Obtaining Configuration Information From XBIOS

;**********************************************************************
;*  XBIOS VxD Query Command
;*  The following code obtains information from XBIOS
;**********************************************************************
xbios_command_block STRUC
opcode     db ?  ;Input: XBIOS opcode 0Eh
reserved   db ?  ;Input: must be zero
bufoff     dw ?  ;Output: ptr to Ontrackr_Ref_Data
bufseg     dw ?  ;Output: ptr to Ontrackr_Ref_Data
xbios_command_block ENDS
;
packet  xbios_command_block <>
;
    push  ds                ;ES = DS
    pop   es                ;ES = DS
    mov   ax,0e000h         ;XBIOS opcode
    mov   bx,offset packet  ;ES:BX = ptr to xbios_command_block
    mov   [bx].opcode,0Eh   ;opcode 0E, VxD Query
    mov   [bx].reserved,0   ;reserved, must be zero
    mov   cx,0              ;signature validation
    mov   dl,80h            ;drive number
    int   13h               ;send it to XBIOS
    jc    VxD_query_not_supported    ;j--XBIOS did not understand
    cmp   cx,1234h          ;signature check?
    jne   VxD_query_not_supported    ;j--XBIOS did not understand

At this point, the bufoff and bufseg fields of the xbios_command_block contain a pointer to the Ontrackr_Ref_Data structure inside the XBIOS driver.

STRUCTURE DEFINITIONS

;**********************************************************************
;   Structure returned for VxD Query command.
;**********************************************************************
Ontrackr_Ref_Data  STRUC
VxD_Data_Size    dw size Ontrackr_Ref_Data  ;size of this struct (33h)
VxD_Chain_Mode   db ?
Drive1_Data      db size Ontrackr_VxD_Data dup(?)
Drive2_Data      db size Ontrackr_VxD_Data dup(?)
Drive3_Data      db size Ontrackr_VxD_Data dup(?)
Drive4_Data      db size Ontrackr_VxD_Data dup(?)
Ontrackr_Ref_Data  ENDS

Note

The VxD_Chain_Mode field provides a mechanism for a device driver to "unhook" XBIOS from the INT13 chain. By placing any non-zero value into this field, XBIOS will simply jump to the next interrupt handler in the INT13 chain.

;**********************************************************************
;   Structure describing a drive controlled by XBIOS
;**********************************************************************
Ontrackr_VxD_Data  STRUC
VxD_INT13_Drive  db ?  ; INT13 drive number
VxD_Delta        dd ?  ; Delta skew value
VxD_Heads        db ?  ; Physical  heads (Word 3 of Identify Data)
VxD_SPT          db ?  ; Physical sectors per track (Word 6 of Identify Data)
VxD_MBS          db ?  ; Multiple Block Size (Blocking factor)
VxD_MBS_Flags    db ?  ; Read/Write Multiple disable flags
VxD_Base_Port    dw ?  ; Base port address (1F0/170)
VxD_IRQ_Channel  db ?  ; Hardware interrupt channel (14/15)
Ontrackr_VxD_Data  ENDS


;**********************************************************************
;Bit Definitions for VxD_MBS_Flags
;**********************************************************************
X_SUPPORT_MULTIPLE   EQU  00001000b   ;drive supports r/w multiple
X_READ_MULT_OFF      EQU  00000100b   ;do not use read multiple
X_WRITE_MULT_OFF     EQU  00000010b   ;do not use write multiple
;