mtdblock: warn if opened on NAND

Warning on every translated mtd partition results in excessive log noise
if this driver is loaded:

  nand: device found, Manufacturer ID: 0xc2, Chip ID: 0xf1
  nand: Macronix MX30LF1G18AC
  nand: 128 MiB, SLC, erase size: 128 KiB, page size: 2048, OOB size: 64
  mt7621-nand 1e003000.nand: ECC strength adjusted to 4 bits
  read_bbt: found bbt at block 1023
  10 fixed-partitions partitions found on MTD device mt7621-nand
  Creating 10 MTD partitions on "mt7621-nand":
  0x000000000000-0x000000080000 : "Bootloader"
  mtdblock: MTD device 'Bootloader' is NAND, please consider using UBI block devices instead.
  0x000000080000-0x000000100000 : "Config"
  mtdblock: MTD device 'Config' is NAND, please consider using UBI block devices instead.
  0x000000100000-0x000000140000 : "Factory"
  mtdblock: MTD device 'Factory' is NAND, please consider using UBI block devices instead.
  0x000000140000-0x000002000000 : "Kernel"
  mtdblock: MTD device 'Kernel' is NAND, please consider using UBI block devices instead.
  0x000000540000-0x000002000000 : "ubi"
  mtdblock: MTD device 'ubi' is NAND, please consider using UBI block devices instead.
  0x000002140000-0x000004000000 : "Kernel2"
  mtdblock: MTD device 'Kernel2' is NAND, please consider using UBI block devices instead.
  0x000004000000-0x000004100000 : "wwan"
  mtdblock: MTD device 'wwan' is NAND, please consider using UBI block devices instead.
  0x000004100000-0x000005100000 : "data"
  mtdblock: MTD device 'data' is NAND, please consider using UBI block devices instead.
  0x000005100000-0x000005200000 : "rom-d"
  mtdblock: MTD device 'rom-d' is NAND, please consider using UBI block devices instead.
  0x000005200000-0x000005280000 : "reserve"
  mtdblock: MTD device 'reserve' is NAND, please consider using UBI block devices instead.
  mtk_soc_eth 1e100000.ethernet eth0: mediatek frame engine at 0xbe100000, irq 21

This is more likely to annoy than to help users of embedded distros where
this driver is enabled by default.  Making the blockdevs available does
not imply that they are in use, and warning about bootloader partitions
or other devices which obviously never will be mounted is more confusing
than helpful.

Move the warning to open(), where it will be of more use - actually warning
anyone who mounts a file system on NAND using mtdblock.

Fixes: e07403a8 ("mtdblock: Warn if added for a NAND device")
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Reviewed-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20220328161108.87757-1-bjorn@mork.no

drivers/mtd/mtdblock.c

@@ -257,6 +257,10 @@ static int mtdblock_open(struct mtd_blktrans_dev *mbd)
 		return 0;
 	}
 
+	if (mtd_type_is_nand(mbd->mtd))
+		pr_warn("%s: MTD device '%s' is NAND, please consider using UBI block devices instead.\n",
+			mbd->tr->name, mbd->mtd->name);
+
 	/* OK, it's not open. Create cache info for it */
 	mtdblk->count = 1;
 	mutex_init(&mtdblk->cache_mutex);
@@ -322,10 +326,6 @@ 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);
 }