source: xtideuniversalbios/trunk/XTIDE_Universal_BIOS/Src/Handlers/Int13h/EBIOS/AH48h_GetExtendedDriveParameters.asm@ 590

; Project name  :   XTIDE Universal BIOS
; Description   :   Int 13h function AH=48h, Get Extended Drive Parameters.

;
; XTIDE Universal BIOS and Associated Tools
; Copyright (C) 2009-2010 by Tomi Tilli, 2011-2013 by XTIDE Universal BIOS Team.
;
; This program is free software; you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation; either version 2 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
; GNU General Public License for more details.
; Visit http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
;

; Section containing code
SECTION .text

;--------------------------------------------------------------------
; Int 13h function AH=48h, Get Extended Drive Parameters.
;
; It is not completely clear what this function should return as total sector count in some cases.
; What is certain is that:
; A) Phoenix Enhanced Disk Drive Specification v3.0 says that P-CHS values
;    are never returned for drives with more than 15,482,880 sectors (16384*15*63).
;    For those drives we can simply return total sector count from
;    ATA ID WORDs 60 and 61 (LBA28) or WORDs 100-103 (LBA48).
; B) IBM PC DOS 7.1 fdisk32 displays warning message if P-CHS values multiplied
;    together are different than total sector count. Therefore for drives with less
;    than or equal 15,482,880 sectors we MUST NOT return total sector count from
;    ATA ID WORDs 60 and 61.
;
;    Lets take an example. 6 GB Hitachi microdrive reports following values in ATA ID:
;    Sector count from WORDs 60 and 61  : 12,000,556
;    Cylinders                          : 11905
;    Heads                              :    16
;    Sectors per track                  :    63
;
;    When multiplying C*H*S we get      : 12,000,240
;    So the CHS size is a little bit less than LBA size. But we must use
;    the smaller value since C*H*S must equal total sector count!
;
; Now we get to the uncertain area where I could not find any information.
; Award BIOS from 1997 Pentium motherboard returns following values:
;    AH=08h L-CHS:   745, 255, 63 (exactly the same as what we return)
;    => Total Sector Count:       745*255*63 = 11,968,425
;    AH=48h P-CHS: 11873,  16, 63
;    AH=48h Total Sector Count: 11873* 16*63 = 11,967,984
;
; Notice how AH=48h returns lesser total sector count than AH=08h! The only
; way I could think of to get 11873 cylinders is to divide AH=08h sector
; count with P-CHS heads and sectors: (745*255*63) / (16*63) = 11873
;
; The only reason I can think of is that the Award BIOS has a bug and
; uses L-CHS when it should use P-CHS values in the calculation.
;
;
; AH48h_GetExtendedDriveParameters
;   Parameters:
;       SI:     Same as in INTPACK
;       DL:     Translated Drive number
;       DS:DI:  Ptr to DPT (in RAMVARS segment)
;       SS:BP:  Ptr to IDEPACK
;   Parameters on INTPACK:
;       DS:SI:  Ptr to Extended Drive Information Table to fill
;   Returns with INTPACK:
;       AH:     Int 13h return status
;       DS:SI:  Ptr to Extended Drive Information Table
;       CF:     0 if successful, 1 if error
;--------------------------------------------------------------------
AH48h_HandlerForGetExtendedDriveParameters:
    mov     si, di
    push    ds
    pop     es      ; ES = RAMVARS segment
    xor     bx, bx
    dec     bx      ; Set to FFFFh to assume we do not return DPTE

    ; Create DPTE (hardware information for device drivers)
%ifdef MODULE_COMPATIBLE_TABLES
    call    AH41h_GetSupportBitsToCX
    test    cl, ENHANCED_DISK_DRIVE_SUPPORT
    jz      SHORT .DoNotCreateDPTE
    call    CompatibleDPT_CreateDeviceParameterTableExtensionToESBXfromDPTinDSSI
.DoNotCreateDPTE:
%endif ; MODULE_COMPATIBLE_TABLES

    ; Point DS:DI to Extended Drive Information Table to fill
    mov     di, [bp+IDEPACK.intpack+INTPACK.si]
    mov     ds, [bp+IDEPACK.intpack+INTPACK.ds]

    ; Check and adjust Extended Drive Information Table size
    ; to MINIMUM_EDRIVEINFO_SIZE or EDRIVEINFO_SIZE_WITH_DPTE
    mov     ax, MINIMUM_EDRIVEINFO_SIZE
    mov     cx, [di+EDRIVE_INFO.wSize]
    cmp     cx, ax
    jb      Prepare_ReturnFromInt13hWithInvalidFunctionError
    mov     [di+EDRIVE_INFO.wSize], ax
    mov     al, EDRIVEINFO_SIZE_WITH_DPTE
    cmp     cx, ax
    jb      SHORT .SkipEddConfigurationParameters
    mov     [di+EDRIVE_INFO.wSize], al

    ; Store DPTE for standard controllers only,
    ; FFFF:FFFF for non standard controllers
%ifdef MODULE_COMPATIBLE_TABLES
    mov     [di+EDRIVE_INFO.fpDPTE], bx
    mov     [di+EDRIVE_INFO.fpDPTE+2], es
    inc     bx
    jnz     SHORT .SkipEddConfigurationParameters   ; Already stored
    dec     bx
    mov     [di+EDRIVE_INFO.fpDPTE+2], bx   ; Segment = FFFFh
%else
    mov     [di+EDRIVE_INFO.fpDPTE], bx
    mov     [di+EDRIVE_INFO.fpDPTE+2], bx
%endif ; MODULE_COMPATIBLE_TABLES

    ; Fill Extended Drive Information Table in DS:DI from DPT in ES:SI
.SkipEddConfigurationParameters:
    mov     WORD [di+EDRIVE_INFO.wFlags], FLG_DMA_BOUNDARY_ERRORS_HANDLED_BY_BIOS

    ; Store total sector count
    call    Registers_ExchangeDSSIwithESDI
    call    AccessDPT_GetLbaSectorCountToBXDXAX
    call    Registers_ExchangeDSSIwithESDI
    mov     [di+EDRIVE_INFO.qwTotalSectors], ax
    mov     [di+EDRIVE_INFO.qwTotalSectors+2], dx
    mov     [di+EDRIVE_INFO.qwTotalSectors+4], bx
    xor     cx, cx
    mov     [di+EDRIVE_INFO.qwTotalSectors+6], cx   ; Always zero
    mov     WORD [di+EDRIVE_INFO.wSectorSize], 512

    ; Store P-CHS. Based on phoenix specification this is returned only if
    ; total sector count is 15,482,880 or less.
    sub     ax, (MAX_SECTOR_COUNT_TO_RETURN_PCHS+1) & 0FFFFh
    sbb     dx, (MAX_SECTOR_COUNT_TO_RETURN_PCHS+1) >> 16
    sbb     bx, cx      ; Zero
    jnc     SHORT .DoNotSetChsFlag
    or      BYTE [di+EDRIVE_INFO.wFlags], FLG_CHS_INFORMATION_IS_VALID

    ; We store something to P-CHS anyway since some HW detection programs
    ; ignore the CHS flag. And we should at least clear the variables anyway
    ; since the same buffer is used for all drives so it contains parameters
    ; from previously scanned drive.
.DoNotSetChsFlag:
    eMOVZX  dx, [es:si+DPT.bPchsHeads]
    mov     [di+EDRIVE_INFO.dwHeads], dx
    mov     [di+EDRIVE_INFO.dwHeads+2], cx

    mov     dl, [es:si+DPT.bPchsSectorsPerTrack]
    mov     [di+EDRIVE_INFO.dwSectorsPerTrack], dx
    mov     [di+EDRIVE_INFO.dwSectorsPerTrack+2], cx

    mov     dx, [es:si+DPT.wPchsCylinders]
    mov     [di+EDRIVE_INFO.dwCylinders], dx
    mov     [di+EDRIVE_INFO.dwCylinders+2], cx

    xchg    ax, cx      ; Success
    jmp     Int13h_ReturnFromHandlerAfterStoringErrorCodeFromAH