linux-kernel - Re: [PATCH] drm: fix up fbdev Kconfig defaults

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Message-ID: <971f1e86-bcc4-4462-81c7-571a05748b46@suse.de>
Date:   Mon, 18 Sep 2023 09:25:52 +0200
From:   Thomas Zimmermann <tzimmermann@...e.de>
To:     Arnd Bergmann <arnd@...nel.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Helge Deller <deller@....de>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Christian König <christian.koenig@....com>,
        Dave Airlie <airlied@...hat.com>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Jim Cromie <jim.cromie@...il.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Arthur Grillo <arthurgrillo@...eup.net>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-fbdev@...r.kernel.org
Subject: Re: [PATCH] drm: fix up fbdev Kconfig defaults

Hi

Am 11.09.23 um 22:52 schrieb Arnd Bergmann:
> From: Arnd Bergmann <arnd@...db.de>
> 
> As a result of the recent Kconfig reworks, the default settings for the
> framebuffer interfaces changed in unexpected ways:
> 
> Configurations that leave CONFIG_FB disabled but use DRM now get
> DRM_FBDEV_EMULATION by default. This also turns on the deprecated /dev/fb
> device nodes for machines that don't actually want it.
> 
> In turn, configurations that previously had DRM_FBDEV_EMULATION enabled
> now only get the /dev/fb front-end but not the more useful framebuffer
> console, which is not selected any more.
> 
> We had previously decided that any combination of the three frontends
> (FB_DEVICE, FRAMEBUFFER_CONSOLE and LOGO) should be selectable, but the
> new default settings mean that a lot of defconfig files would have to
> get adapted.
> 
> Change the defaults back to what they were in Linux 6.5:
> 
>   - Leave DRM_FBDEV_EMULATION turned off unless CONFIG_FB
>     is enabled. Previously this was a hard dependency but now the two are
>     independent. However, configurations that enable CONFIG_FB probably
>     also want to keep the emulation for DRM, while those without FB
>     presumably did that intentionally in the past.
> 
>   - Leave FB_DEVICE turned off for FB=n. Following the same
>     logic, the deprecated option should not automatically get enabled
>     here, most users that had FB turned off in the past do not want it,
>     even if they want the console
> 
>   - Turn the FRAMEBUFFER_CONSOLE option on if
>     DRM_FBDEV_EMULATION is set to avoid having to change defconfig
>     files that relied on it being selected unconditionally in the past.
>     This also makes sense since both LOGO and FB_DEVICE are now disabled
>     by default for builds without CONFIG_FB, but DRM_FBDEV_EMULATION
>     would make no sense if all three are disabled.
> 
> Fixes: a5ae331edb02b ("drm: Drop select FRAMEBUFFER_CONSOLE for DRM_FBDEV_EMULATION")
> Fixes: 701d2054fa317 ("fbdev: Make support for userspace interfaces configurable")
> Reported-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Acked-by: Thomas Zimmermann <tzimmermann@...e.de>

> ---
>   drivers/gpu/drm/Kconfig          | 2 +-
>   drivers/video/console/Kconfig    | 1 +
>   drivers/video/fbdev/core/Kconfig | 2 +-
>   3 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> index 7df8b6875b121..144a9a1d31cea 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -135,7 +135,7 @@ config DRM_FBDEV_EMULATION
>   	bool "Enable legacy fbdev support for your modesetting driver"
>   	depends on DRM
>   	select FRAMEBUFFER_CONSOLE_DETECT_PRIMARY if FRAMEBUFFER_CONSOLE
> -	default y
> +	default FB
>   	help
>   	  Choose this option if you have a need for the legacy fbdev
>   	  support. Note that this support also provides the linux console
> diff --git a/drivers/video/console/Kconfig b/drivers/video/console/Kconfig
> index b575cf54174af..83c2d7329ca58 100644
> --- a/drivers/video/console/Kconfig
> +++ b/drivers/video/console/Kconfig
> @@ -74,6 +74,7 @@ config DUMMY_CONSOLE_ROWS
>   config FRAMEBUFFER_CONSOLE
>   	bool "Framebuffer Console support"
>   	depends on FB_CORE && !UML
> +	default DRM_FBDEV_EMULATION
>   	select VT_HW_CONSOLE_BINDING
>   	select CRC32
>   	select FONT_SUPPORT
> diff --git a/drivers/video/fbdev/core/Kconfig b/drivers/video/fbdev/core/Kconfig
> index 114cb8aa6c8fd..804c2bec9b43c 100644
> --- a/drivers/video/fbdev/core/Kconfig
> +++ b/drivers/video/fbdev/core/Kconfig
> @@ -28,7 +28,7 @@ config FIRMWARE_EDID
>   config FB_DEVICE
>   	bool "Provide legacy /dev/fb* device"
>   	depends on FB_CORE
> -	default y
> +	default FB
>   	help
>   	  Say Y here if you want the legacy /dev/fb* device file and
>   	  interfaces within sysfs anc procfs. It is only required if you

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)

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