[Xenomai-core] Re: [PATCH] Shared irqs v.5

[Jan Kiszka <jan.kiszka@domain.hid>]

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Dmitry Adamushko wrote:
> Hello Jan,
> 
> as I promised earlier today, here is the patch.

I finally had a look at your patch (not yet a try), and it looks really
nice and light-weight. Now I only have two topics on my wish list:

o Handling of edge-triggered IRQs (ISA-cards...). As I tried to explain,
  in this case we have to run the IRQ handler list as long as the full
  list completed without any handler reporting XN_ISR_ENABLE back. Then
  and only then we are safe to not stall the IRQ line. See e.g.
  serial8250_interrupt() in linux/drivers/serial/8250.c for a per-driver
  solution and [1] for some discussion on sharing IRQs (be warned, it's
  from the evil side ;) ).

  On our systems we already have two of those use-cases: the xeno_16550A
  handling up to 4 devices on the same IRQ on an ISA card (I don't want
  to know what worst-case latency can be caused here...) and our
  SJA-1000 CAN driver for PC/104 ISA card with 2 controllers on the same
  interrupt line. So a common solution would reduce the code size and
  potential bug sources.

o Store and display (/proc) the driver name(s) registered on an IRQ line
  somewhere (ipipe?). This is just a nice-to-have. I introduced the RTDM
  API with the required argument in place, would be great if we can use
  this some day.

BTW, making the RTDM API shirq-aware should be as easy as adding some
flags: one for sharing in general and maybe another one for marking
edge-triggered IRQs.

Jan


PS: Still at home? How many degrees Centigrade? I guess our current -9°C
here in Hannover must appear ridiculous, almost subtropical warm to you. ;)

[1] http://www.microsoft.com/whdc/system/sysperf/apic.mspx


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