Add blocking versions of the CDC Class driver streams, for applications requiring blocking reads.

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

@@ -240,6 +240,12 @@ void CDC_Device_CreateStream(USB_ClassInfo_CDC_Device_t* CDCInterfaceInfo, FILE*
 	fdev_set_udata(Stream, CDCInterfaceInfo);
 }
 
+void CDC_Device_CreateBlockingStream(USB_ClassInfo_CDC_Device_t* CDCInterfaceInfo, FILE* Stream)
+{
+	*Stream = (FILE)FDEV_SETUP_STREAM(CDC_Device_putchar, CDC_Device_getchar_Blocking, _FDEV_SETUP_RW);
+	fdev_set_udata(Stream, CDCInterfaceInfo);
+}
+
 static int CDC_Device_putchar(char c, FILE* Stream)
 {
 	return CDC_Device_SendByte((USB_ClassInfo_CDC_Device_t*)fdev_get_udata(Stream), c) ? _FDEV_ERR : 0;
@@ -253,4 +259,15 @@ static int CDC_Device_getchar(FILE* Stream)
 	return CDC_Device_ReceiveByte((USB_ClassInfo_CDC_Device_t*)fdev_get_udata(Stream));
 }
 
+static int CDC_Device_getchar_Blocking(FILE* Stream)
+{
+	while (!(CDC_Device_BytesReceived((USB_ClassInfo_CDC_Device_t*)fdev_get_udata(Stream))))
+	{
+		CDC_Device_USBTask((USB_ClassInfo_CDC_Device_t*)fdev_get_udata(Stream));
+		USB_USBTask();
+	}
+
+	return CDC_Device_ReceiveByte((USB_ClassInfo_CDC_Device_t*)fdev_get_udata(Stream));
+}
+
 #endif

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

@@ -213,6 +213,11 @@
 			/** 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).
 			 *
+			 *  Reading data from this stream is non-blocking, i.e. in most instances, complete strings cannot be read in by a single
+			 *  fetch, as the endpoint will not be ready at some point in the transmission, aborting the transfer. However, this may
+			 *  be used when the read data is processed byte-per-bye (via getc()) or when the user application will implement its own
+			 *  line buffering.
+			 *
 			 *  \note The created stream can be given as stdout if desired to direct the standard output from all <stdio.h> functions
 			 *        to the given CDC interface.
 			 *
@@ -221,12 +226,21 @@
 			 */
 			void CDC_Device_CreateStream(USB_ClassInfo_CDC_Device_t* CDCInterfaceInfo, FILE* Stream);
 
+			/** Identical to CDC_Device_CreateStream(), except that reads are blocking until the calling stream function terminates
+			 *  the transfer. While blocking, the USB and CDC service tasks are called repeatedly to maintain USB communications.
+			 *
+			 *  \param[in,out] CDCInterfaceInfo  Pointer to a structure containing a CDC Class configuration and state
+			 *  \param[in,out] Stream  Pointer to a FILE structure where the created stream should be placed
+			 */
+			void CDC_Device_CreateBlockingStream(USB_ClassInfo_CDC_Device_t* CDCInterfaceInfo, FILE* Stream);
+
 	/* Private Interface - For use in library only: */
 	#if !defined(__DOXYGEN__)
 		/* Function Prototypes: */
 			#if defined(INCLUDE_FROM_CDC_CLASS_DEVICE_C)
 				static int CDC_Device_putchar(char c, FILE* Stream);
 				static int CDC_Device_getchar(FILE* Stream);
+				static int CDC_Device_getchar_Blocking(FILE* Stream);
 				
 				void CDC_Device_Event_Stub(void);
 				void EVENT_CDC_Device_LineEncodingChanged(USB_ClassInfo_CDC_Device_t* const CDCInterfaceInfo)

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

@@ -353,6 +353,17 @@ static int CDC_Host_getchar(FILE* Stream)
 	return CDC_Host_ReceiveByte((USB_ClassInfo_CDC_Host_t*)fdev_get_udata(Stream));
 }
 
+static int CDC_Host_getchar_Blocking(FILE* Stream)
+{
+	while (!(CDC_Host_BytesReceived((USB_ClassInfo_CDC_Host_t*)fdev_get_udata(Stream))))
+	{
+		CDC_Host_USBTask((USB_ClassInfo_CDC_Host_t*)fdev_get_udata(Stream));
+		USB_USBTask();
+	}
+
+	return CDC_Host_ReceiveByte((USB_ClassInfo_CDC_Host_t*)fdev_get_udata(Stream));
+}
+
 void CDC_Host_Event_Stub(void)
 {
 

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

@@ -219,6 +219,14 @@
 			 */
 			void CDC_Host_CreateStream(USB_ClassInfo_CDC_Host_t* CDCInterfaceInfo, FILE* Stream);
 
+			/** Identical to CDC_Host_CreateStream(), except that reads are blocking until the calling stream function terminates
+			 *  the transfer. While blocking, the USB and CDC service tasks are called repeatedly to maintain USB communications.
+			 *
+			 *  \param[in,out] CDCInterfaceInfo  Pointer to a structure containing a CDC Class configuration and state
+			 *  \param[in,out] Stream  Pointer to a FILE structure where the created stream should be placed
+			 */
+			void CDC_Host_CreateBlockingStream(USB_ClassInfo_CDC_Host_t* CDCInterfaceInfo, FILE* Stream);
+
 			/** CDC class driver event for a control line state change on a CDC host interface. This event fires each time the device notifies
 			 *  the host of a control line state change (containing the virtual serial control line states, such as DCD) and may be hooked in the
 			 *  user program by declaring a handler function with the same name and parameters listed here. The new control line states
@@ -247,6 +255,7 @@
 			#if defined(INCLUDE_FROM_CDC_CLASS_HOST_C)
 				static int CDC_Host_putchar(char c, FILE* Stream);
 				static int CDC_Host_getchar(FILE* Stream);
+				static int CDC_Host_getchar_Blocking(FILE* Stream);
 
 				void CDC_Host_Event_Stub(void);
 				void EVENT_CDC_Host_ControLineStateChanged(USB_ClassInfo_CDC_Host_t* const CDCInterfaceInfo)