ftracetest: Add functions file that holds helper functions

Created the file tools/testing/ftrace/test.d/functions that will
hold helper functions.

Current helper functions include:

Add clear_trace() helper to reset the trace file

Used as a descriptive name to show that "echo > trace" is clearing
the trace file.

Add disable/enable_tracing() helper calls

Add calls that disable and enable tracing respectively by echoing
0 or 1 into tracing_on.

Add helper reset_tracer() function

Add a helper function reset_tracer() that will clear the current_tracer
(echo nop > current_tracer).

Link: http://lkml.kernel.org/r/[e-mail]
Link: http://lkml.kernel.org/r/[e-mail]

Acked-by: Masami Hiramatsu <[e-mail]>
Acked-by: Namhyung Kim <[e-mail]>
Signed-off-by: Steven Rostedt <[e-mail]>

tools/testing/selftests/ftrace/ftracetest

···
   fi
 }
 
+# load in the helper functions
+. $TEST_DIR/functions
+
 # Main loop
 for t in $TEST_CASES; do
   run_test $t

tools/testing/selftests/ftrace/test.d/functions

···
+
+clear_trace() { # reset trace output
+    echo > trace
+}
+
+disable_tracing() { # stop trace recording
+    echo 0 > tracing_on
+}
+
+enable_tracing() { # start trace recording
+    echo 1 > tracing_on
+}
+
+reset_tracer() { # reset the current tracer
+    echo nop > current_tracer
+}