Re: genfb(4) vs. screen types and font changes/uses

At Tue, 25 Aug 2026 22:19:02 +0200, Martin Husemann <[email protected]> wrote:
Subject: Re: genfb(4) vs. screen types and font changes/uses
>
> On Tue, Aug 25, 2026 at 01:14:26PM -0700, Greg A. Woods wrote:
> > The bootloader has already changed the resolution, and there is actually
> > already a perfectly good font being used at that resolution to display
> > the initial bootloader and kernel output.
>
> But that font is hidden somewhere in the firmware and the framebuffer
> code has no way to find it in general (or guess the format it is stored
> in).

I'm guessing you say this because the kernel must start drawing
characters directly itself once genfb(4) has attached.

If so, then the kernel should continue to use a font size that matches
what the firmware is/was using.

For UEFI the specification, if I understand correctly, says that the
font is 8x19 pixels (the "standard 'narrow' fixed font").

For BIOS with VESA, presumably one can still copy out the well known VGA
font from the hardware, but if I'm not mistaken unless it's a really
REALLY OLD system they are normally also always 8x19 fonts (else it
would be 8x16, as only ancient i386 and earlier systems used 8x8).

https://www.os2museum.com/wp/8x19-text-mode-font-origins/
https://wiki.osdev.org/Drawing_In_a_Linear_Framebuffer

I see there are lots of 8x16 fonts available for wsfont and if I'm not
mistaken it's common for firmware (at least older versions) to use an
8x16 font with three blank scan lines underneath.

--
					Greg A. Woods <[email protected]>

Kelowna, BC     +1 250 762-7675           RoboHack <[email protected]>
Planix, Inc. <[email protected]>     Avoncote Farms <[email protected]>

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