feat: LED indicators on peripheral side

app/include/zmk/split/bluetooth/central.h

@@ -3,6 +3,9 @@
 
 #include <zephyr/bluetooth/addr.h>
 #include <zmk/behavior.h>
+#include <zmk/hid_indicators_types.h>
 
 int zmk_split_bt_invoke_behavior(uint8_t source, struct zmk_behavior_binding *binding,
-                                 struct zmk_behavior_binding_event event, bool state);
+                                 struct zmk_behavior_binding_event event, bool state);
+
+int zmk_split_bt_update_hid_indicator(zmk_hid_indicators indicators);

app/include/zmk/split/bluetooth/uuid.h

@@ -17,3 +17,4 @@
 #define ZMK_SPLIT_BT_CHAR_POSITION_STATE_UUID ZMK_BT_SPLIT_UUID(0x00000001)
 #define ZMK_SPLIT_BT_CHAR_RUN_BEHAVIOR_UUID ZMK_BT_SPLIT_UUID(0x00000002)
 #define ZMK_SPLIT_BT_CHAR_SENSOR_STATE_UUID ZMK_BT_SPLIT_UUID(0x00000003)
+#define ZMK_SPLIT_BT_UPDATE_HID_INDICATORS_UUID ZMK_BT_SPLIT_UUID(0x00000004)

app/src/hid_indicators.c

@@ -28,8 +28,14 @@ zmk_hid_indicators zmk_hid_indicators_get_profile(struct zmk_endpoint_instance e
 }
 
 static void raise_led_changed_event(struct k_work *_work) {
-    ZMK_EVENT_RAISE(new_zmk_hid_indicators_changed((struct zmk_hid_indicators_changed){
-        .indicators = zmk_hid_indicators_get_current_profile()}));
+    zmk_hid_indicators indicators = zmk_hid_indicators_get_current_profile();
+
+    ZMK_EVENT_RAISE(new_zmk_hid_indicators_changed(
+        (struct zmk_hid_indicators_changed){.indicators = indicators}));
+
+#if IS_ENABLED(CONFIG_ZMK_SPLIT) && IS_ENABLED(CONFIG_ZMK_BLE)
+    zmk_split_bt_update_hid_indicator(indicators);
+#endif
 }
 
 static K_WORK_DEFINE(led_changed_work, raise_led_changed_event);

app/src/split/bluetooth/central.c

@@ -27,6 +27,7 @@ LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
 #include <zmk/event_manager.h>
 #include <zmk/events/position_state_changed.h>
 #include <zmk/events/sensor_event.h>
+#include <zmk/hid_indicators_types.h>
 
 static int start_scanning(void);
 
@@ -46,6 +47,7 @@ struct peripheral_slot {
     struct bt_gatt_subscribe_params sensor_subscribe_params;
     struct bt_gatt_discover_params sub_discover_params;
     uint16_t run_behavior_handle;
+    uint16_t update_hid_indicators;
     uint8_t position_state[POSITION_STATE_DATA_LEN];
     uint8_t changed_positions[POSITION_STATE_DATA_LEN];
 };
@@ -131,6 +133,7 @@ int release_peripheral_slot(int index) {
     // Clean up previously discovered handles;
     slot->subscribe_params.value_handle = 0;
     slot->run_behavior_handle = 0;
+    slot->update_hid_indicators = 0;
 
     return 0;
 }
@@ -329,9 +332,14 @@ static uint8_t split_central_chrc_discovery_func(struct bt_conn *conn,
         slot->discover_params.uuid = NULL;
         slot->discover_params.start_handle = attr->handle + 2;
         slot->run_behavior_handle = bt_gatt_attr_value_handle(attr);
+    } else if (!bt_uuid_cmp(((struct bt_gatt_chrc *)attr->user_data)->uuid,
+                            BT_UUID_DECLARE_128(ZMK_SPLIT_BT_UPDATE_HID_INDICATORS_UUID))) {
+        LOG_DBG("Found update HID indicators handle");
+        slot->update_hid_indicators = bt_gatt_attr_value_handle(attr);
     }
 
-    bool subscribed = slot->run_behavior_handle && slot->subscribe_params.value_handle;
+    bool subscribed = (slot->run_behavior_handle && slot->subscribe_params.value_handle &&
+                       slot->update_hid_indicators);
 #if ZMK_KEYMAP_HAS_SENSORS
     subscribed = subscribed && slot->sensor_subscribe_params.value_handle;
 #endif /* ZMK_KEYMAP_HAS_SENSORS */
@@ -685,6 +693,32 @@ int zmk_split_bt_invoke_behavior(uint8_t source, struct zmk_behavior_binding *bi
     return split_bt_invoke_behavior_payload(wrapper);
 }
 
+static zmk_hid_indicators hid_indicators = 0;
+
+static void split_central_update_indicators_callback(struct k_work *work) {
+    zmk_hid_indicators indicators = hid_indicators;
+    for (int i = 0; i < ZMK_SPLIT_BLE_PERIPHERAL_COUNT; i++) {
+        if (peripherals[i].state != PERIPHERAL_SLOT_STATE_CONNECTED) {
+            continue;
+        }
+
+        int err = bt_gatt_write_without_response(peripherals[i].conn,
+                                                 peripherals[i].update_hid_indicators, &indicators,
+                                                 sizeof(indicators), true);
+
+        if (err) {
+            LOG_ERR("Failed to write HID indicator characteristic (err %d)", err);
+        }
+    }
+}
+
+static K_WORK_DEFINE(split_central_update_indicators, split_central_update_indicators_callback);
+
+int zmk_split_bt_update_hid_indicator(zmk_hid_indicators indicators) {
+    hid_indicators = indicators;
+    return k_work_submit_to_queue(&split_central_split_run_q, &split_central_update_indicators);
+}
+
 int zmk_split_bt_central_init(const struct device *_arg) {
     k_work_queue_start(&split_central_split_run_q, split_central_split_run_q_stack,
                        K_THREAD_STACK_SIZEOF(split_central_split_run_q_stack),

app/src/split/bluetooth/service.c

@@ -21,6 +21,7 @@ LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
 #include <zmk/matrix.h>
 #include <zmk/split/bluetooth/uuid.h>
 #include <zmk/split/bluetooth/service.h>
+#include <zmk/events/hid_indicators_changed.h>
 #include <zmk/events/sensor_event.h>
 #include <zmk/sensors.h>
 
@@ -105,6 +106,29 @@ static void split_svc_pos_state_ccc(const struct bt_gatt_attr *attr, uint16_t va
     LOG_DBG("value %d", value);
 }
 
+static zmk_hid_indicators hid_indicators = 0;
+
+static void split_svc_update_indicators_callback(struct k_work *work) {
+    ZMK_EVENT_RAISE(new_zmk_hid_indicators_changed(
+        (struct zmk_hid_indicators_changed){.indicators = hid_indicators}));
+}
+
+static K_WORK_DEFINE(split_svc_update_indicators_work, split_svc_update_indicators_callback);
+
+static ssize_t split_svc_update_indicators(struct bt_conn *conn, const struct bt_gatt_attr *attr,
+                                           const void *buf, uint16_t len, uint16_t offset,
+                                           uint8_t flags) {
+    if (offset + len > sizeof(zmk_hid_indicators)) {
+        return BT_GATT_ERR(BT_ATT_ERR_INVALID_OFFSET);
+    }
+
+    memcpy((uint8_t *)&hid_indicators + offset, buf, len);
+
+    k_work_submit(&split_svc_update_indicators_work);
+
+    return len;
+}
+
 BT_GATT_SERVICE_DEFINE(
     split_svc, BT_GATT_PRIMARY_SERVICE(BT_UUID_DECLARE_128(ZMK_SPLIT_BT_SERVICE_UUID)),
     BT_GATT_CHARACTERISTIC(BT_UUID_DECLARE_128(ZMK_SPLIT_BT_CHAR_POSITION_STATE_UUID),
@@ -114,6 +138,9 @@ BT_GATT_SERVICE_DEFINE(
     BT_GATT_CHARACTERISTIC(BT_UUID_DECLARE_128(ZMK_SPLIT_BT_CHAR_RUN_BEHAVIOR_UUID),
                            BT_GATT_CHRC_WRITE_WITHOUT_RESP, BT_GATT_PERM_WRITE_ENCRYPT, NULL,
                            split_svc_run_behavior, &behavior_run_payload),
+    BT_GATT_CHARACTERISTIC(BT_UUID_DECLARE_128(ZMK_SPLIT_BT_UPDATE_HID_INDICATORS_UUID),
+                           BT_GATT_CHRC_WRITE_WITHOUT_RESP, BT_GATT_PERM_WRITE_ENCRYPT, NULL,
+                           split_svc_update_indicators, NULL),
     BT_GATT_DESCRIPTOR(BT_UUID_NUM_OF_DIGITALS, BT_GATT_PERM_READ, split_svc_num_of_positions, NULL,
                        &num_of_positions),
 #if ZMK_KEYMAP_HAS_SENSORS