My kernel can cope with both 512 and 2k page NAND. It uses nand_ecc for 
2k and yaffs_ecc for 512 for legacy reasons.
> 
> 
>>               if (yaffsVersion == 1 && mtd->oobblock == 2048) {
>>                       printk(KERN_INFO "yaffs: auto selecting yaffs2\n");
>>                       yaffsVersion = 2;
>>               }
> 
So I add after #ifndef CONFIG_YAFFS_DOES_ECC .. #endif

		/* NCB force NANDECC if yaffs2 */
		if (yaffsVersion == 2)
			dev->useNANDECC = 1;	

Better to use a specific CONFIG option probably.

NB to all 2.4.x backporters: I note that the new yaffs_mtdif2.c computes 
an address to pass to mtd->block_isbad and mtd->block_markbad rather 
than a block index. This breaks by old 2.4.25 port. Use an if 
(LINUX_VERSION_CODE ...) round the relevant places and use 
mtd->block_xxxbad(mtd,blockNo) instead.

Nick