[coreboot] passing EFI-console-like info to payloads

Jeremy Jackson jerj at coplanar.net
Mon Apr 7 21:37:25 CEST 2008

I've been eyeing legacy ISA io/mem range removal, in particular VGA, for
some time.  Concerning early debug output, it seems that EFI has done
this by exporting basic framebuffer info, and Linux has an efifb which
uses it. (framebuffer base address + size, stride, pixel format)

Linuxbios currently passes serial console info.  Idea:  pass key
framebuffer info to payloads, so they can use a video/VGA console for
early debug output (Linux "earlyprintk").

There is a thread "[coreboot] libpayload: Geode video console support"
from a few days ago, which I think is related.

With the libpayload video console support framework, presumably all gfx
chips could have their drivers written, yet again.  There's a headstart
in Linuxbios for initializing RageXL and a couple others, that could be
enhanced to print output also.

Is this necessary, or unnecessary code duplication?  Could the
chip-specific init code be left in Linuxbios, and only a generic video
console (ie font + generic rendering to framebuffer code) be provided in
libpayload (and/or Linux)?

Keeping it in Linuxbios makes sense for onboard video chips, ie keep
board-specific knowledge in the firmware, OTOH, for addin cards, maybe
libpayload could have multiple drivers, and pick at runtime...

Jeremy Jackson
Coplanar Networks
jerj at coplanar.net

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