mtd: nand: Introduce a block iterator

In order to be able to iterate easily across eraseblocks rather than
pages, let's introduce a block iterator inspired from the page iterator.

The main usage of this iterator will be for continuous/sequential reads,
where it is interesting to use a single request rather than split the
requests in smaller chunks (ie. pages) that can be hardly optimized.

So a "continuous" boolean get's added for this purpose.
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20240826101412.20644-3-miquel.raynal@bootlin.com

include/linux/mtd/nand.h

@@ -103,6 +103,8 @@ enum nand_page_io_req_type {
  * @ooblen: the number of OOB bytes to read from/write to this page
  * @oobbuf: buffer to store OOB data in or get OOB data from
  * @mode: one of the %MTD_OPS_XXX mode
+ * @continuous: no need to start over the operation at the end of each page, the
+ * NAND device will automatically prepare the next one
  *
  * This object is used to pass per-page I/O requests to NAND sub-layers. This
  * way all useful information are already formatted in a useful way and
@@ -125,6 +127,7 @@ struct nand_page_io_req {
 		void *in;
 	} oobbuf;
 	int mode;
+	bool continuous;
 };
 
 const struct mtd_ooblayout_ops *nand_get_small_page_ooblayout(void);
@@ -937,6 +940,43 @@ static inline void nanddev_io_page_iter_init(struct nand_device *nand,
 	iter->req.ooblen = min_t(unsigned int,
 				 iter->oobbytes_per_page - iter->req.ooboffs,
 				 iter->oobleft);
+	iter->req.continuous = false;
+}
+
+/**
+ * nand_io_block_iter_init - Initialize a NAND I/O iterator
+ * @nand: NAND device
+ * @offs: absolute offset
+ * @req: MTD request
+ * @iter: NAND I/O iterator
+ *
+ * Initializes a NAND iterator based on the information passed by the MTD
+ * layer for block jumps (no OOB)
+ *
+ * In practice only reads may leverage this iterator.
+ */
+static inline void nanddev_io_block_iter_init(struct nand_device *nand,
+					      enum nand_page_io_req_type reqtype,
+					      loff_t offs, struct mtd_oob_ops *req,
+					      struct nand_io_iter *iter)
+{
+	unsigned int offs_in_eb;
+
+	iter->req.type = reqtype;
+	iter->req.mode = req->mode;
+	iter->req.dataoffs = nanddev_offs_to_pos(nand, offs, &iter->req.pos);
+	iter->req.ooboffs = 0;
+	iter->oobbytes_per_page = 0;
+	iter->dataleft = req->len;
+	iter->oobleft = 0;
+	iter->req.databuf.in = req->datbuf;
+	offs_in_eb = (nand->memorg.pagesize * iter->req.pos.page) + iter->req.dataoffs;
+	iter->req.datalen = min_t(unsigned int,
+				  nanddev_eraseblock_size(nand) - offs_in_eb,
+				  iter->dataleft);
+	iter->req.oobbuf.in = NULL;
+	iter->req.ooblen = 0;
+	iter->req.continuous = true;
 }
 
 /**
@@ -962,6 +1002,25 @@ static inline void nanddev_io_iter_next_page(struct nand_device *nand,
 				 iter->oobleft);
 }
 
+/**
+ * nand_io_iter_next_block - Move to the next block
+ * @nand: NAND device
+ * @iter: NAND I/O iterator
+ *
+ * Updates the @iter to point to the next block.
+ * No OOB handling available.
+ */
+static inline void nanddev_io_iter_next_block(struct nand_device *nand,
+					      struct nand_io_iter *iter)
+{
+	nanddev_pos_next_eraseblock(nand, &iter->req.pos);
+	iter->dataleft -= iter->req.datalen;
+	iter->req.databuf.in += iter->req.datalen;
+	iter->req.dataoffs = 0;
+	iter->req.datalen = min_t(unsigned int, nanddev_eraseblock_size(nand),
+				  iter->dataleft);
+}
+
 /**
  * nand_io_iter_end - Should end iteration or not
  * @nand: NAND device
@@ -997,6 +1056,21 @@ static inline bool nanddev_io_iter_end(struct nand_device *nand,
 	     !nanddev_io_iter_end(nand, iter);				\
 	     nanddev_io_iter_next_page(nand, iter))
 
+/**
+ * nand_io_for_each_block - Iterate over all NAND pages contained in an MTD I/O
+ *			    request, one block at a time
+ * @nand: NAND device
+ * @start: start address to read/write from
+ * @req: MTD I/O request
+ * @iter: NAND I/O iterator
+ *
+ * Should be used for iterating over blocks that are contained in an MTD request.
+ */
+#define nanddev_io_for_each_block(nand, type, start, req, iter)		\
+	for (nanddev_io_block_iter_init(nand, type, start, req, iter);	\
+	     !nanddev_io_iter_end(nand, iter);				\
+	     nanddev_io_iter_next_block(nand, iter))
+
 bool nanddev_isbad(struct nand_device *nand, const struct nand_pos *pos);
 bool nanddev_isreserved(struct nand_device *nand, const struct nand_pos *pos);
 int nanddev_markbad(struct nand_device *nand, const struct nand_pos *pos);