VLAN_GROUP_ARRAY_PART_LEN
vidx = vlan_id / VLAN_GROUP_ARRAY_PART_LEN;
size = sizeof(struct net_device *) * VLAN_GROUP_ARRAY_PART_LEN;
[vlan_id / VLAN_GROUP_ARRAY_PART_LEN];
return array ? array[vlan_id % VLAN_GROUP_ARRAY_PART_LEN] : NULL;
[vlan_id / VLAN_GROUP_ARRAY_PART_LEN];
array[vlan_id % VLAN_GROUP_ARRAY_PART_LEN] = dev;