linux-kernel - Re: [PATCH] platform/x86: never 'select DMI' from a driver

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Date:	Mon, 29 Feb 2016 15:10:54 -0800
From:	Darren Hart <dvhart@...radead.org>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	linux-arm-kernel@...ts.infradead.org,
	Andy Lutomirski <luto@...nel.org>,
	Pali Rohár <pali.rohar@...il.com>,
	platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] platform/x86: never 'select DMI' from a driver

On Mon, Feb 29, 2016 at 01:13:31PM +0100, Arnd Bergmann wrote:
> CONFIG_DMI is a user-selectable Kconfig symbol that some drivers
> depend on. As part of a recent patch, other drivers started
> adding a 'select' for the same symbol, which now causes
> a recursive dependency:
> 
> drivers/gpio/Kconfig:34:error: recursive dependency detected!
> subsection "Kconfig recursive dependency limitations"
> drivers/gpio/Kconfig:34:        symbol GPIOLIB is selected by GEOS
> For a resolution refer to Documentation/kbuild/kconfig-language.txt
> subsection "Kconfig recursive dependency limitations"
> arch/x86/Kconfig:2591:  symbol GEOS depends on DMI
> For a resolution refer to Documentation/kbuild/kconfig-language.txt
> subsection "Kconfig recursive dependency limitations"
> arch/x86/Kconfig:815:   symbol DMI is selected by DELL_LAPTOP
> For a resolution refer to Documentation/kbuild/kconfig-language.txt
> subsection "Kconfig recursive dependency limitations"
> drivers/platform/x86/Kconfig:104:       symbol DELL_LAPTOP depends on BACKLIGHT_CLASS_DEVICE
> For a resolution refer to Documentation/kbuild/kconfig-language.txt
> subsection "Kconfig recursive dependency limitations"
> drivers/video/backlight/Kconfig:158:    symbol BACKLIGHT_CLASS_DEVICE is selected by FB_BACKLIGHT
> For a resolution refer to Documentation/kbuild/kconfig-language.txt
> subsection "Kconfig recursive dependency limitations"
> drivers/video/fbdev/Kconfig:192:        symbol FB_BACKLIGHT is selected by FB_SSD1307
> For a resolution refer to Documentation/kbuild/kconfig-language.txt
> subsection "Kconfig recursive dependency limitations"
> drivers/video/fbdev/Kconfig:2462:       symbol FB_SSD1307 depends on GPIOLIB
> 
> Basically we should either always use 'depends on' or always use 'select'
> to avoid this kind of loop. Using 'depends on' is more useful here,
> as it still allows users to turn off the symbol of they really
> want to, without having to track down every driver selecting it.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> Fixes: cbd9d95b2b27 ("dell-wmi, dell-laptop: select DMI")

Thanks Arnd, queued to testing.

-- 
Darren Hart
Intel Open Source Technology Center