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From:   Ezequiel Garcia <ezequiel@collabora.com>
To:     linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org,
        Richard Weinberger <richard@nod.at>
Cc:     Miquel Raynal <miquel.raynal@bootlin.com>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Ezequiel Garcia <ezequiel@collabora.com>
Subject: [PATCH 3/3] mtdblock: Warn if the added for a NAND device
Date:   Sun,  1 Aug 2021 20:45:05 -0300
Message-Id: <20210801234509.18774-4-ezequiel@collabora.com>
In-Reply-To: <20210801234509.18774-1-ezequiel@collabora.com>
References: <20210801234509.18774-1-ezequiel@collabora.com>
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There is a surprisingly large number of tutorials
that suggest using mtdblock to mount SquashFS filesystems
on flash devices, including NAND devices.

This approach is suboptimal than using UBI. If the flash device
is NAND, this is specially true, due to wear leveling, bit-flips and
badblocks. In this case UBI is strongly preferred, so be nice to users
and print a warning suggesting to consider UBI block, if mtdblock
is added for a NAND device.

Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>

Untracked files not listed
---
 drivers/mtd/mtdblock.c    | 4 ++++
 drivers/mtd/mtdblock_ro.c | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/drivers/mtd/mtdblock.c b/drivers/mtd/mtdblock.c
index b2d5ed1cbc94..7c02643f862f 100644
--- a/drivers/mtd/mtdblock.c
+++ b/drivers/mtd/mtdblock.c
@@ -332,6 +332,10 @@ static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
 	if (!(mtd->flags & MTD_WRITEABLE))
 		dev->mbd.readonly = 1;
 
+	if (mtd_type_is_nand(mtd))
+		pr_warn("%s: MTD device '%s' is NAND, please consider using UBI block devices instead.\n",
+			tr->name, mtd->name);
+
 	if (add_mtd_blktrans_dev(&dev->mbd))
 		kfree(dev);
 }
diff --git a/drivers/mtd/mtdblock_ro.c b/drivers/mtd/mtdblock_ro.c
index fb5dc89369de..a438e2f6089c 100644
--- a/drivers/mtd/mtdblock_ro.c
+++ b/drivers/mtd/mtdblock_ro.c
@@ -60,6 +60,10 @@ static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
 	dev->tr = tr;
 	dev->readonly = 1;
 
+	if (mtd_type_is_nand(mtd))
+		pr_warn("%s: MTD device '%s' is NAND, please consider using UBI block devices instead.\n",
+			tr->name, mtd->name);
+
 	if (add_mtd_blktrans_dev(dev))
 		kfree(dev);
 }
-- 
2.32.0