em pause frames

[lukem.freebsd at cse.unsw.edu.au]

Is there an easy way to enable or disable pause frames and autonegotiation 
of flow control for the em driver? (other than changing em_fc_full to 
em_fc_none and recompiling).

Something similar to linux's "ethtool" command, or an ifconfig parameter 
is the type of thing I'm after.

(And yes, I've googled and looked through the man pages. It sounds like 
the kind of thing that should be obvious and trivial to do, and the 
functionality to do so does appear in the driver, but I don't see any way 
to change it from userlevel.)

-- 
Luke