question about vlan driver

Hello, I have a short question about vlan driver; I see in the vlan driver the following code when creating a new vlan interface: vlan_newlink() { ... if (data[IFLA_VLAN_PROTOCOL]) proto = nla_get_be16(data[IFLA_VLAN_PROTOCOL]); else proto = htons(ETH_P_8021Q); ... } see: http://lxr.free-electrons.com/source/net/8021q/vlan_netlink.c#L105 I understand that in the common case, proto is ETH_P_8021Q. How can it be set to a different value when creating a vlan interface ? And to which other values can it be set ? I did not find anything by "vconfig --help", and also by probing into the userspace code of the vconfig tool. any ideas? Regards, Kevin