diff --git a/src/layer.h b/src/layer.h
index 3893afed3be..1a01b3025c4 100644
--- a/src/layer.h
+++ b/src/layer.h
@@ -49,10 +49,12 @@ class Layer
     // return 0 if success
     virtual int load_model(const ModelBin& mb);
 
-    //
+    // layer implementation specific setup
+    // return 0 if success
     virtual int create_pipeline(const Option& opt = Option());
 
-    //
+    // layer implementation specific clean
+    // return 0 if success
     virtual int destroy_pipeline(const Option& opt = Option());
 
 public:
diff --git a/src/net.h b/src/net.h
index 8a8d631917d..7ad50ceb7cf 100644
--- a/src/net.h
+++ b/src/net.h
@@ -38,15 +38,15 @@ class Net
     ~Net();
 
 public:
-    // option
+    // option can be changed before loading
     Option opt;
 
 #if NCNN_VULKAN
-
+    // set gpu device by index
     void set_vulkan_device(int device_index);
 
+    // set gpu device by device handle, no owner transfer
     void set_vulkan_device(const VulkanDevice* vkdev);
-
 #endif // NCNN_VULKAN
 
 #if NCNN_STRING