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

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Date:   Wed, 23 Feb 2022 18:12:35 +0100
From:   Michal Suchánek <msuchanek@...e.de>
To:     Javier Martinez Canillas <javierm@...hat.com>
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 Wed, Feb 23, 2022 at 05:54:54PM +0100, Javier Martinez Canillas wrote:
> On 2/23/22 17:45, Michal Suchánek wrote:
>
> [snip]
>
> >>>
> >>> To enable use of VESA modes with simplefb in legacy BIOS boot mode drop
> >>
> >> I think you meant "VESA modes with the sysfb driver" ? or something like
> >> that since otherwise it seems that you meant to use it with the simplefb
> >> (drivers/video/fbdev/simplefb.c) fbdev driver, which doesn't support the
> >> "vga=" param as far as I understand (it just uses whatever was setup).
> >
> > And the vga= is whatever was set up by the realmode code. And the config
> > option for realmode code to do that is selected by vesafb and not
> > simplefb so it does not wotk for simplefb/simpledrm/whatewer when efifib
> > is not built into the kernel.
> >
>
> Yes, that's what I tried to say. But your commit message says "To enable
> use of VESA modes with simplefb in legacy BIOS boot mode" and that isn't
> accurate AFAIU (unless you meant sysfb instead).

 config SYSFB_SIMPLEFB
        bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
        depends on SYSFB
+       select BOOT_VESA_SUPPORT if X86

This to me means that it's simplefb specifically that requires it, not sysfb.
More precisely SYSFB_SIMPLEFB which is the simplefb implementation on top of
legacy BIOS.

Thanks

Michal