[SeaBIOS] [coreboot] RFC: Changing CBMEM console to run as a persistent ring-buffer

Julius Werner jwerner at chromium.org
Wed Apr 12 20:29:57 CEST 2017

> Is it possible to figure whenever the cbmem buffer supports rollover or
> not, so a updated seabios version can work correctly with both old and
> new coreboot?

Not explicitly, but it should still work fine with both versions. The old
coreboot can only either not fill up the buffer or fill up the buffer. If
it fills up the buffer I can make SeaBIOS detect that (it would look
different from rollover with the new code) and just not append anything
else, just as it would do right now. If it did not fill the buffer, SeaBIOS
can just continue appending there and roll over if it needs to (the buffer
format stays 100% the same before the first roll over). Then on the next
boot, an old version of coreboot will just unconditionally reinitialize the
buffer anyway.
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