param: add 'param touch <param_name>' command

so that params can be marked as used from scripts.

src/systemcmds/param/param.cpp

@@ -87,6 +87,7 @@ static void	do_show_print(void *arg, param_t param);
 static int	do_set(const char *name, const char *val, bool fail_on_not_found);
 static int	do_compare(const char *name, char *vals[], unsigned comparisons, enum COMPARE_OPERATOR cmd_op);
 static int 	do_reset(const char *excludes[], int num_excludes);
+static int 	do_touch(const char *params[], int num_params);
 static int	do_reset_nostart(const char *excludes[], int num_excludes);
 static int	do_find(const char *name);
 
@@ -140,6 +141,9 @@ $ reboot
 					 "Compare a param with a value. Command will succeed if param is greater than the value");
 	PRINT_MODULE_USAGE_ARG("<param_name> <value>", "Parameter name and value to compare", false);
 
+	PRINT_MODULE_USAGE_COMMAND_DESCR("touch", "Mark a parameter as used");
+	PRINT_MODULE_USAGE_ARG("<param_name1> [<param_name2>]", "Parameter name (one or more)", true);
+
 	PRINT_MODULE_USAGE_COMMAND_DESCR("reset", "Reset params to default");
 	PRINT_MODULE_USAGE_ARG("<exclude1> [<exclude2>]", "Do not reset matching params (wildcard at end allowed)", true);
 	PRINT_MODULE_USAGE_COMMAND_DESCR("reset_nostart",
@@ -275,6 +279,15 @@ param_main(int argc, char *argv[])
 			}
 		}
 
+		if (!strcmp(argv[1], "touch")) {
+			if (argc >= 3) {
+				return do_touch((const char **) &argv[2], argc - 2);
+			} else {
+				PX4_ERR("not enough arguments.");
+				return 1;
+			}
+		}
+
 		if (!strcmp(argv[1], "reset_nostart")) {
 			if (argc >= 3) {
 				return do_reset_nostart((const char **) &argv[2], argc - 2);
@@ -759,6 +772,17 @@ do_reset(const char *excludes[], int num_excludes)
 	return 0;
 }
 
+static int
+do_touch(const char *params[], int num_params)
+{
+	for (int i = 0; i < num_params; ++i) {
+		if (param_find(params[i]) == PARAM_INVALID) {
+			PX4_ERR("param %s not found", params[i]);
+		}
+	}
+	return 0;
+}
+
 static int
 do_reset_nostart(const char *excludes[], int num_excludes)
 {