detect px4io conflicts, don't set sbus as default

platforms/common/include/px4_platform_common/board_common.h

@@ -264,8 +264,10 @@
  */
 #if defined(CONFIG_BOARD_SERIAL_RC)
 #  define RC_SERIAL CONFIG_BOARD_SERIAL_RC
-#else
+#elif defined(RC_SERIAL_PORT)
 #  define RC_SERIAL RC_SERIAL_PORT
+#else
+#  error Board needs to define either CONFIG_BOARD_SERIAL_RC or RC_SERIAL_PORT
 #endif
 
 /*
@@ -511,6 +513,35 @@ static inline bool board_rc_swap_rxtx(const char *device) { return strcmp(device
 static inline bool board_rc_swap_rxtx(const char *device) { return false; }
 #endif
 
+/************************************************************************************
+ * Name: board_rc_conflicting
+ *
+ * Description:
+ *   A board may define its serial RC to be the same as PX4IO_SERIAL_DEVICE,
+ *   especially when using PX4IO.
+ *
+ *   This is problematic when trying to open the serial device used for PX4IO
+ *   for RC.
+ *
+ * Input Parameters:
+ *   device: serial device, e.g. "/dev/ttyS0"
+ *
+ * Returned Value:
+ *   true if the given serial device does conflict with the PX4IO.
+ *   false if not.
+ *
+ ************************************************************************************/
+
+#if defined(RC_SERIAL) && defined(PX4IO_SERIAL_DEVICE)
+static inline bool board_rc_conflicting(const char *device)
+{
+	return strcmp(device, RC_SERIAL) == 0 && strcmp(RC_SERIAL, PX4IO_SERIAL_DEVICE) == 0
+	       && (access("/dev/px4io", R_OK) == 0);
+}
+#else
+static inline bool board_rc_conflicting(const char *device) { return false; }
+#endif
+
 /************************************************************************************
  * Name: board_rc_invert_input
  *

src/drivers/rc/crsf_rc/CrsfRc.cpp

@@ -97,6 +97,11 @@ int CrsfRc::task_spawn(int argc, char *argv[])
 		return PX4_ERROR;
 	}
 
+	if (board_rc_conflicting(device_name)) {
+		PX4_INFO("unable to start, conflict with PX4IO on %s", device_name);
+		return PX4_ERROR;
+	}
+
 	CrsfRc *instance = new CrsfRc(device_name);
 
 	if (instance == nullptr) {

src/drivers/rc/dsm_rc/DsmRc.cpp

@@ -93,6 +93,11 @@ int DsmRc::task_spawn(int argc, char *argv[])
 		return -1;
 	}
 
+	if (board_rc_conflicting(device_name)) {
+		PX4_INFO("unable to start, conflict with PX4IO on %s", device_name);
+		return PX4_ERROR;
+	}
+
 	if (device_name && (access(device_name, R_OK | W_OK) == 0)) {
 		DsmRc *instance = new DsmRc(device_name);
 

src/drivers/rc/ghst_rc/GhstRc.cpp

@@ -88,6 +88,11 @@ int GhstRc::task_spawn(int argc, char *argv[])
 		return -1;
 	}
 
+	if (board_rc_conflicting(device_name)) {
+		PX4_INFO("unable to start, conflict with PX4IO on %s", device_name);
+		return PX4_ERROR;
+	}
+
 	if (device_name && (access(device_name, R_OK | W_OK) == 0)) {
 		GhstRc *instance = new GhstRc(device_name);
 

src/drivers/rc/sbus_rc/SbusRc.cpp

@@ -85,6 +85,11 @@ int SbusRc::task_spawn(int argc, char *argv[])
 		return -1;
 	}
 
+	if (board_rc_conflicting(device_name)) {
+		PX4_INFO("unable to start, conflict with PX4IO on %s", device_name);
+		return PX4_ERROR;
+	}
+
 	if (device_name && (access(device_name, R_OK | W_OK) == 0)) {
 		SbusRc *instance = new SbusRc(device_name);
 

src/drivers/rc/sbus_rc/module.yaml

@@ -4,7 +4,7 @@ serial_config:
       port_config_param:
         name: RC_SBUS_PRT_CFG
         group: Serial
-        default: RC
+        #default: RC
         #depends_on_port: RC
         description_extended: |
             SBUS RC driver.