nimble/transport: Add common HCI RX task

This adds common task for implementing HCI RX. Any transport can simply
register its own function for RX that will be run in separate task
whenever triggered by dedicated API. This for example allows to easily
implement handling HCI RX in a task instead of in an interrupt since
handling RX in an interrupt doesn't work well with monitor enabled.

If selected transport doesn't register its function, all rx_task code
will be compiled out since there won't be any references to that code.

nimble/transport/include/nimble/transport.h

@@ -35,6 +35,11 @@ struct os_mbuf;
 /* Initialization */
 void ble_transport_init(void);
 
+/* Common HCI RX task functions */
+typedef void ble_transport_rx_func_t(void *arg);
+void ble_transport_rx_register(ble_transport_rx_func_t *func, void *arg);
+void ble_transport_rx(void);
+
 /* Allocators for supported data types */
 void *ble_transport_alloc_cmd(void);
 void *ble_transport_alloc_evt(int discardable);

nimble/transport/src/rx_task.c

@@ -0,0 +1,84 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+#include <assert.h>
+#include <syscfg/syscfg.h>
+#if MYNEWT
+#include <os/os_task.h>
+#endif
+#include <os/os_mbuf.h>
+#include <nimble/transport.h>
+#include <nimble/nimble_npl.h>
+
+#if !defined(MYNEWT) || MYNEWT_VAL(BLE_TRANSPORT_RX_STACK_SIZE) > 0
+
+static ble_transport_rx_func_t *rx_func;
+static void *rx_func_arg;
+
+#if MYNEWT
+OS_TASK_STACK_DEFINE(rx_stack, MYNEWT_VAL(BLE_TRANSPORT_RX_STACK_SIZE));
+static struct os_task rx_task;
+#endif
+
+static struct ble_npl_eventq rx_eventq;
+static struct ble_npl_event rx_event;
+
+static void
+rx_event_func(struct ble_npl_event *ev)
+{
+    rx_func(rx_func_arg);
+}
+
+static void
+rx_task_func(void *arg)
+{
+    struct ble_npl_event *ev;
+
+    ble_npl_eventq_init(&rx_eventq);
+
+    while (1) {
+        ev = ble_npl_eventq_get(&rx_eventq, BLE_NPL_TIME_FOREVER);
+        ble_npl_event_run(ev);
+    }
+}
+
+void
+ble_transport_rx_register(ble_transport_rx_func_t *func, void *arg)
+{
+    assert(func && !rx_func);
+
+    rx_func = func;
+    rx_func_arg = arg;
+
+    ble_npl_event_init(&rx_event, rx_event_func, NULL);
+
+#ifdef MYNEWT
+    os_task_init(&rx_task, "hci_rx_task", rx_task_func, NULL,
+                 MYNEWT_VAL(BLE_TRANSPORT_RX_PRIO), OS_WAIT_FOREVER, rx_stack,
+                 MYNEWT_VAL(BLE_TRANSPORT_RX_STACK_SIZE));
+#endif
+}
+
+void
+ble_transport_rx(void)
+{
+    ble_npl_eventq_put(&rx_eventq, &rx_event);
+}
+
+#endif

nimble/transport/syscfg.yml

@@ -110,6 +110,14 @@ syscfg.defs:
             of ISO buffers available for controller.
         value: MYNEWT_VAL(BLE_TRANSPORT_ISO_COUNT)
 
+    BLE_TRANSPORT_RX_PRIO:
+        description: Priority of RX task
+        type: task_priority
+        value: 1
+    BLE_TRANSPORT_RX_STACK_SIZE:
+        description: Stack size of RX task
+        value:
+
 # import monitor and defunct settings from separate file to reduce clutter in main file
 $import:
     - "@apache-mynewt-nimble/nimble/transport/syscfg.monitor.yml"