diff --git a/hgsane/sane_hg_mdw.cpp b/hgsane/sane_hg_mdw.cpp
index 6375078..b0f942c 100644
--- a/hgsane/sane_hg_mdw.cpp
+++ b/hgsane/sane_hg_mdw.cpp
@@ -1114,7 +1114,7 @@ bool hg_sane_middleware::get_current_value(scanner_handle handle, int option, vo
 
 	return ret;
 }
-void* hg_sane_middleware::get_default_value(scanner_handle handle, int option)
+void* hg_sane_middleware::get_default_value(scanner_handle handle, int option, int* bytes)
 {
 	std::string val(get_option_json(handle, option));
 	void* data = nullptr;
@@ -1128,8 +1128,10 @@ void* hg_sane_middleware::get_default_value(scanner_handle handle, int option)
 			bool v = false;
 			jsn->get_value("default", v);
 
-			data = local_utility::acquire_memory(/*sizeof(v)*/4, "");
+			data = local_utility::acquire_memory(sizeof(SANE_Bool), "");
 			memcpy(data, &v, sizeof(v));
+			if (bytes)
+				*bytes = sizeof(SANE_Bool);
 			VLOG_MINI_2(LOG_LEVEL_DEBUG_INFO, "option %d default value is: %s\n", option, v ? "true" : "false");
 		}
 		else if (val == "int")
@@ -1139,6 +1141,8 @@ void* hg_sane_middleware::get_default_value(scanner_handle handle, int option)
 
 			data = local_utility::acquire_memory(sizeof(v), "");
 			memcpy(data, &v, sizeof(v));
+			if (bytes)
+				*bytes = sizeof(v);
 			VLOG_MINI_2(LOG_LEVEL_DEBUG_INFO, "option %d default value is: %d\n", option, v);
 		}
 		else if (val == "float")
@@ -1148,6 +1152,8 @@ void* hg_sane_middleware::get_default_value(scanner_handle handle, int option)
 
 			SANE_Fixed	sd = hg_sane_middleware::double_2_sane_fixed(v);
 			data = local_utility::acquire_memory(sizeof(sd), "");
+			if (bytes)
+				*bytes = sizeof(sd);
 
 			memcpy(data, &sd, sizeof(sd));
 			VLOG_MINI_2(LOG_LEVEL_DEBUG_INFO, "option %d default value is: %f\n", option, v);
@@ -1164,6 +1170,8 @@ void* hg_sane_middleware::get_default_value(scanner_handle handle, int option)
 				size = val.length();
 			data = local_utility::acquire_memory(size + 4, "");
 			strcpy((char*)data, val.c_str());
+			if (bytes)
+				*bytes = val.length();
 			VLOG_MINI_2(LOG_LEVEL_DEBUG_INFO, "option %d default value is: %s\n", option, (char*)data);
 		}
 		else
@@ -1519,26 +1527,26 @@ bool hg_sane_middleware::get_cur_value(SANE_Handle handle, int option, void* val
 
 	return get_current_value(h, option, value, type);
 }
-void* hg_sane_middleware::get_def_value(SANE_Handle handle, int option)
+void* hg_sane_middleware::get_def_value(SANE_Handle handle, int option, int* bytes)
 {
 	scanner_handle	h = find_openning_device(handle);
 
 	if (!h)
 		return NULL;
 
-	return get_default_value(h, option);
+	return get_default_value(h, option, bytes);
 }
 SANE_Status hg_sane_middleware::io_control(SANE_Handle h, unsigned long code, void* data, unsigned* len)
 {
 	OPENDEV			od;
 	scanner_handle	handle = find_openning_device(h, false, &od);
+	int				ret = SANE_STATUS_GOOD;
 
 	// commented at 2022-03-23 for getting app about info before open any device
 	// 
 	//if (!handle)
 	//	return SANE_STATUS_INVAL;
-
-	int ret = hg_scanner_control(handle, code, data, len);
+	ret = hg_scanner_control(handle, code, data, len);
 	if (ret == SCANNER_ERR_CONFIGURATION_CHANGED)
 	{
 		int nc = code;
diff --git a/hgsane/sane_hg_mdw.h b/hgsane/sane_hg_mdw.h
index d4811f6..194eaf5 100644
--- a/hgsane/sane_hg_mdw.h
+++ b/hgsane/sane_hg_mdw.h
@@ -82,7 +82,7 @@ class hg_sane_middleware
 
 	void reload_current_value(scanner_handle handle, std::vector<int>* changed = NULL);
 	bool get_current_value(scanner_handle handle, int option, void* value, SANE_Value_Type* type = NULL);
-	void* get_default_value(scanner_handle handle, int option);	// caller should call local_utility::free_memory to free the returned value
+	void* get_default_value(scanner_handle handle, int option, int* bytes = nullptr);	// caller should call local_utility::free_memory to free the returned value
 
 /// <summary>
 /// 关联项处理
@@ -188,7 +188,7 @@ public:
 	SANE_Option_Descriptor* get_option_descriptor(SANE_Handle h, SANE_Int option);
 	SANE_Status set_option(SANE_Handle h, SANE_Int option, SANE_Action action, void* value, SANE_Int* after_do);
 	bool get_cur_value(SANE_Handle handle, int option, void* value, SANE_Value_Type* type = NULL);	// SANE_type
-	void* get_def_value(SANE_Handle handle, int option);	// caller should call local_utility::free_memory to free the returned value, SANE_type
+	void* get_def_value(SANE_Handle handle, int option, int* bytes = nullptr);	// caller should call local_utility::free_memory to free the returned value, SANE_type
 
 	// extension ...
 	SANE_Status io_control(SANE_Handle h, unsigned long code, void* data, unsigned* len);