[libvirt] "state" drivers?

I'm looking through the network driver, and see the "state" driver registered. Several other drivers also register a state driver. What is this used for? It looks like it's handling a startup/shutdown at a more basic level than then open/close in the network (storage/qemu/etc) driver itself. Is it the case that things that should happen only once as libvirtd is loaded/unloaded should be put in the state driver's Startup/shutdown? It seems possible that these callouts may be unnecessary in my case, since I'll be modifying the OS's own interface config, so the interfaces will already be up and running by the time libvirtd starts, and should remaining running after libvirtd is unloaded. (as for initializing/shutting down netcf, this may be useful for shutting it down before exit, but its init should probably only be called on demand if someone actually calls a virInterface* function -otherwise we're using up resources for nothing. Any other guildelines/advice?