source: xtideuniversalbios/trunk/XTIDE_Universal_BIOS/Src/VariablesAndDPTs/RamVars.asm@ 502

; Project name  :   XTIDE Universal BIOS
; Description   :   Functions for accessings RAMVARS.

;
; XTIDE Universal BIOS and Associated Tools 
; Copyright (C) 2009-2010 by Tomi Tilli, 2011-2012 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

;--------------------------------------------------------------------
; Initializes RAMVARS.
; Drive detection can be started after this function returns.
;
; RamVars_Initialize
;   Parameters:
;       Nothing
;   Returns:
;       DS:     RAMVARS segment
;   Corrupts registers:
;       AX, CX, DI
;--------------------------------------------------------------------
RamVars_Initialize:
    push    es
    ; Fall to .StealMemoryForRAMVARS

;--------------------------------------------------------------------
; .StealMemoryForRAMVARS
;   Parameters:
;       Nothing
;   Returns:
;       DS:     RAMVARS segment
;   Corrupts registers:
;       AX
;--------------------------------------------------------------------
.StealMemoryForRAMVARS:
%ifndef USE_AT
    mov     ax, LITE_MODE_RAMVARS_SEGMENT
    test    BYTE [cs:ROMVARS.wFlags], FLG_ROMVARS_FULLMODE
    jz      SHORT .InitializeRamvars    ; No need to steal RAM
%endif

    LOAD_BDA_SEGMENT_TO ds, ax, !       ; Zero AX
    mov     al, [cs:ROMVARS.bStealSize]
    sub     [BDA.wBaseMem], ax
    mov     ax, [BDA.wBaseMem]
    eSHL_IM ax, 6                       ; Segment to first stolen kB (*=40h)
    ; Fall to .InitializeRamvars

;--------------------------------------------------------------------
; .InitializeRamvars
;   Parameters:
;       AX:     RAMVARS segment
;   Returns:
;       DS:     RAMVARS segment
;   Corrupts registers:
;       AX, CX, DI, ES
;--------------------------------------------------------------------
.InitializeRamvars:
    mov     ds, ax
    mov     es, ax
    mov     cx, RAMVARS_size
    xor     di, di
    call    Memory_ZeroESDIwithSizeInCX
    mov     WORD [RAMVARS.wDrvDetectSignature], RAMVARS_DRV_DETECT_SIGNATURE
    mov     WORD [RAMVARS.wSignature], RAMVARS_RAM_SIGNATURE
    ; Fall to .InitializeInt13hStackChangeVariables

;--------------------------------------------------------------------
; .InitializeInt13hStackChangeVariables
;   Parameters:
;       DS:     RAMVARS segment
;   Returns:
;       Nothing
;   Corrupts registers:
;       AX
;--------------------------------------------------------------------
%ifdef RELOCATE_INT13H_STACK
.InitializeInt13hStackChangeVariables:
    eMOVZX  ax, BYTE [cs:ROMVARS.bStealSize]
    eSHL_IM ax, 10          ; kiB to Bytes = Top of stack offset
    mov     [RAMVARS.wNewStackOffset], ax
%endif

;; There used to be a DriveXlate_Reset call here.  It isn't necessary, as we reset
;; when entering the boot menu and also before transferring control at boot time and
;; for ROM boots (in int19h.asm).
        
    pop     es
    ret

;--------------------------------------------------------------------
; Returns segment to RAMVARS.
; RAMVARS might be located at the top of interrupt vectors (0030:0000h)
; or at the top of system base RAM.
;
; RamVars_GetSegmentToDS
;   Parameters:
;       Nothing
;   Returns:
;       DS:     RAMVARS segment
;   Corrupts registers:
;       DI
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
RamVars_GetSegmentToDS:

%ifndef USE_AT  ; Always in Full Mode for AT builds
    test    BYTE [cs:ROMVARS.wFlags], FLG_ROMVARS_FULLMODE
    jnz     SHORT .GetStolenSegmentToDS
    %ifndef USE_186
        mov     di, LITE_MODE_RAMVARS_SEGMENT
        mov     ds, di
    %else
        push    LITE_MODE_RAMVARS_SEGMENT
        pop     ds
    %endif
    ret
%endif

ALIGN JUMP_ALIGN
.GetStolenSegmentToDS:
    LOAD_BDA_SEGMENT_TO ds, di
    mov     di, [BDA.wBaseMem]      ; Load available base memory size in kB
    eSHL_IM di, 6                   ; Segment to first stolen kB (*=40h)
ALIGN JUMP_ALIGN
.LoopStolenKBs:
    mov     ds, di                  ; EBDA segment to DS
    add     di, BYTE 64             ; DI to next stolen kB
    cmp     WORD [RAMVARS.wSignature], RAMVARS_RAM_SIGNATURE
    jne     SHORT .LoopStolenKBs    ; Loop until sign found (always found eventually)
    ret


;--------------------------------------------------------------------
; RamVars_GetHardDiskCountFromBDAtoAX
;   Parameters:
;       DS:     RAMVARS segment
;   Returns:
;       AX:     Total hard disk count
;   Corrupts registers:
;       BX
;--------------------------------------------------------------------
%ifdef MODULE_BOOT_MENU
RamVars_GetHardDiskCountFromBDAtoAX:
    call    RamVars_GetCountOfKnownDrivesToAX
    push    ds
    LOAD_BDA_SEGMENT_TO ds, cx
    mov     bl, [BDA.bHDCount]
    MAX_U   al, bl
    pop     ds
    ret
%endif


;--------------------------------------------------------------------
; RamVars_GetCountOfKnownDrivesToAX
;   Parameters:
;       DS:     RAMVARS segment
;   Returns:
;       AX:     Total hard disk count
;   Corrupts registers:
;       None
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
RamVars_GetCountOfKnownDrivesToAX:
    mov     ax, [RAMVARS.wFirstDrvAndCount]
    add     al, ah
    and     ax, BYTE 7fh
    ret

;--------------------------------------------------------------------
; RamVars_GetIdeControllerCountToCX
;   Parameters:
;       Nothing
;   Returns:
;       CX:     Number of IDE controllers to handle
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
RamVars_GetIdeControllerCountToCX:
    eMOVZX  cx, [cs:ROMVARS.bIdeCnt]
    ret


%ifdef MODULE_SERIAL_FLOPPY
;--------------------------------------------------------------------
; RamVars_UnpackFlopCntAndFirstToAL
;   Parameters:
;       DS:     RAMVARS segment
;   Returns:
;       AL:     First floppy drive number supported
;       CF:     Number of floppy drives supported (clear = 1, set = 2)
;       SF:     Emulating drives (clear = yes, set = no)
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
RamVars_UnpackFlopCntAndFirstToAL:
    mov     al, [RAMVARS.xlateVars+XLATEVARS.bFlopCntAndFirst]
    sar     al, 1
    ret
%endif


%if 0                           ; unused...
;--------------------------------------------------------------------
; RamVars_IsDriveDetectionInProgress
;   Parameters:
;       DS:     RAMVARS segment
;   Returns:
;       ZF:     Set if drive detection is in progress (ROM initialization)
;   Corrupts registers:
;       None
;--------------------------------------------------------------------
RamVars_IsDriveDetectionInProgress:
    cmp     WORD [RAMVARS.wSignature], RAMVARS_DRV_DETECT_SIGNATURE
    ret
%endif