Re: [rtl] off-topic: PCI interrupts

[Victor Yodaiken <yodaiken@fsmlabs.com>]

My belief is that shared interrupts are not very useful for RT systems - does anyone
think otherwise?

If an interrupt is shared between RT and non RT devices, the RT driver must do

catch_interrupt:
	examine my device 
	if interrupt is mine
		do regular handling
	else
		pend interrupt for Linux/BSD
		find the interrupting non-RT device
		clear device interrupt
		re-enable interrupts from this source

The key point is that the RT driver needs to look at all non-RT devices
in order to clear the interrupt source.
This is not too hard, but it seems not very RT.

	
		
On Sat, Jun 16, 2001 at 04:44:43PM +0200, Herman Bruyninckx wrote:
> On Fri, 15 Jun 2001, Wayne E. Van Loon Sr. wrote:
> 
> > Ken:
> > IMHO, nothing off topic about your question. In my experience, there are
> > 4 interrupts available to the PCI bus in PCs. If you have 5 or more PCI
> > slots, then at least two slots have to share the same interrupt.
> >
> Deos this mean that you have to include code in _any_ device driver
> you write that checks whether the interrupt was really for that device
> drive? And that every interrupt on, let's say, interrupt 4 wakes up
> the interrupt handlers of all the devices that got that interrupt
> number assigned?
> 
> Herman
> 
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