Please excuse me i do not much of motor and how to drive. But i am hearing two ways to drive and getting really confused. One method is to know the position of hall sensors and based on that switch the correct legs. The other method is give 3 phase stator voltage then the effective magnetic flux will be in some direction and rotor will try to align to this flux. Change the stator voltage again the rotor will align and hence will keep rotating. Now my doubt why in the second case hall information is not required. Sorry for not providing enough information as i am only in study phase and don't know much about the motor driving.