[Balloon] need help about yaffs

Hi, sir
I want to use yaffs on my 2410 board. I added mtd source to ./fs/yaffs, make Image , then download to flash , but when I boot the board, errors found,

modprobe: modprobe: Can't open dependencies file /lib/modules/2.4.18-rmk7-pxa1/m
odules.dep (No such file or directory)
mount: Mounting /dev/mtdblock/4 on /usr failed: No such device

I copy the modules directory to /root, and product root.cramfs,
then boot,
modprobe: modprobe: Can't locate module yaffs
mount: Mounting /dev/mtdblock/4 on /usr failed: No such device

I want to compile the yaffs into the kernel, I don't know why ?
Thank you !