Re: Why no interrupt priorities?

Russell King
2004-02-27T13:50:50Z

On Fri, Feb 27, 2004 at 09:31:43PM +0800, Michael Frank wrote:
> On Fri, 27 Feb 2004 09:05:48 +0000, Russell King <rmk+lkml@arm.linux.org.uk> wrote:
> > On Fri, Feb 27, 2004 at 02:26:31PM +0800, Michael Frank wrote:
> >> Is this to imply that edge triggered shared interrupts are used anywhere?
> >
> > It is (or used to be) rather common with serial ports. Remember that
> > COM1 and COM3 were both defined to use IRQ4 and COM2 and COM4 to use
> > IRQ3.
> >
> >> Never occured to me to use shared IRQ's edge triggered as this mode
> >> _cannot_ work reliably for HW limitations.
> >
> > The serial driver takes great care with this - when we service such an
> > interrupt, we keep going until we have scanned all the devices until
> > such time that we can say "all devices are no longer signalling an
> > interrupt".
> >
> > This is something it has always done - it's nothing new.
> >
>
> Sorry, i think the serial driver IRQ is level triggered :)

That's actually incorrect. Serial devices are (were) connected to the
old ISA PICs which are definitely edge triggered.

--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of: 2.6 PCMCIA - http://pcmcia.arm.linux.org.uk/
2.6 Serial core