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.

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INT 2fH 1607H: Device Call Out