Universal Mot C1xx unlocker

[Mychaela Falconia]

Hi David,

> Am I correct in thinking that recent advances made with the firmware on
> the C139 are now transferable to other handset models or are there other
> mountains to be climbed besides locked bootloaders?

The tidbit that the new version of tfc139 is expected to work with all
Mot C1xx variants and not just C139 is a fact that needs to be
documented, but unfortunately it does not enable one to take our
tcs211-c139 firmware and run it on other C1xx models.

I have never encountered a locked-down bootloader on any C1xx variant
besides US-band carrier-branded C139 units; thanks to the fw images I
got from Das Signal back in 2014 we know that the provision for the
possibility of locking down the bootloader is there in the newer fw
versions for C11x, but I don't know if the lock has ever been deployed.
Instead the difficulties with running our own fw on Mot C1xx models
other than C139/140 are elsewhere:

* C11x/12x have too little RAM, and most of them have too little flash
  as well.

* We can run on C155/156, but until we migrate from Wine-built fw to
  our gcc-built gsm-fw, supporting multiple targets is a royal pita,
  hence I'm sticking with just C139 for now.  C155/156 also feature a
  ringtone generator chip for which no docs could be found, so we may
  or may not succeed in making it emit a ringtone - and a phone that
  can't ring won't be practically useful.

> If the prospects for freecalypso on additional models is now as good,
> are any of them more desirable than the good ol basic c139?

Not really.  Mot C11x/12x offer no advantage over C139/140 (more feeble
in every way); C155/156 are a little nicer, but see above regarding the
uncertainty with ringtone generation.  My favourite is still the
Pirelli DP-L10, but the problems with extra chips sans docs and the
lack of schematics are still there. :-(

> The suggestion - why not report your breakthrough on the osmocombb list?
> You never know - a brief, neutral in tone summary of your progress might
> lead to a helpful contribution in our direction. :-)

Let's do it after I make the new packaged release of fc-host-tools
with the new unlocker in it.  We should be able to justify a post on
their ML by referring to previous episodes of people not being able to
use OsmocomBB with some phones because of that locked bootloader
standing in the way, and for some variants like Cingular fw version
1.9.24 there was no previously known unlocking method - and now we've
got our universal unlocker. ;-)

M~