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

[Alexander Couzens]

The old 1bit hamming layout requires the ecc data to be exact at
predefined offsets. This can not changed because old installations
would break.

Signed-off-by: Alexander Couzens <lynxis at fe80.eu>
---
 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. 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;
+	}
+
+	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;
+	}
+
+	if (section == 0) {
+		/* return the space before the ecc */
+		oobregion->offset = 2;
+		oobregion->length = ecc_offset - 2;
+	} else { /* section == 1 */
+		/* return free space after ecc */
+		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)
-- 
2.12.2