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: NBoris Brezillon <boris.brezillon@free-electrons.com>

drivers/mtd/mtdcore.c

@@ -1016,6 +1016,406 @@ int mtd_write_oob(struct mtd_info *mtd, loff_t to,
 }
 EXPORT_SYMBOL_GPL(mtd_write_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 functions return ECC section information in the OOB area. I 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)
+{
+	int eccbyte = 0, cursection = 0, length = 0, eccpos = 0;
+
+	memset(oobecc, 0, sizeof(*oobecc));
+
+	if (!mtd || section < 0)
+		return -EINVAL;
+
+	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;
+}
+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 functions return free bytes position in the OOB area. I 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->ecclayout)
+		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;
+}
+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 functions 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 = 0, ret;
+
+	ret = mtd_ooblayout_find_region(mtd, start, &section,
+					&oobregion, iter);
+
+	while (!ret) {
+		int cnt;
+
+		cnt = oobregion.length > nbytes ? 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 = 0, ret;
+
+	ret = mtd_ooblayout_find_region(mtd, start, &section,
+					&oobregion, iter);
+
+	while (!ret) {
+		int cnt;
+
+		cnt = oobregion.length > nbytes ? 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

@@ -108,6 +108,21 @@ struct nand_ecclayout {
 	struct nand_oobfree oobfree[MTD_MAX_OOBFREE_ENTRIES_LARGE];
 };
 
+/**
+ * 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 module;	/* only needed for owner field in mtd_info */
 
 struct mtd_info {
@@ -253,6 +268,24 @@ 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_of_node(struct mtd_info *mtd,
 				   struct device_node *np)
 {