pci_epc_get_first_free_bar
if (pci_epc_get_first_free_bar(epc_features) != BAR_0) {
test_reg_bar = pci_epc_get_first_free_bar(epc_features);
EXPORT_SYMBOL_GPL(pci_epc_get_first_free_bar);
pci_epc_get_first_free_bar(const struct pci_epc_features *epc_features);