Re: [PATCH 1/3] dummycon: only build module if there are users

["Arnd Bergmann" <arnd@arndb.de>]

On Wed, Feb 26, 2025, at 13:05, Javier Martinez Canillas wrote:
> "Arnd Bergmann" <arnd@arndb.de> writes:
>> in drivers/video/console, with the simpler alternative just
>> calling into fbcon functions. I'm not sure if we can already drop
>> vgacon from normal x86-64 distro configs, i.e. if there are cases
>> that are not already covered by any of efi-earlycon, efifb,
>> vga16fb, vesafb/uvesafb or a PCI DRM driver.
>>
>
> I believe vgacon is still useful for x86 with legacy BIOS, because
> vesafb (and simpledrm) only works if the user defines a mode using
> the vga= kernel cmdline parameter.

Right, at the minimum, a configuration without vgacon would
have to pick a graphical mode in arch/x86/boot/video*.c if one
wasn't already set by grub.

Looking through the git history of that code, it seems that there
are lots of corner cases with weird 32-bit hardware.
Anything from the past 20 years is probably reasonably safe,
but there still needs to be a way to configure vgacon back in
to be safe.

    Arnd