> Livio Tenze wrote:
> ...
> > 5) I mount again the filesystem mount -t yaffs /dev/mtd/5 /mnt
> > 6) If I try to read the previously written data, it is not 
> possibile. 
> > The files I copied are empty or are no longer visibile.
> > 
> > If I do not umount the filesystem yaffs seems to work well, 
> but if I 
> > umount the filesystem I am no longer able to read the written data.
> 
> Check for bad blocks messages in dmesg at mtd NAND chip probe 
> time.  The blocks are probably being marked bad per previous 
> email, and next time the chip is probed the overwritten bad 
> block markers are read.
> 
As Todd said/implied this is almost certainly caused by a bad mtd
hook-up causing scrambling of the tags stored in the oob area.

If you have not yet tried Sergey's patch you might see if that helps.

-- Charles