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

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Date:	Mon, 29 Feb 2016 07:46:58 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Darren Hart <dvhart@...radead.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<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" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] platform/x86: never 'select DMI' from a driver

On Mon, Feb 29, 2016 at 4:13 AM, Arnd Bergmann <arnd@...db.de> 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:

Darren, it may make sense for you to fold the DELL_LAPTOP change in.

--Andy

>
> 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")
> ---
>  drivers/platform/x86/Kconfig | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
> index 659e13b1e6f0..a65d974f387a 100644
> --- a/drivers/platform/x86/Kconfig
> +++ b/drivers/platform/x86/Kconfig
> @@ -105,6 +105,7 @@ config DELL_LAPTOP
>         tristate "Dell Laptop Extras"
>         depends on X86
>         depends on DELL_SMBIOS
> +       depends on DMI
>         depends on BACKLIGHT_CLASS_DEVICE
>         depends on ACPI_VIDEO || ACPI_VIDEO = n
>         depends on RFKILL || RFKILL = n
> @@ -112,7 +113,6 @@ config DELL_LAPTOP
>         select POWER_SUPPLY
>         select LEDS_CLASS
>         select NEW_LEDS
> -       select DMI
>         default n
>         ---help---
>         This driver adds support for rfkill and backlight control to Dell
> @@ -121,10 +121,10 @@ config DELL_LAPTOP
>  config DELL_WMI
>         tristate "Dell WMI extras"
>         depends on ACPI_WMI
> +       depends on DMI
>         depends on INPUT
>         depends on ACPI_VIDEO || ACPI_VIDEO = n
>         select INPUT_SPARSEKMAP
> -       select DMI
>         ---help---
>           Say Y here if you want to support WMI-based hotkeys on Dell laptops.
>
> --
> 2.7.0
>



-- 
Andy Lutomirski
AMA Capital Management, LLC