prep_pci_direct_make_tag
extern pcitag_t prep_pci_direct_make_tag(void *, int, int, int);
tag = prep_pci_direct_make_tag(pc, bus, dev, func);
pc->pc_make_tag = prep_pci_direct_make_tag;
pcitag_t prep_pci_direct_make_tag(void *, int, int, int);