qdev: hotplug: Introduce HotplugHandler.pre_plug() callback

pre_plug callback is to be called before device.realize() is executed.
This would allow to check/set device's properties from HotplugHandler.
Signed-off-by: NIgor Mammedov <imammedo@redhat.com>
Signed-off-by: NBharata B Rao <bharata@linux.vnet.ibm.com>
Reviewed-by: NDavid Gibson <david@gibson.dropbear.id.au>
Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au>

hw/core/hotplug.c

@@ -13,6 +13,17 @@
 #include "hw/hotplug.h"
 #include "qemu/module.h"
 
+void hotplug_handler_pre_plug(HotplugHandler *plug_handler,
+                              DeviceState *plugged_dev,
+                              Error **errp)
+{
+    HotplugHandlerClass *hdc = HOTPLUG_HANDLER_GET_CLASS(plug_handler);
+
+    if (hdc->pre_plug) {
+        hdc->pre_plug(plug_handler, plugged_dev, errp);
+    }
+}
+
 void hotplug_handler_plug(HotplugHandler *plug_handler,
                           DeviceState *plugged_dev,
                           Error **errp)

hw/core/qdev.c

@@ -902,6 +902,14 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
             g_free(name);
         }
 
+        hotplug_ctrl = qdev_get_hotplug_handler(dev);
+        if (hotplug_ctrl) {
+            hotplug_handler_pre_plug(hotplug_ctrl, dev, &local_err);
+            if (local_err != NULL) {
+                goto fail;
+            }
+        }
+
         if (dc->realize) {
             dc->realize(dev, &local_err);
         }
@@ -912,7 +920,6 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
 
         DEVICE_LISTENER_CALL(realize, Forward, dev);
 
-        hotplug_ctrl = qdev_get_hotplug_handler(dev);
         if (hotplug_ctrl) {
             hotplug_handler_plug(hotplug_ctrl, dev, &local_err);
         }

include/hw/hotplug.h

@@ -45,7 +45,8 @@ typedef void (*hotplug_fn)(HotplugHandler *plug_handler,
  * hardware (un)plug functions.
  *
  * @parent: Opaque parent interface.
- * @plug: plug callback.
+ * @pre_plug: pre plug callback called at start of device.realize(true)
+ * @plug: plug callback called at end of device.realize(true).
  * @unplug_request: unplug request callback.
  *                  Used as a means to initiate device unplug for devices that
  *                  require asynchronous unplug handling.
@@ -58,6 +59,7 @@ typedef struct HotplugHandlerClass {
     InterfaceClass parent;
 
     /* <public> */
+    hotplug_fn pre_plug;
     hotplug_fn plug;
     hotplug_fn unplug_request;
     hotplug_fn unplug;
@@ -72,6 +74,16 @@ void hotplug_handler_plug(HotplugHandler *plug_handler,
                           DeviceState *plugged_dev,
                           Error **errp);
 
+/**
+ * hotplug_handler_pre_plug:
+ *
+ * Call #HotplugHandlerClass.pre_plug callback of @plug_handler.
+ */
+void hotplug_handler_pre_plug(HotplugHandler *plug_handler,
+                              DeviceState *plugged_dev,
+                              Error **errp);
+
+
 /**
  * hotplug_handler_unplug_request:
  *