linux-kernel - Re: [PATCH v3] simplefb: Enable boot time VESA graphic mode selection.

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Date:   Wed, 23 Feb 2022 19:34:54 +0100
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Michal Suchánek <msuchanek@...e.de>
Cc:     dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, Martin Mares <mj@....cz>,
        Helge Deller <deller@....de>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Sudeep Holla <sudeep.holla@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Cristian Marussi <cristian.marussi@....com>,
        Simon Trimmer <simont@...nsource.cirrus.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Arnd Bergmann <arnd@...db.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rob Herring <robh@...nel.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        David Herrmann <dh.herrmann@...il.com>,
        linux-kernel@...r.kernel.org, linux-video@...ey.karlin.mff.cuni.cz
Subject: Re: [PATCH v3] simplefb: Enable boot time VESA graphic mode
 selection.

On 2/23/22 19:23, Michal Suchánek wrote:

[snip]

>> My point about the subject line remains thought, I would use something like:
>>
>> firmware: sysfb: Enable boot time VESA graphic mode selection for simplefb
> 
> I see where the confusion comes from.
>

Yeah. And just to clarify, the "simplefb" in the subject line I proposed
was about the sysfb simplefb and not the fbdev simplefb :)
 
> The efifb (and probably vesafb) has implicit unstated dependency on
> sysfb. So the drivers that select BOOT_VESA_SUPPORT should instead
> depend on SYSFB, and then SYSFB can select BOOT_VESA_SUPPORT, and it
> will look much saner.
>

That indeed would be much nicer. And I agree with you that there's an
implicit dependency that should be made explicit since SYSFB is what
registers the "efi-framebuffer" or "vesa-framebuffer" if SYSFB_SIMPLEFB
is not enabled.

Should SYSFB should only select BOOT_VESA_SUPPORT if x86 ? I know that
in practice shouldn't matter because BOOT_VESA_SUPPORT is under x86 but
I guess is more correct if that's the case.

And I think that FB_SIMPLE should depend on SYSFB_SIMPLEFB if !OF (since
a "simple-framebuffer" platform device could be registered by OF if a
Device Tree node with compatible "simple-framebuffer" exists).

Best regards, -- 
Javier Martinez Canillas
Linux Engineering
Red Hat