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

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Message-ID: <637afb25-8ee2-4188-9385-27ee6a97ec59@suse.de>
Date:   Tue, 12 Sep 2023 10:11:43 +0200
From:   Thomas Zimmermann <tzimmermann@...e.de>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Arnd Bergmann <arnd@...nel.org>
Cc:     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>, Arnd Bergmann <arnd@...db.de>,
        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 12.09.23 um 09:14 schrieb Geert Uytterhoeven:
[...]
>> --- 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
> 
> While this is true for existing configs, it is no longer true in general,
> as DRM_FBDEV_EMULATION is no longer related to FB.

Would it make sense to make FRAMEBUFFER_CONSOLE an independent option 
and have FBDEV_EMULATION depend on it? Something like this:

FRAMEBUFFER_CONSOLE
	depends on DRM || FB
	select FB_CORE

FBDEV_EMULATION
	depends on DRM
	depends on FRAMEBUFFER_CONSOLE
	default y

So if any graphics subsystems are enabled, FRAMEBUFFER_CONSOLE is 
select-able. But for DRM, FBDEV_EMULATION disables the console. That 
option remains more for historical reasons than actual usefulness.

Best regards
Thomas

> 
>>          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
> 
> Sounds good to me, although it looks a bit strange at first sight
> (FRAMEBUFFER_CONSOLE defaults to n on a system with real fbdev, but
> y on emulated fbdev?).
> So this is the fix for commit a5ae331edb02b ("drm: Drop select
> FRAMEBUFFER_CONSOLE for 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
> 
> Changing this means possibly causing regressions on systems running
> an fbdev userspace.
> 
>>          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
> 
> Gr{oetje,eeting}s,
> 
>                          Geert
> 

-- 
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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