extmod/modbluetooth: Combine gattc-data-available callbacks into one.

Instead of having the stack indicate a "start", "data"..., "end", pass
through the data in one callback as an array of chunks of data.

This is because the upcoming non-ringbuffer modbluetooth implementation
cannot buffer the data in the ringbuffer and requires instead a single
callback with all the data, to pass to the Python callback.

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

extmod/btstack/modbluetooth_btstack.c

@@ -414,30 +414,21 @@ STATIC void btstack_packet_handler(uint8_t packet_type, uint8_t *packet, uint8_t
         uint16_t value_handle = gatt_event_characteristic_value_query_result_get_value_handle(packet);
         uint16_t len = gatt_event_characteristic_value_query_result_get_value_length(packet);
         const uint8_t *data = gatt_event_characteristic_value_query_result_get_value(packet);
-        mp_uint_t atomic_state;
-        len = mp_bluetooth_gattc_on_data_available_start(MP_BLUETOOTH_IRQ_GATTC_READ_RESULT, conn_handle, value_handle, len, &atomic_state);
-        mp_bluetooth_gattc_on_data_available_chunk(data, len);
-        mp_bluetooth_gattc_on_data_available_end(atomic_state);
+        mp_bluetooth_gattc_on_data_available(MP_BLUETOOTH_IRQ_GATTC_READ_RESULT, conn_handle, value_handle, &data, &len, 1);
     } else if (event_type == GATT_EVENT_NOTIFICATION) {
         DEBUG_printf("  --> gatt notification\n");
         uint16_t conn_handle = gatt_event_notification_get_handle(packet);
         uint16_t value_handle = gatt_event_notification_get_value_handle(packet);
         uint16_t len = gatt_event_notification_get_value_length(packet);
         const uint8_t *data = gatt_event_notification_get_value(packet);
-        mp_uint_t atomic_state;
-        len = mp_bluetooth_gattc_on_data_available_start(MP_BLUETOOTH_IRQ_GATTC_NOTIFY, conn_handle, value_handle, len, &atomic_state);
-        mp_bluetooth_gattc_on_data_available_chunk(data, len);
-        mp_bluetooth_gattc_on_data_available_end(atomic_state);
+        mp_bluetooth_gattc_on_data_available(MP_BLUETOOTH_IRQ_GATTC_NOTIFY, conn_handle, value_handle, &data, &len, 1);
     } else if (event_type == GATT_EVENT_INDICATION) {
         DEBUG_printf("  --> gatt indication\n");
         uint16_t conn_handle = gatt_event_indication_get_handle(packet);
         uint16_t value_handle = gatt_event_indication_get_value_handle(packet);
         uint16_t len = gatt_event_indication_get_value_length(packet);
         const uint8_t *data = gatt_event_indication_get_value(packet);
-        mp_uint_t atomic_state;
-        len = mp_bluetooth_gattc_on_data_available_start(MP_BLUETOOTH_IRQ_GATTC_INDICATE, conn_handle, value_handle, len, &atomic_state);
-        mp_bluetooth_gattc_on_data_available_chunk(data, len);
-        mp_bluetooth_gattc_on_data_available_end(atomic_state);
+        mp_bluetooth_gattc_on_data_available(MP_BLUETOOTH_IRQ_GATTC_INDICATE, conn_handle, value_handle, &data, &len, 1);
     } else if (event_type == GATT_EVENT_CAN_WRITE_WITHOUT_RESPONSE) {
         uint16_t conn_handle = gatt_event_can_write_without_response_get_handle(packet);
         DEBUG_printf("  --> gatt can write without response %d\n", conn_handle);

extmod/modbluetooth.c

@@ -1125,31 +1125,34 @@ void mp_bluetooth_gattc_on_discover_complete(uint8_t event, uint16_t conn_handle
     schedule_ringbuf(atomic_state);
 }
 
-size_t mp_bluetooth_gattc_on_data_available_start(uint8_t event, uint16_t conn_handle, uint16_t value_handle, size_t data_len, mp_uint_t *atomic_state_out) {
+void mp_bluetooth_gattc_on_data_available(uint8_t event, uint16_t conn_handle, uint16_t value_handle, const uint8_t **data, uint16_t *data_len, size_t num) {
     MICROPY_PY_BLUETOOTH_ENTER
-    *atomic_state_out = atomic_state;
     mp_obj_bluetooth_ble_t *o = MP_OBJ_TO_PTR(MP_STATE_VM(bluetooth));
-    data_len = MIN(o->irq_data_data_alloc, data_len);
-    if (enqueue_irq(o, 2 + 2 + 2 + data_len, event)) {
+
+    // Get the total length of the fragmented buffers.
+    uint16_t total_len = 0;
+    for (size_t i = 0; i < num; ++i) {
+        total_len += data_len[i];
+    }
+
+    // Truncate the data at what we'll be able to pass to Python.
+    total_len = MIN(o->irq_data_data_alloc, total_len);
+
+    if (enqueue_irq(o, 2 + 2 + 2 + total_len, event)) {
         ringbuf_put16(&o->ringbuf, conn_handle);
         ringbuf_put16(&o->ringbuf, value_handle);
-        // Length field is 16-bit.
-        data_len = MIN(UINT16_MAX, data_len);
-        ringbuf_put16(&o->ringbuf, data_len);
-        return data_len;
-    } else {
-        return 0;
-    }
-}
 
-void mp_bluetooth_gattc_on_data_available_chunk(const uint8_t *data, size_t data_len) {
-    mp_obj_bluetooth_ble_t *o = MP_OBJ_TO_PTR(MP_STATE_VM(bluetooth));
-    for (size_t i = 0; i < data_len; ++i) {
-        ringbuf_put(&o->ringbuf, data[i]);
-    }
-}
+        ringbuf_put16(&o->ringbuf, total_len);
 
-void mp_bluetooth_gattc_on_data_available_end(mp_uint_t atomic_state) {
+        // Copy total_len from the fragments to the ringbuffer.
+        uint16_t copied_bytes = 0;
+        for (size_t i = 0; i < num; ++i) {
+            for (size_t j = 0; i < data_len[i] && copied_bytes < total_len; ++j) {
+                ringbuf_put(&o->ringbuf, data[i][j]);
+                ++copied_bytes;
+            }
+        }
+    }
     schedule_ringbuf(atomic_state);
 }
 

extmod/modbluetooth.h

@@ -289,11 +289,7 @@ void mp_bluetooth_gattc_on_descriptor_result(uint16_t conn_handle, uint16_t hand
 void mp_bluetooth_gattc_on_discover_complete(uint8_t event, uint16_t conn_handle, uint16_t status);
 
 // Notify modbluetooth that a read has completed with data (or notify/indicate data available, use `event` to disambiguate).
-// Note: these functions are to be called in a group protected by MICROPY_PY_BLUETOOTH_ENTER/EXIT.
-// _start returns the number of bytes to submit to the calls to _chunk, followed by a call to _end.
-size_t mp_bluetooth_gattc_on_data_available_start(uint8_t event, uint16_t conn_handle, uint16_t value_handle, size_t data_len, mp_uint_t *atomic_state_out);
-void mp_bluetooth_gattc_on_data_available_chunk(const uint8_t *data, size_t data_len);
-void mp_bluetooth_gattc_on_data_available_end(mp_uint_t atomic_state);
+void mp_bluetooth_gattc_on_data_available(uint8_t event, uint16_t conn_handle, uint16_t value_handle, const uint8_t **data, uint16_t *data_len, size_t num);
 
 // Notify modbluetooth that a read or write operation has completed.
 void mp_bluetooth_gattc_on_read_write_status(uint8_t event, uint16_t conn_handle, uint16_t value_handle, uint16_t status);

extmod/nimble/modbluetooth_nimble.c

@@ -798,16 +798,35 @@ int mp_bluetooth_set_preferred_mtu(uint16_t mtu) {
 #if MICROPY_PY_BLUETOOTH_ENABLE_CENTRAL_MODE
 
 STATIC void gattc_on_data_available(uint8_t event, uint16_t conn_handle, uint16_t value_handle, const struct os_mbuf *om) {
-    size_t len = OS_MBUF_PKTLEN(om);
-    mp_uint_t atomic_state;
-    len = mp_bluetooth_gattc_on_data_available_start(event, conn_handle, value_handle, len, &atomic_state);
-    while (len > 0 && om != NULL) {
-        size_t n = MIN(om->om_len, len);
-        mp_bluetooth_gattc_on_data_available_chunk(OS_MBUF_DATA(om, const uint8_t *), n);
-        len -= n;
+    // When the HCI data for an ATT payload arrives, the L2CAP channel will
+    // buffer it into its receive buffer. We set BLE_L2CAP_JOIN_RX_FRAGS=1 in
+    // syscfg.h so it should be rare that the mbuf is fragmented, but we do need
+    // to be able to handle it. We pass all the fragments up to modbluetooth.c
+    // which will create a temporary buffer on the MicroPython heap if necessary
+    // to re-assemble them.
+
+    // Count how many links are in the mbuf chain.
+    size_t n = 0;
+    const struct os_mbuf *elem = om;
+    while (elem) {
+        n += 1;
+        elem = SLIST_NEXT(elem, om_next);
+    }
+
+    // Grab data pointers and lengths for each of the links.
+    const uint8_t **data = mp_local_alloc(sizeof(uint8_t *) * n);
+    uint16_t *data_len = mp_local_alloc(sizeof(uint16_t) * n);
+    for (size_t i = 0; i < n; ++i) {
+        data[i] = OS_MBUF_DATA(om, const uint8_t *);
+        data_len[i] = om->om_len;
         om = SLIST_NEXT(om, om_next);
     }
-    mp_bluetooth_gattc_on_data_available_end(atomic_state);
+
+    // Pass all the fragments together.
+    mp_bluetooth_gattc_on_data_available(event, conn_handle, value_handle, data, data_len, n);
+
+    mp_local_free(data_len);
+    mp_local_free(data);
 }
 
 STATIC int gap_scan_cb(struct ble_gap_event *event, void *arg) {