linux-kernel - [PATCH] mtd: dc21285: fix bytewise memcpy()

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Message-Id: <20250807072044.4146480-1-arnd@kernel.org>
Date: Thu,  7 Aug 2025 09:20:34 +0200
From: Arnd Bergmann <arnd@...nel.org>
To: Miquel Raynal <miquel.raynal@...tlin.com>,
	Richard Weinberger <richard@....at>,
	Vignesh Raghavendra <vigneshr@...com>,
	Nathan Chancellor <nathan@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>,
	David Woodhouse <dwmw2@...radead.org>,
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	linux-mtd@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev
Subject: [PATCH] mtd: dc21285: fix bytewise memcpy()

From: Arnd Bergmann <arnd@...db.de>

The commit that split up the 8/16/32-bit operations in 2004 seems to have
broken the 8-bit case, as clang-21 now points out:

drivers/mtd/maps/dc21285.c:129:97: error: parameter 'len' set but not used [-Werror,-Wunused-but-set-parameter]
  129 | static void dc21285_copy_to_8(struct map_info *map, unsigned long to, const void *from, ssize_t len)

Put back the loop that was in linux-2.6.8 and earlier for this case.

Fixes: 67d4878e4e61 ("NOR flash drivers update")
Cc: David Woodhouse <dwmw2@...radead.org>
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/mtd/maps/dc21285.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/mtd/maps/dc21285.c b/drivers/mtd/maps/dc21285.c
index 70a3db3ab856..1d70bf62e91f 100644
--- a/drivers/mtd/maps/dc21285.c
+++ b/drivers/mtd/maps/dc21285.c
@@ -128,12 +128,14 @@ static void dc21285_copy_to_16(struct map_info *map, unsigned long to, const voi
 
 static void dc21285_copy_to_8(struct map_info *map, unsigned long to, const void *from, ssize_t len)
 {
-	map_word d;
-	d.x[0] = *((uint8_t*)from);
-	dc21285_write8(map, d, to);
-	from++;
-	to++;
-	len--;
+	while (len > 0) {
+		map_word d;
+		d.x[0] = *((uint8_t*)from);
+		dc21285_write8(map, d, to);
+		from++;
+		to++;
+		len--;
+	}
 }
 
 static struct map_info dc21285_map = {
-- 
2.39.5