+platform_pre_upgrade() {
+ local file_type=$(platform_identify "$1")
+ local dir="/tmp/sysupgrade-bcm53xx"
+ local trx="$1"
+
+ [ "$(platform_flash_type)" != "nand" ] && return
+
+ # Extract trx
+ case "$file_type" in
+ "chk") trx="/tmp/$(basename $1).trx"; platform_extract_trx_from_chk "$1" "$trx";;
+ "cybertan") trx="/tmp/$(basename $1).trx"; platform_extract_trx_from_cybertan "$1" "$trx";;
+ esac
+
+ # Extract partitions from trx
+ rm -fR $dir
+ mkdir -p $dir
+ otrx extract "$trx" \
+ -1 $dir/kernel \
+ -2 $dir/root
+
+ # Firmwares without UBI image should be flashed "normally"
+ local root_type=$(identify $dir/root)
+ [ "$root_type" != "ubi" ] && {
+ echo "Provided firmware doesn't use UBI for rootfs."
+ return
+ }
+
+ # Prepare TRX file with just a kernel that will replace current one
+ local linux_length=$(grep "\"linux\"" /proc/mtd | sed "s/mtd[0-9]*:[ \t]*\([^ \t]*\).*/\1/")
+ [ -z "$linux_length" ] && {
+ echo "Unable to find \"linux\" partition size"
+ exit 1
+ }
+ linux_length=$((0x$linux_length))
+ local kernel_length=$(wc -c $dir/kernel | cut -d ' ' -f 1)
+ [ $kernel_length -gt $linux_length ] && {
+ echo "New kernel doesn't fit \"linux\" partition."
+ return
+ }
+ rm -f /tmp/null.bin
+ rm -f /tmp/kernel.trx
+ touch /tmp/null.bin
+ otrx create /tmp/kernel.trx \
+ -f $dir/kernel -b $(($linux_length + 28)) \
+ -f /tmp/null.bin
+
+ # Prepare UBI image (drop unwanted extra blocks)
+ local ubi_length=0
+ while [ "$(dd if=$dir/root skip=$ubi_length bs=1 count=4 2>/dev/null)" = "UBI#" ]; do
+ ubi_length=$(($ubi_length + 131072))
+ done
+ dd if=$dir/root of=/tmp/root.ubi bs=131072 count=$((ubi_length / 131072)) 2>/dev/null
+
+ # Flash
+ mtd write /tmp/kernel.trx firmware
+ nand_do_upgrade /tmp/root.ubi
+}
+