param subsystem: Only send the instantiated parameters via telemetry

src/modules/mavlink/mavlink_parameters.cpp

@@ -94,7 +94,7 @@ MavlinkParametersManager::handle_message(const mavlink_message_t *msg)
 					/* enforce null termination */
 					name[MAVLINK_MSG_PARAM_VALUE_FIELD_PARAM_ID_LEN] = '\0';
 					/* attempt to find parameter, set and send it */
-					param_t param = param_find(name);
+					param_t param = param_find_no_notification(name);
 
 					if (param == PARAM_INVALID) {
 						char buf[MAVLINK_MSG_STATUSTEXT_FIELD_TEXT_LEN];
@@ -127,7 +127,7 @@ MavlinkParametersManager::handle_message(const mavlink_message_t *msg)
 					/* enforce null termination */
 					name[MAVLINK_MSG_PARAM_VALUE_FIELD_PARAM_ID_LEN] = '\0';
 					/* attempt to find parameter and send it */
-					send_param(param_find(name));
+					send_param(param_find_no_notification(name));
 
 				} else {
 					/* when index is >= 0, send this parameter again */

src/modules/systemlib/param/param.c

@@ -91,6 +91,9 @@ struct param_wbuf_s {
 	bool			unsaved;
 };
 
+// XXX this should be param_info_count, but need to work out linking
+uint8_t param_changed_storage[(600 / sizeof(uint8_t)) + 1] = {};
+
 /** flexible array holding modified parameter values */
 UT_array	*param_values;
 
@@ -103,6 +106,12 @@ ORB_DEFINE(parameter_update, struct parameter_update_s);
 /** parameter update topic handle */
 static orb_advert_t param_topic = -1;
 
+static bool param_used_internal(param_t param);
+
+static void param_set_used_internal(param_t param);
+
+static param_t param_find_internal(const char *name, bool notification);
+
 /** lock the parameter store */
 static void
 param_lock(void)
@@ -205,20 +214,36 @@ param_notify_changes(void)
 }
 
 param_t
-param_find(const char *name)
+param_find_internal(const char *name, bool notification)
 {
 	param_t param;
 
 	/* perform a linear search of the known parameters */
 	for (param = 0; handle_in_range(param); param++) {
-		if (!strcmp(param_info_base[param].name, name))
+		if (!strcmp(param_info_base[param].name, name)) {
+			if (notification) {
+				param_set_used_internal(param);
+			}
 			return param;
+		}
 	}
 
 	/* not found */
 	return PARAM_INVALID;
 }
 
+param_t
+param_find(const char *name)
+{
+	return param_find_internal(name, true);
+}
+
+param_t
+param_find_no_notification(const char *name)
+{
+	return param_find_internal(name, false);
+}
+
 unsigned
 param_count(void)
 {
@@ -430,6 +455,8 @@ param_set_internal(param_t param, const void *val, bool mark_saved, bool notify_
 	}
 
 out:
+	param_set_used_internal(param);
+
 	param_unlock();
 
 	/*
@@ -454,6 +481,28 @@ param_set_no_notification(param_t param, const void *val)
 	return param_set_internal(param, val, false, false);
 }
 
+bool param_used_internal(param_t param)
+{
+	int param_index = param_get_index(param);
+	if (param_index < 0) {
+		return false;
+	}
+
+	unsigned bitindex = param_index - (param_index / sizeof(param_changed_storage[0]));
+	return param_changed_storage[param_index / sizeof(param_changed_storage[0])] & (1 << bitindex);
+}
+
+void param_set_used_internal(param_t param)
+{
+	int param_index = param_get_index(param);
+	if (param_index < 0) {
+		return;
+	}
+
+	unsigned bitindex = param_index - (param_index / sizeof(param_changed_storage[0]));
+	param_changed_storage[param_index / sizeof(param_changed_storage[0])] |= (1 << bitindex);
+}
+
 int
 param_reset(param_t param)
 {
@@ -717,7 +766,7 @@ param_import_callback(bson_decoder_t decoder, void *private, bson_node_t node)
 	 * Find the parameter this node represents.  If we don't know it,
 	 * ignore the node.
 	 */
-	param_t param = param_find(node->name);
+	param_t param = param_find_no_notification(node->name);
 
 	if (param == PARAM_INVALID) {
 		debug("ignoring unrecognised parameter '%s'", node->name);
@@ -843,15 +892,20 @@ param_load(int fd)
 }
 
 void
-param_foreach(void (*func)(void *arg, param_t param), void *arg, bool only_changed)
+param_foreach(void (*func)(void *arg, param_t param), void *arg, bool only_changed, bool only_used)
 {
 	param_t	param;
 
 	for (param = 0; handle_in_range(param); param++) {
 
 		/* if requested, skip unchanged values */
-		if (only_changed && (param_find_changed(param) == NULL))
+		if (only_changed && (param_find_changed(param) == NULL)) {
 			continue;
+		}
+
+		if (only_used && !param_used_internal(param)) {
+			continue;
+		}
 
 		func(arg, param);
 	}

src/modules/systemlib/param/param.h

@@ -87,9 +87,19 @@ typedef uintptr_t	param_t;
  *
  * @param name		The canonical name of the parameter being looked up.
  * @return		A handle to the parameter, or PARAM_INVALID if the parameter does not exist.
+ *			This call will also set the parameter as "used" in the system, which is used
+ *			to e.g. show the parameter via the RC interface
  */
 __EXPORT param_t	param_find(const char *name);
 
+/**
+ * Look up a parameter by name.
+ *
+ * @param name		The canonical name of the parameter being looked up.
+ * @return		A handle to the parameter, or PARAM_INVALID if the parameter does not exist.
+ */
+__EXPORT param_t	param_find_no_notification(const char *name);
+
 /**
  * Return the total number of parameters.
  *
@@ -254,8 +264,10 @@ __EXPORT int		param_load(int fd);
  * @param arg		Argument passed to the function.
  * @param only_changed	If true, the function is only called for parameters whose values have
  *			been changed from the default.
+ * @param only_changed	If true, the function is only called for parameters which have been
+ *			used in one of the running applications.
  */
-__EXPORT void		param_foreach(void (*func)(void *arg, param_t param), void *arg, bool only_changed);
+__EXPORT void		param_foreach(void (*func)(void *arg, param_t param), void *arg, bool only_changed, bool only_used);
 
 /**
  * Set the default parameter file name.

src/systemcmds/param/param.c

@@ -236,7 +236,7 @@ static void
 do_show(const char *search_string)
 {
 	printf(" + = saved, * = unsaved\n");
-	param_foreach(do_show_print, (char *)search_string, false);
+	param_foreach(do_show_print, (char *)search_string, false, false);
 
 	exit(0);
 }