source: xtideuniversalbios/tags/XTIDE_Universal_BIOS_v2.0.0_beta1/Src/Handlers/Int13h/Tools/Prepare.asm@ 623

; Project name  :   XTIDE Universal BIOS
; Description   :   Functions for preparing data buffer for transfer.

; Section containing code
SECTION .text

;--------------------------------------------------------------------
; Prepare_ByLoadingDapToESSIandVerifyingForTransfer
;   Parameters:
;       SI:     Offset to DAP
;       DS:DI:  Ptr to DPT
;       SS:BP:  Ptr to IDEPACK
;   Parameters on INTPACK:
;       DS:SI:  Ptr to Disk Address Packet
;   Returns:
;       BX:     Index to command lookup table
;       ES:SI:  Ptr to Disk Address Packet (DAP)
;       Exits from INT 13h if invalid DAP
;   Corrupts registers:
;       AX, DX
;--------------------------------------------------------------------
%ifdef MODULE_EBIOS
ALIGN JUMP_ALIGN
Prepare_ByLoadingDapToESSIandVerifyingForTransfer:
    ; Load pointer to DAP to ES:SI and make sure it is valid
    mov     es, [bp+IDEPACK.intpack+INTPACK.ds] ; ES:SI to point Disk Address Packet
    cmp     BYTE [es:si+DAP.bSize], MINIMUM_DAP_SIZE
    jb      SHORT InvalidDAP

    ; Make sure that sector count is valid
    mov     ax, [es:si+DAP.wSectorCount]
    test    ax, ax
    jz      SHORT ZeroSectorsRequestedSoNoErrors
    cmp     ax, BYTE 127
    ja      SHORT InvalidNumberOfSectorsRequested

    ; Get EBIOS command index to BX
    ; LBA28 or LBA48 command
    cwd
    mov     al, [es:si+DAP.qwLBA+3] ; Load LBA48 byte 3 (bits 24...31)
    and     al, 0F0h                ; Clear LBA28 bits 24...27
    or      ax, [es:si+DAP.qwLBA+4] ; Set bits from LBA bytes 4 and 5
    cmp     dx, ax                  ; Set CF if any of bits 28...47 set
    rcl     dx, 1                   ; DX = 0 for LBA28, DX = 1 for LBA48
    call    Prepare_GetOldInt13hCommandIndexToBX
    or      bx, dx                  ; Set block mode / single sector bit
    ret
%endif


;--------------------------------------------------------------------
; Prepare_GetOldInt13hCommandIndexToBX
;   Parameters:
;       DS:DI:  Ptr to DPT
;   Returns:
;       BX:     Index to command lookup table
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
Prepare_GetOldInt13hCommandIndexToBX:
    ; Block mode or single sector
    mov     bl, [di+DPT.bFlagsHigh]
    and     bx, BYTE FLGH_DPT_BLOCK_MODE_SUPPORTED  ; Bit 1
    ret


;---------------------------------------------------------------------
; Prepare_BufferToESSIforOldInt13hTransfer
;   Parameters:
;       AL:     Number of sectors to transfer
;       SS:BP:  Ptr to IDEPACK
;   Parameters on INTPACK:
;       ES:BX:  Ptr to data buffer
;   Returns:
;       ES:SI:  Ptr to normalized data buffer
;       Exits INT 13h if error
;   Corrupts registers:
;       BX
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
Prepare_BufferToESSIforOldInt13hTransfer:
    ; Normalize buffer pointer
    mov     bx, [bp+IDEPACK.intpack+INTPACK.bx] ; Load offset
    mov     si, bx
    eSHR_IM bx, 4                               ; Divide offset by 16
    add     bx, [bp+IDEPACK.intpack+INTPACK.es]
    mov     es, bx                              ; Segment normalized
    and     si, BYTE 0Fh                        ; Offset normalized
    ; Fall to Prepare_ByValidatingSectorsInALforOldInt13h


;---------------------------------------------------------------------
; Prepare_ByValidatingSectorsInALforOldInt13h
;   Parameters:
;       AL:     Number of sectors to transfer
;   Returns:
;       Exits INT 13h if invalid number of sectors in AL
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
Prepare_ByValidatingSectorsInALforOldInt13h:
    test    al, al
    js      SHORT .CheckZeroOffsetFor128Sectors     ; 128 or more
    jz      SHORT InvalidNumberOfSectorsRequested   ; Zero not allowed for old INT 13h
    ret     ; Continue with transfer

ALIGN JUMP_ALIGN
.CheckZeroOffsetFor128Sectors:
    cmp     al, 128
    ja      SHORT InvalidNumberOfSectorsRequested
    test    si, si                              ; Offset must be zero to xfer 128 sectors
    jnz     SHORT CannotAlignPointerProperly
    ret     ; Continue with transfer

InvalidDAP:
InvalidNumberOfSectorsRequested:
Prepare_ReturnFromInt13hWithInvalidFunctionError:
    mov     ah, RET_HD_INVALID
    SKIP2B  f
CannotAlignPointerProperly:
    mov     ah, RET_HD_BOUNDARY
ZeroSectorsRequestedSoNoErrors:
    jmp     Int13h_ReturnFromHandlerAfterStoringErrorCodeFromAH



; Command lookup tables
g_rgbReadCommandLookup:
    db      COMMAND_READ_SECTORS        ; 00b, CHS or LBA28 single sector
    db      COMMAND_READ_SECTORS_EXT    ; 01b, LBA48 single sector
    db      COMMAND_READ_MULTIPLE       ; 10b, CHS or LBA28 block mode
    db      COMMAND_READ_MULTIPLE_EXT   ; 11b, LBA48 block mode

g_rgbWriteCommandLookup:
    db      COMMAND_WRITE_SECTORS
    db      COMMAND_WRITE_SECTORS_EXT
    db      COMMAND_WRITE_MULTIPLE
    db      COMMAND_WRITE_MULTIPLE_EXT

g_rgbVerifyCommandLookup:
    db      COMMAND_VERIFY_SECTORS
    db      COMMAND_VERIFY_SECTORS_EXT
    db      COMMAND_VERIFY_SECTORS
    db      COMMAND_VERIFY_SECTORS_EXT