[PATCH 1/3][v2] mtd/nand: add ooblayout for old hamming layout

Tue May 2 01:41:39 PDT 2017

On Tue, 2 May 2017 10:13:21 +0200
Alexander Couzens <lynxis at fe80.eu> wrote:
> The old 1bit hamming layout requires the ecc data to be exact at
> predefined offsets.

"
The old 1-bit hamming layout requires ECC data to be placed at a
fixed offset, and not necessarily at the end of the OOB area.
"
> This can not changed because old installations
> would break.

"
Add this old layout back in order to fix legacy setup.
"
>> Signed-off-by: Alexander Couzens <lynxis at fe80.eu>

You should probably add Fixes and Cc:stable tags.
> ---
> drivers/mtd/nand/nand_base.c | 71 ++++++++++++++++++++++++++++++++++++++++++++
> include/linux/mtd/nand.h | 1 +
> 2 files changed, 72 insertions(+)
>> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> index b0524f8accb6..daf3df157885 100644
> --- a/drivers/mtd/nand/nand_base.c
> +++ b/drivers/mtd/nand/nand_base.c
> @@ -139,6 +139,77 @@ const struct mtd_ooblayout_ops nand_ooblayout_lp_ops = {
> };
> EXPORT_SYMBOL_GPL(nand_ooblayout_lp_ops);
>> +/* support the old large page layout for Hamming 1 bit where the ECC start at
> + * a defined offset.

Please use regular comment style:
/*
 * <content>
 */
s/support/Support/
BTW, I'm not sure I understand this sentence. How about
"
Support the old "large page" layout used for 1-bit Hamming ECC where ECC
are placed at a fixed offset.
"
> Should only used by old devices to compatible with old
> + * layout. Use nand_ooblayout_lp_ops if possible.
> + */
> +static int nand_ooblayout_ecc_lp_hamming(struct mtd_info *mtd, int section,
> +				 struct mtd_oob_region *oobregion)
> +{
> +	struct nand_chip *chip = mtd_to_nand(mtd);
> +	struct nand_ecc_ctrl *ecc = &chip->ecc;
> +
> +	if (section)
> +		return -ERANGE;
> +
> +	switch (mtd->oobsize) {
> +	case 64:
> +		oobregion->offset = 40;
> +		break;
> +	case 128:
> +		oobregion->offset = 80;
> +		break;
> +	default:
> +		return -ERANGE;

Hm, can you return -EINVAL instead?
> +	}
> +
> +	oobregion->length = ecc->total;
> +	if (oobregion->offset + oobregion->length > mtd->oobsize)
> +		return -ERANGE;
> +
> +	return 0;
> +}
> +
> +static int nand_ooblayout_free_lp_hamming(struct mtd_info *mtd, int section,
> +				 struct mtd_oob_region *oobregion)
> +{
> +	struct nand_chip *chip = mtd_to_nand(mtd);
> +	struct nand_ecc_ctrl *ecc = &chip->ecc;
> +	int ecc_offset = 0;
> +
> +	if (section < 0 || section > 1)
> +		return -ERANGE;
> +
> +	switch (mtd->oobsize) {
> +	case 64:
> +		ecc_offset = 40;
> +		break;
> +	case 128:
> +		ecc_offset = 80;
> +		break;
> +	default:
> +		return -ERANGE;

Ditto.
> +	}
> +
> +	if (section == 0) {
> +		/* return the space before the ecc */

Not sure this comment is needed, it's pretty obvious that this section
is placed before the ECC bytes (and after the BBM).
> +		oobregion->offset = 2;
> +		oobregion->length = ecc_offset - 2;
> +	} else { /* section == 1 */

Drop this comment.
> +		/* return free space after ecc */

Ditto.
> +		oobregion->offset = ecc_offset + ecc->total;
> +		oobregion->length = mtd->oobsize - oobregion->offset;
> +	}
> +
> +	return 0;
> +}
> +
> +const struct mtd_ooblayout_ops nand_ooblayout_lp_hamming_ops = {
> +	.ecc = nand_ooblayout_ecc_lp_hamming,
> +	.free = nand_ooblayout_free_lp_hamming,
> +};
> +EXPORT_SYMBOL_GPL(nand_ooblayout_lp_hamming_ops);
> +
> static int check_offs_len(struct mtd_info *mtd,
> 					loff_t ofs, uint64_t len)
> {
> diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
> index 9591e0fbe5bd..da33933950a5 100644
> --- a/include/linux/mtd/nand.h
> +++ b/include/linux/mtd/nand.h
> @@ -914,6 +914,7 @@ struct nand_chip {
>> extern const struct mtd_ooblayout_ops nand_ooblayout_sp_ops;
> extern const struct mtd_ooblayout_ops nand_ooblayout_lp_ops;
> +extern const struct mtd_ooblayout_ops nand_ooblayout_lp_hamming_ops;
>> static inline void nand_set_flash_node(struct nand_chip *chip,
> 				 struct device_node *np)