[Qemu-devel] [RfC PATCH] usb/vmstate: add parent dev path

[Gerd Hoffmann <kraxel@redhat.com>]

... 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).

Obvious problem with that is that it breaks migration from and to older
versions, thats why it is RfC.  I don't see any way to fix the issue
without breaking though.  So the question is how to deal with that best?

Given that we plan to break the migration anyway for 1.0 one option
would be to just wait a bit and merge this as part of the new migration
protocol patch series.

Comments?

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 hw/usb-bus.c |   15 ++++++++++++++-
 1 files changed, 14 insertions(+), 1 deletions(-)

diff --git a/hw/usb-bus.c b/hw/usb-bus.c
index c0bbc7c..477d57f 100644
--- a/hw/usb-bus.c
+++ b/hw/usb-bus.c
@@ -342,7 +342,20 @@ static void usb_bus_dev_print(Monitor *mon, DeviceState *qdev, int indent)
 static char *usb_get_dev_path(DeviceState *qdev)
 {
     USBDevice *dev = DO_UPCAST(USBDevice, qdev, qdev);
-    return g_strdup(dev->port->path);
+    DeviceState *hcd = qdev->parent_bus->parent;
+    char *id = NULL;
+
+    if (hcd && hcd->parent_bus && hcd->parent_bus->info->get_dev_path) {
+        id = hcd->parent_bus->info->get_dev_path(hcd);
+    }
+    if (id) {
+        int len = strlen(id)+strlen(dev->port->path)+2;
+        char *ret = g_malloc(len);
+        snprintf(ret, len, "%s/%s", id, dev->port->path);
+        return ret;
+    } else {
+        return g_strdup(dev->port->path);
+    }
 }
 
 static char *usb_get_fw_dev_path(DeviceState *qdev)
-- 
1.7.1