[Yaffs] What should i do when i want to mount a yaffs as roo…

         I use mkyaffsimage to make a yaffs image and copy the yaffs
source files to the kernel. I compile the kernel with yaffs support and
boot it, but the yaffs file system can not be mounted.

         I set CONFIG_CMDLINE="root=/dev/mtdblock2 rootfstype=yaffs
ip=off console=ttyS0,115200 mem=64M"

        The situation is same when I want to mount it in shell. I tried
"mount -t yaffs /dev/mtd2 /mnt" and "mount -t yaffs /dev/mtdblock2
/mnt". Both commands report that "No such device"

         In fact I can mount jffs2 ad root file system. I have disabled
the ECC in the NAND driver. The kernel I used is 2.6.9.