linux-kernel - Re: [libgpiod v1.6.x][PATCH] tests: mockup: unbind mockup devices before unloading the module

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Message-ID: <ZOP/n30hYR/8zN60@sol>
Date:   Tue, 22 Aug 2023 08:21:51 +0800
From:   Kent Gibson <warthog618@...il.com>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [libgpiod v1.6.x][PATCH] tests: mockup: unbind mockup devices
 before unloading the module

On Mon, Aug 21, 2023 at 05:33:39PM +0200, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> 
> gpio-mockup relies on the GPIO devices being registered in module's __init
> function and them being unregistered in __exit. This works with the GPIO
> subsystem as it only takes a reference to the underlying owner module when
> a GPIO descriptor is requested and not when the GPIO device is
> instantiated.
> 
> This behavior may change in the future in the kernel so make the behavior
> of libgpiomockup more correct and have it unbind all mockup devices over
> sysfs before unloading the module.
> 

Never knew that unbinding was even an option.
Maybe update gpio-mockup's documentation?

Just clarifying what the potential impact of the existing libgpiomockup
behaviour and future kernel behaviour is - the kernel may log errors but
otherwise correctly handle userspace unloading behaving badly?
So this patch is pre-emptory noise reduction?

Cheers,
Kent.