[PATCH] libtracefs: Add support for setting tracers

[Sameeruddin shaik <sameeross1994@gmail.com>]

tracefs_set_tracer - set the tracer
tracefs_stop_tracer - clear the tracer

Signed-off-by: Sameeruddin shaik <sameeross1994@gmail.com>

diff --git a/include/tracefs.h b/include/tracefs.h
index 55ee867..47d3282 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -173,4 +173,26 @@ int tracefs_function_filter(struct tracefs_instance *instance, const char *filte
 int tracefs_function_notrace(struct tracefs_instance *instance, const char *filter,
 			     const char *module, unsigned int flags);
 
+/*
+ * Tracers
+ */
+enum tracefs_tracers {
+	TRACEFS_TRACER_NOP = 0,
+	TRACEFS_TRACER_FUNCTION,
+	TRACEFS_TRACER_FUNCTION_GRAPH,
+	TRACEFS_TRACER_IRQSOFF,
+	TRACEFS_TRACER_PREEMPTOFF,
+	TRACEFS_TRACER_PREEMPTIRQSOFF,
+	TRACEFS_TRACER_WAKEUP,
+	TRACEFS_TRACER_WAKEUP_RT,
+	TRACEFS_TRACER_WAKEUP_DL,
+	TRACEFS_TRACER_MMIOTRACE,
+	TRACEFS_TRACER_HWLAT,
+	TRACEFS_TRACER_BRANCH,
+	TRACEFS_TRACER_BLOCK,
+};
+
+int tracefs_set_tracer(struct tracefs_instance *instance, enum tracefs_tracers tracer);
+
+int tracefs_stop_tracer(struct tracefs_instance *instance);
 #endif /* _TRACE_FS_H */
diff --git a/src/tracefs-tools.c b/src/tracefs-tools.c
index 6ef17f6..ceddeda 100644
--- a/src/tracefs-tools.c
+++ b/src/tracefs-tools.c
@@ -25,6 +25,7 @@ __hidden pthread_mutex_t toplevel_lock = PTHREAD_MUTEX_INITIALIZER;
 #define TRACE_FILTER		"set_ftrace_filter"
 #define TRACE_NOTRACE		"set_ftrace_notrace"
 #define TRACE_FILTER_LIST	"available_filter_functions"
+#define TRACER			"current_tracer"
 
 /* File descriptor for Top level set_ftrace_filter  */
 static int ftrace_filter_fd = -1;
@@ -910,3 +911,88 @@ int tracefs_function_notrace(struct tracefs_instance *instance, const char *filt
 	tracefs_put_tracing_file(filter_path);
 	return ret;
 }
+
+int write_tracer(int fd, const char *tracer)
+{
+	int ret;
+
+	ret = write(fd, tracer, strlen(tracer));
+	if (ret < strlen(tracer))
+		return -1;
+	return ret;
+}
+
+/**
+* tracefs_set_tracer - fucntion to set the tracer
+* @instance: ftrace instance, can be NULL for top tracing instance
+* @tracer: Tracer that has to be set, which can be integer from 0 - 13
+* or and enum value
+*/
+
+int tracefs_set_tracer(struct tracefs_instance *instance, enum tracefs_tracers tracer)
+{
+	char *tracer_path;
+	int ret = -1;
+	int fd = -1;
+
+	tracer_path = tracefs_instance_get_file(instance, TRACER);
+	if (!tracer_path)
+		return -1;
+
+	fd = open(tracer_path, O_WRONLY);
+	if (fd < 0)
+		goto out;
+
+	switch(tracer) {
+	case 0:
+		ret = write_tracer(fd , "nop");
+		break;
+	case 1:
+		ret = write_tracer(fd, "function");
+		break;
+	case 2:
+		ret = write_tracer(fd, "function_graph");
+		break;
+	case 3:
+		ret = write_tracer(fd, "irqsoff");
+		break;
+	case 4:
+		ret = write_tracer(fd, "preemptoff");
+		break;
+	case 5:
+		ret = write_tracer(fd, "preemptirqsoff");
+		break;
+	case 6:
+		ret = write_tracer(fd, "wakeup");
+		break;
+	case 7:
+		ret = write_tracer(fd, "wakeup_rt");
+		break;
+	case 8:
+		ret = write_tracer(fd, "wakeup_dl");
+		break;
+	case 9:
+		ret = write_tracer(fd, "mmiotrace");
+		break;
+	case 10:
+		ret = write_tracer(fd, "hwlat");
+		break;
+	case 11:
+		ret = write_tracer(fd, "branch");
+		break;
+	case 12:
+		ret = write_tracer(fd, "blk");
+		break;
+	default:
+		ret = -1;
+	}
+
+ out:
+	tracefs_put_tracing_file(tracer_path);
+	return ret;
+}
+
+int  tracefs_stop_tracer(struct tracefs_instance *instance)
+{
+	return tracefs_set_tracer(instance, TRACEFS_TRACER_NOP);
+}
-- 
2.7.4