mtd: 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.

While at it, be consistent in the naming of the mtd_info structures to
ease the understanding of the new hierarchy: these structures are
usually called 'mtd', unless there are multiple instances of the same
structure. In this case, there is usually a parent/child bound so we
will call them 'parent' and 'child'.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200114090952.11232-1-miquel.raynal@bootlin.com

include/linux/mtd/mtd.h

@@ -8,6 +8,7 @@
 
 #include <linux/types.h>
 #include <linux/uio.h>
+#include <linux/list.h>
 #include <linux/notifier.h>
 #include <linux/device.h>
 #include <linux/of.h>
@@ -194,10 +195,43 @@ struct mtd_debug_info {
 	const char *partid;
 };
 
+/**
+ * struct mtd_part - MTD partition specific fields
+ *
+ * @node: list node used to add an MTD partition to the parent partition list
+ * @offset: offset of the partition relatively to the parent offset
+ * @flags: original flags (before the mtdpart logic decided to tweak them based
+ *	   on flash constraints, like eraseblock/pagesize alignment)
+ *
+ * This struct is embedded in mtd_info and contains partition-specific
+ * properties/fields.
+ */
+struct mtd_part {
+	struct list_head node;
+	u64 offset;
+	u32 flags;
+};
+
+/**
+ * struct mtd_master - MTD master specific fields
+ *
+ * @partitions_lock: lock protecting accesses to the partition list. Protects
+ *		     not only the master partition list, but also all
+ *		     sub-partitions.
+ * @suspended: et to 1 when the device is suspended, 0 otherwise
+ *
+ * This struct is embedded in mtd_info and contains master-specific
+ * properties/fields. The master is the root MTD device from the MTD partition
+ * point of view.
+ */
+struct mtd_master {
+	struct mutex partitions_lock;
+	unsigned int suspended : 1;
+};
+
 struct mtd_info {
 	u_char type;
 	uint32_t flags;
-	uint32_t orig_flags; /* Flags as before running mtd checks */
 	uint64_t size;	 // Total size of the MTD
 
 	/* "Major" erase size for the device. Naïve users may take this
@@ -339,8 +373,52 @@ struct mtd_info {
 	int usecount;
 	struct mtd_debug_info dbg;
 	struct nvmem_device *nvmem;
+
+	/*
+	 * Parent device from the MTD partition point of view.
+	 *
+	 * MTD masters do not have any parent, MTD partitions do. The parent
+	 * MTD device can itself be a partition.
+	 */
+	struct mtd_info *parent;
+
+	/* List of partitions attached to this MTD device */
+	struct list_head partitions;
+
+	union {
+		struct mtd_part part;
+		struct mtd_master master;
+	};
 };
 
+static inline struct mtd_info *mtd_get_master(struct mtd_info *mtd)
+{
+	while (mtd->parent)
+		mtd = mtd->parent;
+
+	return mtd;
+}
+
+static inline u64 mtd_get_master_ofs(struct mtd_info *mtd, u64 ofs)
+{
+	while (mtd->parent) {
+		ofs += mtd->part.offset;
+		mtd = mtd->parent;
+	}
+
+	return ofs;
+}
+
+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,
@@ -392,13 +470,16 @@ static inline u32 mtd_oobavail(struct mtd_info *mtd, struct mtd_oob_ops *ops)
 static inline int mtd_max_bad_blocks(struct mtd_info *mtd,
 				     loff_t ofs, size_t len)
 {
-	if (!mtd->_max_bad_blocks)
+	struct mtd_info *master = mtd_get_master(mtd);
+
+	if (!master->_max_bad_blocks)
 		return -ENOTSUPP;
 
 	if (mtd->size < (len + ofs) || ofs < 0)
 		return -EINVAL;
 
-	return mtd->_max_bad_blocks(mtd, ofs, len);
+	return master->_max_bad_blocks(master, mtd_get_master_ofs(mtd, ofs),
+				       len);
 }
 
 int mtd_wunit_to_pairing_info(struct mtd_info *mtd, int wunit,
@@ -439,8 +520,10 @@ int mtd_writev(struct mtd_info *mtd, const struct kvec *vecs,
 
 static inline void mtd_sync(struct mtd_info *mtd)
 {
-	if (mtd->_sync)
-		mtd->_sync(mtd);
+	struct mtd_info *master = mtd_get_master(mtd);
+
+	if (master->_sync)
+		master->_sync(master);
 }
 
 int mtd_lock(struct mtd_info *mtd, loff_t ofs, uint64_t len);
@@ -452,13 +535,31 @@ int mtd_block_markbad(struct mtd_info *mtd, loff_t ofs);
 
 static inline int mtd_suspend(struct mtd_info *mtd)
 {
-	return mtd->_suspend ? mtd->_suspend(mtd) : 0;
+	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
+
+	if (master->master.suspended)
+		return 0;
+
+	ret = master->_suspend ? master->_suspend(master) : 0;
+	if (ret)
+		return ret;
+
+	master->master.suspended = 1;
+	return 0;
 }
 
 static inline void mtd_resume(struct mtd_info *mtd)
 {
-	if (mtd->_resume)
-		mtd->_resume(mtd);
+	struct mtd_info *master = mtd_get_master(mtd);
+
+	if (!master->master.suspended)
+		return;
+
+	if (master->_resume)
+		master->_resume(master);
+
+	master->master.suspended = 0;
 }
 
 static inline uint32_t mtd_div_by_eb(uint64_t sz, struct mtd_info *mtd)
@@ -538,7 +639,9 @@ static inline loff_t mtd_wunit_to_offset(struct mtd_info *mtd, loff_t base,
 
 static inline int mtd_has_oob(const struct mtd_info *mtd)
 {
-	return mtd->_read_oob && mtd->_write_oob;
+	struct mtd_info *master = mtd_get_master((struct mtd_info *)mtd);
+
+	return master->_read_oob && master->_write_oob;
 }
 
 static inline int mtd_type_is_nand(const struct mtd_info *mtd)
@@ -548,7 +651,9 @@ static inline int mtd_type_is_nand(const struct mtd_info *mtd)
 
 static inline int mtd_can_have_bb(const struct mtd_info *mtd)
 {
-	return !!mtd->_block_isbad;
+	struct mtd_info *master = mtd_get_master((struct mtd_info *)mtd);
+
+	return !!master->_block_isbad;
 }
 
 	/* Kernel-side ioctl definitions */