nand: make 1-bit software ECC configurable

The software ECC algorithm is not necessary when hardware ECC
is available and can be left out for a smaller image size.
Enable with CONFIG_MTD_ECC_SOFT.

Signed-off-by: Christian Hitz <christian.hitz@aizo.com>
Cc: Scott Wood <scottwood@freescale.com>
Signed-off-by: Scott Wood <scottwood@freescale.com>

drivers/mtd/nand/Makefile

@@ -39,7 +39,7 @@ COBJS-y += nand_bbt.o
 COBJS-y += nand_ids.o
 COBJS-y += nand_util.o
 endif
-COBJS-y += nand_ecc.o
+COBJS-$(CONFIG_MTD_ECC_SOFT) += nand_ecc.o
 COBJS-y += nand_base.o
 COBJS-$(CONFIG_NAND_ECC_BCH) += nand_bch.o
 

drivers/mtd/nand/nand_base.c

@@ -3028,6 +3028,10 @@ int nand_scan_tail(struct mtd_info *mtd)
 		chip->ecc.mode = NAND_ECC_SOFT;
 
 	case NAND_ECC_SOFT:
+		if (!mtd_nand_has_ecc_soft()) {
+			printk(KERN_WARNING "CONFIG_MTD_ECC_SOFT not enabled\n");
+			return -EINVAL;
+		}
 		chip->ecc.calculate = nand_calculate_ecc;
 		chip->ecc.correct = nand_correct_data;
 		chip->ecc.read_page = nand_read_page_swecc;

include/linux/mtd/nand_ecc.h

@@ -15,6 +15,10 @@
 
 struct mtd_info;
 
+#if defined(CONFIG_MTD_ECC_SOFT)
+
+static inline int mtd_nand_has_ecc_soft(void) { return 1; }
+
 /*
  * Calculate 3 byte ECC code for 256 byte block
  */
@@ -25,4 +29,25 @@ int nand_calculate_ecc(struct mtd_info *mtd, const u_char *dat, u_char *ecc_code
  */
 int nand_correct_data(struct mtd_info *mtd, u_char *dat, u_char *read_ecc, u_char *calc_ecc);
 
+#else
+
+static inline int mtd_nand_has_ecc_soft(void) { return 0; }
+
+static inline int
+nand_calculate_ecc(struct mtd_info *mtd, const u_char *dat, u_char *ecc_code)
+{
+	return -1;
+}
+
+static inline int
+nand_correct_data(struct mtd_info *mtd,
+			u_char *dat,
+			u_char *read_ecc,
+			u_char *calc_ecc)
+{
+	return -1;
+}
+
+#endif
+
 #endif /* __MTD_NAND_ECC_H__ */