[LinuxBIOS] LinuxBIOS panic room

Uwe Hermann uwe at hermann-uwe.de
Thu Aug 30 14:03:31 CEST 2007

On Thu, Aug 30, 2007 at 01:05:32PM +0200, Carl-Daniel Hailfinger wrote:
> On 30.08.2007 06:19, ron minnich wrote:
> > On 8/29/07, Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006 at gmx.net> wrote:
> >> I'd say it should accept a lar archive via serial console, perhaps using
> >> ymodem, and start executing the first member of the lar.
> >>
> >> A bit more detailed: If the BIOS fails to verify its checksum, it
> >> outputs a message telling you about it over serial, waits for signature
> >> to arrive over serial (a standard char sequence with repetitions at the
> >> beginning), reads until it has one complete signature, switches serial
> >> to ymodem and accepts a lar archive. The first member of the lar is then
> >> executed.
> >>
> >> The "wait for signature" is there to allow people to use multiple tries
> >> getting serial speed right. OTOH, if the code outputs a continuous
> >> stream of "TESTTEXT\n" while waiting for serial input, the other side
> >> can verify serial speed settings as well.
> >>
> >> What do you think?
> > 
> > That's the way to go.
> Can we invert the speaker line each time a byte is written out over
> serial? With 115200,8,N,1 we would get an inversion frequency of
> 11.52kHz and a tone frequency of 5.76kHz. Comparing that tone to some
> downloadable audio sample would allow people to find out if serial was
> driven with the right speed.

Should be doable. Have a look at arch/x86/speaker.c in v3 for sample
code if you want to give it a try.

http://www.hermann-uwe.de  | http://www.holsham-traders.de
http://www.crazy-hacks.org | http://www.unmaintained-free-software.org
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