qom: Add check() argument to object_property_add_link()

There are currently three types of object_property_add_link() callers:

1. The link property may be set at any time.
2. The link property of a DeviceState instance may only be set before
   realize.
3. The link property may never be set, it is read-only.

Something similar can already be achieved with
object_property_add_str()'s set() argument.  Follow its example and add
a check() argument to object_property_add_link().

Also provide default check() functions for case #1 and #2.  Case #3 is
covered by passing a NULL function pointer.

Cc: Peter Crosthwaite <peter.crosthwaite@petalogix.com>
Cc: Alexander Graf <agraf@suse.de>
Cc: Anthony Liguori <aliguori@amazon.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
[AF: Tweaked documentation comment]
Signed-off-by: Andreas Färber <afaerber@suse.de>

1 files changed, 11 insertions, 0 deletions

diff --git a/include/hw/qdev-properties.h b/include/hw/qdev-properties.h
index 3c000eea75..c46e908d71 100644
--- a/include/hw/qdev-properties.h
+++ b/include/hw/qdev-properties.h
@@ -204,4 +204,15 @@ void qdev_property_add_static(DeviceState *dev, Property *prop, Error **errp);
  */
 void qdev_prop_set_after_realize(DeviceState *dev, const char *name,
                                  Error **errp);
+
+/**
+ * qdev_prop_allow_set_link_before_realize:
+ *
+ * Set the #Error object if an attempt is made to set the link after realize.
+ * This function should be used as the check() argument to
+ * object_property_add_link().
+ */
+void qdev_prop_allow_set_link_before_realize(Object *obj, const char *name,
+                                             Object *val, Error **errp);
+
 #endif