[Discuss-gnuradio] Get a pointer to UHD "Source" from other block in flow graph

[Simone Ciccia S210664]

How to get a UHD USRP SOURCE OBJECT within my own block ?
  -  I already instantiate an UHD USRP SOURCE in the flowgraph and I want a
pointer within my own block to read parameters. 
  -  Also, which is the effect of creating two times a new USRP SOURCE
block by using "uhd::make(address)" with the same IP address in different
blocks of the flowgraph?

I read from the manual that it is possible to control UHD Source/Sink by
sending commands.
In the case of Source block, are the loops admitted in GNURadio by using
PMTs asynchronous messages for write back parameters?

Regards,
Simone