mtd: add an mtd method for get_len_incl_bad()

The logic to 'spread' mtd partitions needs to calculate the length in
the mtd device, including bad blocks.

This patch introduces a new function, mtd_get_len_incl_bad that can
return both the length including bad blocks and whether that length
was truncated on the device. This new function will be used by the
mtdparts spread command later in this series. The definition of the
function is #ifdef'd out in configurations that do not use the new
'mtdparts spread' command.

Signed-off-by: Ben Gardiner<bengardiner@nanometrics.ca>
CC: Scott Wood <scottwood@freescale.com>

drivers/mtd/mtdcore.c

@@ -142,3 +142,52 @@ void put_mtd_device(struct mtd_info *mtd)
 	c = --mtd->usecount;
 	BUG_ON(c < 0);
 }
+
+#if defined(CONFIG_CMD_MTDPARTS_SPREAD)
+/**
+ * mtd_get_len_incl_bad
+ *
+ * Check if length including bad blocks fits into device.
+ *
+ * @param mtd an MTD device
+ * @param offset offset in flash
+ * @param length image length
+ * @return image length including bad blocks in *len_incl_bad and whether or not
+ *         the length returned was truncated in *truncated
+ */
+void mtd_get_len_incl_bad(struct mtd_info *mtd, uint64_t offset,
+			  const uint64_t length, uint64_t *len_incl_bad,
+			  int *truncated)
+{
+	*truncated = 0;
+	*len_incl_bad = 0;
+
+	if (offset >= mtd->size) {
+		*truncated = 1;
+		return;
+	}
+
+	if (!mtd->block_isbad) {
+		*len_incl_bad = length;
+		return;
+	}
+
+	uint64_t len_excl_bad = 0;
+	uint64_t block_len;
+
+	while (len_excl_bad < length) {
+		block_len = mtd->erasesize - (offset & (mtd->erasesize - 1));
+
+		if (!mtd->block_isbad(mtd, offset & ~(mtd->erasesize - 1)))
+			len_excl_bad += block_len;
+
+		*len_incl_bad += block_len;
+		offset       += block_len;
+
+		if (offset >= mtd->size) {
+			*truncated = 1;
+			break;
+		}
+	}
+}
+#endif /* defined(CONFIG_CMD_MTDPARTS_SPREAD) */

include/linux/mtd/mtd.h

@@ -255,7 +255,9 @@ extern struct mtd_info *get_mtd_device(struct mtd_info *mtd, int num);
 extern struct mtd_info *get_mtd_device_nm(const char *name);
 
 extern void put_mtd_device(struct mtd_info *mtd);
-
+extern void mtd_get_len_incl_bad(struct mtd_info *mtd, uint64_t offset,
+				 const uint64_t length, uint64_t *len_incl_bad,
+				 int *truncated);
 /* XXX U-BOOT XXX */
 #if 0
 struct mtd_notifier {