Added CDC_Host_Flush() function to the CDC Host Class driver to flush sent data to the attached device.

LUFA/Drivers/USB/Class/Host/CDC.c

@@ -374,6 +374,48 @@ uint8_t CDC_Host_ReceiveByte(USB_ClassInfo_CDC_Host_t* const CDCInterfaceInfo)
 	return ReceivedByte;
 }
 
+uint8_t CDC_Host_Flush(USB_ClassInfo_CDC_Host_t* const CDCInterfaceInfo)
+{
+	if ((USB_HostState != HOST_STATE_Configured) || !(CDCInterfaceInfo->State.IsActive))
+	  return PIPE_READYWAIT_DeviceDisconnected;
+	  
+	uint8_t ErrorCode;
+
+	if (CDCInterfaceInfo->State.BidirectionalDataEndpoints)
+	{
+		Pipe_SelectPipe(CDCInterfaceInfo->Config.DataINPipeNumber);
+		Pipe_SetPipeToken(PIPE_TOKEN_OUT);
+	}
+	else
+	{
+		Pipe_SelectPipe(CDCInterfaceInfo->Config.DataOUTPipeNumber);	
+	}
+	
+	Pipe_Unfreeze();
+	
+	if (!(Pipe_BytesInPipe()))
+	  return PIPE_READYWAIT_NoError;
+
+	bool BankFull = !(Pipe_IsReadWriteAllowed());
+
+	Pipe_ClearOUT();
+
+	if (BankFull)
+	{
+		if ((ErrorCode = Pipe_WaitUntilReady()) != PIPE_READYWAIT_NoError)
+		  return ErrorCode;
+
+		Pipe_ClearOUT();
+	}
+
+	Pipe_Freeze();
+
+	if (CDCInterfaceInfo->State.BidirectionalDataEndpoints)
+	  Pipe_SetPipeToken(PIPE_TOKEN_IN);
+	
+	return PIPE_READYWAIT_NoError;
+}
+
 void CDC_Host_CreateStream(USB_ClassInfo_CDC_Host_t* CDCInterfaceInfo, FILE* Stream)
 {
 	*Stream = (FILE)FDEV_SETUP_STREAM(CDC_Host_putchar, CDC_Host_getchar, _FDEV_SETUP_RW);

LUFA/Drivers/USB/Class/Host/CDC.h

@@ -214,6 +214,14 @@
 			 */
 			uint8_t CDC_Host_ReceiveByte(USB_ClassInfo_CDC_Host_t* const CDCInterfaceInfo) ATTR_NON_NULL_PTR_ARG(1);
 			
+			/** Flushes any data waiting to be sent, ensuring that the send buffer is cleared.
+			 *
+			 *  \param[in,out] CDCInterfaceInfo  Pointer to a structure containing a CDC Class host configuration and state
+			 *
+			 *  \return A value from the \ref Pipe_WaitUntilReady_ErrorCodes_t enum
+			 */
+			uint8_t CDC_Host_Flush(USB_ClassInfo_CDC_Host_t* const CDCInterfaceInfo) ATTR_NON_NULL_PTR_ARG(1);
+
 			/** Creates a standard characer stream for the given CDC Device instance so that it can be used with all the regular
 			 *  functions in the avr-libc <stdio.h> library that accept a FILE stream as a destination (e.g. fprintf). The created
 			 *  stream is bidirectional and can be used for both input and output functions.

LUFA/Drivers/USB/HighLevel/StdDescriptors.h

@@ -43,6 +43,7 @@
 	/* Includes: */
 		#include <avr/pgmspace.h>
 		#include <stdbool.h>
+		#include <stddef.h>
 
 		#include "../../../Common/Common.h"
 		#include "USBMode.h"