ssi: Add ssi_realize_and_unref()

Add an ssi_realize_and_unref(), for the benefit of callers
who want to be able to create an SSI device, set QOM properties
on it, and then do the realize-and-unref afterwards.

The API works on the same principle as the recently added
qdev_realize_and_undef(), sysbus_realize_and_undef(), etc.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20200628142429.17111-9-peter.maydell@linaro.org

hw/ssi/ssi.c

@@ -90,11 +90,16 @@ static const TypeInfo ssi_slave_info = {
     .abstract = true,
 };
 
+bool ssi_realize_and_unref(DeviceState *dev, SSIBus *bus, Error **errp)
+{
+    return qdev_realize_and_unref(dev, &bus->parent_obj, errp);
+}
+
 DeviceState *ssi_create_slave(SSIBus *bus, const char *name)
 {
     DeviceState *dev = qdev_new(name);
 
-    qdev_realize_and_unref(dev, &bus->parent_obj, &error_fatal);
+    ssi_realize_and_unref(dev, bus, &error_fatal);
     return dev;
 }
 

include/hw/ssi/ssi.h

@@ -79,6 +79,32 @@ extern const VMStateDescription vmstate_ssi_slave;
 }
 
 DeviceState *ssi_create_slave(SSIBus *bus, const char *name);
+/**
+ * ssi_realize_and_unref: realize and unref an SSI slave device
+ * @dev: SSI slave device to realize
+ * @bus: SSI bus to put it on
+ * @errp: error pointer
+ *
+ * Call 'realize' on @dev, put it on the specified @bus, and drop the
+ * reference to it. Errors are reported via @errp and by returning
+ * false.
+ *
+ * This function is useful if you have created @dev via qdev_new()
+ * (which takes a reference to the device it returns to you), so that
+ * you can set properties on it before realizing it. If you don't need
+ * to set properties then ssi_create_slave() is probably better (as it
+ * does the create, init and realize in one step).
+ *
+ * If you are embedding the SSI slave into another QOM device and
+ * initialized it via some variant on object_initialize_child() then
+ * do not use this function, because that family of functions arrange
+ * for the only reference to the child device to be held by the parent
+ * via the child<> property, and so the reference-count-drop done here
+ * would be incorrect.  (Instead you would want ssi_realize(), which
+ * doesn't currently exist but would be trivial to create if we had
+ * any code that wanted it.)
+ */
+bool ssi_realize_and_unref(DeviceState *dev, SSIBus *bus, Error **errp);
 
 /* Master interface.  */
 SSIBus *ssi_create_bus(DeviceState *parent, const char *name);