hw/core: Introduce device_class_set_props_n

Record the size of the array in DeviceClass.props_count_.
Iterate with known count in qdev_prop_walk.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Tested-by: Lei Yang <leiyang@redhat.com>
Link: https://lore.kernel.org/r/20241218134251.4724-14-richard.henderson@linaro.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

hw/core/qdev-properties.c

@@ -749,16 +749,13 @@ const PropertyInfo qdev_prop_array = {
 
 /* --- public helpers --- */
 
-static const Property *qdev_prop_walk(const Property *props, const char *name)
+static const Property *qdev_prop_walk(DeviceClass *cls, const char *name)
 {
-    if (!props) {
-        return NULL;
+    for (int i = 0, n = cls->props_count_; i < n; ++i) {
+        const Property *prop = &cls->props_[i];
+        if (strcmp(prop->name, name) == 0) {
+            return prop;
         }
-    while (props->name) {
-        if (strcmp(props->name, name) == 0) {
-            return props;
-        }
-        props++;
     }
     return NULL;
 }
@@ -771,7 +768,7 @@ static const Property *qdev_prop_find(DeviceState *dev, const char *name)
     /* device properties */
     class = object_get_class(OBJECT(dev));
     do {
-        prop = qdev_prop_walk(DEVICE_CLASS(class)->props_, name);
+        prop = qdev_prop_walk(DEVICE_CLASS(class), name);
         if (prop) {
             return prop;
         }
@@ -1064,9 +1061,31 @@ static void qdev_class_add_legacy_property(DeviceClass *dc, const Property *prop
 void (device_class_set_props)(DeviceClass *dc, const Property *props)
 {
     const Property *prop;
+    size_t n;
 
     dc->props_ = props;
-    for (prop = props; prop && prop->name; prop++) {
+    for (prop = props, n = 0; prop && prop->name; prop++, n++) {
+        qdev_class_add_legacy_property(dc, prop);
+        qdev_class_add_property(dc, prop->name, prop);
+    }
+
+    /* We used a hole in DeviceClass because that's still a lot. */
+    assert(n <= UINT16_MAX);
+    dc->props_count_ = n;
+}
+
+void device_class_set_props_n(DeviceClass *dc, const Property *props, size_t n)
+{
+    /* We used a hole in DeviceClass because that's still a lot. */
+    assert(n <= UINT16_MAX);
+    assert(n != 0);
+
+    dc->props_ = props;
+    dc->props_count_ = n;
+
+    for (size_t i = 0; i < n; ++i) {
+        const Property *prop = &props[i];
+        assert(prop->name);
         qdev_class_add_legacy_property(dc, prop);
         qdev_class_add_property(dc, prop->name, prop);
     }

hw/core/qdev.c

@@ -703,6 +703,7 @@ static void device_class_base_init(ObjectClass *class, void *data)
      * so do not propagate them to the subclasses.
      */
     klass->props_ = NULL;
+    klass->props_count_ = 0;
 }
 
 static void device_unparent(Object *obj)

include/hw/qdev-core.h

@@ -138,6 +138,12 @@ struct DeviceClass {
      */
     const Property *props_;
 
+    /**
+     * @props_count_: number of elements in @props_; should only be
+     * assigned by using device_class_set_props().
+     */
+    uint16_t props_count_;
+
     /**
      * @user_creatable: Can user instantiate with -device / device_add?
      *
@@ -960,6 +966,18 @@ void device_class_set_props(DeviceClass *dc, const Property *props);
         (device_class_set_props)((dc), (props));                        \
     } while (0)
 
+/**
+ * device_class_set_props_n(): add a set of properties to an device
+ * @dc: the parent DeviceClass all devices inherit
+ * @props: an array of properties, not terminated by DEFINE_PROP_END_OF_LIST.
+ * @n: ARRAY_SIZE(@props)
+ *
+ * This will add a set of properties to the object. It will fault if
+ * you attempt to add an existing property defined by a parent class.
+ * To modify an inherited property you need to use????
+ */
+void device_class_set_props_n(DeviceClass *dc, const Property *props, size_t n);
+
 /**
  * device_class_set_parent_realize() - set up for chaining realize fns
  * @dc: The device class

system/qdev-monitor.c

@@ -752,19 +752,18 @@ DeviceState *qdev_device_add(QemuOpts *opts, Error **errp)
 
 #define qdev_printf(fmt, ...) monitor_printf(mon, "%*s" fmt, indent, "", ## __VA_ARGS__)
 
-static void qdev_print_props(Monitor *mon, DeviceState *dev, const Property *props,
+static void qdev_print_props(Monitor *mon, DeviceState *dev, DeviceClass *dc,
                              int indent)
 {
-    if (!props)
-        return;
-    for (; props->name; props++) {
+    for (int i = 0, n = dc->props_count_; i < n; ++i) {
+        const Property *prop = &dc->props_[i];
         char *value;
-        char *legacy_name = g_strdup_printf("legacy-%s", props->name);
+        char *legacy_name = g_strdup_printf("legacy-%s", prop->name);
 
         if (object_property_get_type(OBJECT(dev), legacy_name, NULL)) {
             value = object_property_get_str(OBJECT(dev), legacy_name, NULL);
         } else {
-            value = object_property_print(OBJECT(dev), props->name, true,
+            value = object_property_print(OBJECT(dev), prop->name, true,
                                           NULL);
         }
         g_free(legacy_name);
@@ -772,7 +771,7 @@ static void qdev_print_props(Monitor *mon, DeviceState *dev, const Property *pro
         if (!value) {
             continue;
         }
-        qdev_printf("%s = %s\n", props->name,
+        qdev_printf("%s = %s\n", prop->name,
                     *value ? value : "<null>");
         g_free(value);
     }
@@ -812,7 +811,7 @@ static void qdev_print(Monitor *mon, DeviceState *dev, int indent)
     }
     class = object_get_class(OBJECT(dev));
     do {
-        qdev_print_props(mon, dev, DEVICE_CLASS(class)->props_, indent);
+        qdev_print_props(mon, dev, DEVICE_CLASS(class), indent);
         class = object_class_get_parent(class);
     } while (class != object_class_by_name(TYPE_DEVICE));
     bus_print_dev(dev->parent_bus, mon, dev, indent);