STM32F1 EP with USB_COMPOSITE (#19281)

Marlin/src/HAL/STM32F1/msc_sd.cpp

 #define PRODUCT_ID 0x29
 
 USBMassStorage MarlinMSC;
-USBCompositeSerial MarlinCompositeSerial;
+MarlinUSBCompositeSerial MarlinCompositeSerial;
 
 #include "../../inc/MarlinConfig.h"
 
 
 #endif
 
+#if ENABLED(EMERGENCY_PARSER)
+  void (*real_rx_callback)(void);
+
+  void my_rx_callback(void) {
+    real_rx_callback();
+    int len = MarlinCompositeSerial.available();
+    while (len-- > 0) // >0 because available() may return a negative value
+      emergency_parser.update(MarlinCompositeSerial.emergency_state, MarlinCompositeSerial.peek());
+  }
+#endif
+
 void MSC_SD_init() {
   USBComposite.setProductId(PRODUCT_ID);
   // Just set MarlinCompositeSerial enabled to true
   // Register composite Serial
   MarlinCompositeSerial.registerComponent();
   USBComposite.begin();
+  #if ENABLED(EMERGENCY_PARSER)
+    //rx is usbSerialPart.endpoints[2]
+    real_rx_callback = usbSerialPart.endpoints[2].callback;
+    usbSerialPart.endpoints[2].callback = my_rx_callback;
+  #endif
 }
 
 #endif // USE_USB_COMPOSITE

Marlin/src/HAL/STM32F1/msc_sd.h

 
 #include <USBComposite.h>
 
+#include "../../inc/MarlinConfigPre.h"
+#if ENABLED(EMERGENCY_PARSER)
+  #include "../../feature/e_parser.h"
+#endif
+
+class MarlinUSBCompositeSerial : public USBCompositeSerial {
+public:
+  MarlinUSBCompositeSerial() : USBCompositeSerial()
+    #if ENABLED(EMERGENCY_PARSER)
+      , emergency_state(EmergencyParser::State::EP_RESET)
+    #endif
+    { }
+
+  #if ENABLED(EMERGENCY_PARSER)
+    EmergencyParser::State emergency_state;
+  #endif
+};
+
 extern USBMassStorage MarlinMSC;
-extern USBCompositeSerial MarlinCompositeSerial;
+extern MarlinUSBCompositeSerial MarlinCompositeSerial;
 
 void MSC_SD_init();