Hello all:
     I compiled the blueZ-2.20 on the mipsel platform, kernel version is 
2.4.21. While execute
the command like "l2ping xx:xx:xx:xx:xx:xx". The shell tips "Connection 
failed: invalid arguments"
immediately.

hcidump the data like this:
/tmp/bin # ../sbin/hcidump -x &
/tmp/bin # HCI sniffer - Bluetooth packet analyzer ver 1.22
device: hci0 snap_len: 1028 filter: 0xffffffff
/tmp/bin # ./l2ping 00:17:4b:54:8d:2e
< HCI Command: Create Connection (0x01|0x0005) plen 13
  2E 8D 54 4B 17 00 18 CC 02 00 00 00 01
Can't connect: Invalid argument
/tmp/bin # > HCI Event: Command Status (0x0f) plen 4
  12 01 05 04

By the way, the bluetooth dongle's HCI version is 1.1

Who could tell me the reason? thanks