[PATCH] perf ftrace: Add ftrace.tracer config option

[Taeung Song]

Currently perf ftrace command will select 'function_graph' or 'function'.
So add ftrace.tracer config option to select tracer

    # cat ~/.perfconfig
    [ftrace]
        tracer = function

    # perf ftrace usleep 123456 | head -10
      <...>-14450 [002] d... 10089.284231: finish_task_switch <-__schedule
      <...>-14450 [002] .... 10089.284232: finish_wait <-pipe_wait
      <...>-14450 [002] .... 10089.284232: mutex_lock <-pipe_wait
      <...>-14450 [002] .... 10089.284232: _cond_resched <-mutex_lock
      <...>-14450 [002] .... 10089.284233: generic_pipe_buf_confirm <-pipe_read

Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Signed-off-by: Taeung Song <treeze.taeung@xxxxxxxxx>
---
 tools/perf/builtin-ftrace.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index 414444d..00e228f 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -17,6 +17,7 @@
 #include "evlist.h"
 #include "target.h"
 #include "thread_map.h"
+#include "util/config.h"
 
 
 #define DEFAULT_TRACER  "function_graph"
@@ -198,6 +199,26 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
 	return done ? 0 : -1;
 }
 
+static int perf_ftrace_config(const char *var, const char *value, void *cb)
+{
+	struct perf_ftrace *ftrace = cb;
+
+	if (!strcmp(var, "ftrace.tracer")) {
+		if (!strcmp(value, "function_graph"))
+			ftrace->tracer = DEFAULT_TRACER;
+		else if (!strcmp(value, "function"))
+			ftrace->tracer = "function";
+		else {
+			pr_err("Please select function_graph(default)"
+			       "or function to use tracer.\n");
+			return -1;
+		}
+		return 0;
+	}
+
+	return 0;
+}
+
 int cmd_ftrace(int argc, const char **argv, const char *prefix __maybe_unused)
 {
 	int ret;
@@ -218,6 +239,10 @@ int cmd_ftrace(int argc, const char **argv, const char *prefix __maybe_unused)
 	OPT_END()
 	};
 
+	ret = perf_config(perf_ftrace_config, &ftrace);
+	if (ret < 0)
+		return -1;
+
 	argc = parse_options(argc, argv, ftrace_options, ftrace_usage,
 			    PARSE_OPT_STOP_AT_NON_OPTION);
 	if (!argc)
-- 
2.7.4