[Yaffs] Yaffs2 ECC in direct using

Hi all.

    I have ported yaffs2 to my platform which using a small rt os(not
linux).As in the Yaffscfg2k.c writing , i config the flashDev structure as
follows.
 flashDev.writeChunkWithTagsToNAND = yflash2k_WriteChunkWithTagsToNAND;
 flashDev.readChunkWithTagsFromNAND = yflash2k_ReadChunkWithTagsFromNAND;
 flashDev.eraseBlockInNAND = yflash2k_EraseBlockInNAND;
 flashDev.initialiseNAND = yflash2k_InitialiseNAND;
 flashDev.markNANDBlockBad = yflash2k_MarkNANDBlockBad;
 flashDev.queryNANDBlock = yflash2k_QueryNANDBlock;

I write all the above functions as Yaffs_flashif.c shows. And each of the
functions uses my only nand flash driver. And all of the funcitons have
changed to be suit for(2k+64Bytes) nand.
But i couldn't find any using yaffs2's ecc! How can i add ecc for my
writing data?I could't find yaffs2 has supported the nand flash(2k+64Bytes),
it only supports yaffs1's ecc .
The yaffs2 in my platform using now doesn't have any ecc in one page
data.

Anybody have any hints in Yaffs2's direct using,or how can i add ecc for
each page data?

Thanks.
zhangYD