Include the serial number in the Bluetooth device name

app/Kconfig

@@ -222,6 +222,16 @@ config ZMK_BLE_MOUSE_REPORT_QUEUE_SIZE
 config ZMK_BLE_CLEAR_BONDS_ON_START
     bool "Configuration that clears all bond information from the keyboard on startup."
 
+config ZMK_BLE_DEVICE_NAME_APPEND_SN
+    bool "Append the device serial number to the Bluetooth device name"
+    default n
+    select BT_DEVICE_NAME_DYNAMIC
+
+config ZMK_BLE_DEVICE_NAME_SN_CHARS
+    int "Number of hexadecimal digits of serial number to append to the BT device name"
+    default 6
+    depends on ZMK_BLE_DEVICE_NAME_APPEND_SN
+
 # HID GATT notifications sent this way are *not* picked up by Linux, and possibly others.
 config BT_GATT_NOTIFY_MULTIPLE
     default n

app/boards/arm/glove80/glove80_lh_defconfig

@@ -16,6 +16,8 @@ CONFIG_USB_DEVICE_VID=0x16c0
 CONFIG_USB_DEVICE_MANUFACTURER="MoErgo"
 CONFIG_USB_DEVICE_SN="moergo.com:GLV80-0123456789ABCDEF"
 
+CONFIG_BT_DEVICE_NAME="Glove80"
+
 CONFIG_BT_DIS_PNP_PID=0x27db
 CONFIG_BT_DIS_PNP_VID=0x16c0
 CONFIG_BT_DIS_MANUF="MoErgo"

app/boards/arm/glove80/usb_serial_number.c

@@ -14,14 +14,15 @@
 LOG_MODULE_DECLARE(usb_descriptor);
 
 int base16_encode(const uint8_t *data, int length, uint8_t *result, int bufSize);
+void fill_serial_number(char *buf, int length);
 
+/**
+ * nrf52840 hwinfo returns a 64-bit hardware id. Glove80 uses this as a
+ * serial number, encoded as base16 into the last 16 characters of the
+ * CONFIG_USB_DEVICE_SN template. If insufficient template space is
+ * available, instead return the static serial number string.
+ */
 uint8_t *usb_update_sn_string_descriptor(void) {
-    /*
-     * nrf52840 hwinfo returns a 64-bit hardware id. Glove80 uses this as a
-     * serial number, encoded as base16 into the last 16 characters of the
-     * CONFIG_USB_DEVICE_SN template. If insufficient template space is
-     * available, instead return the static serial number string.
-     */
     const uint8_t template_len = sizeof(CONFIG_USB_DEVICE_SN);
     const uint8_t sn_len = 16;
 
@@ -33,17 +34,25 @@ uint8_t *usb_update_sn_string_descriptor(void) {
     static uint8_t serial[sizeof(CONFIG_USB_DEVICE_SN)];
     strncpy(serial, CONFIG_USB_DEVICE_SN, template_len);
 
+    const uint8_t offset = template_len - sn_len - 1;
+    fill_serial_number(serial + offset, sn_len);
+    serial[template_len - 1] = '\0';
+
+    return serial;
+}
+
+/**
+ * Writes the first `length` bytes of the device serial number into buf
+ */
+void fill_serial_number(char *buf, int length) {
     uint8_t hwid[8];
     memset(hwid, 0, sizeof(hwid));
     uint8_t hwlen = hwinfo_get_device_id(hwid, sizeof(hwid));
 
     if (hwlen > 0) {
-        const uint8_t offset = template_len - sn_len - 1;
-        LOG_HEXDUMP_DBG(&hwid, sn_len, "Serial Number");
-        base16_encode(hwid, hwlen, serial + offset, sn_len + 1);
+        LOG_HEXDUMP_DBG(&hwid, 16, "Serial Number");
+        base16_encode(hwid, hwlen, buf, length);
     }
-
-    return serial;
 }
 
 int base16_encode(const uint8_t *data, int length, uint8_t *result, int bufSize) {

app/src/ble.c

@@ -62,9 +62,32 @@ enum advertising_type {
 static struct zmk_ble_profile profiles[ZMK_BLE_PROFILE_COUNT];
 static uint8_t active_profile;
 
+#if IS_ENABLED(CONFIG_ZMK_BLE_DEVICE_NAME_APPEND_SN)
+
+static char bt_device_name[sizeof(CONFIG_BT_DEVICE_NAME) + CONFIG_ZMK_BLE_DEVICE_NAME_SN_CHARS + 1];
+
+void fill_serial_number(char *buf, int length);
+
+// configure the BT device name by appending a serial number prefix to
+// CONFIG_BT_DEVICE_NAME
+void init_bt_device_name(void) {
+    strncpy(bt_device_name, CONFIG_BT_DEVICE_NAME, sizeof(bt_device_name));
+    bt_device_name[sizeof(CONFIG_BT_DEVICE_NAME) - 1] = ' ';
+    fill_serial_number(&bt_device_name[sizeof(CONFIG_BT_DEVICE_NAME)],
+                       CONFIG_ZMK_BLE_DEVICE_NAME_SN_CHARS);
+    bt_device_name[sizeof(bt_device_name) - 1] = '\0';
+}
+
+#define DEVICE_NAME bt_device_name
+#define DEVICE_NAME_LEN (sizeof(bt_device_name) - 1)
+
+#else
+
 #define DEVICE_NAME CONFIG_BT_DEVICE_NAME
 #define DEVICE_NAME_LEN (sizeof(DEVICE_NAME) - 1)
 
+#endif
+
 BUILD_ASSERT(DEVICE_NAME_LEN <= 16, "ERROR: BLE device name is too long. Max length: 16");
 
 static const struct bt_data zmk_ble_ad[] = {
@@ -662,6 +685,10 @@ static void zmk_ble_ready(int err) {
 }
 
 static int zmk_ble_init(void) {
+#if IS_ENABLED(CONFIG_ZMK_BLE_DEVICE_NAME_APPEND_SN)
+    init_bt_device_name();
+#endif
+
     int err = bt_enable(NULL);
 
     if (err) {
@@ -682,7 +709,12 @@ static int zmk_ble_init(void) {
 
     settings_load_subtree("ble");
     settings_load_subtree("bt");
+#endif
 
+#if IS_ENABLED(CONFIG_ZMK_BLE_DEVICE_NAME_APPEND_SN)
+    if (strcmp(bt_get_name(), bt_device_name) != 0) {
+        bt_set_name(bt_device_name);
+    }
 #endif
 
 #if IS_ENABLED(CONFIG_ZMK_BLE_CLEAR_BONDS_ON_START)