extmod/modbluetooth: Add support for changing the GAP device name.

This commit allows the user to set/get the GAP device name used by service
0x1800, characteristic 0x2a00.  The usage is:

    BLE.config(gap_name="myname")
    print(BLE.config("gap_name"))

As part of this change the compile-time setting
MICROPY_PY_BLUETOOTH_DEFAULT_NAME is renamed to
MICROPY_PY_BLUETOOTH_DEFAULT_GAP_NAME to emphasise its link to GAP and this
new "gap_name" config value.  And the default value of this for the NimBLE
bindings is changed from "PYBD" to "MPY NIMBLE" to be more generic.

extmod/btstack/modbluetooth_btstack.c

@@ -37,10 +37,20 @@
 
 #define DEBUG_EVENT_printf(...) //printf(__VA_ARGS__)
 
+#ifndef MICROPY_PY_BLUETOOTH_DEFAULT_GAP_NAME
+#define MICROPY_PY_BLUETOOTH_DEFAULT_GAP_NAME "MPY BTSTACK"
+#endif
+
 // How long to wait for a controller to init/deinit.
 // Some controllers can take up to 5-6 seconds in normal operation.
 STATIC const uint32_t BTSTACK_INIT_DEINIT_TIMEOUT_MS = 15000;
 
+// We need to know the attribute handle for the GAP device name (see GAP_DEVICE_NAME_UUID)
+// so it can be put into the gatts_db before registering the services, and accessed
+// efficiently when requesting an attribute in att_read_callback.  Because this is the
+// first characteristic of the first service, it always has a handle value of 3.
+STATIC const uint16_t BTSTACK_GAP_DEVICE_NAME_HANDLE = 3;
+
 volatile int mp_bluetooth_btstack_state = MP_BLUETOOTH_BTSTACK_STATE_OFF;
 
 STATIC btstack_packet_callback_registration_t hci_event_callback_registration;
@@ -250,6 +260,12 @@ int mp_bluetooth_init(void) {
     MP_STATE_PORT(bluetooth_btstack_root_pointers) = m_new0(mp_bluetooth_btstack_root_pointers_t, 1);
     mp_bluetooth_gatts_db_create(&MP_STATE_PORT(bluetooth_btstack_root_pointers)->gatts_db);
 
+    // Set the default GAP device name.
+    const char *gap_name = MICROPY_PY_BLUETOOTH_DEFAULT_GAP_NAME;
+    size_t gap_len = strlen(gap_name);
+    mp_bluetooth_gatts_db_create_entry(MP_STATE_PORT(bluetooth_btstack_root_pointers)->gatts_db, BTSTACK_GAP_DEVICE_NAME_HANDLE, gap_len);
+    mp_bluetooth_gap_set_device_name((const uint8_t *)gap_name, gap_len);
+
     mp_bluetooth_btstack_port_init();
     mp_bluetooth_btstack_state = MP_BLUETOOTH_BTSTACK_STATE_STARTING;
 
@@ -344,6 +360,19 @@ void mp_bluetooth_get_device_addr(uint8_t *addr) {
     mp_hal_get_mac(MP_HAL_MAC_BDADDR, addr);
 }
 
+size_t mp_bluetooth_gap_get_device_name(const uint8_t **buf) {
+    uint8_t *value = NULL;
+    size_t value_len = 0;
+    mp_bluetooth_gatts_db_read(MP_STATE_PORT(bluetooth_btstack_root_pointers)->gatts_db, BTSTACK_GAP_DEVICE_NAME_HANDLE, &value, &value_len);
+    *buf = value;
+    return value_len;
+}
+
+int mp_bluetooth_gap_set_device_name(const uint8_t *buf, size_t len) {
+    mp_bluetooth_gatts_db_write(MP_STATE_PORT(bluetooth_btstack_root_pointers)->gatts_db, BTSTACK_GAP_DEVICE_NAME_HANDLE, buf, len);
+    return 0;
+}
+
 int mp_bluetooth_gap_advertise_start(bool connectable, int32_t interval_us, const uint8_t *adv_data, size_t adv_data_len, const uint8_t *sr_data, size_t sr_data_len) {
     DEBUG_EVENT_printf("mp_bluetooth_gap_advertise_start\n");
     uint16_t adv_int_min = interval_us / 625;
@@ -396,7 +425,9 @@ int mp_bluetooth_gatts_register_service_begin(bool append) {
         att_db_util_init();
 
         att_db_util_add_service_uuid16(GAP_SERVICE_UUID);
-        att_db_util_add_characteristic_uuid16(GAP_DEVICE_NAME_UUID, ATT_PROPERTY_READ, ATT_SECURITY_NONE, ATT_SECURITY_NONE, (uint8_t *)"MPY BTSTACK", 11);
+        uint16_t handle = att_db_util_add_characteristic_uuid16(GAP_DEVICE_NAME_UUID, ATT_PROPERTY_READ | ATT_PROPERTY_DYNAMIC, ATT_SECURITY_NONE, ATT_SECURITY_NONE, NULL, 0);
+        assert(handle == BTSTACK_GAP_DEVICE_NAME_HANDLE);
+        (void)handle;
 
         att_db_util_add_service_uuid16(0x1801);
         att_db_util_add_characteristic_uuid16(0x2a05, ATT_PROPERTY_READ, ATT_SECURITY_NONE, ATT_SECURITY_NONE, NULL, 0);

extmod/modbluetooth.c

@@ -295,6 +295,11 @@ STATIC mp_obj_t bluetooth_ble_config(size_t n_args, const mp_obj_t *args, mp_map
         }
 
         switch (mp_obj_str_get_qstr(args[1])) {
+            case MP_QSTR_gap_name: {
+                const uint8_t *buf;
+                size_t len = mp_bluetooth_gap_get_device_name(&buf);
+                return mp_obj_new_bytes(buf, len);
+            }
             case MP_QSTR_mac: {
                 uint8_t addr[6];
                 mp_bluetooth_get_device_addr(addr);
@@ -315,6 +320,13 @@ STATIC mp_obj_t bluetooth_ble_config(size_t n_args, const mp_obj_t *args, mp_map
             if (MP_MAP_SLOT_IS_FILLED(kwargs, i)) {
                 mp_map_elem_t *e = &kwargs->table[i];
                 switch (mp_obj_str_get_qstr(e->key)) {
+                    case MP_QSTR_gap_name: {
+                        mp_buffer_info_t bufinfo;
+                        mp_get_buffer_raise(e->value, &bufinfo, MP_BUFFER_READ);
+                        int ret = mp_bluetooth_gap_set_device_name(bufinfo.buf, bufinfo.len);
+                        bluetooth_handle_errno(ret);
+                        break;
+                    }
                     case MP_QSTR_rxbuf: {
                         // Determine new buffer sizes
                         mp_int_t ringbuf_alloc = mp_obj_get_int(e->value);

extmod/modbluetooth.h

@@ -171,6 +171,10 @@ bool mp_bluetooth_is_active(void);
 // Gets the MAC addr of this device in big-endian format.
 void mp_bluetooth_get_device_addr(uint8_t *addr);
 
+// Get or set the GAP device name that will be used by service 0x1800, characteristic 0x2a00.
+size_t mp_bluetooth_gap_get_device_name(const uint8_t **buf);
+int mp_bluetooth_gap_set_device_name(const uint8_t *buf, size_t len);
+
 // Start advertisement. Will re-start advertisement when already enabled.
 // Returns errno on failure.
 int mp_bluetooth_gap_advertise_start(bool connectable, int32_t interval_us, const uint8_t *adv_data, size_t adv_data_len, const uint8_t *sr_data, size_t sr_data_len);

extmod/nimble/modbluetooth_nimble.c

@@ -40,8 +40,8 @@
 #include "nimble/nimble_port.h"
 #include "services/gap/ble_svc_gap.h"
 
-#ifndef MICROPY_PY_BLUETOOTH_DEFAULT_NAME
-#define MICROPY_PY_BLUETOOTH_DEFAULT_NAME "PYBD"
+#ifndef MICROPY_PY_BLUETOOTH_DEFAULT_GAP_NAME
+#define MICROPY_PY_BLUETOOTH_DEFAULT_GAP_NAME "MPY NIMBLE"
 #endif
 
 #define DEBUG_EVENT_printf(...) //printf(__VA_ARGS__)
@@ -191,7 +191,7 @@ STATIC void sync_cb(void) {
         assert(rc == 0);
     }
 
-    ble_svc_gap_device_name_set(MICROPY_PY_BLUETOOTH_DEFAULT_NAME);
+    ble_svc_gap_device_name_set(MICROPY_PY_BLUETOOTH_DEFAULT_GAP_NAME);
 
     mp_bluetooth_nimble_ble_state = MP_BLUETOOTH_NIMBLE_BLE_STATE_ACTIVE;
 }
@@ -352,6 +352,22 @@ void mp_bluetooth_get_device_addr(uint8_t *addr) {
     #endif
 }
 
+size_t mp_bluetooth_gap_get_device_name(const uint8_t **buf) {
+    const char *name = ble_svc_gap_device_name();
+    *buf = (const uint8_t *)name;
+    return strlen(name);
+}
+
+int mp_bluetooth_gap_set_device_name(const uint8_t *buf, size_t len) {
+    char tmp_buf[MYNEWT_VAL(BLE_SVC_GAP_DEVICE_NAME_MAX_LENGTH) + 1];
+    if (len + 1 > sizeof(tmp_buf)) {
+        return MP_EINVAL;
+    }
+    memcpy(tmp_buf, buf, len);
+    tmp_buf[len] = '\0';
+    return ble_hs_err_to_errno(ble_svc_gap_device_name_set(tmp_buf));
+}
+
 int mp_bluetooth_gap_advertise_start(bool connectable, int32_t interval_us, const uint8_t *adv_data, size_t adv_data_len, const uint8_t *sr_data, size_t sr_data_len) {
     if (!mp_bluetooth_is_active()) {
         return ERRNO_BLUETOOTH_NOT_ACTIVE;