[PATCH v3] hw/core/qdev: Increase qdev_realize() kindness

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

Since commit 510ef98dca5, qdev_realize() aborts if bus-less device
is realized on a bus. While commits 514db7710b..007d1dbf72 took
care of converting all mainstream uses, QEMU forks weren't. These
forks are usually maintained by hobbyist with interest in following
mainstream development, but with limited time, so usually rebase
from time to time. To avoid them to spend time on debugging and
reading git-log history, display a kind hint about what is wrong.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
Since v2:
- scratch __func__ (armbru)
- reword to justify this is not an impossible case (armbru)
---
 hw/core/qdev.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index 2131c7f951..a16f1270f1 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -392,8 +392,11 @@ bool qdev_realize(DeviceState *dev, BusState *bus, Error **errp)
 
     if (bus) {
         qdev_set_parent_bus(dev, bus);
-    } else {
-        assert(!DEVICE_GET_CLASS(dev)->bus_type);
+    } else if (DEVICE_GET_CLASS(dev)->bus_type) {
+        error_setg(errp, "Unexpected bus '%s' for bus-less device '%s'",
+                   DEVICE_GET_CLASS(dev)->bus_type,
+                   object_get_typename(OBJECT(dev)));
+        return false;
     }
 
     object_property_set_bool(OBJECT(dev), true, "realized", &err);
-- 
2.21.3