[Qemu-devel] [PATCH v4 1/2] Add device listener interface

[Paul Durrant <paul.durrant@citrix.com>]

The Xen ioreq-server API, introduced in Xen 4.5, requires that PCI device
models explicitly register with Xen for config space accesses. This patch
adds a listener interface into qdev-core which can be used by the Xen
interface code to monitor for arrival and departure of PCI devices.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Andreas Faerber" <afaerber@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Markus Armbruster <armbru@redhat.com>
Cc: Thomas Huth <thuth@linux.vnet.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
---
 hw/core/qdev.c          |   54 +++++++++++++++++++++++++++++++++++++++++++++++
 include/hw/qdev-core.h  |   10 +++++++++
 include/qemu/typedefs.h |    1 +
 3 files changed, 65 insertions(+)

diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index fcb1638..4a9c1f6 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -175,6 +175,56 @@ int qdev_init(DeviceState *dev)
     return 0;
 }
 
+static QTAILQ_HEAD(qdev_listeners, DeviceListener) qdev_listeners
+    = QTAILQ_HEAD_INITIALIZER(qdev_listeners);
+
+enum ListenerDirection { Forward, Reverse };
+
+#define QDEV_LISTENER_CALL(_callback, _direction, _args...)     \
+    do {                                                        \
+        DeviceListener *_listener;                              \
+                                                                \
+        switch (_direction) {                                   \
+        case Forward:                                           \
+            QTAILQ_FOREACH(_listener, &qdev_listeners, link) {  \
+                if (_listener->_callback) {                     \
+                    _listener->_callback(_listener, ##_args);   \
+                }                                               \
+            }                                                   \
+            break;                                              \
+        case Reverse:                                           \
+            QTAILQ_FOREACH_REVERSE(_listener, &qdev_listeners,  \
+                                   qdev_listeners, link) {      \
+                if (_listener->_callback) {                     \
+                    _listener->_callback(_listener, ##_args);   \
+                }                                               \
+            }                                                   \
+            break;                                              \
+        default:                                                \
+            abort();                                            \
+        }                                                       \
+    } while (0)
+
+static int qdev_listener_add(DeviceState *dev, void *opaque)
+{
+    QDEV_LISTENER_CALL(realize, Forward, dev);
+
+    return 0;
+}
+
+void qdev_listener_register(DeviceListener *listener)
+{
+    QTAILQ_INSERT_TAIL(&qdev_listeners, listener, link);
+
+    qbus_walk_children(sysbus_get_default(), NULL, NULL, qdev_listener_add,
+                       NULL, NULL);
+}
+
+void qdev_listener_unregister(DeviceListener *listener)
+{
+    QTAILQ_REMOVE(&qdev_listeners, listener, link);
+}
+
 static void device_realize(DeviceState *dev, Error **errp)
 {
     DeviceClass *dc = DEVICE_GET_CLASS(dev);
@@ -186,12 +236,16 @@ static void device_realize(DeviceState *dev, Error **errp)
             return;
         }
     }
+
+    QDEV_LISTENER_CALL(realize, Forward, dev);
 }
 
 static void device_unrealize(DeviceState *dev, Error **errp)
 {
     DeviceClass *dc = DEVICE_GET_CLASS(dev);
 
+    QDEV_LISTENER_CALL(unrealize, Reverse, dev);
+
     if (dc->exit) {
         int rc = dc->exit(dev);
         if (rc < 0) {
diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
index 178fee2..f2dc267 100644
--- a/include/hw/qdev-core.h
+++ b/include/hw/qdev-core.h
@@ -167,6 +167,12 @@ struct DeviceState {
     int alias_required_for_version;
 };
 
+struct DeviceListener {
+    void (*realize)(DeviceListener *listener, DeviceState *dev);
+    void (*unrealize)(DeviceListener *listener, DeviceState *dev);
+    QTAILQ_ENTRY(DeviceListener) link;
+};
+
 #define TYPE_BUS "bus"
 #define BUS(obj) OBJECT_CHECK(BusState, (obj), TYPE_BUS)
 #define BUS_CLASS(klass) OBJECT_CLASS_CHECK(BusClass, (klass), TYPE_BUS)
@@ -368,4 +374,8 @@ static inline void qbus_set_hotplug_handler(BusState *bus, DeviceState *handler,
                              QDEV_HOTPLUG_HANDLER_PROPERTY, errp);
     bus->allow_hotplug = 1;
 }
+
+void qdev_listener_register(DeviceListener *listener);
+void qdev_listener_unregister(DeviceListener *listener);
+
 #endif
diff --git a/include/qemu/typedefs.h b/include/qemu/typedefs.h
index 04df51b..e32bca2 100644
--- a/include/qemu/typedefs.h
+++ b/include/qemu/typedefs.h
@@ -20,6 +20,7 @@ typedef struct Property Property;
 typedef struct PropertyInfo PropertyInfo;
 typedef struct CompatProperty CompatProperty;
 typedef struct DeviceState DeviceState;
+typedef struct DeviceListener DeviceListener;
 typedef struct BusState BusState;
 typedef struct BusClass BusClass;
 
-- 
1.7.10.4