extmod/btstack: Schedule notify/indicate/write ops for bg completion.

The goal of this commit is to allow using ble.gatts_notify() at any time,
even if the stack is not ready to send the notification right now.  It also
addresses the same issue for ble.gatts_indicate() and ble.gattc_write()
(without response).  In addition this commit fixes the case where the
buffer passed to write-with-response wasn't copied, meaning it could be
modified by the caller, affecting the in-progress write.

The changes are:

- gatts_notify/indicate will now run in the background if the ACL buffer is
  currently full, meaning that notify/indicate can be called at any time.

- gattc_write(mode=0) (no response) will now allow for one outstanding
  write.

- gattc_write(mode=1) (with response) will now copy the buffer so that it
  can't be modified by the caller while the write is in progress.

All four paths also now track the buffer while the operation is in
progress, which prevents the GC free'ing the buffer while it's still
needed.

2 files changed, 33 insertions, 0 deletions

diff --git a/tests/multi_bluetooth/ble_characteristic.py b/tests/multi_bluetooth/ble_characteristic.py
index 33d92b823..fd6fd4672 100644
--- a/tests/multi_bluetooth/ble_characteristic.py
+++ b/tests/multi_bluetooth/ble_characteristic.py
@@ -16,6 +16,7 @@ _IRQ_GATTC_READ_RESULT = const(15)
 _IRQ_GATTC_READ_DONE = const(16)
 _IRQ_GATTC_WRITE_DONE = const(17)
 _IRQ_GATTC_NOTIFY = const(18)
+_IRQ_GATTC_INDICATE = const(19)
 
 SERVICE_UUID = bluetooth.UUID("A5A5A5A5-FFFF-9999-1111-5A5A5A5A5A5A")
 CHAR_UUID = bluetooth.UUID("00000000-1111-2222-3333-444444444444")
@@ -59,6 +60,8 @@ def irq(event, data):
         print("_IRQ_GATTC_WRITE_DONE", data[-1])
     elif event == _IRQ_GATTC_NOTIFY:
         print("_IRQ_GATTC_NOTIFY", data[-1])
+    elif event == _IRQ_GATTC_INDICATE:
+        print("_IRQ_GATTC_INDICATE", data[-1])
 
     if waiting_event is not None:
         if (isinstance(waiting_event, int) and event == waiting_event) or (
@@ -115,6 +118,16 @@ def instance0():
         print("gatts_notify")
         ble.gatts_notify(conn_handle, char_handle, "periph2")
 
+        # Wait for a write to the characteristic from the central.
+        wait_for_event(_IRQ_GATTS_WRITE, TIMEOUT_MS)
+
+        # Wait a bit, then notify a new value on the characteristic.
+        time.sleep_ms(1000)
+        print("gatts_write")
+        ble.gatts_write(char_handle, "periph3")
+        print("gatts_indicate")
+        ble.gatts_indicate(conn_handle, char_handle)
+
         # Wait for the central to disconnect.
         wait_for_event(_IRQ_CENTRAL_DISCONNECT, TIMEOUT_MS)
     finally:
@@ -163,6 +176,17 @@ def instance1():
         ble.gattc_read(conn_handle, value_handle)
         wait_for_event(_IRQ_GATTC_READ_RESULT, TIMEOUT_MS)
 
+        # Write to the characteristic, and ask for a response.
+        print("gattc_write")
+        ble.gattc_write(conn_handle, value_handle, "central2", 1)
+        wait_for_event(_IRQ_GATTC_WRITE_DONE, TIMEOUT_MS)
+
+        # Wait for a indicate (should have new data), then read new value.
+        wait_for_event(_IRQ_GATTC_INDICATE, TIMEOUT_MS)
+        print("gattc_read")
+        ble.gattc_read(conn_handle, value_handle)
+        wait_for_event(_IRQ_GATTC_READ_RESULT, TIMEOUT_MS)
+
         # Disconnect from peripheral.
         print("gap_disconnect:", ble.gap_disconnect(conn_handle))
         wait_for_event(_IRQ_PERIPHERAL_DISCONNECT, TIMEOUT_MS)
diff --git a/tests/multi_bluetooth/ble_characteristic.py.exp b/tests/multi_bluetooth/ble_characteristic.py.exp
index d89842ef7..7f66a4d90 100644
--- a/tests/multi_bluetooth/ble_characteristic.py.exp
+++ b/tests/multi_bluetooth/ble_characteristic.py.exp
@@ -6,6 +6,9 @@ gatts_write
 gatts_notify
 _IRQ_GATTS_WRITE b'central1'
 gatts_notify
+_IRQ_GATTS_WRITE b'central2'
+gatts_write
+gatts_indicate
 _IRQ_CENTRAL_DISCONNECT
 --- instance1 ---
 gap_connect
@@ -26,5 +29,11 @@ _IRQ_GATTC_NOTIFY b'periph2'
 gattc_read
 _IRQ_GATTC_READ_RESULT b'central1'
 _IRQ_GATTC_READ_DONE 0
+gattc_write
+_IRQ_GATTC_WRITE_DONE 0
+_IRQ_GATTC_INDICATE b'periph3'
+gattc_read
+_IRQ_GATTC_READ_RESULT b'periph3'
+_IRQ_GATTC_READ_DONE 0
 gap_disconnect: True
 _IRQ_PERIPHERAL_DISCONNECT