It kinda depends on whether you're building an I/O Kit KEXT or some other form of KEXT. For an I/O Kit KEXT, you can stash these sorts of parameters in the personality in your "Info.plist", and I/O Kit will transfer these properties to your I/O registry entry. It's nice, but it's not as useful as you might think. For example, your shouldn't go modifying your "Info.plist" on a user's machine out in the field as a matter of course. That way lies revision control madness. Thus, these properties are typically only useful for debugging and for setting really obscure options.