Hi David,

I suggest you to try this with the latest Yaffs + recent kernel (2.6.19 
or newer):

Use MTD_OOB_AUTO with the following layout (as suggested by Ian):

static struct nand_ecclayout nand_oob_16 = {
    .eccbytes = 6,
    .eccpos = { 9, 8, 10, 14, 13, 15 },
    .oobfree = { { 0, 4 }, { 6, 2 }, { 11, 2 } }
};

with CONFIG_NAND_ECC_SMC = N

or

static struct nand_ecclayout nand_oob_16 = {
    .eccbytes = 6,
    .eccpos = { 8, 9, 10, 13, 14, 15 },
    .oobfree = { { 0, 4 }, { 6, 2 }, { 11, 2 } }
};

with CONFIG_NAND_ECC_SMC = Y


Be sure to use default Yaffs configuration.
Especially CONFIG_YAFFS_DOES_ECC = N

The translate functions (translate_spare2oob) in mtdif.c should work 
fine untouched.

Cheers,
Claudio Lanconelli