extmod/modbluetooth: Add compile-config flag to enable pairing/bonding.

Enable it on STM32/Unix NimBLE only (pairing/bonding requires synchronous
events and full bindings).

Signed-off-by: Jim Mussared <jim.mussared@gmail.com>

extmod/modbluetooth.c

@@ -47,6 +47,10 @@
 #error l2cap channels require synchronous modbluetooth events
 #endif
 
+#if MICROPY_PY_BLUETOOTH_ENABLE_PAIRING_BONDING && !MICROPY_PY_BLUETOOTH_USE_SYNC_EVENTS
+#error pairing and bonding require synchronous modbluetooth events
+#endif
+
 #define MP_BLUETOOTH_CONNECT_DEFAULT_SCAN_DURATION_MS 2000
 
 #define MICROPY_PY_BLUETOOTH_MAX_EVENT_DATA_TUPLE_LEN 5

extmod/modbluetooth.h

@@ -54,6 +54,12 @@
 #define MICROPY_PY_BLUETOOTH_ENABLE_L2CAP_CHANNELS (0)
 #endif
 
+// A port can optionally enable support for pairing and bonding.
+// Requires MICROPY_PY_BLUETOOTH_USE_SYNC_EVENTS.
+#ifndef MICROPY_PY_BLUETOOTH_ENABLE_PAIRING_BONDING
+#define MICROPY_PY_BLUETOOTH_ENABLE_PAIRING_BONDING (0)
+#endif
+
 // This is used to protect the ringbuffer.
 // A port may no-op this if MICROPY_PY_BLUETOOTH_USE_SYNC_EVENTS is enabled.
 #ifndef MICROPY_PY_BLUETOOTH_ENTER

extmod/nimble/nimble.mk

@@ -24,6 +24,11 @@ ifeq ($(MICROPY_BLUETOOTH_NIMBLE_BINDINGS_ONLY),0)
 # UART is also polled by the RX IRQ.
 CFLAGS_MOD += -DMICROPY_PY_BLUETOOTH_USE_SYNC_EVENTS=1
 
+# Without the ringbuffer, and with the full implementation, we can also
+# enable pairing and bonding. This requires both synchronous events and
+# some customisation of the key store.
+CFLAGS_MOD += -DMICROPY_PY_BLUETOOTH_ENABLE_PAIRING_BONDING=1
+
 NIMBLE_LIB_DIR = lib/mynewt-nimble
 
 LIB_SRC_C += $(addprefix $(NIMBLE_LIB_DIR)/, \