PCI_SUBORDINATE_BUS_MASK
subordinate = FIELD_GET(PCI_SUBORDINATE_BUS_MASK, buses);
FIELD_PREP(PCI_SUBORDINATE_BUS_MASK, child->busn_res.end);
res.end = FIELD_GET(PCI_SUBORDINATE_BUS_MASK, buses);
FIELD_PREP(PCI_SUBORDINATE_BUS_MASK, child->busn_res.end);