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

From: "Michal Suchánek" <msuchanek@suse.de>
To: Javier Martinez Canillas <javierm@redhat.com>
Cc: dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org,
	Thomas Zimmermann <tzimmermann@suse.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	Martin Mares <mj@ucw.cz>, Helge Deller <deller@gmx.de>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Daniel Vetter <daniel.vetter@ffwll.ch>,
	Sudeep Holla <sudeep.holla@arm.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>,
	Cristian Marussi <cristian.marussi@arm.com>,
	Simon Trimmer <simont@opensource.cirrus.com>,
	Geert Uytterhoeven <geert+renesas@glider.be>,
	Arnd Bergmann <arnd@arndb.de>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Rob Herring <robh@kernel.org>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	David Herrmann <dh.herrmann@gmail.com>,
	linux-kernel@vger.kernel.org,
	linux-video@atrey.karlin.mff.cuni.cz
Subject: Re: [PATCH v3] simplefb: Enable boot time VESA graphic mode selection.
Date: Wed, 23 Feb 2022 18:12:35 +0100	[thread overview]
Message-ID: <20220223171235.GF3113@kunlun.suse.cz> (raw)
In-Reply-To: <f832a836-b6ee-ffc5-6f83-86c9ba475400@redhat.com>

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