source: xtideuniversalbios/tags/XTIDE_Universal_BIOS_v2.0.0_beta1/Src/Handlers/Int13h/AH0h_HReset.asm

; Project name  :   XTIDE Universal BIOS
; Description   :   Int 13h function AH=0h, Disk Controller Reset.

; Section containing code
SECTION .text

;--------------------------------------------------------------------
; Int 13h function AH=0h, Disk Controller Reset.
;
; Note: We handle all AH=0h calls, even for drives handled by other
; BIOSes!
;
; AH0h_HandlerForDiskControllerReset
;   Parameters:
;       DL:     Translated Drive number (ignored so all drives are reset)
;               If bit 7 is set all hard disks and floppy disks reset.
;       DS:DI:  Ptr to DPT (or Null if foreign drive)
;       SS:BP:  Ptr to IDEPACK
;   Returns with INTPACK:
;       AH:     Int 13h return status (from drive requested in DL)
;       CF:     0 if successful, 1 if error
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
AH0h_HandlerForDiskControllerReset:
    eMOVZX  bx, dl                      ; Copy requested drive to BL, zero BH to assume no errors
    call    ResetFloppyDrivesWithInt40h

%ifdef MODULE_SERIAL_FLOPPY
;
; "Reset" emulated serial floppy drives, if any.  There is nothing to actually do for this reset,
; but record the proper error return code if one of these floppy drives is the drive requested.
;
    call    RamVars_UnpackFlopCntAndFirstToAL
    cbw                                                 ; Clears AH (there are flop drives) or ffh (there are not)
                                                        ; Either AH has success code (flop drives are present)
                                                        ; or it doesn't matter because we won't match drive ffh

    cwd                                                 ; clears DX (there are flop drives) or ffffh (there are not)

    adc     dl, al                                      ; second drive (CF set) if present
                                                        ; If no drive is present, this will result in ffh which
                                                        ; won't match a drive
    call    BackupErrorCodeFromTheRequestedDriveToBH
    mov     dl, al                                      ; We may end up doing the first drive twice (if there is
    call    BackupErrorCodeFromTheRequestedDriveToBH    ; only one drive), but doing it again is not harmful.
%endif

    test    bl, bl                                      ; If we were called with a floppy disk, then we are done,
    jns     SHORT .SkipHardDiskReset                    ; don't do hard disks.

    call    ResetForeignHardDisks

    ; Resetting our hard disks will modify dl and bl to be idevars offset based instead of drive number based,
    ; such that this call must be the last in the list of reset routines called.
    ;
    ; This needs to happen after ResetForeignHardDisks, as that call may have set the error code for 80h,
    ; and we need to override that value if we are xlate'd into 80h with one of our drives.
    ;
    call    ResetHardDisksHandledByOurBIOS

.SkipHardDiskReset:
    mov     ah, bh
    jmp     Int13h_ReturnFromHandlerAfterStoringErrorCodeFromAH


;--------------------------------------------------------------------
; ResetFloppyDrivesWithInt40h
;   Parameters:
;       BL:     Requested drive (DL when entering AH=00h)
;   Returns:
;       BH:     Error code from requested drive (if available)
;   Corrupts registers:
;       AX, DL, DI
;--------------------------------------------------------------------
ResetFloppyDrivesWithInt40h:
    call    GetDriveNumberForForeignHardDiskHandlerToDL
    and     dl, 7Fh                     ; Clear hard disk bit
    xor     ah, ah                      ; Disk Controller Reset
    int     BIOS_DISKETTE_INTERRUPT_40h
    jmp     SHORT BackupErrorCodeFromTheRequestedDriveToBH


;--------------------------------------------------------------------
; ResetForeignHardDisks
;   Parameters:
;       BL:     Requested drive (DL when entering AH=00h)
;       DS:     RAMVARS segment
;   Returns:
;       BH:     Error code from requested drive (if available)
;   Corrupts registers:
;       AX, DL, DI
;--------------------------------------------------------------------
ResetForeignHardDisks:
    call    GetDriveNumberForForeignHardDiskHandlerToDL
    xor     ah, ah                      ; Disk Controller Reset
    call    Int13h_CallPreviousInt13hHandler
;;; fall-through to BackupErrorCodeFromTheRequestedDriveToBH


;--------------------------------------------------------------------
; BackupErrorCodeFromTheRequestedDriveToBH
;   Parameters:
;       AH:     Error code from the last resetted drive
;       DL:     Drive last resetted
;       BL:     Requested drive (DL when entering AH=00h)
;   Returns:
;       BH:     Backuped error code
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
BackupErrorCodeFromTheRequestedDriveToBH:
    cmp     dl, bl              ; Requested drive?
    eCMOVE  bh, ah
    ret


;--------------------------------------------------------------------
; GetDriveNumberForForeignHardDiskHandlerToDL
;   Parameters:
;       BL:     Requested drive (DL when entering AH=00h)
;       DS:     RAMVARS segment
;   Returns:
;       DS:DI:  Ptr to DPT if our drive (or Null if foreign drive)
;       DL:     BL if foreign drive
;               80h if our drive
;--------------------------------------------------------------------
GetDriveNumberForForeignHardDiskHandlerToDL:
    mov     dl, bl
    test    di, di
    jz      SHORT .Return
    mov     dl, 80h             ; First possible Hard Disk should be safe value
.Return:
    ret

AH0h_ResetAllOurHardDisksAtTheEndOfDriveInitialization equ ResetHardDisksHandledByOurBIOS.ErrorCodeNotUsed

;--------------------------------------------------------------------
; ResetHardDisksHandledByOurBIOS
;   Parameters:
;       DS:DI:  Ptr to DPT for requested drive
;               If DPT pointer is not available, or error result in BH won't be used anyway,
;               enter through .ErrorCodeNotUsed.
;       SS:BP:  Ptr to IDEPACK
;   Returns:
;       BH:     Error code from requested drive (if available)
;   Corrupts registers:
;       AX, BX, CX, DX, SI, DI
;--------------------------------------------------------------------
ResetHardDisksHandledByOurBIOS:
    xor     bl, bl                                      ; Assume Null IdevarsOffset for now, assuming foreign drive
    test    di, di
    jz      .ErrorCodeNotUsed
    mov     bl, [di+DPT.bIdevarsOffset]                 ; replace drive number with Idevars pointer for cmp with dl

.ErrorCodeNotUsed:                                      ; BH will be garbage on exit if this entry point is used,
                                                        ; but reset of all drives will still happen

    mov     dl, ROMVARS.ideVars0                        ; starting Idevars offset

    ; Get count of ALL Idevars structures, not just the ones that are configured.  This may seem odd, 
    ; but it catches the .ideVarsSerialAuto structure, which would not be scanned if the count from
    ; RamVars_GetIdeControllerCountToCX was used.  Unused controllers won't make a difference, since no DPT
    ; will point to them.  Performance isn't an issue, as this is a reset operation.
    ;
    mov     cx, (ROMVARS.ideVarsEnd - ROMVARS.ideVarsBegin) / IDEVARS_size

.loop:
    call    FindDPT_ForIdevarsOffsetInDL                ; look for the first drive on this controller, if any
    jc      .notFound

    call    AHDh_ResetDrive                             ; reset master and slave on that controller
    call    BackupErrorCodeFromTheRequestedDriveToBH    ; save error code if same controller as drive from entry

.notFound:
    add     dl, IDEVARS_size                            ; move Idevars pointer forward
    loop    .loop

.done:
    ret