[Yaffs] nand oob erase

Hi,

I read fome of your answers in linux forums
(http://osdir.com/ml/linux.file-systems.yaffs/2007-04/msg00002.html)
I have the same issue but I need to clear the bad block markers in NAND.
I don't have nand_scrub in my u-boot so I need to do that it kernel.
What should I change and implement in the driver so it will format
(erase) the oob?

Thanks in advance,
Stanislav