From 3d4f6cc2c4da827de77e273a36836995e42e0a78 Mon Sep 17 00:00:00 2001
From: Hwurzburg <hwurzburg@yahoo.com>
Date: Sun, 9 Jan 2022 17:15:32 -0600
Subject: [PATCH] AP_GPS: add build options for GPS backends

---
 libraries/AP_GPS/AP_GPS.cpp      | 41 ++++++++++++++++++++++++--------
 libraries/AP_GPS/AP_GPS_ERB.cpp  |  3 +++
 libraries/AP_GPS/AP_GPS_ERB.h    |  6 +++++
 libraries/AP_GPS/AP_GPS_GSOF.cpp |  4 +++-
 libraries/AP_GPS/AP_GPS_GSOF.h   |  6 +++++
 libraries/AP_GPS/AP_GPS_MAV.cpp  |  3 +++
 libraries/AP_GPS/AP_GPS_MAV.h    |  6 +++++
 libraries/AP_GPS/AP_GPS_NMEA.cpp |  2 ++
 libraries/AP_GPS/AP_GPS_NMEA.h   |  6 +++++
 libraries/AP_GPS/AP_GPS_NOVA.cpp |  3 +++
 libraries/AP_GPS/AP_GPS_NOVA.h   |  6 +++++
 libraries/AP_GPS/AP_GPS_SBF.cpp  |  2 ++
 libraries/AP_GPS/AP_GPS_SBF.h    |  7 ++++++
 libraries/AP_GPS/AP_GPS_SBP.cpp  |  4 ++++
 libraries/AP_GPS/AP_GPS_SBP.h    |  6 +++++
 libraries/AP_GPS/AP_GPS_SBP2.cpp |  4 ++++
 libraries/AP_GPS/AP_GPS_SBP2.h   |  7 +++++-
 libraries/AP_GPS/AP_GPS_SIRF.cpp |  2 ++
 libraries/AP_GPS/AP_GPS_SIRF.h   |  7 ++++++
 19 files changed, 113 insertions(+), 12 deletions(-)

diff --git a/libraries/AP_GPS/AP_GPS.cpp b/libraries/AP_GPS/AP_GPS.cpp
index 8cfb06cae5..4b0369d135 100644
--- a/libraries/AP_GPS/AP_GPS.cpp
+++ b/libraries/AP_GPS/AP_GPS.cpp
@@ -140,12 +140,14 @@ const AP_Param::GroupInfo AP_GPS::var_info[] = {
     // @User: Advanced
     AP_GROUPINFO("_INJECT_TO",   7, AP_GPS, _inject_to, GPS_RTK_INJECT_TO_ALL),
 
+#if AP_GPS_SBP2_ENABLED || AP_GPS_SBP_ENABLED
     // @Param: _SBP_LOGMASK
     // @DisplayName: Swift Binary Protocol Logging Mask
     // @Description: Masked with the SBP msg_type field to determine whether SBR1/SBR2 data is logged
     // @Values: 0:None (0x0000),-1:All (0xFFFF),-256:External only (0xFF00)
     // @User: Advanced
     AP_GROUPINFO("_SBP_LOGMASK", 8, AP_GPS, _sbp_logmask, -256),
+#endif //AP_GPS_SBP2_ENABLED || AP_GPS_SBP_ENABLED
 
     // @Param: _RAW_DATA
     // @DisplayName: Raw data logging
@@ -303,6 +305,7 @@ const AP_Param::GroupInfo AP_GPS::var_info[] = {
     AP_GROUPINFO("_DRV_OPTIONS", 22, AP_GPS, _driver_options, 0),
 #endif
 
+#if AP_GPS_SBF_ENABLED
     // @Param: _COM_PORT
     // @DisplayName: GPS physical COM port
     // @Description: The physical COM port on the connected device, currently only applies to SBF GPS
@@ -322,6 +325,7 @@ const AP_Param::GroupInfo AP_GPS::var_info[] = {
     // @RebootRequired: True
     AP_GROUPINFO("_COM_PORT2", 24, AP_GPS, _com_port[1], HAL_GPS_COM_PORT_DEFAULT),
 #endif
+#endif //AP_GPS_SBF_ENABLED
 
 #if GPS_MOVING_BASELINE
 
@@ -568,9 +572,11 @@ void AP_GPS::detect_instance(uint8_t instance)
     // do not try to detect the MAV type, assume it's there
     case GPS_TYPE_MAV:
 #ifndef HAL_BUILD_AP_PERIPH
+#if AP_GPS_MAV_ENABLED
         dstate->auto_detected_baud = false; // specified, not detected
         new_gps = new AP_GPS_MAV(*this, state[instance], nullptr);
         goto found_gps;
+#endif //AP_GPS_MAV_ENABLED
 #endif
         break;
 
@@ -612,19 +618,22 @@ void AP_GPS::detect_instance(uint8_t instance)
     // don't build the less common GPS drivers on F1 AP_Periph
 #if !defined(HAL_BUILD_AP_PERIPH) || !defined(STM32F1)
     switch (_type[instance]) {
+#if AP_GPS_SBF_ENABLED
     // by default the sbf/trimble gps outputs no data on its port, until configured.
     case GPS_TYPE_SBF:
         new_gps = new AP_GPS_SBF(*this, state[instance], _port[instance]);
         break;
-
+#endif //AP_GPS_SBF_ENABLED
+#if AP_GPS_GSOF_ENABLED
     case GPS_TYPE_GSOF:
         new_gps = new AP_GPS_GSOF(*this, state[instance], _port[instance]);
         break;
-
+#endif //AP_GPS_GSOF_ENABLED
+#if AP_GPS_NOVA_ENABLED
     case GPS_TYPE_NOVA:
         new_gps = new AP_GPS_NOVA(*this, state[instance], _port[instance]);
         break;
-
+#endif //AP_GPS_NOVA_ENABLED
     default:
         break;
     }
@@ -644,8 +653,9 @@ void AP_GPS::detect_instance(uint8_t instance)
         dstate->last_baud_change_ms = now;
 
         if (_auto_config >= GPS_AUTO_CONFIG_ENABLE_SERIAL_ONLY && new_gps == nullptr) {
-            if (_type[instance] == GPS_TYPE_HEMI) {
-                send_blob_start(instance, AP_GPS_NMEA_HEMISPHERE_INIT_STRING, strlen(AP_GPS_NMEA_HEMISPHERE_INIT_STRING));
+            if (_type[instance] == GPS_TYPE_UBLOX && (_driver_options & AP_GPS_Backend::DriverOptions::UBX_Use115200)) {
+                static const char blob[] = UBLOX_SET_BINARY_115200;
+                send_blob_start(instance, blob, sizeof(blob));
             } else if ((_type[instance] == GPS_TYPE_UBLOX_RTK_BASE ||
                         _type[instance] == GPS_TYPE_UBLOX_RTK_ROVER) &&
                        ((_driver_options.get() & AP_GPS_Backend::DriverOptions::UBX_MBUseUart2) == 0)) {
@@ -655,9 +665,10 @@ void AP_GPS::detect_instance(uint8_t instance)
                 // link to the flight controller
                 static const char blob[] = UBLOX_SET_BINARY_460800;
                 send_blob_start(instance, blob, sizeof(blob));
-            } else if (_type[instance] == GPS_TYPE_UBLOX && (_driver_options & AP_GPS_Backend::DriverOptions::UBX_Use115200)) {
-                static const char blob[] = UBLOX_SET_BINARY_115200;
-                send_blob_start(instance, blob, sizeof(blob));
+#if AP_GPS_NMEA_ENABLED
+            } else if (_type[instance] == GPS_TYPE_HEMI) {
+                send_blob_start(instance, AP_GPS_NMEA_HEMISPHERE_INIT_STRING, strlen(AP_GPS_NMEA_HEMISPHERE_INIT_STRING));
+#endif // AP_GPS_NMEA_ENABLED        
             } else {
                 send_blob_start(instance, _initialisation_blob, sizeof(_initialisation_blob));
             }
@@ -702,29 +713,39 @@ void AP_GPS::detect_instance(uint8_t instance)
             new_gps = new AP_GPS_UBLOX(*this, state[instance], _port[instance], role);
         }
 #ifndef HAL_BUILD_AP_PERIPH
+#if AP_GPS_SBP2_ENABLED
         else if ((_type[instance] == GPS_TYPE_AUTO || _type[instance] == GPS_TYPE_SBP) &&
                  AP_GPS_SBP2::_detect(dstate->sbp2_detect_state, data)) {
             new_gps = new AP_GPS_SBP2(*this, state[instance], _port[instance]);
         }
+#endif //AP_GPS_SBP2_ENABLED
+#if AP_GPS_SBP_ENABLED
         else if ((_type[instance] == GPS_TYPE_AUTO || _type[instance] == GPS_TYPE_SBP) &&
                  AP_GPS_SBP::_detect(dstate->sbp_detect_state, data)) {
             new_gps = new AP_GPS_SBP(*this, state[instance], _port[instance]);
         }
-#if !HAL_MINIMIZE_FEATURES
+#endif //AP_GPS_SBP_ENABLED
+#if !HAL_MINIMIZE_FEATURES && AP_GPS_SIRF_ENABLED
         else if ((_type[instance] == GPS_TYPE_AUTO || _type[instance] == GPS_TYPE_SIRF) &&
                  AP_GPS_SIRF::_detect(dstate->sirf_detect_state, data)) {
             new_gps = new AP_GPS_SIRF(*this, state[instance], _port[instance]);
         }
 #endif
+#if AP_GPS_ERB_ENABLED
         else if ((_type[instance] == GPS_TYPE_AUTO || _type[instance] == GPS_TYPE_ERB) &&
                  AP_GPS_ERB::_detect(dstate->erb_detect_state, data)) {
             new_gps = new AP_GPS_ERB(*this, state[instance], _port[instance]);
-        } else if ((_type[instance] == GPS_TYPE_NMEA ||
+        }
+#endif // AP_GPS_ERB_ENABLED
+#if AP_GPS_NMEA_ENABLED
+        else if ((_type[instance] == GPS_TYPE_NMEA ||
                     _type[instance] == GPS_TYPE_HEMI ||
                     _type[instance] == GPS_TYPE_ALLYSTAR) &&
                    AP_GPS_NMEA::_detect(dstate->nmea_detect_state, data)) {
             new_gps = new AP_GPS_NMEA(*this, state[instance], _port[instance]);
         }
+#endif //AP_GPS_NMEA_ENABLED
+
 #endif // HAL_BUILD_AP_PERIPH
         if (new_gps) {
             goto found_gps;
diff --git a/libraries/AP_GPS/AP_GPS_ERB.cpp b/libraries/AP_GPS/AP_GPS_ERB.cpp
index a1be658010..7468224abd 100644
--- a/libraries/AP_GPS/AP_GPS_ERB.cpp
+++ b/libraries/AP_GPS/AP_GPS_ERB.cpp
@@ -20,6 +20,8 @@
 #include "AP_GPS.h"
 #include "AP_GPS_ERB.h"
 
+#if AP_GPS_ERB_ENABLED
+
 #define ERB_DEBUGGING 0
 
 #define STAT_FIX_VALID 0x01
@@ -285,3 +287,4 @@ reset:
     }
     return false;
 }
+#endif
diff --git a/libraries/AP_GPS/AP_GPS_ERB.h b/libraries/AP_GPS/AP_GPS_ERB.h
index 449b2e4b1a..c4f3337f1a 100644
--- a/libraries/AP_GPS/AP_GPS_ERB.h
+++ b/libraries/AP_GPS/AP_GPS_ERB.h
@@ -24,6 +24,11 @@
 #include "AP_GPS.h"
 #include "GPS_Backend.h"
 
+#ifndef AP_GPS_ERB_ENABLED
+  #define AP_GPS_ERB_ENABLED 1
+#endif
+
+#if AP_GPS_ERB_ENABLED
 class AP_GPS_ERB : public AP_GPS_Backend
 {
 public:
@@ -153,3 +158,4 @@ private:
     // used to update fix between status and position packets
     AP_GPS::GPS_Status next_fix = AP_GPS::NO_FIX;
 };
+#endif
diff --git a/libraries/AP_GPS/AP_GPS_GSOF.cpp b/libraries/AP_GPS/AP_GPS_GSOF.cpp
index 89476a1a4f..bb420b1f59 100644
--- a/libraries/AP_GPS/AP_GPS_GSOF.cpp
+++ b/libraries/AP_GPS/AP_GPS_GSOF.cpp
@@ -24,6 +24,8 @@
 #include "AP_GPS_GSOF.h"
 #include <AP_Logger/AP_Logger.h>
 
+#if AP_GPS_GSOF_ENABLED
+
 extern const AP_HAL::HAL& hal;
 
 #define gsof_DEBUGGING 0
@@ -343,4 +345,4 @@ AP_GPS_GSOF::process_message(void)
 
     return false;
 }
-
+#endif
diff --git a/libraries/AP_GPS/AP_GPS_GSOF.h b/libraries/AP_GPS/AP_GPS_GSOF.h
index be62ab69ac..c920c78486 100644
--- a/libraries/AP_GPS/AP_GPS_GSOF.h
+++ b/libraries/AP_GPS/AP_GPS_GSOF.h
@@ -22,6 +22,11 @@
 #include "AP_GPS.h"
 #include "GPS_Backend.h"
 
+#ifndef AP_GPS_GSOF_ENABLED
+  #define AP_GPS_GSOF_ENABLED 1
+#endif
+
+#if AP_GPS_GSOF_ENABLED
 class AP_GPS_GSOF : public AP_GPS_Backend
 {
 public:
@@ -82,3 +87,4 @@ private:
     uint8_t gsofmsgreq_index = 0;
     uint8_t gsofmsgreq[5] = {1,2,8,9,12};
 };
+#endif
diff --git a/libraries/AP_GPS/AP_GPS_MAV.cpp b/libraries/AP_GPS/AP_GPS_MAV.cpp
index 0f4cdf715d..04630f4d8c 100644
--- a/libraries/AP_GPS/AP_GPS_MAV.cpp
+++ b/libraries/AP_GPS/AP_GPS_MAV.cpp
@@ -19,6 +19,8 @@
 #include "AP_GPS_MAV.h"
 #include <stdint.h>
 
+#if AP_GPS_MAV_ENABLED
+
 // Reading does nothing in this class; we simply return whether or not
 // the latest reading has been consumed.  By calling this function we assume
 // the caller is consuming the new data;
@@ -172,3 +174,4 @@ void AP_GPS_MAV::handle_msg(const mavlink_message_t &msg)
             break;
     }
 }
+#endif
diff --git a/libraries/AP_GPS/AP_GPS_MAV.h b/libraries/AP_GPS/AP_GPS_MAV.h
index 7566e5f22a..82e1b58fcb 100644
--- a/libraries/AP_GPS/AP_GPS_MAV.h
+++ b/libraries/AP_GPS/AP_GPS_MAV.h
@@ -25,6 +25,11 @@
 #include "AP_GPS.h"
 #include "GPS_Backend.h"
 
+#ifndef AP_GPS_MAV_ENABLED
+  #define AP_GPS_MAV_ENABLED 1
+#endif 
+
+#if AP_GPS_MAV_ENABLED
 class AP_GPS_MAV : public AP_GPS_Backend {
 public:
 
@@ -43,3 +48,4 @@ private:
     uint32_t first_week;
     JitterCorrection jitter{2000};
 };
+#endif
diff --git a/libraries/AP_GPS/AP_GPS_NMEA.cpp b/libraries/AP_GPS/AP_GPS_NMEA.cpp
index 0af6e1f574..826613747c 100644
--- a/libraries/AP_GPS/AP_GPS_NMEA.cpp
+++ b/libraries/AP_GPS/AP_GPS_NMEA.cpp
@@ -38,6 +38,7 @@
 
 #include "AP_GPS_NMEA.h"
 
+#if AP_GPS_NMEA_ENABLED
 extern const AP_HAL::HAL& hal;
 
 // Convenience macros //////////////////////////////////////////////////////////
@@ -603,3 +604,4 @@ AP_GPS_NMEA::_detect(struct NMEA_detect_state &state, uint8_t data)
     }
     return false;
 }
+#endif
diff --git a/libraries/AP_GPS/AP_GPS_NMEA.h b/libraries/AP_GPS/AP_GPS_NMEA.h
index fd0c2e7ed3..f9abe85e14 100644
--- a/libraries/AP_GPS/AP_GPS_NMEA.h
+++ b/libraries/AP_GPS/AP_GPS_NMEA.h
@@ -46,6 +46,11 @@
 #include "AP_GPS.h"
 #include "GPS_Backend.h"
 
+#ifndef AP_GPS_NMEA_ENABLED
+  #define AP_GPS_NMEA_ENABLED 1
+#endif
+
+#if AP_GPS_NMEA_ENABLED
 /// NMEA parser
 ///
 class AP_GPS_NMEA : public AP_GPS_Backend
@@ -199,3 +204,4 @@ private:
         "$JASC,GPVTG,5\r\n" /* VTG at 5Hz */                            \
         "$JASC,GPHDT,5\r\n" /* HDT at 5Hz */                            \
         "$JMODE,SBASR,YES\r\n" /* Enable SBAS */
+#endif
diff --git a/libraries/AP_GPS/AP_GPS_NOVA.cpp b/libraries/AP_GPS/AP_GPS_NOVA.cpp
index 8d453ae6cc..60b17df383 100644
--- a/libraries/AP_GPS/AP_GPS_NOVA.cpp
+++ b/libraries/AP_GPS/AP_GPS_NOVA.cpp
@@ -21,6 +21,8 @@
 #include "AP_GPS_NOVA.h"
 #include <AP_Logger/AP_Logger.h>
 
+#if AP_GPS_NOVA_ENABLED
+
 extern const AP_HAL::HAL& hal;
 
 #define NOVA_DEBUGGING 0
@@ -304,3 +306,4 @@ uint32_t AP_GPS_NOVA::CalculateBlockCRC32(uint32_t length, uint8_t *buffer, uint
     }
     return( crc );
 }
+#endif
diff --git a/libraries/AP_GPS/AP_GPS_NOVA.h b/libraries/AP_GPS/AP_GPS_NOVA.h
index 6ba6428d5f..defcb52416 100644
--- a/libraries/AP_GPS/AP_GPS_NOVA.h
+++ b/libraries/AP_GPS/AP_GPS_NOVA.h
@@ -22,6 +22,11 @@
 #include "AP_GPS.h"
 #include "GPS_Backend.h"
 
+#ifndef AP_GPS_NOVA_ENABLED
+  #define AP_GPS_NOVA_ENABLED 1
+#endif
+
+#if AP_GPS_NOVA_ENABLED
 class AP_GPS_NOVA : public AP_GPS_Backend
 {
 public:
@@ -175,3 +180,4 @@ private:
         uint16_t read;
     } nova_msg;
 };
+#endif
diff --git a/libraries/AP_GPS/AP_GPS_SBF.cpp b/libraries/AP_GPS/AP_GPS_SBF.cpp
index 7b56827e23..bf4af75b9b 100644
--- a/libraries/AP_GPS/AP_GPS_SBF.cpp
+++ b/libraries/AP_GPS/AP_GPS_SBF.cpp
@@ -25,6 +25,7 @@
 #include <stdio.h>
 #include <ctype.h>
 
+#if AP_GPS_SBF_ENABLED
 extern const AP_HAL::HAL& hal;
 
 #define SBF_DEBUGGING 0
@@ -614,3 +615,4 @@ bool AP_GPS_SBF::prepare_for_arming(void) {
 
     return is_logging;
 }
+#endif
diff --git a/libraries/AP_GPS/AP_GPS_SBF.h b/libraries/AP_GPS/AP_GPS_SBF.h
index e80255daad..6812b7a126 100644
--- a/libraries/AP_GPS/AP_GPS_SBF.h
+++ b/libraries/AP_GPS/AP_GPS_SBF.h
@@ -22,6 +22,12 @@
 #include "AP_GPS.h"
 #include "GPS_Backend.h"
 
+#ifndef AP_GPS_SBF_ENABLED
+  #define AP_GPS_SBF_ENABLED 1
+#endif
+
+#if AP_GPS_SBF_ENABLED
+
 #define SBF_DISK_ACTIVITY (1 << 7)
 #define SBF_DISK_FULL     (1 << 8)
 #define SBF_DISK_MOUNTED  (1 << 9)
@@ -262,3 +268,4 @@ private:
     uint8_t portLength;
     bool readyForCommand;
 };
+#endif
diff --git a/libraries/AP_GPS/AP_GPS_SBP.cpp b/libraries/AP_GPS/AP_GPS_SBP.cpp
index 590f2ef3bb..ae08e4f3f4 100644
--- a/libraries/AP_GPS/AP_GPS_SBP.cpp
+++ b/libraries/AP_GPS/AP_GPS_SBP.cpp
@@ -20,10 +20,13 @@
 //  Swift Binary Protocol format: http://docs.swift-nav.com/
 //
 
+
 #include "AP_GPS.h"
 #include "AP_GPS_SBP.h"
 #include <AP_Logger/AP_Logger.h>
 
+#if AP_GPS_SBP_ENABLED
+
 extern const AP_HAL::HAL& hal;
 
 #define SBP_DEBUGGING 1
@@ -456,3 +459,4 @@ AP_GPS_SBP::logging_log_raw_sbp(uint16_t msg_type,
 };
 
 #endif // SBP_HW_LOGGING
+#endif // AP_GPS_SBP_ENABLED
diff --git a/libraries/AP_GPS/AP_GPS_SBP.h b/libraries/AP_GPS/AP_GPS_SBP.h
index 1c37b18d4c..10d6dcae72 100644
--- a/libraries/AP_GPS/AP_GPS_SBP.h
+++ b/libraries/AP_GPS/AP_GPS_SBP.h
@@ -24,6 +24,11 @@
 #include "AP_GPS.h"
 #include "GPS_Backend.h"
 
+#ifndef AP_GPS_SBP_ENABLED
+  #define AP_GPS_SBP_ENABLED 1
+#endif
+
+#if AP_GPS_SBP_ENABLED
 class AP_GPS_SBP : public AP_GPS_Backend
 {
 public:
@@ -185,3 +190,4 @@ private:
 
 
 };
+#endif
diff --git a/libraries/AP_GPS/AP_GPS_SBP2.cpp b/libraries/AP_GPS/AP_GPS_SBP2.cpp
index f3da3dee92..14ed7695a7 100644
--- a/libraries/AP_GPS/AP_GPS_SBP2.cpp
+++ b/libraries/AP_GPS/AP_GPS_SBP2.cpp
@@ -20,12 +20,15 @@
 //  Swift Binary Protocol format: http://docs.swift-nav.com/
 //
 
+
 #include "AP_GPS.h"
 #include "AP_GPS_SBP2.h"
 #include <AP_Logger/AP_Logger.h>
 #include <GCS_MAVLink/GCS_MAVLink.h>
 #include <GCS_MAVLink/GCS.h>
 
+#if AP_GPS_SBP2_ENABLED
+
 extern const AP_HAL::HAL& hal;
 
 #define SBP_DEBUGGING 0
@@ -522,3 +525,4 @@ AP_GPS_SBP2::logging_ext_event() {
     };
     AP::logger().WriteBlock(&pkt, sizeof(pkt));
 };
+#endif //AP_GPS_SBP2_ENABLED
diff --git a/libraries/AP_GPS/AP_GPS_SBP2.h b/libraries/AP_GPS/AP_GPS_SBP2.h
index 676b76bce3..d48fe555f0 100644
--- a/libraries/AP_GPS/AP_GPS_SBP2.h
+++ b/libraries/AP_GPS/AP_GPS_SBP2.h
@@ -24,6 +24,11 @@
 #include "AP_GPS.h"
 #include "GPS_Backend.h"
 
+#ifndef AP_GPS_SBP2_ENABLED
+   #define AP_GPS_SBP2_ENABLED 1
+#endif
+
+#if AP_GPS_SBP2_ENABLED
 class AP_GPS_SBP2 : public AP_GPS_Backend
 {
 public:
@@ -201,4 +206,4 @@ private:
     int32_t distMod(int32_t tow1_ms, int32_t tow2_ms, int32_t mod);
 
 };
-
+#endif
diff --git a/libraries/AP_GPS/AP_GPS_SIRF.cpp b/libraries/AP_GPS/AP_GPS_SIRF.cpp
index ef1e4b4559..18f42155c7 100644
--- a/libraries/AP_GPS/AP_GPS_SIRF.cpp
+++ b/libraries/AP_GPS/AP_GPS_SIRF.cpp
@@ -21,6 +21,7 @@
 #include "AP_GPS_SIRF.h"
 #include <stdint.h>
 
+#if AP_GPS_SIRF_ENABLED
 // Initialisation messages
 //
 // Turn off all messages except for 0x29.
@@ -245,3 +246,4 @@ bool AP_GPS_SIRF::_detect(struct SIRF_detect_state &state, uint8_t data)
     }
     return false;
 }
+#endif
diff --git a/libraries/AP_GPS/AP_GPS_SIRF.h b/libraries/AP_GPS/AP_GPS_SIRF.h
index 297f2025d0..4aa8696909 100644
--- a/libraries/AP_GPS/AP_GPS_SIRF.h
+++ b/libraries/AP_GPS/AP_GPS_SIRF.h
@@ -25,6 +25,12 @@
 #include "AP_GPS.h"
 #include "GPS_Backend.h"
 
+#ifndef AP_GPS_SIRF_ENABLED
+  #define AP_GPS_SIRF_ENABLED 1
+#endif
+
+#if AP_GPS_SIRF_ENABLED
+
 #define SIRF_SET_BINARY "$PSRF100,0,38400,8,1,0*3C\r\n"
 
 class AP_GPS_SIRF : public AP_GPS_Backend {
@@ -107,3 +113,4 @@ private:
 
     static const uint8_t _initialisation_blob[];
 };
+#endif