linux-kernel - Re: [PATCH v6 0/9] devm_led_classdev

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Date: Thu, 14 Mar 2024 12:37:13 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: George Stark <gnstark@...utedevices.com>
Cc: pavel@....cz, lee@...nel.org, vadimp@...dia.com, mpe@...erman.id.au, 
	npiggin@...il.com, christophe.leroy@...roup.eu, hdegoede@...hat.com, 
	mazziesaccount@...il.com, peterz@...radead.org, mingo@...hat.com, 
	will@...nel.org, longman@...hat.com, boqun.feng@...il.com, 
	nikitos.tr@...il.com, marek.behun@....cz, kabel@...nel.org, 
	linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linuxppc-dev@...ts.ozlabs.org, kernel@...utedevices.com
Subject: Re: [PATCH v6 0/9] devm_led_classdev_register() usage problem

On Thu, Mar 14, 2024 at 10:46 AM George Stark <gnstark@...utedevices.com> wrote:
>
> This patch series fixes the problem of devm_led_classdev_register misusing.
>
> The basic problem is described in [1]. Shortly when devm_led_classdev_register()
> is used then led_classdev_unregister() called after driver's remove() callback.
> led_classdev_unregister() calls driver's brightness_set callback and that callback
> may use resources which were destroyed already in driver's remove().
>
> After discussion with maintainers [2] [3] we decided:
> 1) don't touch led subsytem core code and don't remove led_set_brightness() from it

subsystem

> but fix drivers
> 2) don't use devm_led_classdev_unregister
>
> So the solution is to use devm wrappers for all resources
> driver's brightness_set() depends on. And introduce dedicated devm wrapper
> for mutex as it's often used resource.

The leds related changes (except the last one) LGTM, hence FWIW,
Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
(for patches 2-8)

> [1] https://lore.kernel.org/lkml/8704539b-ed3b-44e6-aa82-586e2f895e2b@salutedevices.com/T/
> [2] https://lore.kernel.org/lkml/8704539b-ed3b-44e6-aa82-586e2f895e2b@salutedevices.com/T/#mc132b9b350fa51931b4fcfe14705d9f06e91421f
> [3] https://lore.kernel.org/lkml/8704539b-ed3b-44e6-aa82-586e2f895e2b@salutedevices.com/T/#mdbf572a85c33f869a553caf986b6228bb65c8383

-- 
With Best Regards,
Andy Shevchenko