+static bool pcie_has_upstream_port(PCIDevice *dev)
+{
+ PCIDevice *parent_dev = pci_bridge_get_device(dev->bus);
+
+ /* Device associated with an upstream port.
+ * As there are several types of these, it's easier to check the
+ * parent device: upstream ports are always connected to
+ * root or downstream ports.
+ */
+ return parent_dev &&
+ pci_is_express(parent_dev) &&
+ parent_dev->exp.exp_cap &&
+ (pcie_cap_get_type(parent_dev) == PCI_EXP_TYPE_ROOT_PORT ||
+ pcie_cap_get_type(parent_dev) == PCI_EXP_TYPE_DOWNSTREAM);
+}
+
+PCIDevice *pci_get_function_0(PCIDevice *pci_dev)
+{
+ if(pcie_has_upstream_port(pci_dev)) {
+ /* With an upstream PCIe port, we only support 1 device at slot 0 */
+ return pci_dev->bus->devices[0];
+ } else {
+ /* Other bus types might support multiple devices at slots 0-31 */
+ return pci_dev->bus->devices[PCI_DEVFN(PCI_SLOT(pci_dev->devfn), 0)];
+ }
+}
+