hw/pci: made pci_bus_is_root a PCIBusClass method

Refactoring it as a method of PCIBusClass will allow
different implementations for subclasses.

Removed the assumption that the root bus does not
have a parent device because is specific only
to the default class implementation.

Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>

hw/pci/pci.c

@@ -88,9 +88,15 @@ static void pci_bus_unrealize(BusState *qbus, Error **errp)
     vmstate_unregister(NULL, &vmstate_pcibus, bus);
 }
 
+static bool pcibus_is_root(PCIBus *bus)
+{
+    return !bus->parent_dev;
+}
+
 static void pci_bus_class_init(ObjectClass *klass, void *data)
 {
     BusClass *k = BUS_CLASS(klass);
+    PCIBusClass *pbc = PCI_BUS_CLASS(klass);
 
     k->print_dev = pcibus_dev_print;
     k->get_dev_path = pcibus_get_dev_path;
@@ -98,12 +104,15 @@ static void pci_bus_class_init(ObjectClass *klass, void *data)
     k->realize = pci_bus_realize;
     k->unrealize = pci_bus_unrealize;
     k->reset = pcibus_reset;
+
+    pbc->is_root = pcibus_is_root;
 }
 
 static const TypeInfo pci_bus_info = {
     .name = TYPE_PCI_BUS,
     .parent = TYPE_BUS,
     .instance_size = sizeof(PCIBus),
+    .class_size = sizeof(PCIBusClass),
     .class_init = pci_bus_class_init,
 };
 
@@ -278,7 +287,10 @@ PCIBus *pci_device_root_bus(const PCIDevice *d)
 {
     PCIBus *bus = d->bus;
 
-    while ((d = bus->parent_dev) != NULL) {
+    while (!pci_bus_is_root(bus)) {
+        d = bus->parent_dev;
+        assert(d != NULL);
+
         bus = d->bus;
     }
 
@@ -291,7 +303,6 @@ const char *pci_root_bus_path(PCIDevice *dev)
     PCIHostState *host_bridge = PCI_HOST_BRIDGE(rootbus->qbus.parent);
     PCIHostBridgeClass *hc = PCI_HOST_BRIDGE_GET_CLASS(host_bridge);
 
-    assert(!rootbus->parent_dev);
     assert(host_bridge->bus == rootbus);
 
     if (hc->root_bus_path) {
@@ -325,7 +336,7 @@ bool pci_bus_is_express(PCIBus *bus)
 
 bool pci_bus_is_root(PCIBus *bus)
 {
-    return !bus->parent_dev;
+    return PCI_BUS_GET_CLASS(bus)->is_root(bus);
 }
 
 void pci_bus_new_inplace(PCIBus *bus, size_t bus_size, DeviceState *parent,

include/hw/pci/pci.h

@@ -340,6 +340,8 @@ typedef PCIINTxRoute (*pci_route_irq_fn)(void *opaque, int pin);
 
 #define TYPE_PCI_BUS "PCI"
 #define PCI_BUS(obj) OBJECT_CHECK(PCIBus, (obj), TYPE_PCI_BUS)
+#define PCI_BUS_CLASS(klass) OBJECT_CLASS_CHECK(PCIBusClass, (klass), TYPE_PCI_BUS)
+#define PCI_BUS_GET_CLASS(obj) OBJECT_GET_CLASS(PCIBusClass, (obj), TYPE_PCI_BUS)
 #define TYPE_PCIE_BUS "PCIE"
 
 bool pci_bus_is_express(PCIBus *bus);

include/hw/pci/pci_bus.h

@@ -8,6 +8,14 @@
  * use accessor functions in pci.h, pci_bridge.h
  */
 
+typedef struct PCIBusClass {
+    /*< private >*/
+    BusClass parent_class;
+    /*< public >*/
+
+    bool (*is_root)(PCIBus *bus);
+} PCIBusClass;
+
 struct PCIBus {
     BusState qbus;
     PCIIOMMUFunc iommu_fn;