add jffs2_mark_erase function for erasing jffs2 partitions on the next mount (typically faster than doing mtd erase manually)

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@6978 3c298f89-4303-0410-b956-a3cf2f4a3e73

package/base-files/files/etc/functions.sh

@@ -186,3 +186,13 @@ strtok() { # <string> { <variable> [<separator>] ... }
 
 	return $count
 }
+
+
+jffs2_mark_erase() {
+	local part="$(find_mtd_part "$1")"
+	[ -z "$part" ] && {
+		echo Partition not found.
+		return 1
+	}
+	echo -e "\xde\xad\xc0\xde" | mtd -qq write - "$1"
+}