linux-kernel - Re: [PATCH v2] drm/bridge/sii8620: fix dependency on extcon

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Date:   Fri, 9 Apr 2021 09:37:46 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Robert Foss <robert.foss@...aro.org>, a.hajda@...sung.com,
        narmstrong@...libre.com, Laurent.pinchart@...asonboard.com,
        jonas@...boo.se, jernej.skrabec@...l.net, airlied@...ux.ie,
        daniel@...ll.ch, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org,
        Masahiro Yamada <masahiroy@...nel.org>
Cc:     kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v2] drm/bridge/sii8620: fix dependency on extcon

On 4/8/21 6:07 AM, Robert Foss wrote:
> The DRM_SIL_SII8620 kconfig has a weak `imply` dependency
> on EXTCON, which causes issues when sii8620 is built
> as a builtin and EXTCON is built as a module.
> 
> The symptoms are 'undefined reference' errors caused
> by the symbols in EXTCON not being available
> to the sii8620 driver.
> 
> Signed-off-by: Robert Foss <robert.foss@...aro.org>
> Reported-by: kernel test robot <lkp@...el.com>
> ---
> 
> Changes since v1:
>  - Fix typo on comment
> 
>  drivers/gpu/drm/bridge/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index 22a467abd3e9..2289b44613af 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -169,7 +169,7 @@ config DRM_SIL_SII8620
>  	tristate "Silicon Image SII8620 HDMI/MHL bridge"
>  	depends on OF
>  	select DRM_KMS_HELPER
> -	imply EXTCON
> +	depends on EXTCON || !EXTCON # if EXTCON=m, this cannot be built-in
>  	depends on RC_CORE || !RC_CORE
>  	help
>  	  Silicon Image SII8620 HDMI/MHL bridge chip driver.
> 

That gives me: (on linux-next 20210409)

drivers/gpu/drm/Kconfig:77:error: recursive dependency detected!
drivers/gpu/drm/Kconfig:77:	symbol DRM_KMS_HELPER is selected by DRM_SIL_SII8620
drivers/gpu/drm/bridge/Kconfig:168:	symbol DRM_SIL_SII8620 depends on EXTCON
drivers/extcon/Kconfig:2:	symbol EXTCON is selected by CHARGER_MANAGER
drivers/power/supply/Kconfig:499:	symbol CHARGER_MANAGER depends on POWER_SUPPLY
drivers/power/supply/Kconfig:2:	symbol POWER_SUPPLY is selected by OLPC_XO1_SCI
arch/x86/Kconfig:2757:	symbol OLPC_XO1_SCI depends on GPIO_CS5535
drivers/gpio/Kconfig:1156:	symbol GPIO_CS5535 depends on GPIOLIB
drivers/gpio/Kconfig:14:	symbol GPIOLIB is selected by I2C_MUX_LTC4306
drivers/i2c/muxes/Kconfig:47:	symbol I2C_MUX_LTC4306 depends on I2C
drivers/i2c/Kconfig:8:	symbol I2C is selected by FB_DDC
drivers/video/fbdev/Kconfig:63:	symbol FB_DDC depends on FB
drivers/video/fbdev/Kconfig:12:	symbol FB is selected by DRM_KMS_FB_HELPER
drivers/gpu/drm/Kconfig:83:	symbol DRM_KMS_FB_HELPER depends on DRM_KMS_HELPER
For a resolution refer to Documentation/kbuild/kconfig-language.rst
subsection "Kconfig recursive dependency limitations"

-- 
~Randy