mtd: nand: add support for BBT without OOB

The first (sixt) byte in the OOB area contains vendor's bad block
information. During identification of the NAND chip this information is
collected by scanning the complete chip.
The option NAND_USE_FLASH_BBT is used to store this information in a sector so
we don't have to scan the complete flash. Unfortunately the code stores
a marker in order to recognize the BBT in the OOB area. This will fail
if the OOB area is completely used for ECC.
This patch introduces the option NAND_USE_FLASH_BBT_NO_OOB which has to be
used with NAND_USE_FLASH_BBT. It will then store BBT on flash without
touching the OOB area. The BBT format on flash remains same except the
first page starts with the recognition pattern followed by the version byte.
This change was tested in nandsim and it looks good so far :)
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

include/linux/mtd/bbm.h

@@ -102,6 +102,8 @@ struct nand_bbt_descr {
 #define NAND_BBT_SCANBYTE1AND6 0x00100000
 /* The nand_bbt_descr was created dynamicaly and must be freed */
 #define NAND_BBT_DYNAMICSTRUCT 0x00200000
+/* The bad block table does not OOB for marker */
+#define NAND_BBT_NO_OOB		0x00400000
 
 /* The maximum number of blocks to scan for a bbt */
 #define NAND_BBT_SCAN_MAXBLOCKS	4

include/linux/mtd/nand.h

@@ -206,8 +206,10 @@ typedef enum {
 #define NAND_CHIPOPTIONS_MSK	(0x0000ffff & ~NAND_NO_AUTOINCR)
 
 /* Non chip related options */
-/* Use a flash based bad block table. This option is passed to the
- * default bad block table function. */
+/*
+ * Use a flash based bad block table. OOB identifier is saved in OOB area.
+ * This option is passed to the default bad block table function.
+ */
 #define NAND_USE_FLASH_BBT	0x00010000
 /* This option skips the bbt scan during initialization. */
 #define NAND_SKIP_BBTSCAN	0x00020000
@@ -216,6 +218,11 @@ typedef enum {
 #define NAND_OWN_BUFFERS	0x00040000
 /* Chip may not exist, so silence any errors in scan */
 #define NAND_SCAN_SILENT_NODEV	0x00080000
+/*
+ * If passed additionally to NAND_USE_FLASH_BBT then BBT code will not touch
+ * the OOB area.
+ */
+#define NAND_USE_FLASH_BBT_NO_OOB	0x00100000
 
 /* Options set by nand scan */
 /* Nand scan has allocated controller struct */