mtd: Fallback to ->_read/write_oob() when ->_read/write() is missing

Some MTD sublayers/drivers are implementing ->_read/write_oob() and
provide dummy wrappers for their ->_read/write() implementations.
Let the core handle this case instead of duplicating the logic.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Acked-by: Brian Norris <computersforpeace@gmail.com>
Reviewed-by: Miquel Raynal <miquel.raynal@free-electrons.com>
Tested-by: Ladislav Michl <ladis@linux-mips.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>

drivers/mtd/mtdcore.c

@@ -937,7 +937,20 @@ int mtd_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen,
 	 * representing the maximum number of bitflips that were corrected on
 	 * any one ecc region (if applicable; zero otherwise).
 	 */
-	ret_code = mtd->_read(mtd, from, len, retlen, buf);
+	if (mtd->_read) {
+		ret_code = mtd->_read(mtd, from, len, retlen, buf);
+	} else if (mtd->_read_oob) {
+		struct mtd_oob_ops ops = {
+			.len = len,
+			.datbuf = buf,
+		};
+
+		ret_code = mtd->_read_oob(mtd, from, &ops);
+		*retlen = ops.retlen;
+	} else {
+		return -ENOTSUPP;
+	}
+
 	if (unlikely(ret_code < 0))
 		return ret_code;
 	if (mtd->ecc_strength == 0)
@@ -952,10 +965,24 @@ int mtd_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen,
 	*retlen = 0;
 	if (to < 0 || to > mtd->size || len > mtd->size - to)
 		return -EINVAL;
-	if (!mtd->_write || !(mtd->flags & MTD_WRITEABLE))
+	if ((!mtd->_write && !mtd->_write_oob) ||
+	    !(mtd->flags & MTD_WRITEABLE))
 		return -EROFS;
 	if (!len)
 		return 0;
+
+	if (!mtd->_write) {
+		struct mtd_oob_ops ops = {
+			.len = len,
+			.datbuf = (u8 *)buf,
+		};
+		int ret;
+
+		ret = mtd->_write_oob(mtd, to, &ops);
+		*retlen = ops.retlen;
+		return ret;
+	}
+
 	return mtd->_write(mtd, to, len, retlen, buf);
 }
 EXPORT_SYMBOL_GPL(mtd_write);

drivers/mtd/mtdpart.c

@@ -417,8 +417,10 @@ static struct mtd_part *allocate_partition(struct mtd_info *master,
 	slave->mtd.dev.parent = master->dev.parent;
 #endif
 
-	slave->mtd._read = part_read;
-	slave->mtd._write = part_write;
+	if (master->_read)
+		slave->mtd._read = part_read;
+	if (master->_write)
+		slave->mtd._write = part_write;
 
 	if (master->_panic_write)
 		slave->mtd._panic_write = part_panic_write;

drivers/mtd/nand/nand_base.c

@@ -1864,33 +1864,6 @@ read_retry:
 }
 
 /**
- * nand_read - [MTD Interface] MTD compatibility function for nand_do_read_ecc
- * @mtd: MTD device structure
- * @from: offset to read from
- * @len: number of bytes to read
- * @retlen: pointer to variable to store the number of read bytes
- * @buf: the databuffer to put data
- *
- * Get hold of the chip and call nand_do_read.
- */
-static int nand_read(struct mtd_info *mtd, loff_t from, size_t len,
-		     size_t *retlen, uint8_t *buf)
-{
-	struct mtd_oob_ops ops;
-	int ret;
-
-	nand_get_device(mtd, FL_READING);
-	memset(&ops, 0, sizeof(ops));
-	ops.len = len;
-	ops.datbuf = buf;
-	ops.mode = MTD_OPS_PLACE_OOB;
-	ret = nand_do_read_ops(mtd, from, &ops);
-	*retlen = ops.retlen;
-	nand_release_device(mtd);
-	return ret;
-}
-
-/**
  * nand_read_oob_std - [REPLACEABLE] the most common OOB data read function
  * @mtd: mtd info structure
  * @chip: nand chip info structure
@@ -2675,33 +2648,6 @@ static int panic_nand_write(struct mtd_info *mtd, loff_t to, size_t len,
 }
 
 /**
- * nand_write - [MTD Interface] NAND write with ECC
- * @mtd: MTD device structure
- * @to: offset to write to
- * @len: number of bytes to write
- * @retlen: pointer to variable to store the number of written bytes
- * @buf: the data to write
- *
- * NAND write with ECC.
- */
-static int nand_write(struct mtd_info *mtd, loff_t to, size_t len,
-			  size_t *retlen, const uint8_t *buf)
-{
-	struct mtd_oob_ops ops;
-	int ret;
-
-	nand_get_device(mtd, FL_WRITING);
-	memset(&ops, 0, sizeof(ops));
-	ops.len = len;
-	ops.datbuf = (uint8_t *)buf;
-	ops.mode = MTD_OPS_PLACE_OOB;
-	ret = nand_do_write_ops(mtd, to, &ops);
-	*retlen = ops.retlen;
-	nand_release_device(mtd);
-	return ret;
-}
-
-/**
  * nand_do_write_oob - [MTD Interface] NAND write out-of-band
  * @mtd: MTD device structure
  * @to: offset to write to
@@ -4620,8 +4566,6 @@ int nand_scan_tail(struct mtd_info *mtd)
 	mtd->flags = (chip->options & NAND_ROM) ? MTD_CAP_ROM :
 						MTD_CAP_NANDFLASH;
 	mtd->_erase = nand_erase;
-	mtd->_read = nand_read;
-	mtd->_write = nand_write;
 	mtd->_panic_write = panic_nand_write;
 	mtd->_read_oob = nand_read_oob;
 	mtd->_write_oob = nand_write_oob;

drivers/mtd/onenand/onenand_base.c

@@ -2656,8 +2656,6 @@ int onenand_probe(struct mtd_info *mtd)
 
 	mtd->flags = MTD_CAP_NANDFLASH;
 	mtd->_erase = onenand_erase;
-	mtd->_read = onenand_read;
-	mtd->_write = onenand_write;
 	mtd->_read_oob = onenand_read_oob;
 	mtd->_write_oob = onenand_write_oob;
 	mtd->_sync = onenand_sync;