ftrace: add trace pipe header pluggin

This patch adds a method for open_pipe and open_read to the pluggins
so that they can add a header to the trace pipe call.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index c1ec134..ee53d70 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -135,9 +135,13 @@
 	void			(*init)(struct trace_array *tr);
 	void			(*reset)(struct trace_array *tr);
 	void			(*open)(struct trace_iterator *iter);
+	void			(*pipe_open)(struct trace_iterator *iter);
 	void			(*close)(struct trace_iterator *iter);
 	void			(*start)(struct trace_iterator *iter);
 	void			(*stop)(struct trace_iterator *iter);
+	ssize_t			(*read)(struct trace_iterator *iter,
+					struct file *filp, char __user *ubuf,
+					size_t cnt, loff_t *ppos);
 	void			(*ctrl_update)(struct trace_array *tr);
 #ifdef CONFIG_FTRACE_STARTUP_TEST
 	int			(*selftest)(struct tracer *trace,
@@ -160,6 +164,7 @@
 struct trace_iterator {
 	struct trace_array	*tr;
 	struct tracer		*trace;
+	void			*private;
 	long			last_overrun[NR_CPUS];
 	long			overrun[NR_CPUS];