stm class: Add heartbeat stm source device

Heartbeat stm source may have multiple instances (for connecting to
different stm devices). Each instance will send a periodic test message
over its stm device when it is linked. This can be used for testing stm
class framework, stm device drivers or as a heartbeat over the stm link.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hwtracing/stm/Kconfig

@@ -28,4 +28,15 @@ config STM_SOURCE_CONSOLE
 	  If you want to send kernel console messages over STM devices,
 	  say Y.
 
+config STM_SOURCE_HEARTBEAT
+	tristate "Heartbeat over STM devices"
+	help
+	  This is a kernel space trace source that sends periodic
+	  heartbeat messages to trace hosts over STM devices. It is
+	  also useful for testing stm class drivers and the stm class
+	  framework itself.
+
+	  If you want to send heartbeat messages over STM devices,
+	  say Y.
+
 endif