corrupted empty space - again

[Gupta, Pekon]

Fixed a typo
 
> > It seems that:
> > a) error is of single bit-flip kind (read decay) (I don't suspect currently
> >     unstable bits issue during erasing/writting)
> > b) our NAND driver doesn't protect our empty space (no wonder, as 13
> > bytes ECC used
> >     per 512B subpage should be left 0xFF until written with real data)
> 
[Pekon]: This should not matter, suppose you wanted to write
0x77 to a erase-page byte already having a bit-flip at bit-0. 
So in actual 0x76 would be written on the device. And corresponding 
calculated ECC gets stored in OOB/spare area.

Now when you read the byte, it would read as 0x76, but ECC stored in
spare/OOB area was calculated for 0x77, so nand-driver would detect a
bit-flip and should correct it too.
So whether bit-flips occur on erased-page or whether after writing,
both can be detected and corrected by your driver.