State of read-only filesystems in NAND / MTD bad blocks handling when reading

[Thilo Fromm]

Hello Gregory,

>> Oh, okay, thanks for the info, so we need to take care about bit rot,
>> too. I don't think this is too big a challenge.
>>
>> Hey guys, I think I've got a bold idea. Could I re-use parts of UBI's
>> EB handling code in my readonly FTL? It depends on whether the erase
>> block scrubbing routines within UBIFS are generic enough to be used by
>> other components. Or whether the linux-mtd project is interested in
>> having these routines re-usable at some point in the future when they
>> are not re-usable right now.
>>
>> Comments, suggestions?
>
> I think it's better to use UBI in a whole than just take most of its code.

I wouldn't "take" it so much as write another component which uses it.
Which should improve the code overally :) And I don't think I need
most of it.

> Indeed UBI is better if it handles all the flash, at least for wear leveling.

I don't need wear leveling, I'm readonly.

> That one of the reason we choose to not continue to work on MTDBLCK_RO
> and switch to ubi_blk.

I fully understand this decision. It's just that I don't need (and
frankly, don't want) all that code, especially the read/write parts of
it, for my root fs. I would run into trouble with our (old-ish)
u-boot, too.

On the other hand ubi_blk would be a good choice community-wise, so we
would better integrate with the current ongoing development in
linux-mtd. That's another strong advantage. I'll focus on "blockrom"
for now (as this seems to be the device node's LANANA name, see
Documentation/devices.txt), since blockrom seems to offer everything
we need with just a few extensions we have to add. But I'll definitely
keep ubi_blk in mind.

Regards,
Thilo

-- 
Dipl.-Ing (FH) Thilo Fromm, MSc., Embedded Systems Architect
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