linux-kernel - Re: [PATCH 5.15 808/917] drm: fb_helper: improve CONFIG

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Date:   Fri, 19 Nov 2021 08:50:05 +0100
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Cc:     stable@...r.kernel.org,
        "Acked-by: Jani Nikula" <jani.nikula@...el.com>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 5.15 808/917] drm: fb_helper: improve CONFIG_FB dependency

On 15. 11. 21, 18:05, Greg Kroah-Hartman wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> [ Upstream commit 9d6366e743f37d36ef69347924ead7bcc596076e ]

Hi,

this breaks build on openSUSE's armv7hl config:
$ wget -O .config 
https://raw.githubusercontent.com/openSUSE/kernel-source/stable/config/armv7hl/default
$ make -j168 CROSS_COMPILE=arm-suse-linux-gnueabi- ARCH=arm vmlinux
...
   LD      .tmp_vmlinux.btf
arm-suse-linux-gnueabi-ld: drivers/gpu/drm/panel/panel-simple.o: in 
function `panel_simple_probe':
drivers/gpu/drm/panel/panel-simple.c:803: undefined reference to 
`drm_panel_dp_aux_backlight'
$ grep -E 'CONFIG_(DRM|FB|DRM_KMS_HELPER|DRM_FBDEV_EMULATION)\>' .config
CONFIG_DRM=y
CONFIG_DRM_KMS_HELPER=m
CONFIG_DRM_FBDEV_EMULATION=y
CONFIG_FB=y

5.16-rc1 builds just fine -- investigating why…

> My previous patch correctly addressed the possible link failure, but as
> Jani points out, the dependency is now stricter than it needs to be.
> 
> Change it again, to allow DRM_FBDEV_EMULATION to be used when
> DRM_KMS_HELPER and FB are both loadable modules and DRM is linked into
> the kernel.
> 
> As a side-effect, the option is now only visible when at least one DRM
> driver makes use of DRM_KMS_HELPER. This is better, because the option
> has no effect otherwise.
> 
> Fixes: 606b102876e3 ("drm: fb_helper: fix CONFIG_FB dependency")
> Suggested-by: Acked-by: Jani Nikula <jani.nikula@...el.com>
> Reviewed-by: Javier Martinez Canillas <javierm@...hat.com>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> Signed-off-by: Daniel Vetter <daniel.vetter@...ll.ch>
> Link: https://patchwork.freedesktop.org/patch/msgid/20211029120307.1407047-1-arnd@kernel.org
> Signed-off-by: Sasha Levin <sashal@...nel.org>
> ---
>   drivers/gpu/drm/Kconfig | 5 ++---
>   1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> index 9199f53861cac..6ae4269118af3 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -102,9 +102,8 @@ config DRM_DEBUG_DP_MST_TOPOLOGY_REFS
>   
>   config DRM_FBDEV_EMULATION
>   	bool "Enable legacy fbdev support for your modesetting driver"
> -	depends on DRM
> -	depends on FB=y || FB=DRM
> -	select DRM_KMS_HELPER
> +	depends on DRM_KMS_HELPER
> +	depends on FB=y || FB=DRM_KMS_HELPER
>   	select FB_CFB_FILLRECT
>   	select FB_CFB_COPYAREA
>   	select FB_CFB_IMAGEBLIT
> 


-- 
js
suse labs