[PATCH] mtd: nand: omap: save Bad-Block-Table (BBT) on device

[Gupta, Pekon]

>From: Brian Norris [mailto:computersforpeace at gmail.com]
>>On Wed, Jul 23, 2014 at 05:27:46PM -0300, ezequiel at vanguardiasur.com.ar wrote:
[...]
>> In fact, you do have a simple way to solve this. Just support BBT through
>> the "nand-on-flash-bbt" devicetree property, so a user can tell if his flash
>> has a BBT or not. See pxa3xx-nand.c, which should be correct.
>
>Yes, you can use the 'nand-on-flash-bbt' property, and that probably
>makes the most sense.
>
>The only real backwards-compatibility concern you'd have for
>unconditionally enabling on-flash BBT (like in this patch) is if you had
>previous file system data in the last 4 blocks; nand_bbt will just
>clobber it, breaking your file system. For this reason, using DT is
>probably a good idea -- you're opting in, rather than being forced in by
>a kernel upgrade.
>
>Beyond the backwards-compatibility concern, you still have other
>concerns about on-flash BBT's robustness. Limiting yourself to a region
>of 4 blocks is one potential issue. There are others (e.g., lack of CRC
>protection), but none that have been real show-stoppers. I have a few
>generations of products running it here.
>
>BTW, there's a recent thread about GPMI and its "bad block mark
>swapping", which has led to somebody wanting a new DT binding for
>'on-flash-bbt-no-oob-bbm' or something like that, to mirror the
>(excellently named -- by me) NAND_BBT_NO_OOB_BBM option. I'm not real
>happy with adding a random assortment of configurable BBT flags into the
>DT ABI, without fully describing and standardizing the BBT format. It's
>kind of a vacuous target right now, which is just defined by the
>70%-baked solution in our current implementation... (I guess I need to
>go reply to the GPMI/NO_OOB_BBM thread soon!)
>
>Brian
>
>[1] http://lists.infradead.org/pipermail/linux-mtd/2014-March/052666.html
>    http://lists.infradead.org/pipermail/linux-mtd/2014-March/052796.html
>    http://lists.infradead.org/pipermail/linux-mtd/2014-March/052988.html

Thanks much to both of you.
Yes, "nand-on-flash-bbt" devicetree property seems the correct approach.
I'll study the above threads, and then get back with appropriate patch.
So, please ignore this patch.

with regards, pekon