[PATCH 2/2] mtd: rawnand: Bypass a couple of sanity checks during NAND identification

[Miquel Raynal]

Early during NAND identification, mtd_info fields have not yet been
initialized (namely, writesize and oobsize) and thus cannot be used for
sanity checks yet. Of course if there is a misuse of
nand_change_read_column_op() so early we won't be warned, but there is
anyway no actual check to perform at this stage as we do not yet know
the NAND geometry.

So, if the fields are empty, especially mtd->writesize which is *always*
set quite rapidly after identification, let's skip the sanity checks.

nand_change_read_column_op() is subject to be used early for ONFI/JEDEC
identification in the very unlikely case of:
- bitflips appearing in the parameter page,
- the controller driver not supporting simple DATA_IN cycles.

Fixes: c27842e7e11f ("mtd: rawnand: onfi: Adapt the parameter page read to constraint controllers")
Fixes: daca31765e8b ("mtd: rawnand: jedec: Adapt the parameter page read to constraint controllers")
Cc: stable at vger.kernel.org
Reported-by: Alexander Dahl <ada at thorsis.com>
Closes: https://lore.kernel.org/linux-mtd/20240306-shaky-bunion-d28b65ea97d7@thorsis.com/
Reported-by: Steven Seeger <steven.seeger at flightsystems.net>
Closes: https://lore.kernel.org/linux-mtd/DM6PR05MB4506554457CF95191A670BDEF7062@DM6PR05MB4506.namprd05.prod.outlook.com/
Signed-off-by: Miquel Raynal <miquel.raynal at bootlin.com>
---
 drivers/mtd/nand/raw/nand_base.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
index 248e654ecefd..a66e73cd68cb 100644
--- a/drivers/mtd/nand/raw/nand_base.c
+++ b/drivers/mtd/nand/raw/nand_base.c
@@ -1440,12 +1440,14 @@ int nand_change_read_column_op(struct nand_chip *chip,
 	if (len && !buf)
 		return -EINVAL;
 
-	if (offset_in_page + len > mtd->writesize + mtd->oobsize)
-		return -EINVAL;
+	if (mtd->writesize) {
+		if ((offset_in_page + len > mtd->writesize + mtd->oobsize))
+			return -EINVAL;
 
-	/* Small page NANDs do not support column change. */
-	if (mtd->writesize <= 512)
-		return -ENOTSUPP;
+		/* Small page NANDs do not support column change. */
+		if (mtd->writesize <= 512)
+			return -ENOTSUPP;
+	}
 
 	if (nand_has_exec_op(chip)) {
 		const struct nand_interface_config *conf =
-- 
2.40.1