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>

9 files changed, 33 insertions, 3 deletions

diff --git a/hw/core/qdev-properties.c b/hw/core/qdev-properties.c
index 77d0c66635..c67acf58b5 100644
--- a/hw/core/qdev-properties.c
+++ b/hw/core/qdev-properties.c
@@ -21,6 +21,18 @@ void qdev_prop_set_after_realize(DeviceState *dev, const char *name,
     }
 }
 
+void qdev_prop_allow_set_link_before_realize(Object *obj, const char *name,
+                                             Object *val, Error **errp)
+{
+    DeviceState *dev = DEVICE(obj);
+
+    if (dev->realized) {
+        error_setg(errp, "Attempt to set link property '%s' on device '%s' "
+                   "(type '%s') after it was realized",
+                   name, dev->id, object_get_typename(obj));
+    }
+}
+
 void *qdev_get_prop_ptr(DeviceState *dev, Property *prop)
 {
     void *ptr = dev;
diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index a182917222..97acf62906 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -97,7 +97,10 @@ static void bus_add_child(BusState *bus, DeviceState *child)
     snprintf(name, sizeof(name), "child[%d]", kid->index);
     object_property_add_link(OBJECT(bus), name,
                              object_get_typename(OBJECT(child)),
-                             (Object **)&kid->child, 0, NULL);
+                             (Object **)&kid->child,
+                             NULL, /* read-only property */
+                             0, /* return ownership on prop deletion */
+                             NULL);
 }
 
 void qdev_set_parent_bus(DeviceState *dev, BusState *bus)
@@ -823,7 +826,7 @@ static void device_initfn(Object *obj)
     } while (class != object_class_by_name(TYPE_DEVICE));
 
     object_property_add_link(OBJECT(dev), "parent_bus", TYPE_BUS,
-                             (Object **)&dev->parent_bus, 0,
+                             (Object **)&dev->parent_bus, NULL, 0,
                              &error_abort);
 }
 
@@ -945,6 +948,7 @@ static void qbus_initfn(Object *obj)
     object_property_add_link(obj, QDEV_HOTPLUG_HANDLER_PROPERTY,
                              TYPE_HOTPLUG_HANDLER,
                              (Object **)&bus->hotplug_handler,
+                             object_property_allow_set_link,
                              OBJ_PROP_LINK_UNREF_ON_RELEASE,
                              NULL);
     object_property_add_bool(obj, "realized",
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);
 
diff --git a/hw/net/xilinx_axienet.c b/hw/net/xilinx_axienet.c
index 7ecf9251a7..839d97ca86 100644
--- a/hw/net/xilinx_axienet.c
+++ b/hw/net/xilinx_axienet.c
@@ -946,10 +946,12 @@ static void xilinx_enet_realize(DeviceState *dev, Error **errp)
 
     object_property_add_link(OBJECT(ds), "enet", "xlnx.axi-ethernet",
                              (Object **) &ds->enet,
+                             object_property_allow_set_link,
                              OBJ_PROP_LINK_UNREF_ON_RELEASE,
                              &local_errp);
     object_property_add_link(OBJECT(cs), "enet", "xlnx.axi-ethernet",
                              (Object **) &cs->enet,
+                             object_property_allow_set_link,
                              OBJ_PROP_LINK_UNREF_ON_RELEASE,
                              &local_errp);
     if (local_errp) {
@@ -987,11 +989,13 @@ static void xilinx_enet_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);
 
diff --git a/hw/pcmcia/pxa2xx.c b/hw/pcmcia/pxa2xx.c
index 6949214df3..96f377453d 100644
--- a/hw/pcmcia/pxa2xx.c
+++ b/hw/pcmcia/pxa2xx.c
@@ -198,7 +198,9 @@ static void pxa2xx_pcmcia_initfn(Object *obj)
     s->slot.irq = qemu_allocate_irqs(pxa2xx_pcmcia_set_irq, s, 1)[0];
 
     object_property_add_link(obj, "card", TYPE_PCMCIA_CARD,
-                             (Object **)&s->card, 0, NULL);
+                             (Object **)&s->card,
+                             NULL, /* read-only property */
+                             0, NULL);
 }
 
 /* Insert a new card into a slot */
diff --git a/hw/s390x/s390-virtio-bus.c b/hw/s390x/s390-virtio-bus.c
index 930b4f7cd0..9c71afa031 100644
--- a/hw/s390x/s390-virtio-bus.c
+++ b/hw/s390x/s390-virtio-bus.c
@@ -314,6 +314,7 @@ static void s390_virtio_rng_instance_init(Object *obj)
     object_property_add_child(obj, "virtio-backend", OBJECT(&dev->vdev), NULL);
     object_property_add_link(obj, "rng", TYPE_RNG_BACKEND,
                              (Object **)&dev->vdev.conf.rng,
+                             qdev_prop_allow_set_link_before_realize,
                              OBJ_PROP_LINK_UNREF_ON_RELEASE, NULL);
 }
 
diff --git a/hw/s390x/virtio-ccw.c b/hw/s390x/virtio-ccw.c
index aebb2dec6d..2bf0af8f0a 100644
--- a/hw/s390x/virtio-ccw.c
+++ b/hw/s390x/virtio-ccw.c
@@ -1273,6 +1273,7 @@ static void virtio_ccw_rng_instance_init(Object *obj)
     object_property_add_child(obj, "virtio-backend", OBJECT(&dev->vdev), NULL);
     object_property_add_link(obj, "rng", TYPE_RNG_BACKEND,
                              (Object **)&dev->vdev.conf.rng,
+                             qdev_prop_allow_set_link_before_realize,
                              OBJ_PROP_LINK_UNREF_ON_RELEASE, NULL);
 }
 
diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index eebb819d98..ce97514b69 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -1518,6 +1518,7 @@ static void virtio_rng_initfn(Object *obj)
     object_property_add_child(obj, "virtio-backend", OBJECT(&dev->vdev), NULL);
     object_property_add_link(obj, "rng", TYPE_RNG_BACKEND,
                              (Object **)&dev->vdev.conf.rng,
+                             qdev_prop_allow_set_link_before_realize,
                              OBJ_PROP_LINK_UNREF_ON_RELEASE, NULL);
 
 }
diff --git a/hw/virtio/virtio-rng.c b/hw/virtio/virtio-rng.c
index 2efda8b443..cbf01389a2 100644
--- a/hw/virtio/virtio-rng.c
+++ b/hw/virtio/virtio-rng.c
@@ -224,6 +224,7 @@ static void virtio_rng_initfn(Object *obj)
 
     object_property_add_link(obj, "rng", TYPE_RNG_BACKEND,
                              (Object **)&vrng->conf.rng,
+                             qdev_prop_allow_set_link_before_realize,
                              OBJ_PROP_LINK_UNREF_ON_RELEASE, NULL);
 }