mtd: create an mtd_ooblayout_ops struct to ease ECC layout definition

ECC layout definitions are currently exposed using the nand_ecclayout
struct which embeds oobfree and eccpos arrays with predefined size.
This approach was acceptable when NAND chips were providing relatively
small OOB regions, but MLC and TLC now provide OOB regions of several
hundreds of bytes, which implies a non negligible overhead for everybody
even those who only need to support legacy NANDs.

Create an mtd_ooblayout_ops interface providing the same functionality
(expose the ECC and oobfree layout) without the need for this huge
structure.

The mtd->ecclayout is now deprecated and should be replaced by the
equivalent mtd_ooblayout_ops. In the meantime we provide a wrapper around
the ->ecclayout field to ease migration to this new model.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

1 files changed, 121 insertions, 44 deletions

diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 0290c41e44fc..134ed2f7b919 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -1035,49 +1035,15 @@ EXPORT_SYMBOL_GPL(mtd_write_oob);
 int mtd_ooblayout_ecc(struct mtd_info *mtd, int section,
 		      struct mtd_oob_region *oobecc)
 {
-	int eccbyte = 0, cursection = 0, length = 0, eccpos = 0;
-
 	memset(oobecc, 0, sizeof(*oobecc));
 
 	if (!mtd || section < 0)
 		return -EINVAL;
 
-	if (!mtd->ecclayout)
+	if (!mtd->ooblayout || !mtd->ooblayout->ecc)
 		return -ENOTSUPP;
 
-	/*
-	 * This logic allows us to reuse the ->ecclayout information and
-	 * expose them as ECC regions (as done for the OOB free regions).
-	 *
-	 * TODO: this should be dropped as soon as we get rid of the
-	 * ->ecclayout field.
-	 */
-	for (eccbyte = 0; eccbyte < mtd->ecclayout->eccbytes; eccbyte++) {
-		eccpos = mtd->ecclayout->eccpos[eccbyte];
-
-		if (eccbyte < mtd->ecclayout->eccbytes - 1) {
-			int neccpos = mtd->ecclayout->eccpos[eccbyte + 1];
-
-			if (eccpos + 1 == neccpos) {
-				length++;
-				continue;
-			}
-		}
-
-		if (section == cursection)
-			break;
-
-		length = 0;
-		cursection++;
-	}
-
-	if (cursection != section || eccbyte >= mtd->ecclayout->eccbytes)
-		return -ERANGE;
-
-	oobecc->length = length + 1;
-	oobecc->offset = eccpos - length;
-
-	return 0;
+	return mtd->ooblayout->ecc(mtd, section, oobecc);
 }
 EXPORT_SYMBOL_GPL(mtd_ooblayout_ecc);
 
@@ -1106,16 +1072,10 @@ int mtd_ooblayout_free(struct mtd_info *mtd, int section,
 	if (!mtd || section < 0)
 		return -EINVAL;
 
-	if (!mtd->ecclayout)
+	if (!mtd->ooblayout || !mtd->ooblayout->free)
 		return -ENOTSUPP;
 
-	if (section >= MTD_MAX_OOBFREE_ENTRIES_LARGE)
-		return -ERANGE;
-
-	oobfree->offset = mtd->ecclayout->oobfree[section].offset;
-	oobfree->length = mtd->ecclayout->oobfree[section].length;
-
-	return 0;
+	return mtd->ooblayout->free(mtd, section, oobfree);
 }
 EXPORT_SYMBOL_GPL(mtd_ooblayout_free);
 
@@ -1416,6 +1376,123 @@ int mtd_ooblayout_count_eccbytes(struct mtd_info *mtd)
 }
 EXPORT_SYMBOL_GPL(mtd_ooblayout_count_eccbytes);
 
+/**
+ * mtd_ecclayout_ecc - Default ooblayout_ecc iterator implementation
+ * @mtd: MTD device structure
+ * @section: ECC section. Depending on the layout you may have all the ECC
+ *	     bytes stored in a single contiguous section, or one section
+ *	     per ECC chunk (and sometime several sections for a single ECC
+ *	     ECC chunk)
+ * @oobecc: OOB region struct filled with the appropriate ECC position
+ *	    information
+ *
+ * This function is just a wrapper around the mtd->ecclayout field and is
+ * here to ease the transition to the mtd_ooblayout_ops approach.
+ * All it does is convert the layout->eccpos information into proper oob
+ * region definitions.
+ *
+ * Returns zero on success, a negative error code otherwise.
+ */
+static int mtd_ecclayout_ecc(struct mtd_info *mtd, int section,
+			     struct mtd_oob_region *oobecc)
+{
+	int eccbyte = 0, cursection = 0, length = 0, eccpos = 0;
+
+	if (!mtd->ecclayout)
+		return -ENOTSUPP;
+
+	/*
+	 * This logic allows us to reuse the ->ecclayout information and
+	 * expose them as ECC regions (as done for the OOB free regions).
+	 *
+	 * TODO: this should be dropped as soon as we get rid of the
+	 * ->ecclayout field.
+	 */
+	for (eccbyte = 0; eccbyte < mtd->ecclayout->eccbytes; eccbyte++) {
+		eccpos = mtd->ecclayout->eccpos[eccbyte];
+
+		if (eccbyte < mtd->ecclayout->eccbytes - 1) {
+			int neccpos = mtd->ecclayout->eccpos[eccbyte + 1];
+
+			if (eccpos + 1 == neccpos) {
+				length++;
+				continue;
+			}
+		}
+
+		if (section == cursection)
+			break;
+
+		length = 0;
+		cursection++;
+	}
+
+	if (cursection != section || eccbyte >= mtd->ecclayout->eccbytes)
+		return -ERANGE;
+
+	oobecc->length = length + 1;
+	oobecc->offset = eccpos - length;
+
+	return 0;
+}
+
+/**
+ * mtd_ecclayout_ecc - Default ooblayout_free iterator implementation
+ * @mtd: MTD device structure
+ * @section: Free section. Depending on the layout you may have all the free
+ *	     bytes stored in a single contiguous section, or one section
+ *	     per ECC chunk (and sometime several sections for a single ECC
+ *	     ECC chunk)
+ * @oobfree: OOB region struct filled with the appropriate free position
+ *	     information
+ *
+ * This function is just a wrapper around the mtd->ecclayout field and is
+ * here to ease the transition to the mtd_ooblayout_ops approach.
+ * All it does is convert the layout->oobfree information into proper oob
+ * region definitions.
+ *
+ * Returns zero on success, a negative error code otherwise.
+ */
+static int mtd_ecclayout_free(struct mtd_info *mtd, int section,
+			      struct mtd_oob_region *oobfree)
+{
+	struct nand_ecclayout *layout = mtd->ecclayout;
+
+	if (!layout)
+		return -ENOTSUPP;
+
+	if (section >= MTD_MAX_OOBFREE_ENTRIES_LARGE ||
+	    !layout->oobfree[section].length)
+		return -ERANGE;
+
+	oobfree->offset = layout->oobfree[section].offset;
+	oobfree->length = layout->oobfree[section].length;
+
+	return 0;
+}
+
+static const struct mtd_ooblayout_ops mtd_ecclayout_wrapper_ops = {
+	.ecc = mtd_ecclayout_ecc,
+	.free = mtd_ecclayout_free,
+};
+
+/**
+ * mtd_set_ecclayout - Attach an ecclayout to an MTD device
+ * @mtd: MTD device structure
+ * @ecclayout: The ecclayout to attach to the device
+ *
+ * Returns zero on success, a negative error code otherwise.
+ */
+void mtd_set_ecclayout(struct mtd_info *mtd, struct nand_ecclayout *ecclayout)
+{
+	if (!mtd || !ecclayout)
+		return;
+
+	mtd->ecclayout = ecclayout;
+	mtd_set_ooblayout(mtd, &mtd_ecclayout_wrapper_ops);
+}
+EXPORT_SYMBOL_GPL(mtd_set_ecclayout);
+
 /*
  * Method to access the protection register area, present in some flash
  * devices. The user data is one time programmable but the factory data is read