[telemetry] disabling telemetry made easier

- reorganize telemetry makefiles for FW
- protect some calls and provide default implementation of
  register_periodic
- improve generator with attribute unused keyword

sw/airborne/firmwares/fixedwing/autopilot.c

@@ -77,7 +77,9 @@ static void send_mode(struct transport_tx *trans, struct link_device *dev) {
 
 void autopilot_send_mode(void) {
   // use default telemetry here
+#if DOWNLINK
   send_mode(&(DefaultChannel).trans_tx, &(DefaultDevice).device);
+#endif
 }
 
 static void send_attitude(struct transport_tx *trans, struct link_device *dev) {

sw/airborne/firmwares/fixedwing/main_ap.c

@@ -241,7 +241,9 @@ void init_ap( void ) {
   /** - start interrupt task */
   mcu_int_enable();
 
+#if DOWNLINK
   downlink_init();
+#endif
 
 #if defined AEROCOMM_DATA_PIN
   IO0DIR |= _BV(AEROCOMM_DATA_PIN);
@@ -449,7 +451,9 @@ void reporting_task( void ) {
   /** then report periodicly */
   else {
     //PeriodicSendAp(DefaultChannel, DefaultDevice);
+#if PERIODIC_TELEMETRY
     periodic_telemetry_send_Ap(&(DefaultChannel).trans_tx, &(DefaultDevice).device);
+#endif
   }
 }
 

sw/airborne/firmwares/rotorcraft/main.c

@@ -176,7 +176,9 @@ STATIC_INLINE void main_init( void ) {
 
   mcu_int_enable();
 
+#if DOWNLINK
   downlink_init();
+#endif
 
   // register the timers for the periodic functions
   main_periodic_tid = sys_time_register_timer((1./PERIODIC_FREQUENCY), NULL);
@@ -220,14 +222,20 @@ STATIC_INLINE void main_periodic( void ) {
   SetActuatorsFromCommands(commands, autopilot_mode);
 
   if (autopilot_in_flight) {
-    RunOnceEvery(PERIODIC_FREQUENCY, { autopilot_flight_time++; datalink_time++; });
+    RunOnceEvery(PERIODIC_FREQUENCY, { autopilot_flight_time++;
+#if defined DATALINK || defined SITL
+        datalink_time++;
+#endif
+        });
   }
 
   RunOnceEvery(10, LED_PERIODIC());
 }
 
 STATIC_INLINE void telemetry_periodic(void) {
+#if PERIODIC_TELEMETRY
   periodic_telemetry_send_Main(&(DefaultChannel).trans_tx, &(DefaultDevice).device);
+#endif
 }
 
 /** mode to enter when RC is lost while using a mode with RC input (not AP_MODE_NAV) */

sw/airborne/subsystems/datalink/telemetry.c

@@ -36,6 +36,8 @@
  * @return TRUE if message registered with success, FALSE otherwise
  */
 bool_t register_periodic_telemetry(struct pprz_telemetry * _pt, const char * _msg, telemetry_cb _cb) {
+  // return FALSE if NULL is passed as pprz_telemetry
+  if (_pt == NULL) return FALSE;
   // look for message name
   uint8_t i;
   for (i = 0; i < _pt->nb; i++) {

sw/airborne/subsystems/datalink/telemetry_common.h

@@ -34,6 +34,12 @@
 #include "mcu_periph/link_device.h"
 #include "subsystems/datalink/transport.h"
 
+/** Set default periodic telemetry to NULL
+ */
+#ifndef DefaultPeriodic
+#define DefaultPeriodic NULL
+#endif
+
 /** Telemetry callback definition
  */
 typedef void (*telemetry_cb)(struct transport_tx *trans, struct link_device *dev);
@@ -55,12 +61,17 @@ struct pprz_telemetry {
 };
 
 /** Register a telemetry callback function.
+ * empty implementation is provided if PERIODIC_TELEMETRY is not set or set to FALSE
  * @param _pt periodic telemetry structure to register
  * @param _msg message name (string) as defined in telemetry xml file
  * @param _cb callback function, called according to telemetry mode and specified period
  * @return TRUE if message registered with success, FALSE otherwise
  */
+#if PERIODIC_TELEMETRY
 extern bool_t register_periodic_telemetry(struct pprz_telemetry * _pt, const char * _msg, telemetry_cb _cb);
+#else
+static inline bool_t register_periodic_telemetry(struct pprz_telemetry * _pt __attribute__((unused)), const char * _msg __attribute__((unused)), telemetry_cb _cb __attribute__((unused))) { return FALSE; }
+#endif
 
 #if USE_PERIODIC_TELEMETRY_REPORT
 /** Send an error report when trying to send message that as not been register

sw/tools/generators/gen_messages.ml

@@ -166,17 +166,20 @@ module Gen_onboard = struct
       print_macro_param h f;
       List.iter (fun f -> fprintf h ", "; print_macro_param h f) fields
 
-  let print_fun_param h = function
-      (Array (t, _), s, _) -> fprintf h "uint8_t %s, %s *_%s" (Syntax.length_name s) (c_type (Syntax.nameof (Basic t))) s
-    | (FixedArray (t, _, _), s, _) -> fprintf h "%s *_%s" (c_type (Syntax.nameof (Basic t))) s
-    | (t, s, _) -> fprintf h "%s *_%s" (c_type (Syntax.nameof t)) s
+  let print_unused_param = fun unused ->
+    if unused then " __attribute__((unused))" else ""
 
-  let print_function_parameters h = function
+  let print_fun_param ?(unused=false) h = function
+      (Array (t, _), s, _) -> fprintf h "uint8_t %s%s, %s *_%s%s" (Syntax.length_name s) (print_unused_param unused) (c_type (Syntax.nameof (Basic t))) s (print_unused_param unused)
+    | (FixedArray (t, _, _), s, _) -> fprintf h "%s *_%s%s" (c_type (Syntax.nameof (Basic t))) s (print_unused_param unused)
+    | (t, s, _) -> fprintf h "%s *_%s%s" (c_type (Syntax.nameof t)) s (print_unused_param unused)
+
+  let print_function_parameters ?(unused=false) h = function
       [] -> ()
     | f::fields ->
       fprintf h ", ";
-      print_fun_param h f;
-      List.iter (fun f -> fprintf h ", "; print_fun_param h f) fields
+      print_fun_param ~unused h f;
+      List.iter (fun f -> fprintf h ", "; print_fun_param ~unused h f) fields
 
   let rec size_fields = fun fields size ->
     match fields with
@@ -222,8 +225,8 @@ module Gen_onboard = struct
     fprintf h "#define DOWNLINK_SEND_%s(_trans, _dev" s;
     print_macro_parameters h fields;
     fprintf h ") {}\n";
-    fprintf h "void pprz_msg_send_%s(struct transport_tx *trans, struct link_device *dev, uint8_t ac_id" s;
-    print_function_parameters h fields;
+    fprintf h "static inline void pprz_msg_send_%s(struct transport_tx *trans __attribute__((unused)), struct link_device *dev __attribute__((unused)), uint8_t ac_id __attribute__((unused))" s;
+    print_function_parameters ~unused:true h fields;
     fprintf h ") {}\n"
 
   (** Prints the messages ids *)
@@ -370,7 +373,7 @@ let () =
 
     (** Macros for airborne downlink (sending) *)
     if class_name = "telemetry" then begin (** FIXME *)
-      Printf.fprintf h "#ifdef DOWNLINK\n"
+      Printf.fprintf h "#if DOWNLINK\n"
     end;
     Gen_onboard.print_downlink_macros h class_name messages;
     if class_name = "telemetry" then begin