Re: Handling interrupts from userspace

Alan Cox (alan@lxorguk.ukuu.org.uk)
Sun, 1 Aug 1999 01:47:26 +0100 (BST)

> On Thu, 29 Jul 1999, Alan Cox wrote:
>
> > The kernel has to clear the IRQ cause on PCI or Nubus which means it has
> > to know about the card. Writing a small card specific driver to send
> > a signal each irq and clear the irq in kernel space works
>
> The interrupt handler can also disable the IRQ in the PIC. This
> will prevent further interrupts after exiting the handler.

It doesnt work for PCI for all cases

> 2) you do a read() on the device. This enables the interrupt in the
> PIC and blocks the process until an interrupt occurs. Then the
> interrupt is disabled again (in the PIC) and the read() returns 0.
> 3) you clear the IRQ on the card.
> 4) goto 2) if you want.
> When you close the device, the interrupt is freed.

The card is on IRQ 9 you disable IRQ 9 you return to user space. IRQ 9 is shared with the
disk. You do a disk I/O. Goodbye computer

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