source: xtideuniversalbios/tags/v2.0.0_beta_3/XTIDE_Universal_BIOS/Src/Initialization/Interrupts.asm@ 529

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

;
; 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

;--------------------------------------------------------------------
; Drives must be detected before this function is called!
;
; Interrupts_InitializeInterruptVectors
;   Parameters:
;       DS:     RAMVARS segment
;       ES:     BDA and Interrupt Vector segment (zero)
;   Returns:
;       Nothing
;   Corrupts registers:
;       All except segments
;--------------------------------------------------------------------
Interrupts_InitializeInterruptVectors:
    ; Install INT 19h handler to properly reset the system
    mov     al, BIOS_BOOT_LOADER_INTERRUPT_19h  ; INT 19h interrupt vector offset
    mov     si, Int19hReset_Handler             ; INT 19h handler to reboot the system
    call    Interrupts_InstallHandlerToVectorInALFromCSSI

    ; If no drives detected, leave system INT 13h and 40h handlers
    ; in place. We need our INT 13h handler to swap drive letters.
%ifndef MODULE_DRIVEXLATE
    cmp     BYTE [RAMVARS.bDrvCnt], 0
    je      SHORT Interrupts_InstallHandlerToVectorInALFromCSSI.Interrupts_Return
%endif
    ; 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

    ; NOTE! Installing INT 40h handler is currently uncommented to test
    ; if it is really needed. I suspect that it is not. Many bytes can be
    ; saved if INT 40h related code can be removed.
%if 0

    ; 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:
%endif ; 0

    mov     al, BIOS_DISK_INTERRUPT_13h         ; INT 13h interrupt vector offset
    mov     si, Int13h_DiskFunctionsHandler
%ifdef RELOCATE_INT13H_STACK
    test    BYTE [cs:ROMVARS.wFlags], FLG_ROMVARS_FULLMODE
    eCMOVNZ si, Int13h_DiskFunctionsHandlerWithStackChange
%endif

%ifndef MODULE_IRQ
    ; Fall to Interrupts_InstallHandlerToVectorInALFromCSSI
%else
    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+IDEVARS.bIRQ   ; CS:SI points to first IDEVARS
.IdeControllerLoop:
    mov     al, [cs:di]
    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
%endif ; MODULE_IRQ


;--------------------------------------------------------------------
; 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
.Interrupts_Return:
    ret


%ifdef MODULE_IRQ
;--------------------------------------------------------------------
; Interrupts_UnmaskInterruptControllerForDriveInDSDI
;   Parameters:
;       DS:DI:  Ptr to DPT
;   Returns:
;       Nothing
;   Corrupts registers:
;       AX, BX, DX
;--------------------------------------------------------------------
Interrupts_UnmaskInterruptControllerForDriveInDSDI:
    eMOVZX  bx, [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

%endif ; MODULE_IRQ