-u64 ring_buffer_time_stamp(int cpu);
-void ring_buffer_normalize_time_stamp(int cpu, u64 *ts);
+u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu);
+void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,
+ int cpu, u64 *ts);
+void ring_buffer_set_clock(struct ring_buffer *buffer,
+ u64 (*clock)(void));