USRP2 FPGA register control

Dear all,

I searched the email achieve and Internet, only usrp FPGA control
information can be found.
u = usrp.source_c()
u._write_fpga_reg(regno, val)
set_register(FR_ADC_OFFSET_0, 0);

Nothing related to usrp2 was reported.

If I want to write to USRP2 FPGA register, is there any similar function
I can call?

Can I write to user-defined registers which I manually add into the
verilog .v file?

Thanks and have a good day!