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

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

;
; XTIDE Universal BIOS and Associated Tools
; Copyright (C) 2009-2010 by Tomi Tilli, 2011-2023 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, DX, DI
;--------------------------------------------------------------------
RamVars_Initialize:
    push    es

    mov     ax, [cs:ROMVARS.wRamVars]
    test    ax, ax                      ; UMB segment or LITE_MODE_RAMVARS_SEGMENT?
    jnz     SHORT .InitializeRamvars    ; No need to steal RAM

    mov     ds, ax
    mov     al, [cs:ROMVARS.bStealSize]
    sub     [BDA.wBaseMem], ax
%ifdef USE_186
    imul    ax, [BDA.wBaseMem], 64
%else
    mov     al, 64
    mul     WORD [BDA.wBaseMem]
%endif

.InitializeRamvars:
    xor     di, di
    mov     ds, ax
    mov     es, ax
    mov     cx, RAMVARS_size
    call    Memory_ZeroESDIwithSizeInCX
    mov     WORD [RAMVARS.wDrvDetectSignature], RAMVARS_DRV_DETECT_SIGNATURE
    mov     WORD [RAMVARS.wSignature], RAMVARS_RAM_SIGNATURE
%ifdef MODULE_DRIVEXLATE
    call    DriveXlate_Reset
%endif

    pop     es
    ret


;--------------------------------------------------------------------
; Returns segment to RAMVARS.
; RAMVARS might be located at the top of interrupt vectors (0030:0000h),
; at the top of system base RAM or in a user configured UMB.
;
; RamVars_GetSegmentToDS
;   Parameters:
;       Nothing
;   Returns:
;       DS:     RAMVARS segment
;   Corrupts registers:
;       DI
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
RamVars_GetSegmentToDS:
    mov     ds, [cs:ROMVARS.wRamVars]
    mov     di, ds
    test    di, di                  ; UMB segment or LITE_MODE_RAMVARS_SEGMENT?
    jnz     SHORT .Return

;%ifdef USE_186
;   imul    di, [BDA.wBaseMem], 64  ; 2 bytes less but slower, especially on 386/486 processors
;%else
    mov     di, [BDA.wBaseMem]      ; Load available base memory size in kB
    eSHL_IM di, 6                   ; Segment to first stolen kB (*=40h)
;%endif
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)
.Return:
    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, bx
    mov     bl, [BDA.bHDCount]
    MAX_U   al, bl
    pop     ds
    ret
%endif


%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


;--------------------------------------------------------------------
; 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


;--------------------------------------------------------------------
; 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