qom: add new dynamic property infrastructure based on Visitors (v2)

qdev properties are settable only during construction and static to classes.
This isn't flexible enough for QOM.

This patch introduces a property interface for qdev that provides dynamic
properties that are tied to objects, instead of classes.  These properties are
Visitor based instead of string based too.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

hw/qdev.c

@@ -98,6 +98,7 @@ static DeviceState *qdev_create_from_info(BusState *bus, DeviceInfo *info)
         qdev_hot_added = true;
     }
     dev->instance_id_alias = -1;
+    QTAILQ_INIT(&dev->properties);
     dev->state = DEV_STATE_CREATED;
     return dev;
 }
@@ -395,12 +396,31 @@ void qdev_init_nofail(DeviceState *dev)
     }
 }
 
+static void qdev_property_del_all(DeviceState *dev)
+{
+    while (!QTAILQ_EMPTY(&dev->properties)) {
+        DeviceProperty *prop = QTAILQ_FIRST(&dev->properties);
+
+        QTAILQ_REMOVE(&dev->properties, prop, node);
+
+        if (prop->release) {
+            prop->release(dev, prop->name, prop->opaque);
+        }
+
+        g_free(prop->name);
+        g_free(prop->type);
+        g_free(prop);
+    }
+}
+
 /* Unlink device from bus and free the structure.  */
 void qdev_free(DeviceState *dev)
 {
     BusState *bus;
     Property *prop;
 
+    qdev_property_del_all(dev);
+
     if (dev->state == DEV_STATE_INITIALIZED) {
         while (dev->num_child_bus) {
             bus = QLIST_FIRST(&dev->child_bus);
@@ -978,3 +998,80 @@ void qdev_unref(DeviceState *dev)
     g_assert(dev->ref > 0);
     dev->ref--;
 }
+
+void qdev_property_add(DeviceState *dev, const char *name, const char *type,
+                       DevicePropertyAccessor *get, DevicePropertyAccessor *set,
+                       DevicePropertyRelease *release,
+                       void *opaque, Error **errp)
+{
+    DeviceProperty *prop = g_malloc0(sizeof(*prop));
+
+    prop->name = g_strdup(name);
+    prop->type = g_strdup(type);
+
+    prop->get = get;
+    prop->set = set;
+    prop->release = release;
+    prop->opaque = opaque;
+
+    QTAILQ_INSERT_TAIL(&dev->properties, prop, node);
+}
+
+static DeviceProperty *qdev_property_find(DeviceState *dev, const char *name)
+{
+    DeviceProperty *prop;
+
+    QTAILQ_FOREACH(prop, &dev->properties, node) {
+        if (strcmp(prop->name, name) == 0) {
+            return prop;
+        }
+    }
+
+    return NULL;
+}
+
+void qdev_property_get(DeviceState *dev, Visitor *v, const char *name,
+                       Error **errp)
+{
+    DeviceProperty *prop = qdev_property_find(dev, name);
+
+    if (prop == NULL) {
+        error_set(errp, QERR_PROPERTY_NOT_FOUND, dev->id?:"", name);
+        return;
+    }
+
+    if (!prop->get) {
+        error_set(errp, QERR_PERMISSION_DENIED);
+    } else {
+        prop->get(dev, v, prop->opaque, name, errp);
+    }
+}
+
+void qdev_property_set(DeviceState *dev, Visitor *v, const char *name,
+                       Error **errp)
+{
+    DeviceProperty *prop = qdev_property_find(dev, name);
+
+    if (prop == NULL) {
+        error_set(errp, QERR_PROPERTY_NOT_FOUND, dev->id?:"", name);
+        return;
+    }
+
+    if (!prop->set) {
+        error_set(errp, QERR_PERMISSION_DENIED);
+    } else {
+        prop->set(dev, prop->opaque, v, name, errp);
+    }
+}
+
+const char *qdev_property_get_type(DeviceState *dev, const char *name, Error **errp)
+{
+    DeviceProperty *prop = qdev_property_find(dev, name);
+
+    if (prop == NULL) {
+        error_set(errp, QERR_PROPERTY_NOT_FOUND, dev->id?:"", name);
+        return NULL;
+    }
+
+    return prop->type;
+}

hw/qdev.h

@@ -5,6 +5,7 @@
 #include "qemu-queue.h"
 #include "qemu-char.h"
 #include "qemu-option.h"
+#include "qapi/qapi-visit-core.h"
 
 typedef struct Property Property;
 
@@ -27,6 +28,44 @@ enum {
     DEV_NVECTORS_UNSPECIFIED = -1,
 };
 
+/**
+ * @DevicePropertyAccessor - called when trying to get/set a property
+ *
+ * @dev the device that owns the property
+ * @v the visitor that contains the property data
+ * @opaque the device property opaque
+ * @name the name of the property
+ * @errp a pointer to an Error that is filled if getting/setting fails.
+ */
+typedef void (DevicePropertyAccessor)(DeviceState *dev,
+                                      Visitor *v,
+                                      void *opaque,
+                                      const char *name,
+                                      Error **errp);
+
+/**
+ * @DevicePropertyRelease - called when a property is removed from a device
+ *
+ * @dev the device that owns the property
+ * @name the name of the property
+ * @opaque the opaque registered with the property
+ */
+typedef void (DevicePropertyRelease)(DeviceState *dev,
+                                     const char *name,
+                                     void *opaque);
+
+typedef struct DeviceProperty
+{
+    gchar *name;
+    gchar *type;
+    DevicePropertyAccessor *get;
+    DevicePropertyAccessor *set;
+    DevicePropertyRelease *release;
+    void *opaque;
+
+    QTAILQ_ENTRY(DeviceProperty) node;
+} DeviceProperty;
+
 /* This structure should not be accessed directly.  We declare it here
    so that it can be embedded in individual device state structures.  */
 struct DeviceState {
@@ -51,6 +90,8 @@ struct DeviceState {
      * more information.
      */
     uint32_t ref;
+
+    QTAILQ_HEAD(, DeviceProperty) properties;
 };
 
 typedef void (*bus_dev_printfn)(Monitor *mon, DeviceState *dev, int indent);
@@ -355,4 +396,83 @@ void qdev_ref(DeviceState *dev);
  */
 void qdev_unref(DeviceState *dev);
 
+/**
+ * @qdev_property_add - add a new property to a device
+ *
+ * @dev - the device to add a property to
+ *
+ * @name - the name of the property.  This can contain any character except for
+ *         a forward slash.  In general, you should use hyphens '-' instead of
+ *         underscores '_' when naming properties.
+ *
+ * @type - the type name of the property.  This namespace is pretty loosely
+ *         defined.  Sub namespaces are constructed by using a prefix and then
+ *         to angle brackets.  For instance, the type 'virtio-net-pci' in the
+ *         'link' namespace would be 'link<virtio-net-pci>'.
+ *
+ * @get - the getter to be called to read a property.  If this is NULL, then
+ *        the property cannot be read.
+ *
+ * @set - the setter to be called to write a property.  If this is NULL,
+ *        then the property cannot be written.
+ *
+ * @release - called when the property is removed from the device.  This is
+ *            meant to allow a property to free its opaque upon device
+ *            destruction.  This may be NULL.
+ *
+ * @opaque - an opaque pointer to pass to the callbacks for the property
+ *
+ * @errp - returns an error if this function fails
+ */
+void qdev_property_add(DeviceState *dev, const char *name, const char *type,
+                       DevicePropertyAccessor *get, DevicePropertyAccessor *set,
+                       DevicePropertyRelease *release,
+                       void *opaque, Error **errp);
+
+/**
+ * @qdev_property_get - reads a property from a device
+ *
+ * @dev - the device
+ *
+ * @v - the visitor that will receive the property value.  This should be an
+ *      Output visitor and the data will be written with @name as the name.
+ *
+ * @name - the name of the property
+ *
+ * @errp - returns an error if this function fails
+ */
+void qdev_property_get(DeviceState *dev, Visitor *v, const char *name,
+                       Error **errp);
+
+/**
+ * @qdev_property_set - writes a property to a device
+ *
+ * @dev - the device
+ *
+ * @v - the visitor that will be used to write the property value.  This should
+ *      be an Input visitor and the data will be first read with @name as the
+ *      name and then written as the property value.
+ *
+ * @name - the name of the property
+ *
+ * @errp - returns an error if this function fails
+ */
+void qdev_property_set(DeviceState *dev, Visitor *v, const char *name,
+                       Error **errp);
+
+/**
+ * @qdev_property_get_type - returns the type of a property
+ *
+ * @dev - the device
+ *
+ * @name - the name of the property
+ *
+ * @errp - returns an error if this function fails
+ *
+ * Returns:
+ *   The type name of the property.
+ */
+const char *qdev_property_get_type(DeviceState *dev, const char *name,
+                                   Error **errp);
+
 #endif

qerror.c

@@ -185,6 +185,10 @@ static const QErrorStringTable qerror_table[] = {
         .error_fmt = QERR_OPEN_FILE_FAILED,
         .desc      = "Could not open '%(filename)'",
     },
+    {
+        .error_fmt = QERR_PERMISSION_DENIED,
+        .desc      = "Insufficient permission to perform this operation",
+    },
     {
         .error_fmt = QERR_PROPERTY_NOT_FOUND,
         .desc      = "Property '%(device).%(property)' not found",

qerror.h

@@ -156,6 +156,9 @@ QError *qobject_to_qerror(const QObject *obj);
 #define QERR_OPEN_FILE_FAILED \
     "{ 'class': 'OpenFileFailed', 'data': { 'filename': %s } }"
 
+#define QERR_PERMISSION_DENIED \
+    "{ 'class': 'PermissionDenied', 'data': {} }"
+
 #define QERR_PROPERTY_NOT_FOUND \
     "{ 'class': 'PropertyNotFound', 'data': { 'device': %s, 'property': %s } }"