parameters: add param dump to read and decode bson to console

src/lib/parameters/param.h

@@ -349,6 +349,17 @@ __EXPORT int		param_import(int fd, bool mark_saved);
  */
 __EXPORT int		param_load(int fd);
 
+/**
+ * Read saved parameters from file and dump to console.
+ *
+ * This function reads the file and dumps all contents to console
+ * values from a file.
+ *
+ * @param fd		File descriptor to read from.
+ * @return		Zero on success, nonzero if an error occurred during import.
+ */
+__EXPORT int		param_dump(int fd);
+
 /**
  * Apply a function to each parameter.
  *

src/lib/parameters/parameters.cpp

@@ -1405,6 +1405,38 @@ out:
 	return result;
 }
 
+static int
+param_dump_callback(bson_decoder_t decoder, void *priv, bson_node_t node)
+{
+	switch (node->type) {
+	case BSON_EOO:
+		PX4_INFO_RAW("BSON_EOO\n");
+		return 0;
+
+	case BSON_DOUBLE:
+		PX4_INFO_RAW("BSON_DOUBLE: %s = %.6f\n", node->name, node->d);
+		return 1;
+
+	case BSON_BOOL:
+		PX4_INFO_RAW("BSON_BOOL:   %s = %d\n", node->name, node->b);
+		return 1;
+
+	case BSON_INT32:
+		PX4_INFO_RAW("BSON_INT32:  %s = %" PRIi32 "\n", node->name, node->i32);
+		return 1;
+
+	case BSON_INT64:
+		PX4_INFO_RAW("BSON_INT64:  %s = %" PRIi64 "\n", node->name, node->i64);
+		return 1;
+
+	default:
+		PX4_INFO_RAW("ERROR %s unhandled bson type %d\n", node->name, node->type);
+		return 1; // just skip this entry
+	}
+
+	return -1;
+}
+
 static int
 param_import_internal(int fd, bool mark_saved)
 {
@@ -1468,6 +1500,43 @@ param_load(int fd)
 	return param_import_internal(fd, true);
 }
 
+int
+param_dump(int fd)
+{
+	bson_decoder_s decoder{};
+	param_import_state state;
+
+	if (bson_decoder_init_file(&decoder, fd, param_dump_callback, &state) == 0) {
+		PX4_INFO_RAW("BSON document size %" PRId32 "\n", decoder.total_document_size);
+
+		int result = -1;
+
+		do {
+			result = bson_decoder_next(&decoder);
+
+		} while (result > 0);
+
+		if (result == 0) {
+			PX4_INFO_RAW("BSON decoded %" PRId32 " bytes (double:%" PRIu16 ", string:%" PRIu16 ", bin:%" PRIu16 ", bool:%" PRIu16
+				     ", int32:%" PRIu16 ", int64:%" PRIu16 ")\n",
+				     decoder.total_decoded_size,
+				     decoder.count_node_double, decoder.count_node_string, decoder.count_node_bindata, decoder.count_node_bool,
+				     decoder.count_node_int32, decoder.count_node_int64);
+
+			return 0;
+
+		} else if (result == -ENODATA) {
+			PX4_WARN("BSON: no data");
+			return 0;
+
+		} else {
+			PX4_ERR("param dump failed (%d)", result);
+		}
+	}
+
+	return -1;
+}
+
 void
 param_foreach(void (*func)(void *arg, param_t param), void *arg, bool only_changed, bool only_used)
 {

src/systemcmds/param/param.cpp

@@ -83,6 +83,7 @@ enum class COMPARE_ERROR_LEVEL {
 
 static int 	do_save(const char *param_file_name);
 static int	do_save_default();
+static int 	do_dump(const char *param_file_name);
 static int 	do_load(const char *param_file_name);
 static int	do_import(const char *param_file_name = nullptr);
 static int	do_show(const char *search_string, bool only_changed);
@@ -135,6 +136,8 @@ $ reboot
 	PRINT_MODULE_USAGE_ARG("<file>", "File name (use default if not given)", true);
 	PRINT_MODULE_USAGE_COMMAND_DESCR("save", "Save params to a file");
 	PRINT_MODULE_USAGE_ARG("<file>", "File name (use default if not given)", true);
+	PRINT_MODULE_USAGE_COMMAND_DESCR("dump", "Dump params from a file");
+	PRINT_MODULE_USAGE_ARG("<file>", "File name (use default if not given)", true);
 
 	PRINT_MODULE_USAGE_COMMAND_DESCR("select", "Select default file");
 	PRINT_MODULE_USAGE_ARG("<file>", "File name (use <root>/eeprom/parameters if not given)", true);
@@ -206,6 +209,15 @@ param_main(int argc, char *argv[])
 			}
 		}
 
+		if (!strcmp(argv[1], "dump")) {
+			if (argc >= 3) {
+				return do_dump(argv[2]);
+
+			} else {
+				return do_dump(param_get_default_file());
+			}
+		}
+
 		if (!strcmp(argv[1], "load")) {
 			if (argc >= 3) {
 				return do_load(argv[2]);
@@ -423,6 +435,43 @@ do_save(const char *param_file_name)
 	return 0;
 }
 
+static int
+do_dump(const char *param_file_name)
+{
+	int fd = -1;
+
+	if (param_file_name) { // passing NULL means to select the flash storage
+
+		fd = open(param_file_name, O_RDONLY);
+
+		if (fd < 0) {
+			PX4_ERR("open '%s' failed (%i)", param_file_name, errno);
+			return 1;
+		} else {
+			PX4_INFO_RAW("[param] reading from %s\n\n", param_file_name);
+		}
+	}
+
+	int result = param_dump(fd);
+
+	if (fd >= 0) {
+		close(fd);
+	}
+
+	if (result < 0) {
+		if (param_file_name) {
+			PX4_ERR("reading from '%s' failed (%i)", param_file_name, result);
+
+		} else {
+			PX4_ERR("reading failed (%i)", result);
+		}
+
+		return 1;
+	}
+
+	return 0;
+}
+
 static int
 do_load(const char *param_file_name)
 {