AP_Airspeed: allow for an AIRSPEED list in hwdef.dat

this saves a lot of flash by only including specific drivers

libraries/AP_Airspeed/AP_Airspeed.cpp

@@ -294,6 +294,36 @@ AP_Airspeed::AP_Airspeed()
     _singleton = this;
 }
 
+// macro for use by HAL_INS_PROBE_LIST
+#define GET_I2C_DEVICE(bus, address) hal.i2c_mgr->get_device(bus, address)
+
+bool AP_Airspeed::add_backend(AP_Airspeed_Backend *backend)
+{
+    if (!backend) {
+        return false;
+    }
+    if (num_sensors >= AIRSPEED_MAX_SENSORS) {
+        AP_HAL::panic("Too many airspeed drivers");
+    }
+    const uint8_t i = num_sensors;
+    sensor[num_sensors++] = backend;
+    if (!sensor[i]->init()) {
+        GCS_SEND_TEXT(MAV_SEVERITY_INFO, "Airspeed %u init failed", i+1);
+        delete sensor[i];
+        sensor[i] = nullptr;
+    }
+    return true;
+}
+
+/*
+  macro to add a backend with check for too many sensors
+  We don't try to start more than the maximum allowed
+ */
+#define ADD_BACKEND(backend) \
+    do { add_backend(backend);     \
+    if (num_sensors == AIRSPEED_MAX_SENSORS) { return; } \
+    } while (0)
+
 void AP_Airspeed::init()
 {   
     if (sensor[0] != nullptr) {
@@ -318,6 +348,11 @@ void AP_Airspeed::init()
     }
 #endif
 
+#ifdef HAL_AIRSPEED_PROBE_LIST
+    // load sensors via a list from hwdef.dat
+    HAL_AIRSPEED_PROBE_LIST;
+#else
+    // look for sensors based on type parameters
     for (uint8_t i=0; i<AIRSPEED_MAX_SENSORS; i++) {
 #if AP_AIRSPEED_AUTOCAL_ENABLE
         state[i].calibration.init(param[i].ratio);
@@ -404,6 +439,7 @@ void AP_Airspeed::init()
             num_sensors = i+1;
         }
     }
+#endif // HAL_AIRSPEED_PROBE_LIST
 }
 
 // read the airspeed sensor

libraries/AP_Airspeed/AP_Airspeed.h

@@ -279,6 +279,8 @@ private:
     AP_Airspeed_Backend *sensor[AIRSPEED_MAX_SENSORS];
 
     void Log_Airspeed();
+
+    bool add_backend(AP_Airspeed_Backend *backend);
 };
 
 namespace AP {

libraries/AP_Airspeed/AP_Airspeed_DLVR.cpp

@@ -36,13 +36,29 @@ AP_Airspeed_DLVR::AP_Airspeed_DLVR(AP_Airspeed &_frontend, uint8_t _instance, co
     range_inH2O(_range_inH2O)
 {}
 
-// probe and initialise the sensor
-bool AP_Airspeed_DLVR::init()
+/*
+  probe for a sensor on a given i2c address
+ */
+AP_Airspeed_Backend *AP_Airspeed_DLVR::probe(AP_Airspeed &_frontend,
+                                             uint8_t _instance,
+                                             AP_HAL::OwnPtr<AP_HAL::I2CDevice> _dev,
+                                             const float _range_inH2O)
 {
-    dev = hal.i2c_mgr->get_device(get_bus(), DLVR_I2C_ADDR);
-    if (!dev) {
-        return false;
+    if (!_dev) {
+        return nullptr;
+    }
+    AP_Airspeed_DLVR *sensor = new AP_Airspeed_DLVR(_frontend, _instance, _range_inH2O);
+    if (!sensor) {
+        return nullptr;
     }
+    sensor->dev = std::move(_dev);
+    sensor->setup();
+    return sensor;
+}
+
+// initialise the sensor
+void AP_Airspeed_DLVR::setup()
+{
     WITH_SEMAPHORE(dev->get_semaphore());
     dev->set_speed(AP_HAL::Device::SPEED_LOW);
     dev->set_retries(2);
@@ -51,6 +67,16 @@ bool AP_Airspeed_DLVR::init()
 
     dev->register_periodic_callback(1000000UL/50U,
                                     FUNCTOR_BIND_MEMBER(&AP_Airspeed_DLVR::timer, void));
+}
+
+// probe and initialise the sensor
+bool AP_Airspeed_DLVR::init()
+{
+    dev = hal.i2c_mgr->get_device(get_bus(), DLVR_I2C_ADDR);
+    if (!dev) {
+        return false;
+    }
+    setup();
     return true;
 }
 

libraries/AP_Airspeed/AP_Airspeed_DLVR.h

@@ -29,6 +29,8 @@ class AP_Airspeed_DLVR : public AP_Airspeed_Backend
 public:
 
     AP_Airspeed_DLVR(AP_Airspeed &frontend, uint8_t _instance, const float _range_inH2O);
+    static AP_Airspeed_Backend *probe(AP_Airspeed &frontend, uint8_t _instance, AP_HAL::OwnPtr<AP_HAL::I2CDevice> _dev, const float _range_inH2O);
+
     ~AP_Airspeed_DLVR(void) {}
     
     // probe and initialise the sensor
@@ -53,5 +55,8 @@ private:
     uint32_t last_sample_time_ms;
     const float range_inH2O;
 
+    // initialise the sensor
+    void setup();
+    
     AP_HAL::OwnPtr<AP_HAL::I2CDevice> dev;
 };