gap: support sniff subrating

CHANGELOG.md

@@ -23,6 +23,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - GATT Client: Scan Parameters Service Client 
 - GATT Client: HID-over-GATT (HOG) Client, Report and Boot Host
 - GAP: add `gap_set_page_scan_activity` and `gap_set_page_scan_type`
+- GAP: support sniff subrating with `gap_sniff_subrating_configure`
 - AVRCP: new field `button_pressed` in `AVRCP_SUBEVENT_OPERATION`
 - AVRCP: `AVRCP_SUBEVENT_OPERATION` emitted for button release
 - AVRCP Controller: avrcp_controller_start_press_and_hold_cmd helps to support device buttons

src/gap.h

@@ -801,6 +801,15 @@ uint8_t gap_sniff_mode_enter(hci_con_handle_t con_handle, uint16_t sniff_min_int
  */
 uint8_t gap_sniff_mode_exit(hci_con_handle_t con_handle);
 
+/**
+ * @brief Configure Sniff Subrating
+ * @param con_handle
+ * @param max_latency range: 0x0002 to 0xFFFE; Time = N * 0.625 ms
+ * @param min_remote_timeout range:  0x0002 to 0xFFFE; Time = N * 0.625 ms
+ * @param min_local_timeout range:  0x0002 to 0xFFFE; Time = N * 0.625 ms
+ */
+uint8_t gap_sniff_subrating_configure(hci_con_handle_t con_handle, uint16_t max_latency, uint16_t min_remote_timeout, uint16_t min_local_timeout);
+
 // LE
 
 /**

src/hci.c

@@ -212,6 +212,7 @@ static hci_connection_t * create_connection_for_bd_addr_and_type(const bd_addr_t
     conn->requested_security_level = LEVEL_0;
 #ifdef ENABLE_CLASSIC
     conn->request_role = HCI_ROLE_INVALID;
+    conn->sniff_subrating_max_latency = 0xffff;
     btstack_run_loop_set_timer_handler(&conn->timeout, hci_connection_timeout_handler);
     btstack_run_loop_set_timer_context(&conn->timeout, conn);
     hci_connection_timestamp(conn);
@@ -4493,8 +4494,15 @@ static bool hci_run_general_pending_commands(void){
                 return true;
         }
 
+        if (connection->sniff_subrating_max_latency != 0xffff){
+            uint16_t max_latency = connection->sniff_subrating_max_latency;
+            connection->sniff_subrating_max_latency = 0;
+            hci_send_cmd(&hci_sniff_subrating, connection->con_handle, max_latency, connection->sniff_subrating_min_remote_timeout, connection->sniff_subrating_min_local_timeout);
+            return true;
+        }
+
         if (connection->request_role != HCI_ROLE_INVALID){
-            hci_role_t  role = connection->request_role;
+            hci_role_t role = connection->request_role;
             connection->request_role = HCI_ROLE_INVALID;
             hci_send_cmd(&hci_switch_role_command, connection->address, role);
             return true;
@@ -6357,6 +6365,15 @@ uint8_t gap_sniff_mode_exit(hci_con_handle_t con_handle){
     return 0;
 }
 
+uint8_t gap_sniff_subrating_configure(hci_con_handle_t con_handle, uint16_t max_latency, uint16_t min_remote_timeout, uint16_t min_local_timeout){
+    hci_connection_t * conn = hci_connection_for_handle(con_handle);
+    if (!conn) return GAP_CONNECTION_INVALID;
+    conn->sniff_subrating_max_latency = max_latency;
+    conn->sniff_subrating_min_remote_timeout = min_remote_timeout;
+    conn->sniff_subrating_min_local_timeout = min_local_timeout;
+    hci_run();
+}
+
 void gap_set_page_scan_activity(uint16_t page_scan_interval, uint16_t page_scan_window){
     hci_stack->new_page_scan_interval = page_scan_interval;
     hci_stack->new_page_scan_window = page_scan_window;

src/hci.h

@@ -541,6 +541,11 @@ typedef struct {
     uint16_t sniff_attempt;
     uint16_t sniff_timeout;
 
+    // sniff subrating
+    uint16_t sniff_subrating_max_latency;   // 0xffff = not set
+    uint16_t sniff_subrating_min_remote_timeout;
+    uint16_t sniff_subrating_min_local_timeout;
+
 #ifdef ENABLE_SCO_OVER_HCI
     // track SCO rx event
     uint32_t sco_rx_ms;