A more robust test for swapped RedBoot FIS directory partitions.  This
changes the test to check the flash_base value for the FIS directory,
since we know where the FIS directory base is we can work out whether
the flash address stored in the directory itself is byte swapped under
most circumstances.  If the value is 0 the directory is at the start
of the flash and the test fails.  In this case the fallback is to use
the original test made slightly more robust.

Signed-off-by: John Bowler <jbowler@acm.org>

--- linux-2.6.15/drivers/mtd/redboot.c	1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.15/drivers/mtd/redboot.c	1970-01-01 00:00:00.000000000 +0000
@@ -91,14 +91,41 @@ static int parse_redboot_partitions(stru
 		}
 		if (!memcmp(buf[i].name, "FIS directory", 14)) {
 			/* This is apparently the FIS directory entry for the
-			 * FIS directory itself.  The FIS directory size is
-			 * one erase block; if the buf[i].size field is
-			 * swab32(erasesize) then we know we are looking at
-			 * a byte swapped FIS directory - swap all the entries!
-			 * (NOTE: this is 'size' not 'data_length'; size is
-			 * the full size of the entry.)
+			 * FIS directory itself.  To discover whether the entries
+			 * in this are native byte sex or byte swapped look at
+			 * the flash_base field - we know the FIS directory is
+			 * at 'offset' within the flash.
 			 */
-			if (swab32(buf[i].size) == master->erasesize) {
+			int maybe_native, maybe_swapped;
+			if (fis_origin != 0) {
+				maybe_native =
+					buf[i].flash_base == fis_origin + offset;
+				maybe_swapped =
+					swab32(buf[i].flash_base) == fis_origin + offset;
+			} else if (offset != 0 || buf[i].flash_base != 0) {
+				maybe_native =
+					(buf[i].flash_base & (master->size-1)) == offset;
+				maybe_swapped =
+					(swab32(buf[i].flash_base) & (master->size-1)) == offset;
+			} else {
+				/* The FIS directory is at the start of the flash and
+				 * the 'flash_base' field is 0.  The critical case is when
+				 * we are booting off this flash, but then we don't expect
+				 * this because the boot loader is pretty much always at
+				 * the start!  Since the FIS directory is always less than
+				 * or equal to one erase block do the following:
+				 */
+				maybe_native = buf[i].size <= master->erasesize;
+				maybe_swapped = swab32(buf[i].size) <= master->erasesize;
+			}
+
+			if (maybe_native && maybe_swapped)
+				printk(KERN_WARNING "RedBoot directory 0x%lx(0x%lx) assumed native\n",
+					buf[i].flash_base, buf[i].size);
+			else if (!maybe_native && !maybe_swapped)
+				printk(KERN_ERR "RedBoot directory 0x%lx(0x%lx) forced native\n",
+					buf[i].flash_base, buf[i].size);
+			else if (maybe_swapped) {
 				int j;
 				for (j = 0; j < numslots && buf[j].name[0] != 0xff; ++j) {
 					/* The unsigned long fields were written with the
@@ -112,7 +139,11 @@ static int parse_redboot_partitions(stru
 					swab32s(&buf[j].desc_cksum);
 					swab32s(&buf[j].file_cksum);
 				}
-			}
+				printk(KERN_NOTICE "RedBoot directory 0x%lx(0x%lx) swapped\n",
+					buf[i].flash_base, buf[i].size);
+			} else
+				printk(KERN_NOTICE "RedBoot directory 0x%lx(0x%lx) native\n",
+					buf[i].flash_base, buf[i].size);
 			break;
 		}
 	}