mtd nand erase and bad block

[Matteo Facchinetti <matteo.facchinetti@sirius-es.it>]

Hi,

I'm developing a mtd driver for a nand flash controller and I need help;
I'm to the end of the work, and I have problems and dubts about bad 
block handling.

For test, I mark manually bad block byte on flash block.
When I erase with flash_erase, all works and skip the bad block:
:~# flash_erase /dev/mtd6 0 0
Erasing 1024 Kibyte @ 100000 --  2 % complete flash_erase: Skipping bad 
block at 00200000
Erasing 1024 Kibyte @ 2700000 -- 100 % complete

If I try to erase with -N parameter I read the following output:
~# flash_erase -N /dev/mtd6 0 0 

Erasing 1024 Kibnand_erase_nand: attempt to erase a bad block at page 
0x00001600
yte @ 200000 --  5 % complete libmtd: error!: MEMERASE64 ioctl failed 
for eraseblock 2 (mtd6)
         error 5 (Input/output error)
flash_erase: error!: /dev/mtd6: MTD Erase failure
              error 5 (Input/output error)
Erasing 1024 Kibyte @ 2700000 -- 100 % complete

I espected that with -N option, flash_erase should erase the 
hand-damaged block, recovering the usability of the block. Is it true?

What's going wrong?

Best Regards,
Matteo