Some improvements

- Rename mutex to csMutex to better represent its purpose
- Move the empty transfer to update the line polarity to separate function

hal/src/fsfw_hal/linux/spi/SpiComIF.cpp

@@ -27,7 +27,7 @@ SpiComIF::SpiComIF(object_id_t objectId, std::string devname, GpioIF* gpioComIF)
 #endif /* FSFW_VERBOSE_LEVEL >= 1 */
   }
 
-  spiMutex = MutexFactory::instance()->createMutex();
+  csMutex = MutexFactory::instance()->createMutex();
 }
 
 ReturnValue_t SpiComIF::initializeInterface(CookieIF* cookie) {
@@ -197,7 +197,7 @@ ReturnValue_t SpiComIF::performRegularSendOperation(SpiCookie* spiCookie, const
 
   /* Pull SPI CS low. For now, no support for active high given  */
   if (gpioId != gpio::NO_GPIO) {
-    result = spiMutex->lockMutex(timeoutType, timeoutMs);
+    result = csMutex->lockMutex(timeoutType, timeoutMs);
     if (result != RETURN_OK) {
 #if FSFW_VERBOSE_LEVEL >= 1
 #if FSFW_CPP_OSTREAM_ENABLED == 1
@@ -208,6 +208,7 @@ ReturnValue_t SpiComIF::performRegularSendOperation(SpiCookie* spiCookie, const
 #endif
       return result;
     }
+    updateLinePolarity(fileDescriptor);
     ReturnValue_t result = gpioComIF->pullLow(gpioId);
     if (result != HasReturnvaluesIF::RETURN_OK) {
 #if FSFW_VERBOSE_LEVEL >= 1
@@ -219,6 +220,8 @@ ReturnValue_t SpiComIF::performRegularSendOperation(SpiCookie* spiCookie, const
 #endif
       return result;
     }
+  } else {
+    updateLinePolarity(fileDescriptor);
   }
 
   /* Execute transfer */
@@ -248,7 +251,7 @@ ReturnValue_t SpiComIF::performRegularSendOperation(SpiCookie* spiCookie, const
 
   if (gpioId != gpio::NO_GPIO) {
     gpioComIF->pullHigh(gpioId);
-    result = spiMutex->unlockMutex();
+    result = csMutex->unlockMutex();
     if (result != RETURN_OK) {
 #if FSFW_CPP_OSTREAM_ENABLED == 1
       sif::error << "SpiComIF::sendMessage: Failed to unlock mutex" << std::endl;
@@ -291,7 +294,7 @@ ReturnValue_t SpiComIF::performHalfDuplexReception(SpiCookie* spiCookie) {
 
   gpioId_t gpioId = spiCookie->getChipSelectPin();
   if (gpioId != gpio::NO_GPIO) {
-    result = spiMutex->lockMutex(timeoutType, timeoutMs);
+    result = csMutex->lockMutex(timeoutType, timeoutMs);
     if (result != RETURN_OK) {
 #if FSFW_CPP_OSTREAM_ENABLED == 1
       sif::error << "SpiComIF::getSendSuccess: Failed to lock mutex" << std::endl;
@@ -314,7 +317,7 @@ ReturnValue_t SpiComIF::performHalfDuplexReception(SpiCookie* spiCookie) {
 
   if (gpioId != gpio::NO_GPIO) {
     gpioComIF->pullHigh(gpioId);
-    result = spiMutex->unlockMutex();
+    result = csMutex->unlockMutex();
     if (result != RETURN_OK) {
 #if FSFW_CPP_OSTREAM_ENABLED == 1
       sif::error << "SpiComIF::getSendSuccess: Failed to unlock mutex" << std::endl;
@@ -350,7 +353,7 @@ MutexIF* SpiComIF::getMutex(MutexIF::TimeoutType* timeoutType, uint32_t* timeout
   if (timeoutMs != nullptr) {
     *timeoutMs = this->timeoutMs;
   }
-  return spiMutex;
+  return csMutex;
 }
 
 void SpiComIF::performSpiWiretapping(SpiCookie* spiCookie) {
@@ -398,14 +401,6 @@ void SpiComIF::setSpiSpeedAndMode(int spiFd, spi::SpiModes mode, uint32_t speed)
   if (retval != 0) {
     utility::handleIoctlError("SpiComIF::setSpiSpeedAndMode: Setting SPI speed failed");
   }
-  // This updates the SPI clock default polarity. Only setting the mode does not update
-  // the line state, which can be an issue on mode switches because the clock line will
-  // switch the state after the chip select is pulled low
-  clockUpdateTransfer.len = 0;
-  retval = ioctl(spiFd, SPI_IOC_MESSAGE(1), &clockUpdateTransfer);
-  if (retval != 0) {
-    utility::handleIoctlError("SpiComIF::setSpiSpeedAndMode: Updating SPI default clock failed");
-  }
 }
 
 void SpiComIF::getSpiSpeedAndMode(int spiFd, spi::SpiModes& mode, uint32_t& speed) const {
@@ -422,4 +417,14 @@ void SpiComIF::getSpiSpeedAndMode(int spiFd, spi::SpiModes& mode, uint32_t& spee
   }
 }
 
-const std::string& SpiComIF::getSpiDev() const { return dev; }
+const std::string& SpiComIF::getSpiDev() const {
+  return dev;
+}
+
+void SpiComIF::updateLinePolarity(int spiFd) {
+  clockUpdateTransfer.len = 0;
+  int retval = ioctl(spiFd, SPI_IOC_MESSAGE(1), &clockUpdateTransfer);
+  if (retval != 0) {
+    utility::handleIoctlError("SpiComIF::setSpiSpeedAndMode: Updating SPI default clock failed");
+  }
+}

hal/src/fsfw_hal/linux/spi/SpiComIF.h

@@ -59,6 +59,17 @@ class SpiComIF : public DeviceCommunicationIF, public SystemObject {
 
   GpioIF* getGpioInterface();
   void setSpiSpeedAndMode(int spiFd, spi::SpiModes mode, uint32_t speed);
+
+  /**
+   * This updates the SPI clock default polarity. Only setting the mode does not update
+   * the line state, which can be an issue on mode switches because the clock line will
+   * switch the state after the chip select is pulled low.
+   *
+   * It is recommended to call this function after #setSpiSpeedAndMode if the SPI bus
+   * has multiple SPI devices with different speed and SPI modes attached.
+   * @param spiFd
+   */
+  void updateLinePolarity(int spiFd);
   void getSpiSpeedAndMode(int spiFd, spi::SpiModes& mode, uint32_t& speed) const;
 
   const std::string& getSpiDev() const;
@@ -74,7 +85,11 @@ class SpiComIF : public DeviceCommunicationIF, public SystemObject {
 
   GpioIF* gpioComIF = nullptr;
   std::string dev = "";
-  MutexIF* spiMutex = nullptr;
+  /**
+   * Protects the chip select operations. Lock when GPIO is pulled low, unlock after it was
+   * pulled high
+   */
+  MutexIF* csMutex = nullptr;
   MutexIF::TimeoutType timeoutType = MutexIF::TimeoutType::WAITING;
   uint32_t timeoutMs = 20;
   spi_ioc_transfer clockUpdateTransfer = {};