q-dev: fire pre-event for assignment

Extension may need this, e.g., usb extension check if assignment contains options

Author: piotrbartman

qubes/devices.py

@@ -249,6 +249,10 @@ async def assign(self, assignment: DeviceAssignment):
 
         self._set.add(assignment)
 
+        await self._vm.fire_event_async(
+            'device-pre-assign:' + self._bus,
+            pre_event=True, device=device, options=assignment.options)
+
         await self._vm.fire_event_async(
             'device-assign:' + self._bus,
             device=device, options=assignment.options)
@@ -291,6 +295,11 @@ async def update_assignment(
             return
 
         new_assignment = assignment.clone(mode=mode)
+
+        await self._vm.fire_event_async(
+            'device-pre-assign:' + self._bus,
+            pre_event=True, device=device, options=new_assignment.options)
+
         self._set.discard(assignment)
         self._set.add(new_assignment)
         await self._vm.fire_event_async(