linux-kernel - Re: [PATCH v2 6/7] clocksource/drivers/exynos

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Message-ID: <CANDhNCo-UF7uVWWMPEYyCzT0R7BTHb+uLq4d8ZfxURuk5r2AwQ@mail.gmail.com>
Date: Wed, 16 Apr 2025 14:00:25 -0700
From: John Stultz <jstultz@...gle.com>
To: Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: Will McVicker <willmcvicker@...gle.com>, Catalin Marinas <catalin.marinas@....com>, 
	Will Deacon <will@...nel.org>, Peter Griffin <peter.griffin@...aro.org>, 
	André Draszik <andre.draszik@...aro.org>, 
	Tudor Ambarus <tudor.ambarus@...aro.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Alim Akhtar <alim.akhtar@...sung.com>, Thomas Gleixner <tglx@...utronix.de>, 
	Saravana Kannan <saravanak@...gle.com>, Krzysztof Kozlowski <krzk@...nel.org>, 
	Donghoon Yu <hoony.yu@...sung.com>, Hosung Kim <hosung0.kim@...sung.com>, kernel-team@...roid.com, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	Youngmin Nam <youngmin.nam@...sung.com>, linux-samsung-soc@...r.kernel.org, 
	devicetree@...r.kernel.org
Subject: Re: [PATCH v2 6/7] clocksource/drivers/exynos_mct: Add module support

On Wed, Apr 16, 2025 at 12:48 PM John Stultz <jstultz@...gle.com> wrote:
> On Wed, Apr 16, 2025 at 6:46 AM Daniel Lezcano
> <daniel.lezcano@...aro.org> wrote:
> > So the whole clockevent / clocksource drivers policy would have to be making
> > impossible to unload a module once it is loaded.
> >
> > Do you have any ideas how to ensure that the converted drivers follow this
> > rule without putting more burden on the maintainer?
>
> Permanent modules just don't have a module_exit() hook, so that is
> pretty easy to look for.
> Obviously, I don't want to add more burden to the maintainership.
>
> From a given clockevent driver (or maybe a function pointer), we could
> check on the registration by calling __module_address(addr) [thanks to
> Sami Tolvanen for pointing that function out to me] on one of the
> function pointers provided, and check that there isn't a module->exit
> pointer.

Saravana also pointed out to me another approach that the irqchip code
uses: macros to populate an owner field with THIS_MODULE so that one
can easily get to the module struct
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/irqchip.h#n41

thanks
-john