How can I disable ipv6 module only for oneway DVB receiving card?

Hi!

I am porting pentavalue driver to kernel 2.6.
But when unload module, the following messages are displayed
and I can't unload it.

unregister_netdevice: waiting for pentaval0 to become free. Usage count = 5
unregister_netdevice: waiting for pentaval0 to become free. Usage count = 5

I insert printk("refcnt=%d\n,atomic_read(&dev->refcnt)); at dev_hold and dev_put
in include/linux/netdevice.h, and I found ipv6 module increase refcnt at 3 times,
but at unloading module, decrease one only one time.

I built linux kernel no ipv6, refcnt problem did not occur.

Can I disable ipv6 only for my pentaval driver?

Test kernel version is 2.6.15.

Bye!