Re: [Qemu-devel] [PATCH 04/16] qom: add QObject-based property get/set wrappers

[Anthony Liguori]

On 02/02/2012 10:45 AM, Paolo Bonzini wrote:
Move the creation of QmpInputVisitor and QmpOutputVisitor from
qmp.c to qom/object.c, since it's the only practical way to access
object properties.
Signed-off-by: Paolo Bonzini<pbonz...@redhat.com>
---
  include/qemu/object.h |   24 ++++++++++++++++++++++++
  qmp.c                 |   17 ++---------------
  qom/object.c          |   29 +++++++++++++++++++++++++++++
  3 files changed, 55 insertions(+), 15 deletions(-)

I don't want object.h to have a dependency on QObject.  We need to phase out 
QObject.

Couple things:

1) We shouldn't use generic interfaces to read/write properties from objects. 
We should use type-safe accessors provided by the types themselves.

2) If we want to get fancy, we can add property_set_int, etc. and then implement 
(1) via header files that just call these functions.

Regards,

Anthony Liguori


diff --git a/include/qemu/object.h b/include/qemu/object.h
index 947cf29..71090f2 100644
--- a/include/qemu/object.h
+++ b/include/qemu/object.h
@@ -542,6 +542,18 @@ void object_property_get(Object *obj, struct Visitor *v, 
const char *name,
                           struct Error **errp);

  /**
+ * object_property_get_qobject:
+ * @obj: the object
+ * @name: the name of the property
+ * @errp: returns an error if this function fails
+ *
+ * Returns: the value of the property, converted to QObject, or NULL if
+ * an error occurs.
+ */
+struct QObject *object_property_get_qobject(Object *obj, const char *name,
+                                            struct Error **errp);
+
+/**
   * object_property_set:
   * @obj: the object
   * @v: the visitor that will be used to write the property value.  This should
@@ -556,6 +568,18 @@ void object_property_set(Object *obj, struct Visitor *v, 
const char *name,
                           struct Error **errp);

  /**
+ * object_property_set_qobject:
+ * @obj: the object
+ * @ret: The value that will be written to the property.
+ * @name: the name of the property
+ * @errp: returns an error if this function fails
+ *
+ * Writes a property to a object.
+ */
+void object_property_set_qobject(Object *obj, struct QObject *qobj,
+                                 const char *name, struct Error **errp);
+
+/**
   * @object_property_get_type:
   * @obj: the object
   * @name: the name of the property
diff --git a/qmp.c b/qmp.c
index 45052cc..c7a81cc 100644
--- a/qmp.c
+++ b/qmp.c
@@ -21,8 +21,6 @@
  #include "kvm.h"
  #include "arch_init.h"
  #include "hw/qdev.h"
-#include "qapi/qmp-input-visitor.h"
-#include "qapi/qmp-output-visitor.h"
  #include "blockdev.h"

  NameInfo *qmp_query_name(Error **errp)
@@ -198,7 +196,6 @@ int qmp_qom_set(Monitor *mon, const QDict *qdict, QObject 
**ret)
      const char *property = qdict_get_str(qdict, "property");
      QObject *value = qdict_get(qdict, "value");
      Error *local_err = NULL;
-    QmpInputVisitor *mi;
      Object *obj;

      obj = object_resolve_path(path, NULL);
@@ -207,10 +204,7 @@ int qmp_qom_set(Monitor *mon, const QDict *qdict, QObject 
**ret)
          goto out;
      }

-    mi = qmp_input_visitor_new(value);
-    object_property_set(obj, qmp_input_get_visitor(mi), property,&local_err);
-
-    qmp_input_visitor_cleanup(mi);
+    object_property_set_qobject(obj, value, property,&local_err);

  out:
      if (local_err) {
@@ -227,7 +221,6 @@ int qmp_qom_get(Monitor *mon, const QDict *qdict, QObject 
**ret)
      const char *path = qdict_get_str(qdict, "path");
      const char *property = qdict_get_str(qdict, "property");
      Error *local_err = NULL;
-    QmpOutputVisitor *mo;
      Object *obj;

      obj = object_resolve_path(path, NULL);
@@ -236,13 +229,7 @@ int qmp_qom_get(Monitor *mon, const QDict *qdict, QObject 
**ret)
          goto out;
      }

-    mo = qmp_output_visitor_new();
-    object_property_get(obj, qmp_output_get_visitor(mo), property,&local_err);
-    if (!local_err) {
-        *ret = qmp_output_get_qobject(mo);
-    }
-
-    qmp_output_visitor_cleanup(mo);
+    *ret = object_property_get_qobject(obj, property,&local_err);

  out:
      if (local_err) {
diff --git a/qom/object.c b/qom/object.c
index 299e146..13c8bec 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -13,6 +13,8 @@
  #include "qemu/object.h"
  #include "qemu-common.h"
  #include "qapi/qapi-visit-core.h"
+#include "qapi/qmp-input-visitor.h"
+#include "qapi/qmp-output-visitor.h"

  #define MAX_INTERFACES 32

@@ -646,6 +648,33 @@ void object_property_set(Object *obj, Visitor *v, const 
char *name,
      }
  }

+void object_property_set_qobject(Object *obj, QObject *value,
+                                 const char *name, Error **errp)
+{
+    QmpInputVisitor *mi;
+    mi = qmp_input_visitor_new(value);
+    object_property_set(obj, qmp_input_get_visitor(mi), name, errp);
+
+    qmp_input_visitor_cleanup(mi);
+}
+
+QObject *object_property_get_qobject(Object *obj, const char *name,
+                                     Error **errp)
+{
+    QObject *ret = NULL;
+    Error *local_err = NULL;
+    QmpOutputVisitor *mo;
+
+    mo = qmp_output_visitor_new();
+    object_property_get(obj, qmp_output_get_visitor(mo), name,&local_err);
+    if (!local_err) {
+        ret = qmp_output_get_qobject(mo);
+    }
+    error_propagate(errp, local_err);
+    qmp_output_visitor_cleanup(mo);
+    return ret;
+}
+
  const char *object_property_get_type(Object *obj, const char *name, Error 
**errp)
  {
      ObjectProperty *prop = object_property_find(obj, name);