param_export: add optional filter method

src/lib/parameters/flashparams/flashparams.cpp

@@ -76,7 +76,7 @@ struct param_wbuf_s {
 };
 
 static int
-param_export_internal(bool only_unsaved)
+param_export_internal(bool only_unsaved, param_filter_func filter)
 {
 	struct param_wbuf_s *s = nullptr;
 	struct bson_encoder_s encoder;
@@ -105,6 +105,10 @@ param_export_internal(bool only_unsaved)
 			continue;
 		}
 
+		if (filter && !filter(s->param)) {
+			continue;
+		}
+
 		s->unsaved = false;
 
 		/* append the appropriate BSON type object */
@@ -345,9 +349,9 @@ out:
 	return result;
 }
 
-int flash_param_save(bool only_unsaved)
+int flash_param_save(bool only_unsaved, param_filter_func filter)
 {
-	return param_export_internal(only_unsaved);
+	return param_export_internal(only_unsaved, filter);
 }
 
 int flash_param_load()

src/lib/parameters/flashparams/flashparams.h

@@ -63,7 +63,7 @@ __EXPORT int param_set_external(param_t param, const void *val, bool mark_saved,
 __EXPORT const void *param_get_value_ptr_external(param_t param);
 
 /* The interface hooks to the Flash based storage. The caller is responsible for locking */
-__EXPORT int flash_param_save(bool only_unsaved);
+__EXPORT int flash_param_save(bool only_unsaved, param_filter_func filter);
 __EXPORT int flash_param_load();
 __EXPORT int flash_param_import();
 

src/lib/parameters/param.h

@@ -278,6 +278,8 @@ __EXPORT void		param_reset_all(void);
  */
 __EXPORT void		param_reset_excludes(const char *excludes[], int num_excludes);
 
+typedef bool(*param_filter_func)(param_t handle);
+
 /**
  * Reset only specific parameters to their default values.
  *
@@ -294,9 +296,11 @@ __EXPORT void		param_reset_specific(const char *resets[], int num_resets);
  *
  * @param fd		File descriptor to export to (-1 selects the FLASH storage).
  * @param only_unsaved	Only export changed parameters that have not yet been exported.
+ * @param filter	Filter parameters to be exported. The method should return true if
+ * 			the parameter should be exported. No filtering if nullptr is passed.
  * @return		Zero on success, nonzero on failure.
  */
-__EXPORT int		param_export(int fd, bool only_unsaved);
+__EXPORT int		param_export(int fd, bool only_unsaved, param_filter_func filter);
 
 /**
  * Import parameters from a file, discarding any unrecognized parameters.

src/lib/parameters/parameters.cpp

@@ -71,7 +71,7 @@ using namespace time_literals;
 #include "flashparams/flashparams.h"
 static const char *param_default_file = nullptr; // nullptr means to store to FLASH
 #else
-inline static int flash_param_save(bool only_unsaved) { return -1; }
+inline static int flash_param_save(bool only_unsaved, param_filter_func filter) { return -1; }
 inline static int flash_param_load() { return -1; }
 inline static int flash_param_import() { return -1; }
 static const char *param_default_file = PX4_ROOTFSDIR"/eeprom/parameters";
@@ -948,7 +948,7 @@ int param_save_default()
 	if (!filename) {
 		perf_begin(param_export_perf);
 		param_lock_writer();
-		res = flash_param_save(false);
+		res = flash_param_save(false, nullptr);
 		param_unlock_writer();
 		perf_end(param_export_perf);
 		return res;
@@ -976,7 +976,7 @@ int param_save_default()
 	int attempts = 5;
 
 	while (res != OK && attempts > 0) {
-		res = param_export(fd, false);
+		res = param_export(fd, false, nullptr);
 		attempts--;
 
 		if (res != PX4_OK) {
@@ -1035,7 +1035,7 @@ param_load_default()
 }
 
 int
-param_export(int fd, bool only_unsaved)
+param_export(int fd, bool only_unsaved, param_filter_func filter)
 {
 	int	result = -1;
 	perf_begin(param_export_perf);
@@ -1043,7 +1043,7 @@ param_export(int fd, bool only_unsaved)
 	if (fd < 0) {
 		param_lock_writer();
 		// flash_param_save() will take the shutdown lock
-		result = flash_param_save(only_unsaved);
+		result = flash_param_save(only_unsaved, filter);
 		param_unlock_writer();
 		perf_end(param_export_perf);
 		return result;
@@ -1081,6 +1081,10 @@ param_export(int fd, bool only_unsaved)
 			continue;
 		}
 
+		if (filter && !filter(s->param)) {
+			continue;
+		}
+
 		s->unsaved = false;
 
 		const char *name = param_name(s->param);

src/lib/parameters/parameters_shmem.cpp

@@ -991,7 +991,7 @@ param_save_default()
 		goto do_exit;
 	}
 
-	res = param_export(fd, false);
+	res = param_export(fd, false, nullptr);
 
 	if (res != OK) {
 		PX4_ERR("failed to write parameters to file: %s", filename);
@@ -1088,7 +1088,7 @@ param_load_default_no_notify()
 }
 
 int
-param_export(int fd, bool only_unsaved)
+param_export(int fd, bool only_unsaved, param_filter_func filter)
 {
 	perf_begin(param_export_perf);
 
@@ -1129,6 +1129,10 @@ param_export(int fd, bool only_unsaved)
 			continue;
 		}
 
+		if (filter && !filter(s->param)) {
+			continue;
+		}
+
 		s->unsaved = false;
 
 		/* Make sure to get latest from shmem before saving. */

src/systemcmds/param/param.cpp

@@ -381,7 +381,7 @@ do_save(const char *param_file_name)
 		return 1;
 	}
 
-	int result = param_export(fd, false);
+	int result = param_export(fd, false, nullptr);
 	close(fd);
 
 	if (result < 0) {