net: lwm2m: add send scheduler helper objects

Introduce the optional OMA 10523/10524 send scheduler extension to manage
cached resources, including control and sampling rule objects, cache filter with
gt/lt/st and pmin/pmax handling, max-age/max-sample limits, and registration
flush helper.

Signed-off-by: Julien Vermillard <[email protected]>

Author: Julien Vermillard

include/zephyr/net/lwm2m_send_scheduler.h

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2025 Clunky Machines
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef ZEPHYR_NET_LWM2M_SEND_SCHEDULER_H_
+#define ZEPHYR_NET_LWM2M_SEND_SCHEDULER_H_
+
+#include <stdbool.h>
+#include <zephyr/net/lwm2m.h>
+
+/**
+ * @brief Register the send scheduler LwM2M objects and initialise state.
+ *
+ * This installs the Scheduler Control (10523) and Sampling Rules (10524)
+ * objects and prepares bookkeeping needed by the cache filter helpers.
+ */
+int lwm2m_send_sched_init(void);
+
+/**
+ * @brief Cache filter that enforces the configured scheduler rules.
+ *
+ * Hook this up via @ref lwm2m_set_cache_filter for each cached resource you
+ * want the scheduler to control.
+ */
+bool lwm2m_send_sched_cache_filter(const struct lwm2m_obj_path *path,
+				   const struct lwm2m_time_series_elem *element);
+
+/**
+ * @brief Handle a registration or registration-update completion event.
+ *
+ * Applications should call this when their LwM2M RD client reports a successful
+ * registration or registration update so the send scheduler can apply its
+ * flush-on-update policy.
+ */
+void lwm2m_send_sched_handle_registration_event(void);
+
+#endif /* ZEPHYR_NET_LWM2M_SEND_SCHEDULER_H_ */

subsys/net/lib/lwm2m/CMakeLists.txt

@@ -35,6 +35,10 @@ zephyr_library_sources_ifdef(CONFIG_LWM2M_FIRMWARE_UPDATE_PULL_SUPPORT
     lwm2m_obj_firmware_pull.c
     lwm2m_pull_context.c
     )
+zephyr_library_sources_ifdef(CONFIG_LWM2M_SEND_SCHEDULER
+    send_scheduler/send_scheduler_core.c
+    send_scheduler/send_scheduler_lwm2m.c
+    )
 zephyr_library_sources_ifdef(CONFIG_LWM2M_LOCATION_OBJ_SUPPORT
     lwm2m_obj_location.c
     )

subsys/net/lib/lwm2m/Kconfig

@@ -253,6 +253,24 @@ endchoice
 
 endif # LWM2M_RESOURCE_DATA_CACHE_SUPPORT
 
+config LWM2M_SEND_SCHEDULER
+	bool "LwM2M send scheduler helper objects (10523/10524)"
+	depends on LWM2M_VERSION_1_1
+	depends on LWM2M_RESOURCE_DATA_CACHE_SUPPORT
+	select CBPRINTF_FP_SUPPORT
+	help
+	  Enable the optional send scheduler extension which exposes vendor
+	  objects to configure sampling rules, buffer limits, and SEND trigger
+	  policies on top of cached resources. Requires LwM2M 1.1 SEND support
+	  and resource data caching.
+
+if LWM2M_SEND_SCHEDULER
+module = LWM2M_SEND_SCHEDULER
+module-str = Log level for LwM2M send scheduler helper
+module-dep = LOG
+source "subsys/net/Kconfig.template.log_config.net"
+endif # LWM2M_SEND_SCHEDULER
+
 endmenu # "Engine features"
 
 menu "Memory and buffer size configuration"