DPSK dynamic filename

[CERON Emile]

Hello everyone,

I'm currently working on an authentication system based on the 
Freeradius DPSK module. To avoid the DPSK scaling issue, I try to adopt 
a strategy where I would like to split my list of PSK keys in different 
CSV files.  The help file states that it is possible to dynamically 
expand the csv filename:


   #  The filename is dynamically expanded, so it can reference
     #  other attributes.  This expansion lets you split up DPSK
     #  files by location, which can drastically reduce the overall
     #  search space, and thus the CPU requirements.
     #
#    filename = "${modconfdir}/${..:name}/psk.csv"

I'v tryed many configurations, but it seems the filename is only 
expanded once when Freeradius is loaded.
Has someone been able to achieve this type of configuration and share a 
sample ?

Thank you in advance for your reply.

Emile