/* we have two rings to choose from, but we only use txLo for now
* If we start using the Hi ring as well, we'll need to update
* typhoon_stop_runtime(), typhoon_interrupt(), typhoon_num_free_tx(),
/* we have two rings to choose from, but we only use txLo for now
* If we start using the Hi ring as well, we'll need to update
* typhoon_stop_runtime(), typhoon_interrupt(), typhoon_num_free_tx(),