source: xtideuniversalbios/trunk/XTIDE_Universal_BIOS/Src/Handlers/Int13h/AH25h_HDrvID.asm @ 88

; Project name  :   XTIDE Universal BIOS
; Description   :   Int 13h function AH=25h, Get Drive Information.

; Section containing code
SECTION .text

;--------------------------------------------------------------------
; Int 13h function AH=25h, Get Drive Information.
;
; AH25h_HandlerForGetDriveInformation
;   Parameters:
;       AH:     Bios function 25h
;       DL:     Drive number
;       ES:BX:  Ptr to buffer to receive 512-byte drive information
;   Parameters loaded by Int13h_Jump:
;       DS:     RAMVARS segment
;   Returns:
;       ES:BX:  Ptr to 512-byte buffer to receive drive Information
;       AH:     Int 13h return status
;       CF:     0 if succesfull, 1 if error
;       IF:     1
;   Corrupts registers:
;       Flags
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
AH25h_HandlerForGetDriveInformation:
    push    dx
    push    cx
    push    bx
    push    ax
    push    es

    ; Wait until previously selected drive is ready
    call    FindDPT_ForDriveNumber      ; DS:DI now points to DPT
    call    HDrvSel_SelectDriveAndDisableIRQ
    jc      SHORT .Return               ; Return if error

    ; Get drive information
    call    HPIO_NormalizeDataPointer
    push    bx
    mov     dx, [RAMVARS.wIdeBase]      ; Load base port address
    eMOVZX  bx, BYTE [di+DPT.bIdeOff]   ; Load offset to IDEVARS
    mov     bl, [cs:bx+IDEVARS.bBusType]; Load bus type to BL
    mov     bh, [di+DPT.bDrvSel]        ; Load drive sel byte to BH
    pop     di                          ; Pop buffer offset to DI
    call    AH25h_GetDriveInfo          ; Get drive information
.Return:
    pop     es
    jmp     Int13h_PopXRegsAndReturn


;--------------------------------------------------------------------
; Gets drive information using Identify Device command.
;
; AH25h_GetDriveInfo
;   Parameters:
;       BH:     Drive Select byte for Drive and Head Select Register
;       BL:     Bus type
;       DX:     IDE Controller base port address
;       DS:     Segment to RAMVARS
;       ES:DI:  Ptr to buffer to receive 512 byte drive information
;   Returns:
;       AH:     Int 13h return status (will be stored to BDA)
;       CF:     0 if succesfull, 1 if error
;   Corrupts registers:
;       AL, CX
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
AH25h_GetDriveInfo:
    push    di
    push    dx
    push    bx

    ; Select Master or Slave drive.
    ; DO NOT WAIT UNTIL CURRENTLY SELECTED IS READY!
    ; It makes slave drive detection impossible if master is not present.
    mov     [RAMVARS.wIdeBase], dx      ; Store IDE Base port to RAMVARS
    add     dx, BYTE REG_IDE_DRVHD      ; DX to Drive and Head Sel Register
    mov     al, bh                      ; Drive Select byte to AL
    out     dx, al                      ; Select Master or Slave drive
    sub     dx, BYTE REG_IDE_DRVHD      ; Back to IDE Base port
    call    AH25h_GetDriveDetectionTimeoutValue
    call    HStatus_WaitRdy             ; Wait until ready to accept commands
    jc      SHORT .Return               ; Return if error

    ; Output command
    mov     al, HCMD_ID_DEV             ; Load Identify Device command to AL
    out     dx, al                      ; Output command
    call    HStatus_WaitDrqDefTime      ; Wait until ready to transfer (no IRQ!)
    jc      SHORT .Return               ; Return if error

    ; Transfer data
    sub     dx, BYTE REGR_IDE_ST        ; DX to IDE Data Reg
    xor     bh, bh                      ; BX now contains bus type
    mov     cx, 256                     ; Transfer 256 words (single sector)
    cld                                 ; INSW to increment DI
    call    [cs:bx+g_rgfnPioRead]       ; Read ID sector
    call    HStatus_WaitRdyDefTime      ; Wait until drive ready

    ; Return
.Return:
    pop     bx
    pop     dx
    pop     di
    ret


;--------------------------------------------------------------------
; Returns timeout value for drive detection.
; Long timeout is required for detecing first drive to make sure it is
; ready after power-on (ATA specification says up to 31 seconds).
; Short timeout is used for additional drives to prevent long boot time
; when drive has failed or it is not present.
;
; AH25h_GetDriveDetectionTimeoutValue
;   Parameters:
;       DS:     Segment to RAMVARS
;   Returns:
;       CL:     Timeout value
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
AH25h_GetDriveDetectionTimeoutValue:
    cmp     BYTE [RAMVARS.bDrvCnt], 0   ; Detecting first drive?
    je      SHORT .GetLongDelayForInitialDetection
    mov     cl, B_TIMEOUT_DRVINFO       ; Load short timeout
    ret
ALIGN JUMP_ALIGN
.GetLongDelayForInitialDetection:
    mov     cl, B_TIMEOUT_RESET         ; Load long timeout
    ret