feat(split): add split transport changed event

app/CMakeLists.txt

@@ -96,6 +96,7 @@ target_sources_ifdef(CONFIG_ZMK_BATTERY_REPORTING app PRIVATE src/battery.c)
 target_sources_ifdef(CONFIG_ZMK_HID_INDICATORS app PRIVATE src/events/hid_indicators_changed.c)
 
 target_sources_ifdef(CONFIG_ZMK_SPLIT app PRIVATE src/events/split_peripheral_status_changed.c)
+target_sources_ifdef(CONFIG_ZMK_SPLIT app PRIVATE src/events/split_transport_changed.c)
 add_subdirectory_ifdef(CONFIG_ZMK_SPLIT src/split)
 
 target_sources_ifdef(CONFIG_USB_DEVICE_STACK app PRIVATE src/usb.c)

app/include/zmk/events/split_transport_changed.h

@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) 2025 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#pragma once
+
+#include <zephyr/kernel.h>
+#include <zmk/event_manager.h>
+#include <zmk/split/transport/types.h>
+
+struct zmk_split_transport_changed {
+    uint32_t addr;
+    struct zmk_split_transport_status status;
+};
+
+ZMK_EVENT_DECLARE(zmk_split_transport_changed)

app/include/zmk/split/central.h

@@ -46,3 +46,5 @@ int zmk_split_central_update_hid_indicator(zmk_hid_indicators_t indicators);
 int zmk_split_central_get_peripheral_battery_level(uint8_t source, uint8_t *level);
 
 #endif // IS_ENABLED(CONFIG_ZMK_SPLIT_BLE_CENTRAL_BATTERY_LEVEL_FETCHING)
+
+bool zmk_split_transport_get_available(uint32_t addr);

app/include/zmk/split/peripheral.h

@@ -9,3 +9,5 @@
 #include <zmk/split/transport/types.h>
 
 int zmk_split_peripheral_report_event(const struct zmk_split_transport_peripheral_event *event);
+
+bool zmk_split_transport_get_available(uint32_t addr);

app/src/events/split_transport_changed.c

@@ -0,0 +1,10 @@
+/*
+ * Copyright (c) 2025 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <zephyr/kernel.h>
+#include <zmk/events/split_transport_changed.h>
+
+ZMK_EVENT_IMPL(zmk_split_transport_changed);

app/src/split/central.c

@@ -19,6 +19,8 @@
 #include <zmk/events/position_state_changed.h>
 #include <zmk/events/sensor_event.h>
 
+#include <zmk/events/split_transport_changed.h>
+
 LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
 
 const struct zmk_split_transport_central *active_transport;
@@ -198,6 +200,8 @@ static int select_first_available_transport(void) {
 
 static int transport_status_changed_cb(const struct zmk_split_transport_central *central,
                                        struct zmk_split_transport_status status) {
+    raise_zmk_split_transport_changed(
+        (struct zmk_split_transport_changed){.addr = (uint32_t)central, .status = status});
     if (central == active_transport) {
         LOG_DBG("Central at %p changed status: enabled %d, available %d, connections %d", central,
                 status.enabled, status.available, status.connections);
@@ -212,6 +216,16 @@ static int transport_status_changed_cb(const struct zmk_split_transport_central
     return 0;
 }
 
+bool zmk_split_transport_get_available(uint32_t addr) {
+    STRUCT_SECTION_FOREACH(zmk_split_transport_central, t) {
+        if ((uint32_t)t == addr) {
+            return t->api->get_status().available;
+        }
+    }
+
+    return 0;
+}
+
 static int central_init(void) {
     STRUCT_SECTION_FOREACH(zmk_split_transport_central, t) {
         if (!t->api->set_status_callback) {

app/src/split/peripheral.c

@@ -18,6 +18,8 @@
 #include <zmk/events/sensor_event.h>
 #include <zmk/events/battery_state_changed.h>
 
+#include <zmk/events/split_transport_changed.h>
+
 #if IS_ENABLED(CONFIG_ZMK_SPLIT_PERIPHERAL_HID_INDICATORS)
 #include <zmk/events/hid_indicators_changed.h>
 #endif
@@ -115,6 +117,8 @@ static int select_first_available_transport(void) {
 
 static int transport_status_changed_cb(const struct zmk_split_transport_peripheral *p,
                                        struct zmk_split_transport_status status) {
+    raise_zmk_split_transport_changed(
+        (struct zmk_split_transport_changed){.addr = (uint32_t)p, .status = status});
     if (p == active_transport) {
         LOG_DBG("Peripheral at %p changed status: enabled %d, available %d, connections %d", p,
                 status.enabled, status.available, status.connections);
@@ -130,6 +134,16 @@ static int transport_status_changed_cb(const struct zmk_split_transport_peripher
     return 0;
 }
 
+bool zmk_split_transport_get_available(uint32_t addr) {
+    STRUCT_SECTION_FOREACH(zmk_split_transport_peripheral, t) {
+        if ((uint32_t)t == addr) {
+            return t->api->get_status().available;
+        }
+    }
+
+    return 0;
+}
+
 static int peripheral_init(void) {
     STRUCT_SECTION_FOREACH(zmk_split_transport_peripheral, t) {
         if (!t->api->set_status_callback) {