mesa: added comment
diff --git a/src/mesa/shader/prog_parameter.c b/src/mesa/shader/prog_parameter.c
index 6b9e73b..2f029b0 100644
--- a/src/mesa/shader/prog_parameter.c
+++ b/src/mesa/shader/prog_parameter.c
@@ -100,6 +100,7 @@
* \param type type of parameter, such as
* \param name the parameter name, will be duplicated/copied!
* \param size number of elements in 'values' vector (1..4, or more)
+ * \param datatype GL_FLOAT, GL_FLOAT_VECx, GL_INT, GL_INT_VECx or GL_NONE.
* \param values initial parameter value, up to 4 GLfloats, or NULL
* \param state state indexes, or NULL
* \return index of new parameter in the list, or -1 if error (out of mem)