int pcibios_root_bridge_prepare(struct pci_host_bridge *bridge)
{
- if (!acpi_disabled) {
- struct pci_config_window *cfg = bridge->bus->sysdata;
- struct acpi_device *adev = to_acpi_device(cfg->parent);
- struct device *bus_dev = &bridge->bus->dev;
+ struct pci_config_window *cfg;
+ struct acpi_device *adev;
+ struct device *bus_dev;
- ACPI_COMPANION_SET(&bridge->dev, adev);
- set_dev_node(bus_dev, acpi_get_node(acpi_device_handle(adev)));
- }
+ if (acpi_disabled)
+ return 0;
+
+ cfg = bridge->bus->sysdata;
+
+ /*
+ * On Hyper-V there is no corresponding ACPI device for a root bridge,
+ * therefore ->parent is set as NULL by the driver. And set 'adev' as
+ * NULL in this case because there is no proper ACPI device.
+ */
+ if (!cfg->parent)
+ adev = NULL;
+ else
+ adev = to_acpi_device(cfg->parent);
+
+ bus_dev = &bridge->bus->dev;
+
+ ACPI_COMPANION_SET(&bridge->dev, adev);
+ set_dev_node(bus_dev, acpi_get_node(acpi_device_handle(adev)));
return 0;
}