linux-kernel - Re: [PATCH v6 0/4] Allow disabling all native fbdev drivers and only keeping DRM emulation

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Date:   Wed, 19 Jul 2023 19:49:17 +0200
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Helge Deller <deller@....de>, linux-kernel@...r.kernel.org
Cc:     Thomas Zimmermann <tzimmermann@...e.de>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Arnd Bergmann <arnd@...db.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Borislav Petkov <bp@...en8.de>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Daniel Vetter <daniel@...ll.ch>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        David Airlie <airlied@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Jacek Lawrynowicz <jacek.lawrynowicz@...ux.intel.com>,
        Jeffrey Hugo <quic_jhugo@...cinc.com>,
        Jingoo Han <jingoohan1@...il.com>, Lee Jones <lee@...nel.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Nipun Gupta <nipun.gupta@....com>,
        Oded Gabbay <ogabbay@...nel.org>,
        Pieter Jansen van Vuuren <pieter.jansen-van-vuuren@....com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Sam Ravnborg <sam@...nborg.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
        x86@...nel.org
Subject: Re: [PATCH v6 0/4] Allow disabling all native fbdev drivers and
 only keeping DRM emulation

Helge Deller <deller@....de> writes:

Hello Helge,

> Hi Javier,
>
> On 7/19/23 10:15, Javier Martinez Canillas wrote:
>> This patch series splits the fbdev core support in two different Kconfig
>> symbols: FB and FB_CORE. The motivation for this is to allow CONFIG_FB to
>> be disabled, while still having the the core fbdev support needed for the
>
> One "the" too much.
> (correcting just because this is a cover letter)
>
>> CONFIG_DRM_FBDEV_EMULATION to be enabled. The motivation is automatically
>> disabling all fbdev drivers instead of having to be disabled individually.
>>
>> The reason for doing this is that now with simpledrm, there's no need for
>> the legacy fbdev (e.g: efifb or vesafb) drivers anymore and many distros
>> now disable them. > But it would simplify the config a lot fo have a single
>> Kconfig symbol to disable all fbdev drivers.
>
> I suggest to rephrase this, e.g.:
> The reason for doing this is that with simpledrm, mainstream Linux distributions
> like Fedora, SUSE or Ubuntu can then more easily enable the DRM drivers only
> by switching off legacy fbdev drivers with one Kconfig option (e.g. for efifb or
> vesafb).
>
> (note: there are quite many other distributions, e.g. debian and the derivates,
> which still need the fbdev drivers for the various other architectures)
>

Right, I meant that there is no need anymore for the remaining fbdev
drivers that many distributions used to enable only to have fallback
fbcon/VT (like vesafb, efifb, simplefb, etc). But I'm OK with your
rephrasing and agree that's more accurate to cover all the distros.

>> I've built tested with possible combinations of CONFIG_FB, CONFIG_FB_CORE,
>> CONFIG_DRM_FBDEV_EMULATION and CONFIG_FB_DEVICE symbols set to 'y' or 'n'.
>>
>> Patch #1 moves the auxdisplay drivers to "Graphics support" Kconfig menu,
>> patch #2 moves the core fbdev Kconfig symbols to a separate Kconfig file,
>> patch #3 does the FB symbol split and introduces the FB_CORE symbol and
>> finally patch #4 makes the DRM symbol to select FB_CORE if the DRM fbdev
>> emualtion support was enabled.
>>
>> Since this series touches three subsystems (auxdisplay, fbdev and DRM),
>> I would like to merge it through DRM with the acks of these maintainers.
>
> Sure. Ack from me.
>
> The patch series look good otherwise. You may add:
> Acked-by: Helge Deller <deller@....de>
>

Thanks!

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat