can robot hardware interface get the access to controller (not through controller manager)

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In ros control, we can add specific functions in the robot hardware interface class (ex: MyRobot) as described in ros wiki:

1. Write functions in robot hardware interface class.
2. Register itself.

By doing so, the robot controller can call those specific functions.

Hence, following this way, I can make my robot controller and robot hardware interface to transfer different kinds of data with each other. And such is realized like the way that controller gets the access to the hardware interface.

I want to ask that, can I realize the same thing (transfer different kinds of data) but through the reverse way (hardware interface gets the access to the controller), is it possible?