Re: Testing a linksys WRT54GS.

[Peter Dambier <]

Henk Uijterwaal wrote:
> Rickard,
>
> > However, one issue keeps nagging me and that's the legal part of it.
> > It's more or less clear that a user would void the warranty if he
> > installs a custom firmware. So what if RIPE distributes a firmware that
> > breaks peoples devices? I have no idea if this is a problem or not since
> > I'm not a lawyer, but it might be a good thing to investigate.
>
> Trying to understand the issues here:
>
> (1) Let's assume for a second that the RIPE NCC distributes a broken
> firmware, the user uploads it to his WRT54GS and finds out that the
> device suddenly stops doing anything useful.
>
> I guess that the first thing one wants to do then, is to restore
> the original firmware.  This requires a copy of whatever was originally
> installed.  Is this available?  Can the user make one?  Is it
> possible to force a firmware onto the device?  If this can be done,
> then the problem is relatively easy: we distribute our firmware as is,
> with no guarantees.
>
> (2) Is it possible that a broken firmware will actually break the device.
> I have read warnings that using the wrong Xwindows driver can damage
> a graphics card but I've never seen this in practice, and to be honest,
> I always find it a bit hard to believe that software can damage hardware.
On the original IBM PC there used to be a monochrome display adapter.
It could not do any graphics.

The hercules monochrome graphics card was a replacement that could to
the same high resolution charater mode plus the hercules 720 x 364
graphics mode.

If you wrote a programme to reading the mode register of the grphics
chip you would kill the Monitor.

How that?

The mode register was not supped to be read. It would interpret the
read as a write 0xff to the mode register. As a result the timing
would generate an illegally high line frequency. The line frequency
like in old TV sets would produce the high voltage for the cathode
ray tube. Too much current would flow and the highvoltage unit
which was a the same time the horizontal driver would burn out.

We could reproduce it. You could do it accidently.


> (3) We obviously do not plan to distribute broken firmware upgrades
> so we will extensively test them before distributing.  BUT this obviously
> requires that the Linksys we use, is identical to what the user has.
> Are all these devices identical?  Are there flavors, (i.e. if one buys
> a PC from D***, one often finds small difference between series)?
Even with good software there is the risk of the EEPROM sometime breaking.

There could be a powerfailure leaving you with a half programmed EEPROM

...

This only happens in one of 2000 units. But somebody might be unlucky
enough to be number 2000.

Nevertheless I would risk it.


Kind regards,
Peter and Karin Dambier
--
Peter and Karin Dambier
The Public-Root Consortium
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