doc: can send now is only valid until packet handler exit

doc/manual/docs/appendix/events_errors.md

@@ -21,7 +21,8 @@ L2CAP_DATA_PACKET packet type. L2CAP provides the following events:
 -   L2CAP_EVENT_CAN_SEND_NOW - Indicates that an L2CAP data packet could
     be sent on the reported l2cap_cid. It is emitted after a call to
     *l2cap_request_can_send_now*. See [Sending L2CAP Data](protocols/#sec:l2capSendProtocols)
-
+    Please note that the guarantee that a packet can be sent is only valid when the event is received.
+    After returning from the packet handler, BTstack might need to send itself.
 
 Event      | Event Code
 -----------|----------------------------------------
@@ -65,6 +66,8 @@ by RFCOMM:
 -   RFCOMM_EVENT_CAN_SEND_NOW - Indicates that an RFCOMM data packet could
     be sent on the reported rfcomm_cid. It is emitted after a call to
     *rfcomm_request_can_send_now*. See [Sending RFCOMM Data](protocols/#sec:rfcommSendProtocols)
+    Please note that the guarantee that a packet can be sent is only valid when the event is received.
+    After returning from the packet handler, BTstack might need to send itself.
 
 
 Event      | Event Code

doc/manual/docs/protocols.md

@@ -303,6 +303,9 @@ as soon as possible. It might happen that the event is received via
 packet handler before the *l2cap_request_can_send_now_event* function returns.
 The L2CAP_EVENT_CAN_SEND_NOW indicates a channel ID on which sending is possible.
 
+Please note that the guarantee that a packet can be sent is only valid when the event is received.
+After returning from the packet handler, BTstack might need to send itself.
+
 ### LE Data Channels
 
 The full title for LE Data Channels is actually LE Connection-Oriented Channels with LE Credit-Based Flow-Control Mode. In this mode, data is sent as Service Data Units (SDUs) that can be larger than an individual HCI LE ACL packet.
@@ -559,6 +562,9 @@ When there is a need to send a packet, call *rcomm_request_can_send_now*
 and wait for the reception of the RFCOMM_EVENT_CAN_SEND_NOW event 
 to send the packet, as shown in Listing [below](#lst:rfcommRequestCanSendNow).
 
+Please note that the guarantee that a packet can be sent is only valid when the event is received.
+After returning from the packet handler, BTstack might need to send itself.
+
 ~~~~ {#lst:rfcommRequestCanSendNow .c caption="{Preparing and sending data.}"}    
     void prepare_data(uint16_t rfcomm_channel_id){
         ...

doc/manual/mkdocs.yml

@@ -16,6 +16,6 @@ pages:
 - 'Existing Ports': ports/existing_ports.md
 - 'Integrating with Existing Systems': integration.md
 - 'APIs': appendix/apis.md
-- 'Eventts and Errors': appendix/events_errors.md
+- 'Events and Errors': appendix/events_errors.md
 - 'Migration to v1.0': appendix/migration.md
 theme: readthedocs