qmk_firmware/tmk_core/protocol/midi/qmk_midi.h

#pragma once

#ifdef MIDI_ENABLE
  #include "midi.h"
  extern MidiDevice midi_device;
  void setup_midi(void);
  void send_midi_packet(MIDI_EventPacket_t* event);
  bool recv_midi_packet(MIDI_EventPacket_t* const event);
#endif