[PATCH] ftrace/samples: Add missing prototype for my_direct_func

[Jiri Olsa <jolsa@redhat.com>]

There's compilation fail reported kernel test robot for W=1 build:

  >> samples/ftrace/ftrace-direct-multi.c:8:6: warning: no previous
  prototype for function 'my_direct_func' [-Wmissing-prototypes]
     void my_direct_func(unsigned long ip)

The inlined assembly is used outside function, so we can't make
my_direct_func static and pass it as asm input argument.

However my_tramp is already extern so I think there's no problem
keeping my_direct_func extern as well and just add its prototype.

Reported-by: kernel test robot <lkp@intel.com>
Fixes: 5fae941b9a6f ("ftrace/samples: Add multi direct interface test module")
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 samples/ftrace/ftrace-direct-multi.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/samples/ftrace/ftrace-direct-multi.c b/samples/ftrace/ftrace-direct-multi.c
index 2a5b1fb7ac14..e0ccf43da0c9 100644
--- a/samples/ftrace/ftrace-direct-multi.c
+++ b/samples/ftrace/ftrace-direct-multi.c
@@ -10,6 +10,7 @@ void my_direct_func(unsigned long ip)
 	trace_printk("ip %lx\n", ip);
 }
 
+extern void my_direct_func(unsigned long ip);
 extern void my_tramp(void *);
 
 asm (
-- 
2.32.0