Get a pointer to UHD "Source" from other block in flow graph

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
    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?