As you know I've been working on driver interface for our OSes. In doing my research I have ran into a snag because I'm unfamiliar with 16-bit protected mode and the use of the associated registers. This is due to Plug and Play as well as Systems Management BIOS. Both use 16-bit protected mode for calling them in determining the installed devices. I tried a direct 32-bit call, but imagine what happens upon a return from a call? It calls another routine not within the original sequence.

So, do I need to do anything special, other than setup registers (ie. DS, SS) and jump to 16-bit code? Then re-setup 32-bit code and registers? What should I look out for? Any pitfalls anyone else has encoutnered?