memdev: remove "id" property

The "id" property is unnecessary and can be replaced simply with
object_get_canonical_path_component.  This patch mostly undoes commit
e1ff3c67 ("monitor: fix qmp/hmp query-memdev not reporting IDs of
memory backends", 2017-01-12).
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

backends/hostmem.c

@@ -369,24 +369,6 @@ host_memory_backend_can_be_deleted(UserCreatable *uc)
     }
 }
 
-static char *get_id(Object *o, Error **errp)
-{
-    HostMemoryBackend *backend = MEMORY_BACKEND(o);
-
-    return g_strdup(backend->id);
-}
-
-static void set_id(Object *o, const char *str, Error **errp)
-{
-    HostMemoryBackend *backend = MEMORY_BACKEND(o);
-
-    if (backend->id) {
-        error_setg(errp, "cannot change property value");
-        return;
-    }
-    backend->id = g_strdup(str);
-}
-
 static bool host_memory_backend_get_share(Object *o, Error **errp)
 {
     HostMemoryBackend *backend = MEMORY_BACKEND(o);
@@ -434,18 +416,11 @@ host_memory_backend_class_init(ObjectClass *oc, void *data)
         &HostMemPolicy_lookup,
         host_memory_backend_get_policy,
         host_memory_backend_set_policy, &error_abort);
-    object_class_property_add_str(oc, "id", get_id, set_id, &error_abort);
     object_class_property_add_bool(oc, "share",
         host_memory_backend_get_share, host_memory_backend_set_share,
         &error_abort);
 }
 
-static void host_memory_backend_finalize(Object *o)
-{
-    HostMemoryBackend *backend = MEMORY_BACKEND(o);
-    g_free(backend->id);
-}
-
 static const TypeInfo host_memory_backend_info = {
     .name = TYPE_MEMORY_BACKEND,
     .parent = TYPE_OBJECT,
@@ -454,7 +429,6 @@ static const TypeInfo host_memory_backend_info = {
     .class_init = host_memory_backend_class_init,
     .instance_size = sizeof(HostMemoryBackend),
     .instance_init = host_memory_backend_init,
-    .instance_finalize = host_memory_backend_finalize,
     .interfaces = (InterfaceInfo[]) {
         { TYPE_USER_CREATABLE },
         { }

include/sysemu/hostmem.h

@@ -52,7 +52,6 @@ struct HostMemoryBackend {
     Object parent;
 
     /* protected */
-    char *id;
     uint64_t size;
     bool merge, dump;
     bool prealloc, force_prealloc, is_mapped, share;

numa.c

@@ -580,7 +580,7 @@ static int query_memdev(Object *obj, void *opaque)
 
         m->value = g_malloc0(sizeof(*m->value));
 
-        m->value->id = object_property_get_str(obj, "id", NULL);
+        m->value->id = object_get_canonical_path_component(obj);
         m->value->has_id = !!m->value->id;
 
         m->value->size = object_property_get_uint(obj, "size",

qom/object_interfaces.c

@@ -65,12 +65,6 @@ Object *user_creatable_add_type(const char *type, const char *id,
 
     assert(qdict);
     obj = object_new(type);
-    if (object_property_find(obj, "id", NULL)) {
-        object_property_set_str(obj, id, "id", &local_err);
-        if (local_err) {
-            goto out;
-        }
-    }
     visit_start_struct(v, NULL, NULL, 0, &local_err);
     if (local_err) {
         goto out;