Error while "rxe_cfg start"

Hi, I have an SoftRoCE setup on CentOS 6.6 and its throws an error related to default_roce_mode. I have the configfs mounted and even if I try to add the version manually it throws the same error.

Here are the details -

# cat /etc/*release

CentOS release 6.6 (Final)

$ ibv_devices

    device                 node GUID

    ------              ----------------

    rxe0                2a6ed4fffe0feba7

# mount

.

.

.

none on /sys/kernel/config type configfs (rw)

# rxe_cfg start

IBOE V2

tee: /sys/kernel/config/rdma_cm/rxe0/default_roce_mode: Invalid argument

  Name  Link  Driver  Speed  NMTU  IPv4_addr      RDEV  RMTU

  eth0  no    tg3            1500

  eth1  no    tg3            1500

  eth2  no    tg3            1500

  eth3  no    tg3            1500

  eth4  no    tg3            1500

  eth5  yes   tg3            1500  10.213.41.228  rxe0  1024  (3)

Trying to add the version manually -

# mkdir /sys/kernel/config/rdma_cm/rxe0

# cat /sys/kernel/config/rdma_cm/rxe0/default_roce_mode

IB/RoCE V1

# echo IBOE V2 > /sys/kernel/config/rdma_cm/rxe0/default_roce_mode

bash: echo: write error: Invalid argument

Can you please share the possible cause of this error.