diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index 98dac7e396c..c3516d49d09 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -2813,7 +2813,17 @@ nir_block_last_phi_instr(nir_block *block)
 
 typedef enum {
    nir_selection_control_none = 0x0,
+
+   /**
+    * Defined by SPIR-V spec 3.22 "Selection Control".
+    * The application prefers to remove control flow.
+    */
    nir_selection_control_flatten = 0x1,
+
+   /**
+    * Defined by SPIR-V spec 3.22 "Selection Control".
+    * The application prefers to keep control flow.
+    */
    nir_selection_control_dont_flatten = 0x2,
 } nir_selection_control;