INT 2fH 1607H: Device Call Out

                                                      Compatibility: Win 3.x 
  Expect: AX    1607H
          BX    Device ID (see VxD IDs)
          ??    other regs, as defined per device
  Return: ??    varies per device
    Info: TSRs and DOS-level device drivers may intercept this function as
          a way to receive communication from a Windows device driver.

          This is normally used by a TSR which has loaded a windows virtual
          device (and therefore knows its ID) or to access APIs published
          for existing Windows Virtual Device drivers (VxD).  The virtual
          device invokes this fn to request specific actions.  You may
          return information in registers.

          The INT 2fH 1684H (get device entry-point) service provides
          another means of communication.

See Also: INT 2fH 16xxH: Enh386 Windows Services & Notifications
          INT 2fH: Multiplex Interrupt
          DOS Functions