C programming Language only Support either Variable Declarations or Enum Declarations at the starting of the File. For that reason,Added the below mentioned code at the starting of the File(hci_transport_h2_libusb.c)

typedef enum { 193 H2_W4_SCO_HEADER = 1, 194 H2_W4_PAYLOAD, 195 } H2_SCO_STATE; 196
197 static uint8_t sco_buffer[255+3 + SCO_PACKET_SIZE]; 198 static uint16_t sco_read_pos; 199 static uint16_t sco_bytes_to_read; 200 static H2_SCO_STATE sco_state;

Hi. Do you have a particular compiler that give a warning or error? Yes, typedefs and vars should be a the beginning. Fixed in r3192