stm32f7: Add the option to include RTR in CAN header

Signed-off-by: Claudio Micheli <claudio@auterion.com>

arch/arm/src/stm32f7/stm32_can.c

@@ -1288,8 +1288,11 @@ static int stm32can_send(FAR struct can_dev_s *dev,
     }
 
 #else
-  regval &= ~CAN_TIR_STID_MASK;
-  regval |= (uint32_t)msg->cm_hdr.ch_id << CAN_TIR_STID_SHIFT;
+  regval |= ( ( (uint32_t) msg->cm_hdr.ch_id << CAN_TIR_STID_SHIFT) & CAN_TIR_STID_MASK );
+
+#ifdef CONFIG_CAN_USE_RTR
+  regval |= (msg->cm_hdr.ch_rtr ? CAN_TIR_RTR : 0);
+#endif
 #endif
 
   stm32can_putreg(priv, STM32_CAN_TIR_OFFSET(txmb), regval);

drivers/can/Kconfig

@@ -128,6 +128,12 @@ config CAN_NPOLLWAITERS
 	---help---
 		The maximum number of threads that may be waiting on the
 		poll method.
+		
+config CAN_USE_RTR
+	bool "Include RTR in CAN header"
+	default n
+	---help---
+		This selection includes RTR bitfield in the CAN header.
 
 comment "CAN Bus Controllers:"