40.2.2.2. Unit Masks

If the cpu_type is not timer, unit masks may also be required to further define the event.
Unit masks for each event are listed with the op_help command. The values for each unit mask are listed in hexadecimal format. To specify more than one unit mask, the hexadecimal values must be combined using a bitwise or operation.
opcontrol --event=<event-name>:<sample-rate>:<unit-mask>