Some TYPE_SYS_BUS_DEVICEs can be optionally dynamically
plugged on the TYPE_PLATFORM_BUS_DEVICE.
Rather than sometimes noting that with comment around
the 'user_creatable = true' line in each DeviceRealize
handler, introduce an abstract TYPE_DYNAMIC_SYS_BUS_DEVICE
class.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alexander Graf <graf@amazon.com>
Reviewed-by: Clément Mathieu--Drif <clement.mathieu--drif@eviden.com>
Message-Id: <20250125181343.59151-4-philmd@linaro.org>
---
 include/hw/sysbus.h |  2 ++
 hw/core/sysbus.c    | 14 ++++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/include/hw/sysbus.h b/include/hw/sysbus.h
index c9b1e0e90e3..81bbda10d37 100644
--- a/include/hw/sysbus.h
+++ b/include/hw/sysbus.h
@@ -19,6 +19,8 @@ DECLARE_INSTANCE_CHECKER(BusState, SYSTEM_BUS,
 OBJECT_DECLARE_TYPE(SysBusDevice, SysBusDeviceClass,
                     SYS_BUS_DEVICE)
 
+#define TYPE_DYNAMIC_SYS_BUS_DEVICE "dynamic-sysbus-device"
+
 /**
  * SysBusDeviceClass:
  *
diff --git a/hw/core/sysbus.c b/hw/core/sysbus.c
index 075c7dfd69b..98819d5dc61 100644
--- a/hw/core/sysbus.c
+++ b/hw/core/sysbus.c
@@ -320,6 +320,14 @@ BusState *sysbus_get_default(void)
     return main_system_bus;
 }
 
+static void dynamic_sysbus_device_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *k = DEVICE_CLASS(klass);
+
+    k->user_creatable = true;
+    k->hotpluggable = false;
+}
+
 static const TypeInfo sysbus_types[] = {
     {
         .name           = TYPE_SYSTEM_BUS,
@@ -335,6 +343,12 @@ static const TypeInfo sysbus_types[] = {
         .class_size     = sizeof(SysBusDeviceClass),
         .class_init     = sysbus_device_class_init,
     },
+    {
+        .name           = TYPE_DYNAMIC_SYS_BUS_DEVICE,
+        .parent         = TYPE_SYS_BUS_DEVICE,
+        .class_init     = dynamic_sysbus_device_class_init,
+        .abstract       = true,
+    }
 };
 
 DEFINE_TYPES(sysbus_types)
-- 
2.47.1