[OLPC-devel] Requirements for a field BIOS reflashing tool.

[Stefan Reinauer]

* Jim Gettys <jg at laptop.org> [060616 19:07]:
> > > We are planning, as I believe has been mentioned on the mailing list, to
> > > have the embedded controller disable the flash write line unless and
> > > until the space bar has been held down for a 5 second period, to make it
> > > difficult for worms/viruses to "brick" the machines.
> > 
> > The 5 second period is a software thing in the flash writer, not a hardware 
> > issue, right?
> 
> No, the current plan is to enforce this in the embedded controller,
> where the flash enable pin is controlled, not in the flash writer.

hm. embedded controller sounds kind of expensive. what kind of part is
this?
 
> > Running an unchecked firmware image is frivolous. Is there any chance we
> > can stuff a "fallback" and "normal" image in the development and/or
> > production chips with LinuxBIOS?  The fallback image should just be good
> > enough to flash the bios from an external device (floppy, cd, usb stick,
> > whatever the final version of the OLPC will allow) as we don't want two
> > Linux images in flash under any circumstances.
> 
> I don't think we have the space for the luxury of a full Linux as
> bootloader redundant image.  There might be something else that could be
> squirreled away, but I'm not a LinuxBIOS expert.
 
I don't think we do need Linux as a firmware payload. I know it is a
viable solution and Ron prefers it for many good reasons. In this case
where flash memory is tight we might as well run something much smaller
and rather pack a normal/fallback mechanism into the firmware instead.

> > >    3) the model of machine gets checked against the model(s) the
> > > firmware image will work on.
> > 
> > LinuxBIOS features a model number in flash, and the "flashrom" tool
> > which is part of LinuxBIOS checks this prior to flashing.
> 
> Great.
 
The only thing it does not support (yet) is serial flash parts(which
seem to be used in the OLPC?) This part is probably trivial though.

> I was trying to document what it took to get something idiot proof on a
> machine similar to OLPC in which the boot flash is soldered into the
> board so flash chip swaps are not a possibility, and in which the
> consequences of idiotic behavior results in a dead,
> unrepairable-in-the-field machine.

Perfectly fine. Sorry I came in a bit late in the discussion here and
started babbling right away ;-) I'll improve on this one 

Stefan 



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