[PATCH] nandwrite: add --nobad to write bad blocks

[Jon Povey]

Iwo Mergler wrote:
> Jon Povey wrote:
> Although I would always use an in-flash BBT for this kind of
> situation. As you say, there are bootloaders, filesystems and
> hardware ECC that will only work if you re-purpose the bad block
> marker region in the OOB.
>
> In such a case, just do the bad block scan once, at production time,
> and write the BBT. Then change everything else to use that BBT. And
> you leave the BBT alone during reflash.

I agree this is a nice way to do it, if it's practical.

> In the case you describe, I would use the old BBT to create the
> new one directly, without attempting to write to the bad blocks.

That's what I did, but note mtd won't allow you to rewrite the BBTs,
they are hardwired to be off-limits in the kernel. So, you have to
do something like write a new bootloader that can translate it on
reboot. Happily that has been OK for me, but it's not ideal, and one
may be in a position where that is difficult (restricted code size for
bootloader and such)

The inability to rewrite the BBT from linux is a separate issue though.

>> Either way, I for one need to do these kind of low-level hacks, and
>> if mtd kernel or utils have policy hardwired into them, happily I
>> have the source and a compiler and can fix that locally.
>
> I agree. I only wrote what I did to maybe contribute to the
> documentation. There seemed to be the sentiment that the tools
> only skiped bad blocks because of some silly tradition.
>
> I'm all in favour of adding the feature.

Ah, I thought you were against it.
Jolly good.

--
Jon Povey
jon.povey at racelogic.co.uk

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