From 189747f8fde9eb3d02508a9098f295a764df2b04 Mon Sep 17 00:00:00 2001
From: Adrien Chardon <adrienchardon@mailoo.org>
Date: Wed, 21 Dec 2016 15:02:39 +0100
Subject: [PATCH] Fix can_read() return value for STM32 boards

---
 targets/TARGET_STM/TARGET_STM32F0/can_api.c | 6 ++++++
 targets/TARGET_STM/TARGET_STM32F1/can_api.c | 6 ++++++
 targets/TARGET_STM/TARGET_STM32F2/can_api.c | 6 ++++++
 targets/TARGET_STM/TARGET_STM32F3/can_api.c | 6 ++++++
 targets/TARGET_STM/TARGET_STM32F4/can_api.c | 6 ++++++
 targets/TARGET_STM/TARGET_STM32F7/can_api.c | 6 ++++++
 targets/TARGET_STM/TARGET_STM32L4/can_api.c | 6 ++++++
 7 files changed, 42 insertions(+)

diff --git a/targets/TARGET_STM/TARGET_STM32F0/can_api.c b/targets/TARGET_STM/TARGET_STM32F0/can_api.c
index d6483cede1..d8938fca7d 100644
--- a/targets/TARGET_STM/TARGET_STM32F0/can_api.c
+++ b/targets/TARGET_STM/TARGET_STM32F0/can_api.c
@@ -235,6 +235,12 @@ int can_read(can_t *obj, CAN_Message *msg, int handle)
 
     CAN_TypeDef *can = (CAN_TypeDef *)(obj->can);    
     
+    // check FPM0 which holds the pending message count in FIFO 0
+    // if no message is pending, return 0
+    if ((can->RF0R & CAN_RF0R_FMP0) == 0) {
+        return 0;
+    }
+
     /* Get the Id */
     msg->format = (CANFormat)((uint8_t)0x04 & can->sFIFOMailBox[handle].RIR);
     if (!msg->format) {
diff --git a/targets/TARGET_STM/TARGET_STM32F1/can_api.c b/targets/TARGET_STM/TARGET_STM32F1/can_api.c
index 6f3f265a5c..2b16c47953 100644
--- a/targets/TARGET_STM/TARGET_STM32F1/can_api.c
+++ b/targets/TARGET_STM/TARGET_STM32F1/can_api.c
@@ -238,6 +238,12 @@ int can_read(can_t *obj, CAN_Message *msg, int handle)
 
     CAN_TypeDef *can = (CAN_TypeDef *)(obj->can);    
     
+    // check FPM0 which holds the pending message count in FIFO 0
+    // if no message is pending, return 0
+    if ((can->RF0R & CAN_RF0R_FMP0) == 0) {
+        return 0;
+    }
+
     /* Get the Id */
     msg->format = (CANFormat)((uint8_t)0x04 & can->sFIFOMailBox[handle].RIR);
     if (!msg->format) {
diff --git a/targets/TARGET_STM/TARGET_STM32F2/can_api.c b/targets/TARGET_STM/TARGET_STM32F2/can_api.c
index 1a1aeec10b..e1097e2d2b 100644
--- a/targets/TARGET_STM/TARGET_STM32F2/can_api.c
+++ b/targets/TARGET_STM/TARGET_STM32F2/can_api.c
@@ -248,6 +248,12 @@ int can_read(can_t *obj, CAN_Message *msg, int handle)
 
     CAN_TypeDef *can = (CAN_TypeDef *)(obj->can);
 
+    // check FPM0 which holds the pending message count in FIFO 0
+    // if no message is pending, return 0
+    if ((can->RF0R & CAN_RF0R_FMP0) == 0) {
+        return 0;
+    }
+
     /* Get the Id */
     msg->format = (CANFormat)((uint8_t)0x04 & can->sFIFOMailBox[handle].RIR);
     if (!msg->format) {
diff --git a/targets/TARGET_STM/TARGET_STM32F3/can_api.c b/targets/TARGET_STM/TARGET_STM32F3/can_api.c
index a0416a61c4..7bccf28639 100644
--- a/targets/TARGET_STM/TARGET_STM32F3/can_api.c
+++ b/targets/TARGET_STM/TARGET_STM32F3/can_api.c
@@ -238,6 +238,12 @@ int can_read(can_t *obj, CAN_Message *msg, int handle)
 
     CAN_TypeDef *can = (CAN_TypeDef *)(obj->can);    
     
+    // check FPM0 which holds the pending message count in FIFO 0
+    // if no message is pending, return 0
+    if ((can->RF0R & CAN_RF0R_FMP0) == 0) {
+        return 0;
+    }
+
     /* Get the Id */
     msg->format = (CANFormat)((uint8_t)0x04 & can->sFIFOMailBox[handle].RIR);
     if (!msg->format) {
diff --git a/targets/TARGET_STM/TARGET_STM32F4/can_api.c b/targets/TARGET_STM/TARGET_STM32F4/can_api.c
index 446b4fdfbb..1bad14ac5d 100644
--- a/targets/TARGET_STM/TARGET_STM32F4/can_api.c
+++ b/targets/TARGET_STM/TARGET_STM32F4/can_api.c
@@ -251,6 +251,12 @@ int can_read(can_t *obj, CAN_Message *msg, int handle)
 
     CAN_TypeDef *can = (CAN_TypeDef *)(obj->can);    
     
+    // check FPM0 which holds the pending message count in FIFO 0
+    // if no message is pending, return 0
+    if ((can->RF0R & CAN_RF0R_FMP0) == 0) {
+        return 0;
+    }
+
     /* Get the Id */
     msg->format = (CANFormat)((uint8_t)0x04 & can->sFIFOMailBox[handle].RIR);
     if (!msg->format) {
diff --git a/targets/TARGET_STM/TARGET_STM32F7/can_api.c b/targets/TARGET_STM/TARGET_STM32F7/can_api.c
index 3e716fa7b9..7c4cac4010 100644
--- a/targets/TARGET_STM/TARGET_STM32F7/can_api.c
+++ b/targets/TARGET_STM/TARGET_STM32F7/can_api.c
@@ -251,6 +251,12 @@ int can_read(can_t *obj, CAN_Message *msg, int handle)
 
     CAN_TypeDef *can = (CAN_TypeDef *)(obj->can);    
     
+    // check FPM0 which holds the pending message count in FIFO 0
+    // if no message is pending, return 0
+    if ((can->RF0R & CAN_RF0R_FMP0) == 0) {
+        return 0;
+    }
+
     /* Get the Id */
     msg->format = (CANFormat)((uint8_t)0x04 & can->sFIFOMailBox[handle].RIR);
     if (!msg->format) {
diff --git a/targets/TARGET_STM/TARGET_STM32L4/can_api.c b/targets/TARGET_STM/TARGET_STM32L4/can_api.c
index e5cb5db98b..363cfe245f 100644
--- a/targets/TARGET_STM/TARGET_STM32L4/can_api.c
+++ b/targets/TARGET_STM/TARGET_STM32L4/can_api.c
@@ -238,6 +238,12 @@ int can_read(can_t *obj, CAN_Message *msg, int handle)
 
     CAN_TypeDef *can = (CAN_TypeDef *)(obj->can);    
     
+    // check FPM0 which holds the pending message count in FIFO 0
+    // if no message is pending, return 0
+    if ((can->RF0R & CAN_RF0R_FMP0) == 0) {
+        return 0;
+    }
+
     /* Get the Id */
     msg->format = (CANFormat)((uint8_t)0x04 & can->sFIFOMailBox[handle].RIR);
     if (!msg->format) {