fix(ble): enforce maximum length for dynamic device name (#2784)

Author: xudongzheng

app/Kconfig

@@ -238,6 +238,11 @@ config BT_PERIPHERAL_PREF_LATENCY
 config BT_PERIPHERAL_PREF_TIMEOUT
     default 400
 
+# The device name should be 16 characters or less so it fits within the
+# advertising data.
+config BT_DEVICE_NAME_MAX
+    default 16
+
 endif # ZMK_BLE
 
 endmenu # Output Types

app/src/ble.c

@@ -66,7 +66,9 @@ static uint8_t active_profile;
 #define DEVICE_NAME CONFIG_BT_DEVICE_NAME
 #define DEVICE_NAME_LEN (sizeof(DEVICE_NAME) - 1)
 
-BUILD_ASSERT(DEVICE_NAME_LEN <= 16, "ERROR: BLE device name is too long. Max length: 16");
+BUILD_ASSERT(
+    DEVICE_NAME_LEN <= CONFIG_BT_DEVICE_NAME_MAX,
+    "ERROR: BLE device name is too long. Max length: " STRINGIFY(CONFIG_BT_DEVICE_NAME_MAX));
 
 static struct bt_data zmk_ble_ad[] = {
     BT_DATA_BYTES(BT_DATA_GAP_APPEARANCE, 0xC1, 0x03),