qom: add container_get

This is QOM "mkdir -p".  It is useful when referring to
container objects such as "/machine".

Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

hw/qdev-monitor.c

@@ -180,9 +180,7 @@ static Object *qdev_get_peripheral(void)
     static Object *dev;
 
     if (dev == NULL) {
-        dev = object_new("container");
-        object_property_add_child(object_get_root(), "peripheral",
-                                  OBJECT(dev), NULL);
+        dev = container_get("/peripheral");
     }
 
     return dev;
@@ -193,9 +191,7 @@ static Object *qdev_get_peripheral_anon(void)
     static Object *dev;
 
     if (dev == NULL) {
-        dev = object_new("container");
-        object_property_add_child(object_get_root(), "peripheral-anon",
-                                  OBJECT(dev), NULL);
+        dev = container_get("/peripheral-anon");
     }
 
     return dev;

include/qemu/object.h

@@ -836,6 +836,18 @@ Object *object_resolve_path(const char *path, bool *ambiguous);
 Object *object_resolve_path_type(const char *path, const char *typename,
                                  bool *ambiguous);
 
+/**
+ * object_resolve_path_component:
+ * @parent: the object in which to resolve the path
+ * @part: the component to resolve.
+ *
+ * This is similar to object_resolve_path with an absolute path, but it
+ * only resolves one element (@part) and takes the others from @parent.
+ *
+ * Returns: The resolved object or NULL on path lookup failure.
+ */
+Object *object_resolve_path_component(Object *parent, gchar *part);
+
 /**
  * object_property_add_child:
  * @obj: the object to add a property to
@@ -891,4 +903,16 @@ void object_property_add_str(Object *obj, const char *name,
                              void (*set)(Object *, const char *, struct Error **),
                              struct Error **errp);
 
+/**
+ * container_get:
+ * @path: path to the container
+ *
+ * Return a container object whose path is @path.  Create more containers
+ * along the path if necessary.
+ *
+ * Returns: the container object.
+ */
+Object *container_get(const char *path);
+
+
 #endif

qom/container.c

@@ -12,6 +12,7 @@
 
 #include "qemu/object.h"
 #include "module.h"
+#include <assert.h>
 
 static TypeInfo container_info = {
     .name          = "container",
@@ -24,4 +25,26 @@ static void container_register_types(void)
     type_register_static(&container_info);
 }
 
+Object *container_get(const char *path)
+{
+    Object *obj, *child;
+    gchar **parts;
+    int i;
+
+    parts = g_strsplit(path, "/", 0);
+    assert(parts != NULL && parts[0] != NULL && !parts[0][0]);
+    obj = object_get_root();
+
+    for (i = 1; parts[i] != NULL; i++, obj = child) {
+        child = object_resolve_path_component(obj, parts[i]);
+        if (!child) {
+            child = object_new("container");
+            object_property_add_child(obj, parts[i], child, NULL);
+        }
+    }
+
+    return obj;
+}
+
+
 type_init(container_register_types)

qom/object.c

@@ -1022,12 +1022,27 @@ gchar *object_get_canonical_path(Object *obj)
     return newpath;
 }
 
+Object *object_resolve_path_component(Object *parent, gchar *part)
+{
+    ObjectProperty *prop = object_property_find(parent, part);
+    if (prop == NULL) {
+        return NULL;
+    }
+
+    if (strstart(prop->type, "link<", NULL)) {
+        return *(Object **)prop->opaque;
+    } else if (strstart(prop->type, "child<", NULL)) {
+        return prop->opaque;
+    } else {
+        return NULL;
+    }
+}
+
 static Object *object_resolve_abs_path(Object *parent,
                                           gchar **parts,
                                           const char *typename,
                                           int index)
 {
-    ObjectProperty *prop;
     Object *child;
 
     if (parts[index] == NULL) {
@@ -1038,21 +1053,7 @@ static Object *object_resolve_abs_path(Object *parent,
         return object_resolve_abs_path(parent, parts, typename, index + 1);
     }
 
-    prop = object_property_find(parent, parts[index]);
-    if (prop == NULL) {
-        return NULL;
-    }
-
-    child = NULL;
-    if (strstart(prop->type, "link<", NULL)) {
-        Object **pchild = prop->opaque;
-        if (*pchild) {
-            child = *pchild;
-        }
-    } else if (strstart(prop->type, "child<", NULL)) {
-        child = prop->opaque;
-    }
-
+    child = object_resolve_path_component(parent, parts[index]);
     if (!child) {
         return NULL;
     }