Add USB Midi support.

It also introduces a txbuffer which copies data into it but passes
the buffer straight to the USB rather than another copy.

src/class/midi/midi.h

@@ -0,0 +1,84 @@
+/**************************************************************************/
+/*!
+    @file     cdc.h
+    @author   hathach (tinyusb.org)
+
+    @section LICENSE
+
+    Software License Agreement (BSD License)
+
+    Copyright (c) 2013, hathach (tinyusb.org)
+    All rights reserved.
+
+    Redistribution and use in source and binary forms, with or without
+    modification, are permitted provided that the following conditions are met:
+    1. Redistributions of source code must retain the above copyright
+    notice, this list of conditions and the following disclaimer.
+    2. Redistributions in binary form must reproduce the above copyright
+    notice, this list of conditions and the following disclaimer in the
+    documentation and/or other materials provided with the distribution.
+    3. Neither the name of the copyright holders nor the
+    names of its contributors may be used to endorse or promote products
+    derived from this software without specific prior written permission.
+
+    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ''AS IS'' AND ANY
+    EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+    WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+    DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY
+    DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+    INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION HOWEVER CAUSED AND
+    ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+    INCLUDING NEGLIGENCE OR OTHERWISE ARISING IN ANY WAY OUT OF THE USE OF THIS
+    SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+    This file is part of the tinyusb stack.
+*/
+/**************************************************************************/
+
+/** \ingroup group_class
+ *  \defgroup ClassDriver_CDC Communication Device Class (CDC)
+ *            Currently only Abstract Control Model subclass is supported
+ *  @{ */
+
+#ifndef _TUSB_MIDI_H__
+#define _TUSB_MIDI_H__
+
+#include "common/tusb_common.h"
+
+#ifdef __cplusplus
+ extern "C" {
+#endif
+
+//--------------------------------------------------------------------+
+// FUNCTIONAL DESCRIPTOR (COMMUNICATION INTERFACE)
+//--------------------------------------------------------------------+
+/// Header Functional Descriptor (Communication Interface)
+typedef struct ATTR_PACKED
+{
+  uint8_t bLength            ; ///< Size of this descriptor in bytes.
+  uint8_t bDescriptorType    ; ///< Descriptor Type, must be Class-Specific
+  uint8_t bDescriptorSubType ; ///< Descriptor SubType one of above MIDI_FUCN_DESC_
+  uint16_t bcdMSC            ; ///< MidiStreaming SubClass release number in Binary-Coded Decimal
+  uint16_t wTotalLength      ;
+}midi_desc_func_header_t;
+
+/// Union Functional Descriptor (Communication Interface)
+typedef struct ATTR_PACKED
+{
+  uint8_t bLength                  ; ///< Size of this descriptor in bytes.
+  uint8_t bDescriptorType          ; ///< Descriptor Type, must be Class-Specific
+  uint8_t bDescriptorSubType       ; ///< Descriptor SubType one of above CDC_FUCN_DESC_
+  uint8_t bControlInterface        ; ///< Interface number of Communication Interface
+  uint8_t bSubordinateInterface    ; ///< Array of Interface number of Data Interface
+}cdc_desc_func_union_t;
+
+/** @} */
+
+#ifdef __cplusplus
+ }
+#endif
+
+#endif
+
+/** @} */