1 files changed, 16 insertions, 0 deletions
diff --git a/opl/opl.h b/opl/opl.h
index 352e6696..515950b1 100644
--- a/opl/opl.h
+++ b/opl/opl.h
@@ -27,6 +27,8 @@
 #ifndef OPL_OPL_H
 #define OPL_OPL_H
 
+typedef void (*opl_callback_t)(void *data);
+
 typedef enum
 {
     OPL_REGISTER_PORT = 0,
@@ -72,5 +74,19 @@ void OPL_WritePort(opl_port_t port, unsigned int value);
 
 unsigned int OPL_ReadPort(opl_port_t port);
 
+// Set a timer callback.  After the specified number of milliseconds
+// have elapsed, the callback will be invoked.
+
+void OPL_SetCallback(unsigned int ms, opl_callback_t callback, void *data);
+
+// Begin critical section, during which, OPL callbacks will not be
+// invoked.
+
+void OPL_Lock(void);
+
+// End critical section.
+
+void OPL_Unlock(void);
+
 #endif