Andrew McKay wrote:
> yaffs@piments.com wrote:
>> > > Yes, do some manual operations on an unmounted yaffs partition.
>> >
>> > Thanks for the help Charles
>> >
>> > I did this with mtd-utils and writing to the mtdblock device using 
>> dd. I
>> > didn't seem to have any issues. The blocks that YAFFS2 were saying
>> > couldn't be erased were erased successfully (and thus not marked 
>> bad). I
>> > will test a bit more with it.
>>
>> Is using dd to write to mtdblock device safer or better than using 
>> hacked flash_eraseall that ignores bad blocks?
> I'm not sure what you mean, dd doesn't erase blocks, and accesses 
> through the MTD driver, so it pays attention to bad blocks.  It also 
> doesn't appear to erase a block for attempting to write it, so you need 
> to use flash_eraseall prior to testing with dd or else you will get a 
> lot of ECC errors while reading NAND.
>>
>> Is the block size relevant in the way it writes to the underlying 
>> device or is it best to specify bs=2048 for a 2k NAND device?
> Yes I usually set the bs to the size of the blocks on the NAND part when 
> testing with dd to make sure that each block only gets one write cycle.  
> This may also be enforced through buffering in the MTD layer but I can't 
> confirm this off the top of my head.
> 
> Any questions about that stuff would probably best be posted to the MTD 
> mailing list.
> 
> Andrew
> 
> 
Hi Andrew,

thanks very much for putting me straight. I was not expecting to have to 
get involve is all this low level detail to recover this hardware from 
the effects of a "robust" fs like yaffs2.

I've been looking at the output of nanddump trying to understand what 
state it is in.

I suspect I may be able clear that bad block marker and use something 
like nanddump -m to detect the true faulty blocks.

Its a 128MiB device bit the output stops at 7d00000 am I right in 
guessing that the remainder is bad block table I have read about?

Is there a way to get the current bad block table off the device before 
I attempt to force an eraseall ignoring bad blocks.

Any wisdom will be a great help.

best regards.