ramips: Cleanup Genexis EX400 upgrade script

The code can be made more efficient by not extracting the sysupgrade.tar but
rather just querying for the filesize within the archive. Resorting to
manual update of UBI volume is extra work too, setting CI_KERNPART=rootfs_0
is enough.

Suggested-by: Andreas Gnau <[email protected]>
Signed-off-by: Mauri Sandberg <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/17806
Signed-off-by: Hauke Mehrtens <[email protected]>

target/linux/ramips/mt7621/base-files/lib/upgrade/inteno.sh

@@ -17,15 +17,8 @@
 . /lib/upgrade/nand.sh
 
 inteno_do_upgrade () {
-	local tar_file=$1
-	local cmd=cat
-	# WARNING: This fails if tar contains more than one 'sysupgrade-*' directory.
-	local board_dir="$(tar tf "$tar_file" | grep -m 1 '^sysupgrade-.*/$')"
-	board_dir="${board_dir%/}"
-	tar -xaf "$tar_file"
-
 	# get the size of the new bootfs
-	local _bootfs_size=$(wc -c < "$board_dir/kernel")
+	local _bootfs_size=$(tar -tvf $1 | grep kernel | awk '{print $3}')
 	[ -n "$_bootfs_size" -a "$_bootfs_size" -gt "0" ] || nand_do_upgrade_failed
 
 	# remove existing rootfses and recreate rootfs_0
@@ -35,15 +28,11 @@ inteno_do_upgrade () {
 	ubirmvol /dev/ubi0 --name=rootfs_data > /dev/null 2>&1
 	ubimkvol /dev/ubi0 --type=static --size=${_bootfs_size} --name=rootfs_0
 
-	# update the rootfs_0 contents
-	local _kern_ubivol=$( nand_find_volume "ubi0" "rootfs_0" )
-	ubiupdatevol "/dev/$_kern_ubivol" "$board_dir/kernel"
-
 	fw_setenv root_vol rootfs_0
 	fw_setenv boot_cnt_primary 0
 	fw_setenv boot_cnt_alt 0
 
 	# proceed to upgrade the default way
-	CI_KERNPART=none
+	CI_KERNPART=rootfs_0
 	nand_do_upgrade "$1"
 }