mtd: add mtd_ooblayout_xxx() helper functions

In order to make the ecclayout definition completely dynamic we need to
rework the way the OOB layout are defined and iterated.

Create a few mtd_ooblayout_xxx() helpers to ease OOB bytes manipulation
and hide ecclayout internals to their users.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
[Linux commit: 75eb2cec251fda33c9bb716ecc372819abb9278a]
[masahiro:
 cherry-pick more code from adbbc3bc827eb1f43a932d783f09ba55c8ec8379]
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

drivers/mtd/mtdcore.c

@@ -1005,6 +1005,366 @@ int mtd_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops)
 }
 EXPORT_SYMBOL_GPL(mtd_read_oob);
 
+/**
+ * mtd_ooblayout_ecc - Get the OOB region definition of a specific ECC section
+ * @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 returns ECC section information in the OOB area. If you want
+ * to get all the ECC bytes information, then you should call
+ * mtd_ooblayout_ecc(mtd, section++, oobecc) until it returns -ERANGE.
+ *
+ * Returns zero on success, a negative error code otherwise.
+ */
+int mtd_ooblayout_ecc(struct mtd_info *mtd, int section,
+		      struct mtd_oob_region *oobecc)
+{
+	memset(oobecc, 0, sizeof(*oobecc));
+
+	if (!mtd || section < 0)
+		return -EINVAL;
+
+	if (!mtd->ooblayout || !mtd->ooblayout->ecc)
+		return -ENOTSUPP;
+
+	return mtd->ooblayout->ecc(mtd, section, oobecc);
+}
+EXPORT_SYMBOL_GPL(mtd_ooblayout_ecc);
+
+/**
+ * mtd_ooblayout_free - Get the OOB region definition of a specific free
+ *			section
+ * @mtd: MTD device structure
+ * @section: Free section you are interested in. Depending on the layout
+ *	     you may have all the free bytes stored in a single contiguous
+ *	     section, or one section per ECC chunk plus an extra section
+ *	     for the remaining bytes (or other funky layout).
+ * @oobfree: OOB region struct filled with the appropriate free position
+ *	     information
+ *
+ * This function returns free bytes position in the OOB area. If you want
+ * to get all the free bytes information, then you should call
+ * mtd_ooblayout_free(mtd, section++, oobfree) until it returns -ERANGE.
+ *
+ * Returns zero on success, a negative error code otherwise.
+ */
+int mtd_ooblayout_free(struct mtd_info *mtd, int section,
+		       struct mtd_oob_region *oobfree)
+{
+	memset(oobfree, 0, sizeof(*oobfree));
+
+	if (!mtd || section < 0)
+		return -EINVAL;
+
+	if (!mtd->ooblayout || !mtd->ooblayout->free)
+		return -ENOTSUPP;
+
+	return mtd->ooblayout->free(mtd, section, oobfree);
+}
+EXPORT_SYMBOL_GPL(mtd_ooblayout_free);
+
+/**
+ * mtd_ooblayout_find_region - Find the region attached to a specific byte
+ * @mtd: mtd info structure
+ * @byte: the byte we are searching for
+ * @sectionp: pointer where the section id will be stored
+ * @oobregion: used to retrieve the ECC position
+ * @iter: iterator function. Should be either mtd_ooblayout_free or
+ *	  mtd_ooblayout_ecc depending on the region type you're searching for
+ *
+ * This function returns the section id and oobregion information of a
+ * specific byte. For example, say you want to know where the 4th ECC byte is
+ * stored, you'll use:
+ *
+ * mtd_ooblayout_find_region(mtd, 3, &section, &oobregion, mtd_ooblayout_ecc);
+ *
+ * Returns zero on success, a negative error code otherwise.
+ */
+static int mtd_ooblayout_find_region(struct mtd_info *mtd, int byte,
+				int *sectionp, struct mtd_oob_region *oobregion,
+				int (*iter)(struct mtd_info *,
+					    int section,
+					    struct mtd_oob_region *oobregion))
+{
+	int pos = 0, ret, section = 0;
+
+	memset(oobregion, 0, sizeof(*oobregion));
+
+	while (1) {
+		ret = iter(mtd, section, oobregion);
+		if (ret)
+			return ret;
+
+		if (pos + oobregion->length > byte)
+			break;
+
+		pos += oobregion->length;
+		section++;
+	}
+
+	/*
+	 * Adjust region info to make it start at the beginning at the
+	 * 'start' ECC byte.
+	 */
+	oobregion->offset += byte - pos;
+	oobregion->length -= byte - pos;
+	*sectionp = section;
+
+	return 0;
+}
+
+/**
+ * mtd_ooblayout_find_eccregion - Find the ECC region attached to a specific
+ *				  ECC byte
+ * @mtd: mtd info structure
+ * @eccbyte: the byte we are searching for
+ * @sectionp: pointer where the section id will be stored
+ * @oobregion: OOB region information
+ *
+ * Works like mtd_ooblayout_find_region() except it searches for a specific ECC
+ * byte.
+ *
+ * Returns zero on success, a negative error code otherwise.
+ */
+int mtd_ooblayout_find_eccregion(struct mtd_info *mtd, int eccbyte,
+				 int *section,
+				 struct mtd_oob_region *oobregion)
+{
+	return mtd_ooblayout_find_region(mtd, eccbyte, section, oobregion,
+					 mtd_ooblayout_ecc);
+}
+EXPORT_SYMBOL_GPL(mtd_ooblayout_find_eccregion);
+
+/**
+ * mtd_ooblayout_get_bytes - Extract OOB bytes from the oob buffer
+ * @mtd: mtd info structure
+ * @buf: destination buffer to store OOB bytes
+ * @oobbuf: OOB buffer
+ * @start: first byte to retrieve
+ * @nbytes: number of bytes to retrieve
+ * @iter: section iterator
+ *
+ * Extract bytes attached to a specific category (ECC or free)
+ * from the OOB buffer and copy them into buf.
+ *
+ * Returns zero on success, a negative error code otherwise.
+ */
+static int mtd_ooblayout_get_bytes(struct mtd_info *mtd, u8 *buf,
+				const u8 *oobbuf, int start, int nbytes,
+				int (*iter)(struct mtd_info *,
+					    int section,
+					    struct mtd_oob_region *oobregion))
+{
+	struct mtd_oob_region oobregion;
+	int section, ret;
+
+	ret = mtd_ooblayout_find_region(mtd, start, &section,
+					&oobregion, iter);
+
+	while (!ret) {
+		int cnt;
+
+		cnt = min_t(int, nbytes, oobregion.length);
+		memcpy(buf, oobbuf + oobregion.offset, cnt);
+		buf += cnt;
+		nbytes -= cnt;
+
+		if (!nbytes)
+			break;
+
+		ret = iter(mtd, ++section, &oobregion);
+	}
+
+	return ret;
+}
+
+/**
+ * mtd_ooblayout_set_bytes - put OOB bytes into the oob buffer
+ * @mtd: mtd info structure
+ * @buf: source buffer to get OOB bytes from
+ * @oobbuf: OOB buffer
+ * @start: first OOB byte to set
+ * @nbytes: number of OOB bytes to set
+ * @iter: section iterator
+ *
+ * Fill the OOB buffer with data provided in buf. The category (ECC or free)
+ * is selected by passing the appropriate iterator.
+ *
+ * Returns zero on success, a negative error code otherwise.
+ */
+static int mtd_ooblayout_set_bytes(struct mtd_info *mtd, const u8 *buf,
+				u8 *oobbuf, int start, int nbytes,
+				int (*iter)(struct mtd_info *,
+					    int section,
+					    struct mtd_oob_region *oobregion))
+{
+	struct mtd_oob_region oobregion;
+	int section, ret;
+
+	ret = mtd_ooblayout_find_region(mtd, start, &section,
+					&oobregion, iter);
+
+	while (!ret) {
+		int cnt;
+
+		cnt = min_t(int, nbytes, oobregion.length);
+		memcpy(oobbuf + oobregion.offset, buf, cnt);
+		buf += cnt;
+		nbytes -= cnt;
+
+		if (!nbytes)
+			break;
+
+		ret = iter(mtd, ++section, &oobregion);
+	}
+
+	return ret;
+}
+
+/**
+ * mtd_ooblayout_count_bytes - count the number of bytes in a OOB category
+ * @mtd: mtd info structure
+ * @iter: category iterator
+ *
+ * Count the number of bytes in a given category.
+ *
+ * Returns a positive value on success, a negative error code otherwise.
+ */
+static int mtd_ooblayout_count_bytes(struct mtd_info *mtd,
+				int (*iter)(struct mtd_info *,
+					    int section,
+					    struct mtd_oob_region *oobregion))
+{
+	struct mtd_oob_region oobregion;
+	int section = 0, ret, nbytes = 0;
+
+	while (1) {
+		ret = iter(mtd, section++, &oobregion);
+		if (ret) {
+			if (ret == -ERANGE)
+				ret = nbytes;
+			break;
+		}
+
+		nbytes += oobregion.length;
+	}
+
+	return ret;
+}
+
+/**
+ * mtd_ooblayout_get_eccbytes - extract ECC bytes from the oob buffer
+ * @mtd: mtd info structure
+ * @eccbuf: destination buffer to store ECC bytes
+ * @oobbuf: OOB buffer
+ * @start: first ECC byte to retrieve
+ * @nbytes: number of ECC bytes to retrieve
+ *
+ * Works like mtd_ooblayout_get_bytes(), except it acts on ECC bytes.
+ *
+ * Returns zero on success, a negative error code otherwise.
+ */
+int mtd_ooblayout_get_eccbytes(struct mtd_info *mtd, u8 *eccbuf,
+			       const u8 *oobbuf, int start, int nbytes)
+{
+	return mtd_ooblayout_get_bytes(mtd, eccbuf, oobbuf, start, nbytes,
+				       mtd_ooblayout_ecc);
+}
+EXPORT_SYMBOL_GPL(mtd_ooblayout_get_eccbytes);
+
+/**
+ * mtd_ooblayout_set_eccbytes - set ECC bytes into the oob buffer
+ * @mtd: mtd info structure
+ * @eccbuf: source buffer to get ECC bytes from
+ * @oobbuf: OOB buffer
+ * @start: first ECC byte to set
+ * @nbytes: number of ECC bytes to set
+ *
+ * Works like mtd_ooblayout_set_bytes(), except it acts on ECC bytes.
+ *
+ * Returns zero on success, a negative error code otherwise.
+ */
+int mtd_ooblayout_set_eccbytes(struct mtd_info *mtd, const u8 *eccbuf,
+			       u8 *oobbuf, int start, int nbytes)
+{
+	return mtd_ooblayout_set_bytes(mtd, eccbuf, oobbuf, start, nbytes,
+				       mtd_ooblayout_ecc);
+}
+EXPORT_SYMBOL_GPL(mtd_ooblayout_set_eccbytes);
+
+/**
+ * mtd_ooblayout_get_databytes - extract data bytes from the oob buffer
+ * @mtd: mtd info structure
+ * @databuf: destination buffer to store ECC bytes
+ * @oobbuf: OOB buffer
+ * @start: first ECC byte to retrieve
+ * @nbytes: number of ECC bytes to retrieve
+ *
+ * Works like mtd_ooblayout_get_bytes(), except it acts on free bytes.
+ *
+ * Returns zero on success, a negative error code otherwise.
+ */
+int mtd_ooblayout_get_databytes(struct mtd_info *mtd, u8 *databuf,
+				const u8 *oobbuf, int start, int nbytes)
+{
+	return mtd_ooblayout_get_bytes(mtd, databuf, oobbuf, start, nbytes,
+				       mtd_ooblayout_free);
+}
+EXPORT_SYMBOL_GPL(mtd_ooblayout_get_databytes);
+
+/**
+ * mtd_ooblayout_get_eccbytes - set data bytes into the oob buffer
+ * @mtd: mtd info structure
+ * @eccbuf: source buffer to get data bytes from
+ * @oobbuf: OOB buffer
+ * @start: first ECC byte to set
+ * @nbytes: number of ECC bytes to set
+ *
+ * Works like mtd_ooblayout_get_bytes(), except it acts on free bytes.
+ *
+ * Returns zero on success, a negative error code otherwise.
+ */
+int mtd_ooblayout_set_databytes(struct mtd_info *mtd, const u8 *databuf,
+				u8 *oobbuf, int start, int nbytes)
+{
+	return mtd_ooblayout_set_bytes(mtd, databuf, oobbuf, start, nbytes,
+				       mtd_ooblayout_free);
+}
+EXPORT_SYMBOL_GPL(mtd_ooblayout_set_databytes);
+
+/**
+ * mtd_ooblayout_count_freebytes - count the number of free bytes in OOB
+ * @mtd: mtd info structure
+ *
+ * Works like mtd_ooblayout_count_bytes(), except it count free bytes.
+ *
+ * Returns zero on success, a negative error code otherwise.
+ */
+int mtd_ooblayout_count_freebytes(struct mtd_info *mtd)
+{
+	return mtd_ooblayout_count_bytes(mtd, mtd_ooblayout_free);
+}
+EXPORT_SYMBOL_GPL(mtd_ooblayout_count_freebytes);
+
+/**
+ * mtd_ooblayout_count_freebytes - count the number of ECC bytes in OOB
+ * @mtd: mtd info structure
+ *
+ * Works like mtd_ooblayout_count_bytes(), except it count ECC bytes.
+ *
+ * Returns zero on success, a negative error code otherwise.
+ */
+int mtd_ooblayout_count_eccbytes(struct mtd_info *mtd)
+{
+	return mtd_ooblayout_count_bytes(mtd, mtd_ooblayout_ecc);
+}
+EXPORT_SYMBOL_GPL(mtd_ooblayout_count_eccbytes);
+
 /*
  * 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

include/linux/mtd/mtd.h

@@ -103,6 +103,36 @@ struct mtd_oob_ops {
 #else
 #define MTD_MAX_ECCPOS_ENTRIES_LARGE	680
 #endif
+/**
+ * struct mtd_oob_region - oob region definition
+ * @offset: region offset
+ * @length: region length
+ *
+ * This structure describes a region of the OOB area, and is used
+ * to retrieve ECC or free bytes sections.
+ * Each section is defined by an offset within the OOB area and a
+ * length.
+ */
+struct mtd_oob_region {
+	u32 offset;
+	u32 length;
+};
+
+/*
+ * struct mtd_ooblayout_ops - NAND OOB layout operations
+ * @ecc: function returning an ECC region in the OOB area.
+ *	 Should return -ERANGE if %section exceeds the total number of
+ *	 ECC sections.
+ * @free: function returning a free region in the OOB area.
+ *	  Should return -ERANGE if %section exceeds the total number of
+ *	  free sections.
+ */
+struct mtd_ooblayout_ops {
+	int (*ecc)(struct mtd_info *mtd, int section,
+		   struct mtd_oob_region *oobecc);
+	int (*free)(struct mtd_info *mtd, int section,
+		    struct mtd_oob_region *oobfree);
+};
 
 /*
  * Internal ECC layout control structure. For historical reasons, there is a
@@ -179,6 +209,9 @@ struct mtd_info {
 #endif
 	int index;
 
+	/* OOB layout description */
+	const struct mtd_ooblayout_ops *ooblayout;
+
 	/* ECC layout structure pointer - read only! */
 	struct nand_ecclayout *ecclayout;
 
@@ -278,6 +311,30 @@ struct mtd_info {
 	int usecount;
 };
 
+int mtd_ooblayout_ecc(struct mtd_info *mtd, int section,
+		      struct mtd_oob_region *oobecc);
+int mtd_ooblayout_find_eccregion(struct mtd_info *mtd, int eccbyte,
+				 int *section,
+				 struct mtd_oob_region *oobregion);
+int mtd_ooblayout_get_eccbytes(struct mtd_info *mtd, u8 *eccbuf,
+			       const u8 *oobbuf, int start, int nbytes);
+int mtd_ooblayout_set_eccbytes(struct mtd_info *mtd, const u8 *eccbuf,
+			       u8 *oobbuf, int start, int nbytes);
+int mtd_ooblayout_free(struct mtd_info *mtd, int section,
+		       struct mtd_oob_region *oobfree);
+int mtd_ooblayout_get_databytes(struct mtd_info *mtd, u8 *databuf,
+				const u8 *oobbuf, int start, int nbytes);
+int mtd_ooblayout_set_databytes(struct mtd_info *mtd, const u8 *databuf,
+				u8 *oobbuf, int start, int nbytes);
+int mtd_ooblayout_count_freebytes(struct mtd_info *mtd);
+int mtd_ooblayout_count_eccbytes(struct mtd_info *mtd);
+
+static inline void mtd_set_ooblayout(struct mtd_info *mtd,
+				     const struct mtd_ooblayout_ops *ooblayout)
+{
+	mtd->ooblayout = ooblayout;
+}
+
 static inline int mtd_oobavail(struct mtd_info *mtd, struct mtd_oob_ops *ops)
 {
 	return ops->mode == MTD_OPS_AUTO_OOB ? mtd->oobavail : mtd->oobsize;