DDJ, December 1995: Examining the Windows 95 Layered File System
by Mark Russinovich and Bryce Cogswell

Listing Two

BeginProc VSD_Device_Init

        ; call IOS to register.  Before returning: IOS will call our
        ; Async_Event routine with the following messages:
        ;       AEP_INITIALIZE
        ;       AEP_CONFIG_DCB

        push    OFFSET32 _Drv_Reg_Pkt   ;packet (DRP)
        VxDCall IOS_Register            ;call registration
        add     esp,04                  ;Clean up stack

        ; decide our status based on the information that IOS gives us
        cmp     _Drv_Reg_Pkt.DRP_reg_result,DRP_REMAIN_RESIDENT
                    ; should we stay?
        je      short VSD_Init_Done     ; yes: return
        cmp     _Drv_Reg_Pkt.DRP_reg_result,DRP_MINIMIZE ; should we minimize?
        je      short VSD_Init_Done     ; yes: we can't minimize any more than
                                        ; normal, so just return with success
        stc                             ; error
VSD_Init_Done:
        ret