Re: [Qemu-devel] [PATCH v2 1/2] qom: Implement object_property_add_const_link()

[Paolo Bonzini <pbonzini@redhat.com>]

On 01/05/2015 16:09, Eduardo Habkost wrote:
> +void object_property_add_const_link(Object *obj, const char *name,
> +                                       const char *type, Object *child,
> +                                       ObjectPropertyLinkFlags flags,
> +                                       Error **errp)
> +{
> +    Object **childp = g_new0(Object*, 1);
> +
> +    *childp = child;
> +    object_property_add_link(obj, name, type, childp, NULL,
> +                             flags | OBJ_PROP_LINK_FREE_CHILD_POINTER, errp);
> +}
> +

This works, but is the extra functionality needed, compared to
an alias?  Namely, when is flags going to be != 0?

FWIW, here is my ./.. patch.  I'm all for adding a helper like
object_property_add_const_link on top if we go for it.

Another possibility is to not introduce any of our patches and reuse
the child<> getter and resolve functions in
object_property_add_const_link.

-------------------- 8< ---------------
>From 653ca80e93fcaa94c7fa172edbaef75457d4952d Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Tue, 31 Mar 2015 13:56:24 +0200
Subject: [PATCH] qom: add . and .. properties

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 qom/object.c | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/qom/object.c b/qom/object.c
index b8dff43..3dd87b7 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -1783,9 +1783,51 @@ void object_property_set_description(Object *obj, const char *name,
     op->description = g_strdup(description);
 }
 
+static void property_get_dot(Object *obj, struct Visitor *v, void *opaque,
+                             const char *name, Error **errp)
+{
+    gchar *path = object_get_canonical_path(obj);
+    visit_type_str(v, &path, name, errp);
+    g_free(path);
+}
+
+static Object *property_resolve_dot(Object *obj, void *opaque,
+                                      const gchar *part)
+{
+    return obj;
+}
+
+static void property_get_dotdot(Object *obj, struct Visitor *v, void *opaque,
+                                const char *name, Error **errp)
+{
+    if (obj->parent) {
+        gchar *path = object_get_canonical_path(obj);
+        visit_type_str(v, &path, name, errp);
+        g_free(path);
+    } else {
+        gchar *path = (gchar *)"";
+        visit_type_str(v, &path, name, errp);
+    }
+}
+
+static Object *property_resolve_dotdot(Object *obj, void *opaque,
+                                      const gchar *part)
+{
+    return obj->parent;
+}
+
 static void object_instance_init(Object *obj)
 {
+    ObjectProperty *op;
     object_property_add_str(obj, "type", qdev_get_type, NULL, NULL);
+
+    op = object_property_add(obj, ".", "link<Object>", property_get_dot,
+                             NULL, NULL, NULL, NULL);
+    op->resolve = property_resolve_dot;
+
+    op = object_property_add(obj, "..", "link<Object>", property_get_dotdot,
+                             NULL, NULL, NULL, NULL);
+    op->resolve = property_resolve_dotdot;
 }
 
 static void register_types(void)
-- 
2.3.5