add macro for custom event tracing

include/eventlog.h

@@ -9,6 +9,19 @@
 
 #define EVENTLOG_TYPE_STRING 0
 
+#define EVENTLOG_TRACE(event_name, ...) \
+    eventlog_trace_##event_name(__VA_ARGS__)
+
+typedef void (*event_printer_t)(const void* data, char* buf, size_t buf_size);
+
+typedef struct {
+    uint32_t id;
+    const char* name;
+    event_printer_t printer;
+} event_def_t;
+
+#define EVENTLOG_REGISTER_EVENT_C(event_name, print_func) \
+    { .id = EVENT_ID_##event_name, .name = #event_name, .printer = print_func }
 
 struct eventlog_entry
 {