ARM: bL_switcher/trace: Add kernel trace trigger interface

This patch exports a bL_switcher_trace_trigger() function to
provide a means for drivers using the trace events to get the
current status when starting a trace session.

Calling this function is equivalent to pinging the trace_trigger
file in sysfs.
Signed-off-by: Dave Martin <dave.martin@linaro.org>

arch/arm/common/bL_switcher.c

@@ -537,7 +537,7 @@ static void bL_switcher_trace_trigger_cpu(void *__always_unused info)
 	trace_cpu_migrate_current(get_ns(), read_mpidr());
 }
 
-static int bL_switcher_trace_trigger(void)
+int bL_switcher_trace_trigger(void)
 {
 	int ret;
 
@@ -550,6 +550,7 @@ static int bL_switcher_trace_trigger(void)
 
 	return ret;
 }
+EXPORT_SYMBOL_GPL(bL_switcher_trace_trigger);
 
 static int bL_switcher_enable(void)
 {

arch/arm/include/asm/bL_switcher.h

@@ -54,6 +54,8 @@ int bL_switcher_unregister_notifier(struct notifier_block *nb);
 bool bL_switcher_get_enabled(void);
 void bL_switcher_put_enabled(void);
 
+int bL_switcher_trace_trigger(void);
+
 #else
 static inline int bL_switcher_register_notifier(struct notifier_block *nb)
 {
@@ -67,6 +69,7 @@ static inline int bL_switcher_unregister_notifier(struct notifier_block *nb)
 
 static inline bool bL_switcher_get_enabled(void) { return false; }
 static inline void bL_switcher_put_enabled(void) { }
+static inline int bL_switcher_trace_trigger(void) { return 0; }
 #endif /* CONFIG_BL_SWITCHER */
 
 #endif