rdos/kernel/intr.asm

; Data table for interrupts
; cs:word for service routine
intr_table0:
  dw iret ; 00 Divide by Zero
  dw iret ; 01 Single Step
  dw iret ; 02 Parity error routine (NMI)
  dw debug_reg_ir ; 03 Break
  dw iret ; 04 Overflow
  dw iret ; 05 Print Screen
  dw iret ; 06 Mouse button control
  dw isr_dosmain ; 07 Reserved
  dw irq0 ; 08 System Clock interrupt
  dw irq1 ; 09 Keyboard interrupt
  dw irq2 ; 0a RTC interrupt
  dw irq3 ; 0b COMMS
  dw irq4 ; 0c COMMS
  dw irq5 ; 0d Hard Disk
  dw irq6 ; 0e Floppy Disk interrupt routine
  dw irq7 ; 0f Printer interrupt
intr_table2:
  dw iret ; 20
  dw isr_dosmain ; 21
  dw iret ; 22
  dw iret ; 23
  dw iret ; 24
  dw iret ; 25
  dw iret ; 26
  dw iret ; 27
  dw iret ; 28
  dw iret ; 29
  dw iret ; 2a
  dw iret ; 2b
  dw iret ; 2c
  dw iret ; 2d
  dw iret ; 2e
  dw iret ; 2f

; LSB is IRQ0, MSB is IRQ16
; A IRQ will set their bit to 1, so userspace may poll it via wait_irq
intr_flip:
  dw 0

intr_init:
  push ds
  push es
  ; backup intr 0x0n to 0x4n
  xor ax, ax
  mov ds, ax ; read from IVT
  mov es, ax ; write to IVT
  mov si, ax ; read from start of IVT table
  mov di, 0x0100 ; write to offset of int 0x40 address
  mov cx, 0x0020 ; 0x10 vectors, segment:offset each
  repe movsw
  ; now setup our own handlers (0x0n)
  mov ax, cs
  mov ds, ax ; read from local segment
  mov si, intr_table0 ; read from intr_table
  mov di, 0x0000 ; write to start of IVT table
  mov cx, 0x0010 ; 0x10 vectors, one offset each
.loop0:
  movsw ; read offset; write offset
  mov ax,cs
  stosw ; write segment
  loop .loop0
  ; second vector block (0x2n)
  mov si, intr_table2 ; read from intr_table
  mov di, 0x0080 ; write to int 20h vector and above
  mov cx, 0x0010 ; 0x10 vectors, one offset each
.loop2:
  movsw ; read offset; write offset
  mov ax,cs
  stosw ; write segment
  loop .loop2
  pop es
  pop ds
  ret

irq0:
  int 0x48
  or byte [intr_flip], 0x01
  jmp irqret

irq1:
  int 0x49
  or byte [intr_flip], 0x02
  jmp irqret

irq2:
  int 0x4A
  or byte [intr_flip], 0x04
  jmp irqret

irq3:
  int 0x4B
  or byte [intr_flip], 0x08
  jmp irqret

irq4:
  int 0x4C
  or byte [intr_flip], 0x10
  jmp irqret

irq5:
  int 0x4D
  or byte [intr_flip], 0x20
  jmp irqret

irq6:
  int 0x4E
  or byte [intr_flip], 0x40
  jmp irqret

irq7:
  int 0x4F
  or byte [intr_flip], 0x80
  jmp irqret

hwiret:
  mov al,20h
  out 20h,al
irqret:
iret:
  iret