tracing: add __print_symbolic to trace events

This patch adds __print_symbolic which is similar to __print_flags but
works for an enumeration type instead. That is, there is only a one to one
mapping between the values and the symbols. When a match is made, then
it is printed, otherwise the hex value is outputed.

[ Impact: add interface for showing symbol names in events ]

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

2 files changed, 11 insertions, 0 deletions

diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 4b58cf1a11c2..bbf40f624fc8 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -20,6 +20,9 @@ const char *ftrace_print_flags_seq(struct trace_seq *p, const char *delim,
                                    unsigned long flags,
                                    const struct trace_print_flags *flag_array);
 
+const char *ftrace_print_symbols_seq(struct trace_seq *p, unsigned long val,
+                                     const struct trace_print_flags *symbol_array);
+
 /*
  * The trace entry - the most basic unit of tracing. This is what
  * is printed in the end as a single line in the trace output, such as:
diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index 22c94719c569..87fc227c6fbe 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -130,6 +130,14 @@
                 ftrace_print_flags_seq(p, delim, flag, flags);          \
         })
 
+#undef __print_symbolic
+#define __print_symbolic(value, symbol_array...)                        \
+        ({                                                              \
+                static const struct trace_print_flags symbols[] =       \
+                        { symbol_array, { -1, NULL }};                  \
+                ftrace_print_symbols_seq(p, value, symbols);            \
+        })
+
 #undef TRACE_EVENT
 #define TRACE_EVENT(call, proto, args, tstruct, assign, print)          \
 enum print_line_t                                                       \