add flag to track if hci packet buffer is reserved

src/hci.c

@@ -273,6 +273,24 @@ int hci_can_send_packet_now(uint8_t packet_type){
     }
 }
 
+// same as hci_can_send_packet_now, but also checks if packet buffer is free for use
+int hci_can_send_packet_now_using_packet_buffer(uint8_t packet_type){
+    if (hci_stack->hci_packet_buffer_reserved) return 0;
+    return hci_can_send_packet_now(packet_type);
+}
+
+// reserves outgoing packet buffer. @returns 1 if successful
+int hci_reserve_packet_buffer(void){
+    if (hci_stack->hci_packet_buffer_reserved) return 0;
+    hci_stack->hci_packet_buffer_reserved = 1;
+    return 1;    
+}
+
+// assumption: synchronous implementations don't provide can_send_packet_now as they don't keep the buffer after the call
+int hci_transport_synchronous(void){
+    return hci_stack->hci_transport->can_send_packet_now == NULL;
+}
+
 int hci_send_acl_packet(uint8_t *packet, int size){
 
     // check for free places on BT module
@@ -289,7 +307,12 @@ int hci_send_acl_packet(uint8_t *packet, int size){
 
     // send packet 
     int err = hci_stack->hci_transport->send_packet(HCI_ACL_DATA_PACKET, packet, size);
-    
+
+    // free packet buffer for synchronous transport implementations    
+    if (hci_transport_synchronous()){
+        hci_stack->hci_packet_buffer_reserved = 0;
+    }
+
     return err;
 }
 
@@ -806,6 +829,12 @@ static void event_handler(uint8_t *packet, int size){
             }
             break;
 
+        case DAEMON_EVENT_HCI_PACKET_SENT:
+            // free packet buffer for asynchronous transport
+            if (hci_transport_synchronous()) break;
+            hci_stack->hci_packet_buffer_reserved = 0;
+            break;
+
 #ifdef HAVE_BLE
         case HCI_EVENT_LE_META:
             switch (packet[2]) {
@@ -1688,9 +1717,15 @@ int hci_send_cmd_packet(uint8_t *packet, int size){
     }
 #endif
 
-
     hci_stack->num_cmd_packets--;
-    return hci_stack->hci_transport->send_packet(HCI_COMMAND_DATA_PACKET, packet, size);
+    int err = hci_stack->hci_transport->send_packet(HCI_COMMAND_DATA_PACKET, packet, size);
+
+    // free packet buffer for synchronous transport implementations    
+    if (hci_transport_synchronous()){
+        hci_stack->hci_packet_buffer_reserved = 0;
+    }
+
+    return err;
 }
 
 // disconnect because of security block

src/hci.h

@@ -323,7 +323,8 @@ typedef struct {
     linked_list_t     connections;
 
     // single buffer for HCI Command assembly
-    uint8_t          hci_packet_buffer[HCI_PACKET_BUFFER_SIZE]; // opcode (16), len(8)
+    uint8_t   hci_packet_buffer[HCI_PACKET_BUFFER_SIZE]; // opcode (16), len(8)
+    uint8_t   hci_packet_buffer_reserved;
     
     /* host to controller flow control */
     uint8_t  num_cmd_packets;
@@ -386,6 +387,15 @@ int hci_send_acl_packet(uint8_t *packet, int size);
 
 // non-blocking UART driver needs
 int hci_can_send_packet_now(uint8_t packet_type);
+
+// same as hci_can_send_packet_now, but also checks if packet buffer is free for use
+int hci_can_send_packet_now_using_packet_buffer(uint8_t packet_type);
+
+// reserves outgoing packet buffer. @returns 1 if successful
+int hci_reserve_packet_buffer(void);
+
+// get point to packet buffer
+uint8_t* hci_get_outgoing_acl_packet_buffer(void);
     
 bd_addr_t * hci_local_bd_addr(void);
 hci_connection_t * hci_connection_for_handle(hci_con_handle_t con_handle);
@@ -395,7 +405,6 @@ uint8_t  hci_number_free_acl_slots(void);
 int      hci_authentication_active_for_handle(hci_con_handle_t handle);
 uint16_t hci_max_acl_data_packet_length(void);
 uint16_t hci_usable_acl_packet_types(void);
-uint8_t* hci_get_outgoing_acl_packet_buffer(void);
 
 // 
 void hci_emit_state(void);

src/l2cap.c

@@ -339,6 +339,10 @@ uint8_t *l2cap_get_outgoing_buffer(void){
     return hci_get_outgoing_acl_packet_buffer() + COMPLETE_L2CAP_HEADER; // 8 bytes
 }
 
+int l2cap_reserve_packet_buffer(void){
+    return hci_reserve_packet_buffer();
+}
+
 int l2cap_send_prepared(uint16_t local_cid, uint16_t len){
     
     if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)){