linux-kernel - [RFC] mtd: ubi: skip programming unused bits in ubi headers

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Message-Id: <20250812051949.983040-1-linchengming884@gmail.com>
Date: Tue, 12 Aug 2025 13:19:49 +0800
From: Cheng Ming Lin <linchengming884@...il.com>
To: richard@....at,
	chengzhihao1@...wei.com,
	miquel.raynal@...tlin.com,
	vigneshr@...com,
	linux-mtd@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Cc: alvinzhou@...c.com.tw,
	leoyu@...c.com.tw,
	Cheng Ming Lin <chengminglin@...c.com.tw>
Subject: [RFC] mtd: ubi: skip programming unused bits in ubi headers

From: Cheng Ming Lin <chengminglin@...c.com.tw>

This patch prevents unnecessary programming of bits in ec_hdr and
vid_hdr that are not used or read during normal UBI operation. These
unused bits are typically already set to 1 in erased flash and do not
need to be explicitly programmed to 0 if they are not used.

Programming such unused areas offers no functional benefit and may
result in unnecessary flash wear, reducing the overall lifetime of the
device. By skipping these writes, we preserve the flash state as much
as possible and minimize wear caused by redundant operations.

This change ensures that only necessary fields are written when
preparing UBI headers, improving flash efficiency without affecting
functionality.

Signed-off-by: Cheng Ming Lin <chengminglin@...c.com.tw>
---
 drivers/mtd/ubi/io.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/mtd/ubi/io.c b/drivers/mtd/ubi/io.c
index a4999bce435f..ccab4691b338 100644
--- a/drivers/mtd/ubi/io.c
+++ b/drivers/mtd/ubi/io.c
@@ -868,6 +868,7 @@ int ubi_io_write_ec_hdr(struct ubi_device *ubi, int pnum,
 		return -EROFS;
 	}

+	memset((char *)ec_hdr + UBI_EC_HDR_SIZE, 0xFF, ubi->ec_hdr_alsize - UBI_EC_HDR_SIZE);
 	err = ubi_io_write(ubi, ec_hdr, pnum, 0, ubi->ec_hdr_alsize);
 	return err;
 }
@@ -1150,6 +1151,7 @@ int ubi_io_write_vid_hdr(struct ubi_device *ubi, int pnum,
 		return -EROFS;
 	}

+	memset((char *)p + ubi->vid_hdr_shift, 0xFF, ubi->vid_hdr_alsize - UBI_VID_HDR_SIZE);
 	err = ubi_io_write(ubi, p, pnum, ubi->vid_hdr_aloffset,
 			   ubi->vid_hdr_alsize);
 	return err;
-- 
2.25.1