.

...

> +	scoped_guard(mutex, &gpio_devices_lock) {

This is a lot of churn with this because of switching to RAII.
Can the body be firstly moved to a helper?

> +		/*
> +		 * TODO: this allocates a Linux GPIO number base in the global
> +		 * GPIO numberspace for this chip. In the long run we want to
> +		 * get *rid* of this numberspace and use only descriptors, but
> +		 * it may be a pipe dream. It will not happen before we get rid
> +		 * of the sysfs interface anyways.
> +		 */

...

>  	list_for_each_entry(gdev, &gpio_devices, list)
> +		if (index-- == 0)
>  			return gdev;

I believe this is better with outer {}.

-- 
With Best Regards,
Andy Shevchenko