Questions on XML register descriptions

Hi,

I have been looking at the XML register descriptions, and I have a 
couple of questions, as I'm trying to add gdb remote support to an 
emulator, which involves additional system-level registers as well as 
memory spaces.

1. Some registers can't be written to, and some registers may affect 
other registers. What, if anything, is the best way to handle that?

2. How do the G/g commands interact with the XML target descriptions? Do 
they apply specifically to group="general", or are there other rules?

3. Is there any concept at all of different address spaces in gdb? 
Alternatively, is there any way to tell gdb that it should communicate 
addresses wider than the pointer type of the base architecture (which 
would allow a Python helper script to define a convenience API.)

4. There doesn't seem to be a way to trigger a Python function when a 
connection is *established*, which is as far as I understand the point 
at which the XML register description is downloaded from the remote, and 
definitely the first point at which register values can be examined. Am 
I missing something obvious?

5. I presume the byte codes use for the Z commands are the same as the 
agent bytecode in Appendix F, even though the latter specifically seems 
to be referring to tracepoints?

Many thanks,

	-hpa