.global pit_init
.global pit_interrupt_handler
.global pit_get_ticks

ticks:
.int 0

pit_get_ticks:
    
    mov (ticks),%eax
    ret

pit_interrupt_handler:

    push %eax // persist

    // INC TICK COUNTER
    mov $ticks, %eax    
    incl (%eax)

    // ACK IRQ
    mov $0x20,%al
    out %al,$0x20   

    pop %eax // load original
    
    ///////

    pusha          //Push all standard registers
    push %ds       //Push data segment
    push %es       //etc...
    push %fs
    push %gs

    mov %esp, %eax          // remember current %esp
    movl $stack_top, %esp   // switch to our small scheduler stack

    push %eax               // set original %esp as param and... 
    call task_switch_next   // call scheduler
    mov  %eax, %esp         // use %esp we got from scheduler

    pop %gs
    pop %fs
    pop %es
    pop %ds
    popa           

    iret

pit_init:

    // configure ticking 25 times a second
    // 1193180 / 25 = 47727.2
    mov $47727, %dx

    mov $0b00110100, %al
    outb %al,$0x43

    mov %dx,%ax

    out %al, $0x40
    xchg %ah,%al
    out %al, $0x40

    ret