Devel Digest, Vol 41, Issue 56
wmb at laptop.org
Wed Jul 29 13:01:41 EDT 2009
> 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
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
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