mtd: support reading OOB without ECC

This fixes issues with `nanddump -n' and the MEMREADOOB[64] ioctls on
hardware that performs error correction when reading only OOB data. A
driver for such hardware needs to know when we're doing a RAW vs. a
normal write, but mtd_do_read_oob does not pass such information to the
lower layers (e.g., NAND). We should pass MTD_OOB_RAW or MTD_OOB_PLACE
based on the MTD file mode.

For now, most drivers can get away with just setting:

  chip->ecc.read_oob_raw = chip->ecc.read_oob

This is done by default; but for systems that behave as described above,
you must supply your own replacement function.

This was tested with nandsim as well as on actual SLC NAND.

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Cc: Jim Quinlan <jim2101024@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@intel.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index b61a7c7bd097..ad40607f5f24 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -1787,7 +1787,10 @@ static int nand_do_read_oob(struct mtd_info *mtd, loff_t from,
         page = realpage & chip->pagemask;
 
         while (1) {
-                sndcmd = chip->ecc.read_oob(mtd, chip, page, sndcmd);
+                if (ops->mode == MTD_OOB_RAW)
+                        sndcmd = chip->ecc.read_oob_raw(mtd, chip, page, sndcmd);
+                else
+                        sndcmd = chip->ecc.read_oob(mtd, chip, page, sndcmd);
 
                 len = min(len, readlen);
                 buf = nand_transfer_oob(chip, buf, ops, len);
@@ -3385,6 +3388,8 @@ int nand_scan_tail(struct mtd_info *mtd)
         }
 
         /* For many systems, the standard OOB write also works for raw */
+        if (!chip->ecc.read_oob_raw)
+                chip->ecc.read_oob_raw = chip->ecc.read_oob;
         if (!chip->ecc.write_oob_raw)
                 chip->ecc.write_oob_raw = chip->ecc.write_oob;