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, 4 insertions, 0 deletions

diff --git a/hw/dma/xilinx_axidma.c b/hw/dma/xilinx_axidma.c
index c8fda39122..14b887bfa8 100644
--- a/hw/dma/xilinx_axidma.c
+++ b/hw/dma/xilinx_axidma.c
@@ -538,10 +538,12 @@ static void xilinx_axidma_realize(DeviceState *dev, Error **errp)
 
     object_property_add_link(OBJECT(ds), "dma", TYPE_XILINX_AXI_DMA,
                              (Object **)&ds->dma,
+                             object_property_allow_set_link,
                              OBJ_PROP_LINK_UNREF_ON_RELEASE,
                              &local_errp);
     object_property_add_link(OBJECT(cs), "dma", TYPE_XILINX_AXI_DMA,
                              (Object **)&cs->dma,
+                             object_property_allow_set_link,
                              OBJ_PROP_LINK_UNREF_ON_RELEASE,
                              &local_errp);
     if (local_errp) {
@@ -576,11 +578,13 @@ static void xilinx_axidma_init(Object *obj)
 
     object_property_add_link(obj, "axistream-connected", TYPE_STREAM_SLAVE,
                              (Object **)&s->tx_data_dev,
+                             qdev_prop_allow_set_link_before_realize,
                              OBJ_PROP_LINK_UNREF_ON_RELEASE,
                              &error_abort);
     object_property_add_link(obj, "axistream-control-connected",
                              TYPE_STREAM_SLAVE,
                              (Object **)&s->tx_control_dev,
+                             qdev_prop_allow_set_link_before_realize,
                              OBJ_PROP_LINK_UNREF_ON_RELEASE,
                              &error_abort);