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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.
I wrote a kernel module that implements this. It works as follows:
1) you open a special character device. The module grabs the IRQ and
disables it.
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.
I attached the code to this mail. I've tested it with 2.2.9 and
printer port interrupts generated with a button attached to /ACK.
There's no poll() support but it would be trivial to add that.
Eric
-- Eric Lammerts <eric@scintilla.utwente.nl>"Don't you know there ain't no devil? There's just God when he's drunk." -- Tom Waits
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