[OLPC-devel] Re: belt and suspenders...

[Jim Gettys]

I'd rather the energy go into a really paranoid flash update program
right now.

Only after that is finished might it be worth serious investigation as
to whether additional recover paths might make sense.

I wrote up this paranoia and posted it about a month ago, from the
school of iPAQ hard knocks...

                        Best regards,
                              - Jim


On Tue, 2006-07-11 at 14:34 -0700, John R. wrote:
> On 7/11/06, Ronald G Minnich <rminnich at lanl.gov> wrote:
> > John R. wrote:
> > > On 7/11/06, Jim Gettys <jg at laptop.org> wrote:
> > >
> > >> Yeah, that was my guess.  And building a USB stack is *lots* of work.
> > >>
> > >
> > > Is it a lot of work? I guess a general purpose USB stack is, but what
> > > about just accessing USB storage?
> >
> > well, go for it, but I can only tell you that my one experience with
> > "small, simple" USB stacks is in the bios world, and they don't work
> > very well at all.
> >
> > The Linux USB stack is large and complex, and handles all kinds of
> > corner cases, because USB is large and complex, and loaded with corner
> > cases. It's not that linux USB is somehow a "bad" implementation, but
> > more that USB is a real mess to cover completely. I had a lot of trouble
> > with simple mass stores on the Insyde bios when I tried it, and all the
> > little USB mass stores I had worked just fine in linux.
> >
> > ron
> >
> >
> 
> Yeah, I see what you're saying, corner cases are a pain and it's hard
> to know what's there until one gets neck deep into it. Is the proposed
> requirement to boot from any usb-storage device?  Can we just qualify
> 10 or 20 different makes/models and call it a day? Or would such a
> driver really have to boot from anything that calls itself
> usb-storage?
> 
> What we can do that Linux can't is remove any api layers, and
> genericity. I imagine you're right that Linux USB isn't a bad or
> bloated implementation, it's probably just generic. It's got to plug
> and play with every type of USB device. For usb-storage devices it
> must have to work with arbitrary file systems.
> 
> If we can construct the requirement as "load the first so many sectors
> from a random sample of usb flash or hard drives formatted in a
> particular way to RAM when nothing else is connected to the bus" I
> think it's more likely to be doable.
> 
> -- John.
-- 
Jim Gettys
One Laptop Per Child