Well, we use DQMH in systems (PXIe) where we need to communicate with multiple FPGA targets (R-series PXIe cards). We also use DQMH on cRIOs, making use of the onboard FPGA.
Those DQMH modules that need access to the FPGA work with a subset of FPGA resources specific to their feature set. An Analog Input module, for example, will require an FPGA reference containing all AI-specific I/O etc. A module dealing with Profinet communication will require an FPGA reference that contains exactly all the I/O etc. for PN.
Seeing as any FPGA target most probably caters to more than one single module (i.e. contains code for multiple features like AIO, DIO, comms etc) and contains all the I/O and resources, we load the reference to the FPGA target(s) in one place and then use the "Dynamic FPGA Interface Cast" to cast the target reference(s) to the above mentioned module-specific references.
That way, the dependencies per module are nicely defined and encapsulated, and we can reuse those modules quite easily across systems and projects. The only downside here - where we haven't found a good solution so far - is that you must not forget to manually update all the typedef'ed dynamic FPGA references when you make changes to your FPGA program.
(edited for clarity)
