octeon: determine sysupgrade-* directory for upgrade automatically

So far, the sysupgrade-* folder used during upgrade in octeon was
hardcoded to contain the board name. Therefore, changing board name
or BOARD_NAME variable in image/Makefile might have broken upgrade.

Improve this by adding a step to determine the folder name via
a wildcard, as it is done for generic nand_upgrade_tar() in
lib/upgrade/nand.sh.

While this still does not remove the problem for existing devices
(which still have the old script), it will entirely remove the
issue on newly added devices on this platform.

Signed-off-by: Donald Hoskins <grommish@gmail.com>
[split into separate patch, add commit message, add return values]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

target/linux/octeon/base-files/lib/upgrade/platform.sh

@@ -37,6 +37,10 @@ platform_do_flash() {
 	local kernel=$3
 	local rootfs=$4
 
+	local board_dir=$(tar tf "$tar_file" | grep -m 1 '^sysupgrade-.*/$')
+	board_dir=${board_dir%/}
+	[ -n "$board_dir" ] || return 1
+
 	mkdir -p /boot
 	mount -t vfat /dev/$kernel /boot
 
@@ -46,10 +50,10 @@ platform_do_flash() {
 	}
 
 	echo "flashing kernel to /dev/$kernel"
-	tar xf $tar_file sysupgrade-$board/kernel -O > /boot/vmlinux.64
+	tar xf $tar_file $board_dir/kernel -O > /boot/vmlinux.64
 	md5sum /boot/vmlinux.64 | cut -f1 -d " " > /boot/vmlinux.64.md5
 	echo "flashing rootfs to ${rootfs}"
-	tar xf $tar_file sysupgrade-$board/root -O | dd of="${rootfs}" bs=4096
+	tar xf $tar_file $board_dir/root -O | dd of="${rootfs}" bs=4096
 	sync
 	umount /boot
 }
@@ -80,13 +84,17 @@ platform_do_upgrade() {
 
 platform_check_image() {
 	local board=$(board_name)
+	local tar_file="$1"
+
+	local board_dir=$(tar tf "$tar_file" | grep -m 1 '^sysupgrade-.*/$')
+	board_dir=${board_dir%/}
+	[ -n "$board_dir" ] || return 1
 
 	case "$board" in
 	er | \
 	erlite)
-		local tar_file="$1"
+		local kernel_length=$(tar xf $tar_file $board_dir/kernel -O | wc -c 2> /dev/null)
-		local kernel_length=$(tar xf $tar_file sysupgrade-$board/kernel -O | wc -c 2> /dev/null)
+		local rootfs_length=$(tar xf $tar_file $board_dir/root -O | wc -c 2> /dev/null)
-		local rootfs_length=$(tar xf $tar_file sysupgrade-$board/root -O | wc -c 2> /dev/null)
 		[ "$kernel_length" = 0 -o "$rootfs_length" = 0 ] && {
 			echo "The upgrade image is corrupt."
 			return 1