[Yaffs] about yaffs

Hello!

I has used yaffs from CVS on montavista-cee3.1 today, the step is:

flash_eraseall /dev/mtd/0
(I found some bad block:(

mount /dev/mtd/0 /mnt/flash -t yaffs

cp -a /mydir /mnt/flash
(yaffs printed some error messages:
ecc error unfixed on chunk **
Block ** marked for retirement
....)

and when i unmounted mtd/0, and called flash_eraseall, i found
some more bad blocks:(

so, what's wrong with it? yaffs or nand driver?

Thank you for your reply!