[LinuxBIOS] LinuxBIOS panic room

[Carl-Daniel Hailfinger]

On 29.08.2007 23:28, Peter Stuge wrote:
> On Wed, Aug 29, 2007 at 04:43:27PM -0400, pyro wrote:
>>>> Agreed. That way, we could even abuse a fallback image for early
>>>> porting without the need to reflash continuously.
>>> Yes - this has been a thought of mine all the way since the
>>> Symposium.
>> I've been thinking about that a good bit lately. Once the serial
>> port and CAR is up, a very simple monitor program should be able to
>> accept simple commands and programs from the serial console.
> 
> Right - this is what I've called the panic room code.

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?

Carl-Daniel