mtd: mtdpart: implement proper partition handling

Instead of collecting partitions in a flat list, create a hierarchy
within the mtd_info structure: use a partitions list to keep track of
the partitions of an MTD device (which might be itself a partition of
another MTD device), a pointer to the parent device (NULL when the MTD
device is the root one, not a partition).

By also saving directly in mtd_info the offset of the partition, we
can get rid of the mtd_part structure.
Signed-off-by: NMiquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: NStefan Roese <sr@denx.de>
Reviewed-by: NBoris Brezillon <boris.brezillon@bootlin.com>

drivers/mtd/mtdcore.c

@@ -426,6 +426,8 @@ int add_mtd_device(struct mtd_info *mtd)
 	mtd->index = i;
 	mtd->usecount = 0;
 
+	INIT_LIST_HEAD(&mtd->partitions);
+
 	/* default value if not set by driver */
 	if (mtd->bitflip_threshold == 0)
 		mtd->bitflip_threshold = mtd->ecc_strength;

include/linux/mtd/mtd.h

@@ -20,6 +20,7 @@
 #include <linux/compat.h>
 #include <mtd/mtd-abi.h>
 #include <linux/errno.h>
+#include <linux/list.h>
 #include <div64.h>
 #if IS_ENABLED(CONFIG_DM)
 #include <dm/device.h>
@@ -307,6 +308,27 @@ struct mtd_info {
 	struct udevice *dev;
 #endif
 	int usecount;
+
+	/* MTD devices do not have any parent. MTD partitions do. */
+	struct mtd_info *parent;
+
+	/*
+	 * Offset of the partition relatively to the parent offset.
+	 * Is 0 for real MTD devices (ie. not partitions).
+	 */
+	u64 offset;
+
+	/*
+	 * List node used to add an MTD partition to the parent
+	 * partition list.
+	 */
+	struct list_head node;
+
+	/*
+	 * List of partitions attached to this MTD device (the parent
+	 * MTD device can itself be a partition).
+	 */
+	struct list_head partitions;
 };
 
 #if IS_ENABLED(CONFIG_DM)
@@ -334,6 +356,16 @@ static inline const struct device_node *mtd_get_of_node(struct mtd_info *mtd)
 }
 #endif
 
+static inline bool mtd_is_partition(const struct mtd_info *mtd)
+{
+	return mtd->parent;
+}
+
+static inline bool mtd_has_partitions(const struct mtd_info *mtd)
+{
+	return !list_empty(&mtd->partitions);
+}
+
 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,

include/linux/mtd/partitions.h

@@ -81,7 +81,6 @@ extern void register_mtd_parser(struct mtd_part_parser *parser);
 extern void deregister_mtd_parser(struct mtd_part_parser *parser);
 #endif
 
-int mtd_is_partition(const struct mtd_info *mtd);
 int mtd_add_partition(struct mtd_info *master, const char *name,
 		      long long offset, long long length);
 int mtd_del_partition(struct mtd_info *master, int partno);