parameters: add new param_get_default_value()

src/lib/parameters/param.h

@@ -215,6 +215,16 @@ __EXPORT size_t		param_size(param_t param);
  */
 __EXPORT int		param_get(param_t param, void *val);
 
+/**
+ * Copy the default value of a parameter.
+ *
+ * @param param		A handle returned by param_find or passed by param_foreach.
+ * @param val		Where to return the value, assumed to point to suitable storage for the parameter type.
+ *			For structures, a bitwise copy of the structure is performed to this address.
+ * @return		Zero if the parameter's deafult value could be returned, nonzero otherwise.
+ */
+__EXPORT int		param_get_default_value(param_t param, void *val);
+
 /**
  * Set the value of a parameter.
  *

src/lib/parameters/parameters.cpp

@@ -581,6 +581,24 @@ param_get(param_t param, void *val)
 	return result;
 }
 
+int
+param_get_default_value(param_t param, void *default_val)
+{
+	if (default_val && handle_in_range(param)) {
+		switch (param_type(param)) {
+		case PARAM_TYPE_INT32:
+			memcpy(default_val, &param_info_base[param].val.i, param_size(param));
+			return 0;
+
+		case PARAM_TYPE_FLOAT:
+			memcpy(default_val, &param_info_base[param].val.f, param_size(param));
+			return 0;
+		}
+	}
+
+	return -1;
+}
+
 /**
  * worker callback method to save the parameters
  * @param arg unused