source: xtideuniversalbios/trunk/XTIDE_Universal_BIOS/Src/Initialization/Interrupts.asm@ 267

; Project name  :   XTIDE Universal BIOS
; Description   :   Functions for initializing the BIOS.

; Section containing code
SECTION .text

;--------------------------------------------------------------------
; Interrupts_InitializeInterruptVectors
;   Parameters:
;       DS:     RAMVARS segment
;       ES:     BDA and Interrupt Vector segment (zero)
;   Returns:
;       Nothing
;   Corrupts registers:
;       All except segments
;--------------------------------------------------------------------
Interrupts_InitializeInterruptVectors:
    ; Fall to .InitializeInt13hAnd40h

;--------------------------------------------------------------------
; .InitializeInt13hAnd40h
;   Parameters:
;       DS:     RAMVARS segment
;       ES:     BDA and Interrupt Vector segment (zero)
;   Returns:
;       Nothing
;   Corrupts registers:
;       AX, BX, CX, DX, SI, DI
;--------------------------------------------------------------------
.InitializeInt13hAnd40h:
    mov     ax, [es:BIOS_DISK_INTERRUPT_13h*4+2]; Load old INT 13h segment
    mov     [RAMVARS.fpOldI13h+2], ax           ; Store old INT 13h segment
    xchg    dx, ax
    mov     ax, [es:BIOS_DISK_INTERRUPT_13h*4]  ; Load old INT 13h offset
    mov     [RAMVARS.fpOldI13h], ax             ; Store old INT 13h offset

    ; Only store INT 13h handler to 40h if 40h is not already installed.
    ; At least AMI BIOS for 286 stores 40h handler by itself and calls
    ; 40h from 13h. That system locks to infinite loop if we copy 13h to 40h.
    call    FloppyDrive_IsInt40hInstalled
    jc      SHORT .Int40hAlreadyInstalled
    mov     [es:BIOS_DISKETTE_INTERRUPT_40h*4], ax      ; Store old INT 13h offset
    mov     [es:BIOS_DISKETTE_INTERRUPT_40h*4+2], dx    ; Store old INT 13h segment
.Int40hAlreadyInstalled:

    mov     al, BIOS_DISK_INTERRUPT_13h         ; INT 13h interrupt vector offset
    mov     si, Int13h_DiskFunctionsHandler     ; Interrupt handler offset
    call    Interrupts_InstallHandlerToVectorInALFromCSSI
    ; Fall to .InitializeHardwareIrqHandlers

;--------------------------------------------------------------------
; .InitializeHardwareIrqHandlers
;   Parameters:
;       ES:     BDA and Interrupt Vector segment (zero)
;   Returns:
;       Nothing
;   Corrupts registers:
;       BX, CX, DX, SI, DI, AX
;--------------------------------------------------------------------
.InitializeHardwareIrqHandlers:
    call    RamVars_GetIdeControllerCountToCX
    mov     di, ROMVARS.ideVars0            ; CS:SI points to first IDEVARS
.IdeControllerLoop:
    mov     al, BYTE [cs:di+IDEVARS.bIRQ]
    add     di, BYTE IDEVARS_size           ; Increment to next controller
    call    .InstallLowOrHighIrqHandler
    loop    .IdeControllerLoop
.Return:
    ret     ; This ret is shared with .InstallLowOrHighIrqHandler

;--------------------------------------------------------------------
; .InstallLowOrHighIrqHandler
;   Parameters:
;       AL:     IRQ number, 0 if IRQ disabled
;       ES:     BDA and Interrupt Vector segment (zero)
;   Returns:
;       Nothing
;   Corrupts registers:
;       BX, SI
;--------------------------------------------------------------------
.InstallLowOrHighIrqHandler:
    test    al, al
    jz      SHORT .Return   ; IRQ not used
    cmp     al, 8
    jb      SHORT .InstallLowIrqHandler
    ; Fall to .InstallHighIrqHandler

;--------------------------------------------------------------------
; .InstallHighIrqHandler
;   Parameters:
;       BX:     IRQ number (8...15)
;       ES:     BDA and Interrupt Vector segment (zero)
;   Returns:
;       Nothing
;   Corrupts registers:
;       AL, BX, SI
;--------------------------------------------------------------------
.InstallHighIrqHandler:
    add     al, BYTE HARDWARE_IRQ_8_INTERRUPT_70h - 8   ; Interrupt vector number
    mov     si, IdeIrq_InterruptServiceRoutineForIrqs8to15
    jmp     SHORT Interrupts_InstallHandlerToVectorInALFromCSSI

;--------------------------------------------------------------------
; .InstallLowIrqHandler
;   Parameters:
;       AL:     IRQ number (0...7)
;       ES:     BDA and Interrupt Vector segment (zero)
;   Returns:
;       Nothing
;   Corrupts registers:
;       AL, BX, SI
;--------------------------------------------------------------------
.InstallLowIrqHandler:
    add     al, BYTE HARDWARE_IRQ_0_INTERRUPT_08h       ; Interrupt vector number
    mov     si, IdeIrq_InterruptServiceRoutineForIrqs2to7
    ; Fall to Interrupts_InstallHandlerToVectorInALFromCSSI


;--------------------------------------------------------------------
; Interrupts_InstallHandlerToVectorInALFromCSSI
;   Parameters:
;       AL:     Interrupt vector number (for example 13h)
;       ES:     BDA and Interrupt Vector segment (zero)
;       CS:SI:  Ptr to interrupt handler
;   Returns:
;       Nothing
;   Corrupts registers:
;       AX, BX
;--------------------------------------------------------------------
Interrupts_InstallHandlerToVectorInALFromCSSI:
    mov     bl, 4                   ; Shift for DWORD offset, MUL smaller than other alternatives
    mul     bl
    xchg    ax, bx
    mov     [es:bx], si             ; Store offset
    mov     [es:bx+2], cs           ; Store segment
    ret


;--------------------------------------------------------------------
; Interrupts_UnmaskInterruptControllerForDriveInDSDI
;   Parameters:
;       DS:DI:  Ptr to DPT
;   Returns:
;       Nothing
;   Corrupts registers:
;       AX, BX, DX
;--------------------------------------------------------------------
Interrupts_UnmaskInterruptControllerForDriveInDSDI:
    eMOVZX  bx, BYTE [di+DPT.bIdevarsOffset]
    mov     al, [cs:bx+IDEVARS.bIRQ]
    test    al, al
    jz      SHORT .Return   ; Interrupts disabled
    cmp     al, 8
    jb      SHORT .UnmaskLowIrqController
    ; Fall to .UnmaskHighIrqController

;--------------------------------------------------------------------
; .UnmaskHighIrqController
;   Parameters:
;       AL:     IRQ number (8...15)
;   Returns:
;       Nothing
;   Corrupts registers:
;       AX, DX
;--------------------------------------------------------------------
.UnmaskHighIrqController:
    sub     al, 8               ; Slave interrupt number
    mov     dx, SLAVE_8259_IMR
    call    .ClearBitFrom8259MaskRegister
    mov     al, 2               ; Master IRQ 2 to allow slave IRQs
    ; Fall to .UnmaskLowIrqController

;--------------------------------------------------------------------
; .UnmaskLowIrqController
;   Parameters:
;       AL:     IRQ number (0...7)
;   Returns:
;       Nothing
;   Corrupts registers:
;       AX, DX
;--------------------------------------------------------------------
.UnmaskLowIrqController:
    mov     dx, MASTER_8259_IMR
    ; Fall to .ClearBitFrom8259MaskRegister

;--------------------------------------------------------------------
; .ClearBitFrom8259MaskRegister
;   Parameters:
;       AL:     8259 interrupt index (0...7)
;       DX:     Port address to Interrupt Mask Register
;   Returns:
;       Nothing
;   Corrupts registers:
;       AX
;--------------------------------------------------------------------
.ClearBitFrom8259MaskRegister:
    push    cx
    xchg    ax, cx              ; IRQ index to CL
    mov     ch, 1               ; Load 1 to be shifted
    shl     ch, cl              ; Shift bit to correct position
    not     ch                  ; Invert to create bit mask for clearing
    in      al, dx              ; Read Interrupt Mask Register
    and     al, ch              ; Clear wanted bit
    out     dx, al              ; Write modified Interrupt Mask Register
    pop     cx
.Return:
    ret