usb/vmstate: add parent dev path

... to make vmstate id string truely unique with multiple host
controllers, i.e. move from "1/usb-ptr" to "0000:00:01.3/1/usb-ptr"
(usb tabled connected to piix3 uhci).

This obviously breaks migration.  To handle this the usb bus
property "full-path" is added.  When setting this to false old
behavior is maintained.  This way current qemu will be compatible
with old versions when started using '-M pc-$oldversion'.
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

hw/pc_piix.c

@@ -377,6 +377,10 @@ static QEMUMachine pc_machine_v1_1 = {
             .driver   = "apic",\
             .property = "vapic",\
             .value    = "off",\
+        },{\
+            .driver   = "USB",\
+            .property = "full-path",\
+            .value    = "no",\
         }
 
 static QEMUMachine pc_machine_v1_0 = {

hw/usb.h

@@ -182,12 +182,17 @@ struct USBEndpoint {
     QTAILQ_HEAD(, USBPacket) queue;
 };
 
+enum USBDeviceFlags {
+    USB_DEV_FLAG_FULL_PATH,
+};
+
 /* definition of a USB device */
 struct USBDevice {
     DeviceState qdev;
     USBPort *port;
     char *port_path;
     void *opaque;
+    uint32_t flags;
 
     /* Actual connected speed */
     int speed;

hw/usb/bus.c

@@ -19,6 +19,8 @@ static struct BusInfo usb_bus_info = {
     .get_fw_dev_path = usb_get_fw_dev_path,
     .props      = (Property[]) {
         DEFINE_PROP_STRING("port", USBDevice, port_path),
+        DEFINE_PROP_BIT("full-path", USBDevice, flags,
+                        USB_DEV_FLAG_FULL_PATH, true),
         DEFINE_PROP_END_OF_LIST()
     },
 };
@@ -460,7 +462,20 @@ static void usb_bus_dev_print(Monitor *mon, DeviceState *qdev, int indent)
 static char *usb_get_dev_path(DeviceState *qdev)
 {
     USBDevice *dev = USB_DEVICE(qdev);
-    return g_strdup(dev->port->path);
+    DeviceState *hcd = qdev->parent_bus->parent;
+    char *id = NULL;
+
+    if ((dev->flags & (1 << USB_DEV_FLAG_FULL_PATH)) &&
+        hcd && hcd->parent_bus && hcd->parent_bus->info->get_dev_path) {
+        id = hcd->parent_bus->info->get_dev_path(hcd);
+    }
+    if (id) {
+        char *ret = g_strdup_printf("%s/%s", id, dev->port->path);
+        g_free(id);
+        return ret;
+    } else {
+        return g_strdup(dev->port->path);
+    }
 }
 
 static char *usb_get_fw_dev_path(DeviceState *qdev)