Messages in this thread | | | Date | Fri, 27 Feb 2004 22:51:05 +0800 | From | "Michael Frank" <> | Subject | Re: Why no interrupt priorities? |
| |
On Fri, 27 Feb 2004 13:50:19 +0000, Russell King <rmk+lkml@arm.linux.org.uk> wrote:
> 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. >
I was under the impression that the PIC's are historically set to level triggered, certainly was the case with (IBM) PC's/AT's and with embedded system I am working with.
At least it explains why I was never able to share IRQ's on hardware with PIC's under linux.
Regards Michael
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |