Re: interrupt magic

From: Daniel Phillips (news-innominate.list.linux.kernel@innominate.de)
Date: Sat Sep 23 2000 - 15:11:30 EDT

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    Anton Altaparmakov wrote:
    >
    > I can't remember anything about protected mode interrupt handlers nor have
    > I ever looked at Linux interrupt handling but at least in real mode from my
    > good old PC/DOS programming days I seem to remember that if you are hooking
    > a hardware interrupt vector then you have to issue a end of interrupt (EOI)
    > to the 8259A interrupt controller (PIC) before doing the iret, for example
    > like so:
    >
    > ; Note: this uses "dst, src" operand ordering not the
    > ; "reversed" ordering used by gcc asm.
    > push ax
    > mov al,20h ; Nonspecific EOI
    > out 20h,al ; Write PIC output control word OCW2
    > pop ax
    > iret
    >
    > Might this be the problem (or whatever the equivalent specific is in Linux
    > / pmode)?

    Oh yes, nothing has changed, this is still required, and don't forget to
    signal the slave PIC as well if your IRQ is 8 or higher. Lovely stuff.
    :P 

    --
Daniel
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