Re: [PATCH 01/10] reset: ath79: add driver Kconfig option

From: Masahiro Yamada <yamada.masahiro@socionext.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	Axel Lin <axel.lin@ingics.com>,
	Hans de Goede <hdegoede@redhat.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Alban Bedel <albeu@free.fr>,
	Philipp Zabel <p.zabel@pengutronix.de>,
	Maxime Ripard <maxime.ripard@free-electrons.com>,
	Lee Jones <lee.jones@linaro.org>
Subject: Re: [PATCH 01/10] reset: ath79: add driver Kconfig option
Date: Thu, 25 Aug 2016 11:43:31 +0900	[thread overview]
Message-ID: <CAK7LNATduVA5bAuq-FxSbPcvhtR1iV7NckyNnwZmaz6yV-9gqg@mail.gmail.com> (raw)
In-Reply-To: <1779401.H3WQxbgf2J@wuerfel>

2016-08-25 5:06 GMT+09:00 Arnd Bergmann <arnd@arndb.de>:
> On Thursday, August 25, 2016 3:18:55 AM CEST Masahiro Yamada wrote:
>> Hi Arnd,
>>
>>
>> 2016-08-25 0:51 GMT+09:00 Arnd Bergmann <arnd@arndb.de>:
>> > On Wednesday, August 24, 2016 3:28:53 PM CEST Philipp Zabel wrote:
>> >>  if RESET_CONTROLLER
>> >>
>> >> +config RESET_ATH79
>> >> +       bool "AR71xx Reset Driver" if COMPILE_TEST
>> >> +       default ATH79
>> >> +       help
>> >> +         This enables the ATH79 reset controller driver that supports the
>> >> +         AR71xx SoC reset controller.
>> >> +
>> >>
>> >
>> > Nice series!
>> >
>> > Just note that there is one possible problem with COMPILE_TEST
>> > when the platforms are enabled, as you can then disable a driver
>> > that is normally there, and that can in turn cause problems in
>> > rare cases, e.g. when the driver has a global function that is
>> > called from platform code. I don't know if any of the drivers
>> > do that, but if they do, you'd have to use
>> >
>> > config RESET_ATH79
>> >        bool "AR71xx Reset Driver" if COMPILE_TEST && !ATH79
>> >        default ATH79
>> >
>> > to ensure that it's impossible to disable the driver on platforms
>> > that require it.
>>
>> Hmm,
>> Can we do this only when we really have to do so?
>> I think we should not care about such a rare case that may not happen.
>>
>> Let's start with only "if COMPILE_TEST",
>> and take a look at it if a build error is detected.
>>
>> Anyway, depending on platform code is a sign of weird implementation.
>>
>> It might be better to find a potential issue rather than hide it.
>>
>>
>>
>
> I just checked the object files in an allyesconfig build and found
> one instance:
>
> arch/arm/mach-sunxi/sunxi.c:extern void __init sun6i_reset_init(void);
> arch/arm/mach-sunxi/sunxi.c:            sun6i_reset_init();
> drivers/reset/reset-sunxi.c:void __init sun6i_reset_init(void)
>
> We should definitely make sure this one is handled right, and maybe
> check the source code for other instances.

Hmm.

Is is solved with RESET_OF_DECLARE(),
like we have CLK_OF_DECLARE() ?

Or, use something like postcore_initcall() to probe it really early?
Not sure...

-- 
Best Regards
Masahiro Yamada