>   I take it that the probe routines should call bus_space_unmap on
> allocated things if they fail to find a card?
>   What is an invalid value for bus_space_handle_t? 0? ~0? 

there are no defined valid or invalid values.  the only indication of
'validity' is the return value from bus_space_map().


>   Should a probe routine unmap everything and let the attach routine
> map it back in?

yes.  there should be no permanent allocations or initializations done
in the match/probe routine, EVER.


cgd