[PATCH 4/4] tracing: update the trace/events.txt documentation

[Yuanhan Liu <yuanhan.liu@linux.intel.com>]

Describe the usage of trace_set_clr_module_event in events.txt

Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
---
 Documentation/trace/events.txt |   25 +++++++++++++++++++++++++
 1 files changed, 25 insertions(+), 0 deletions(-)

diff --git a/Documentation/trace/events.txt b/Documentation/trace/events.txt
index 09bd8e9..120c1fe 100644
--- a/Documentation/trace/events.txt
+++ b/Documentation/trace/events.txt
@@ -93,6 +93,31 @@ In order to facilitate early boot debugging, use boot option:
 event-list is a comma separated list of events. See section 2.1 for event
 format.
 
+2.4 Module load option
+----------------------
+
+In order to track the events at the early module load phase, add the
+following codes in your module:
+
+    char *xxx_trace = NULL;
+    module_param_named(trace, xxx_trace, charp, 0400);
+
+
+    /* Your module init function */
+    xxx_init()
+    {
+        ....
+        if (xxx_trace)
+                trace_set_clr_module_event(THIS_MODULE, xxx_trace, 1);
+        ....
+    }
+
+where the xxx_trace is same as event-list described above, besides DO
+NOT include the subsystem.
+
+You can check the sample code for more information.
+
+
 3. Defining an event-enabled tracepoint
 =======================================
 
-- 
1.7.2.3