[PATCH v2] partitions: dos: improve guess of disk size

[Uwe Kleine-König]

The code used to ineffectively take the end of the last partition as guess
for the disk size. Better use the end of the partition that has its end
rearmost.

Also return an unsigned type instead of int as the result is always
non-negative.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig at pengutronix.de>
---
 common/partitions/dos.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/common/partitions/dos.c b/common/partitions/dos.c
index 9afd122..64314a8 100644
--- a/common/partitions/dos.c
+++ b/common/partitions/dos.c
@@ -27,19 +27,23 @@
  * @param table partition table
  * @return sector count
  */
-static int disk_guess_size(struct device_d *dev, struct partition_entry *table)
+static uint64_t disk_guess_size(struct device_d *dev,
+		struct partition_entry *table)
 {
 	uint64_t size = 0;
 	int i;
 
 	for (i = 0; i < 4; i++) {
-		if (table[i].partition_start != 0) {
-			size += get_unaligned_le32(&table[i].partition_start) - size;
-			size += get_unaligned_le32(&table[i].partition_size);
+		if (get_unaligned_le32(&table[i].partition_start) != 0) {
+			uint64_t part_end = get_unaligned_le32(&table[i].partition_start) +
+				get_unaligned_le32(&table[i].partition_size);
+
+			if (size < part_end)
+				size = part_end;
 		}
 	}
 
-	return (int)size;
+	return size;
 }
 
 static void *read_mbr(struct block_device *blk)
-- 
1.8.4.rc3