þa‹Rþdþwÿÿÿÿÿÿÿÿÿÿþ m^9þhEntryPoint.Incý oPþ nSystem-wide NAME Start ; This is start.asm. This acts as a main ; module for gridlink & phonelink driver. This has to ; be done because the Intel linker does not have a start ; command. CGROUP GROUP CODE DGROUP GROUP DATA %IF (%MsDOs) THEN ( PUBLIC RamEntryPOint )FI %IF (%ForRom) THEN ( EXTRN CpGetMySLot: NEAR, CpSetActiveSlot: NEAR PUBLIC MySlotNo )FI CODE SEGMENT BYTE PUBLIC 'CODE' ASSUME CS:CGROUP EXTRN EntryPoint: NEAR $EJECT ;&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& ; ; RomEntryPoint ; ; For every driver request, the Os calls RamEntryPoint. It sets up the ; DS and the right ROM bank and calls this routine in ROM without adding ; any paramters. Hence the following is on the stack. ; ; RamEntryPoint's CS:IP ; OSes BP ; OSes DS ; OSes CS:IP ; pError ; pointer to param List ; request ; ; This routine pushes the original three parameters again on the stack & ; makes a short call to the plm entrypoint in the phonelink driver. ; ;&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& RomEntryPoint PROC FAR Parameters STRUC RamBP DW ? ; BP of Ram EntryPOint RamRetAddr DD ? ; Return Address in RamEntryPoint %IF (%ForRom) THEN ( SlotNo DW ? ; Slot # is saved here by RamEntryPoint )FI OSBPnDS DD ? ; OS's BP & DS OsRetAddr DD ? ; Return Address in OS. pError DD ? ; pointer to error variable. pPl DD ? ; pointer to param list for request. request DW ? ; the request itself. Parameters ENDS ; do the usual stuff PUSH BP MOV BP, SP ; push the original 3 parameters and call the actual entrypoint PUSH WORD PTR SS:[BP].request ; push request PUSH WORD PTR SS:[BP].pPl+2 ; push segment of param list PUSH WORD PTR SS:[BP].pPl ; push offset of param list PUSH WORD PTR SS:[BP].pError+2 ; push segment of pError PUSH WORD PTR SS:[BP].pError ; push offset of pError CALL EntryPoint POP BP ; restore RamEntryPoint's BP. RET ; this should be a long return. RomEntryPoint ENDP CODE ENDS PURGE request,pPl,pError,OsRetAddr,OsBPnDS $EJECT DATA SEGMENT BYTE PUBLIC 'DATA' ASSUME CS:DGROUP %IF (%ForRom) THEN ( ddInitialize EQU 0 ; copied from Os.Device.Inc PhoneLinkRomID EQU 10 ; Unique Rom ID for this version of phonelink. MySlotNO DB ? ; Data Seg Vrbl fr saving Phonelink's Slot# )FI ;&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& ; ; RamEntryPoint ; ; For every driver request, the Os calls RamEntryPoint. Since this is ; in the data segemnt, the CS is what we want for DS. Setting up DS is ; a piece of cake. Do bank switching to set the ROM containing the ; phonelink ROM, and call RomEntryPoint. ; ; This routine is placed in the data segement. Hence all the fix-ups ; are in RAM. The stack at this time contains: ; ; OSes CS:IP ; pError ; pointer to param List ; request ; ;&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& RamEntryPoint PROC FAR StackParameters STRUC OSBPnDS DD ? ; OS's BP & DS OsRetAddr DD ? ; Return Address in OS. pError DD ? ; pointer to error variable. pPl DD ? ; pointer to param list for request. request DW ? ; the request itself. StackParameters ENDS PUSH DS ; Save OSes DS. PUSH BP ; Save OSes BP. ; Set up DS for the driver MOV AX,CS MOV DS,AX %IF (%ForRom) THEN ( ; ; If the request is ddInitialize then find the ROM slot no and save it in a ; static data segment variable. It is assumed that ddInitialize will be the ; very first request. ; CMP WORD PTR SS:[BP].request, ddInitialize JNZ SlotNoIsKnown MOV AX, PhonelinkRomID ; param for CpGetMySlot PUSH AX CALL CpGetMySlot ; my slot # will be returned in AL MOV DS:MySLotNo, AL ; save my slot number in DS variable ; ; Set the current ROM slot to Phonelink slot, the slot no is ; saved in mySlotNo. ; SlotNoIsKnown: XOR AX, AX ; clear AH MOV AL, DS:MySlotNo ; get slot number for phonelink rom PUSH AX ; param 1 for CpSetActiveSlot CALL CpSetActiveSlot ; set new slot & returns old slot PUSH AX ; save old slot on stack so that slot ; can be restored when request is done. )FI ; ; Now call rom entrypoint, which knows that the stack contains the original ; 3 parameters plus whatever is put on stack by RomEntryPoint. ; CALL RomEntryPoint ; Make a long call into ROM %IF (%ForRom) THEN ( ; ; Restore the current ROM slot to the ROM slot in use when this driver was ; called. The OldSlotNo is already on the stack. CALL CpSetActiveSlot )FI ; Now restore OS's environment and return. ; POP BP ; save OSes BP POP DS ; save OSes DS RET 10 ; 10 bytes of parameters RamEntryPoint ENDP DATA ENDS %IF (%MSDOS) THEN (END) ELSE (END RamEntryPoint)FI