Devel Digest, Vol 41, Issue 56

[Mitch Bradley]

> Wish I knew how to create drivers for OFW so it could boot from UBIFS.
>
>   

Normally I would encourage adding such drivers to OFW, but in this case 
I think it's wasted effort that could be much better spent in other ways.

a) XO OFW already has well-elaborated partition support.  It's 
interaction with the security mechanism is understood. The NANDblaster 
tool for recovery and mass update supports it fully.

b) No new official OFW releases for the XO-1 are in the pipeline, as the 
customers are happy with the latest one.  That doesn't mean that we 
wouldn't do one if necessary, but rather that, lacking the necessity, we 
prefer to focus our resources on the new hardware.  Of course, one could 
always install a custom firmware image, but that would make migration 
more difficult and thus hamper the adoption of an ubifs-based OS image.

c) There is enough work to do already for migrating to ubifs without 
adding the unnecessary work of implementing, testing, and stabilizing 
the firmware support for ubifs.

d) The long-term value of having ubifs support in the OFW source tree is 
questionable, since raw NAND is on the way out, industry-wide.  There 
are several reasons: (1) New NAND chips are sprouting wider and wider 
ECC making the error detection infeasible except for specialized 
interface chips (2) The engineering effort of supporting the variations 
among raw NAND chips at the system level is becoming prohibitive (3) The 
price crossover has already happened in some cases - you can buy 
packaged "managed NAND" (e.g. SD cards or modules) for less than the 
price of individual chips.  (The economics includes not only the cost of 
producing the chips, but also inventory costs, supply chain logistics, 
factory scheduling, long-term vs. short-term pricing, the ability to buy 
chips from different sources, and who pays for the cost of qualifying 
different sources).


Looking to the future, it would be much more useful to add a btrfs 
driver to OFW.  ubifs, nice as it is, came along near the end of life of 
the problem it solves.  btrfs, on the other hand, is widely believed to 
be the Next Big Thing.

If someone wants to undertake a btrfs project for OFW, I'll be glad to 
assist.