Re: [Xen-devel] [PATCH] abstract request_evtchn

[Matt Chapman <matthewc@xxxxxx>]

On Tue, Aug 02, 2005 at 12:43:43PM +0100, Keir Fraser wrote:
> 
> On 1 Aug 2005, at 23:32, Matt Chapman wrote:
> 
> >This patch provides request_evtchn and free_evtchn, intended
> >to be used instead of bind_evtchn_to_irq/request_irq and
> >free_irq/unbind_evtchn_from_irq.  This allows architectures
> >to implement event channels as they see fit, not necessarily
> >using Linux IRQs.
> 
> Why would you not hook into the IRQ subsystem? This doesn't seem like a 
> useful patch to me.

I'm trying to keep all the Xen drivers and related infrastructure in
modules - IMHO domains that aren't paravirtualised should be able to
use the optimised drivers too, plus it makes development easier.

irq_desc isn't exported from the Linux kernel on most architectures,
so I'm not sure how one would "hook into" the IRQ subsystem in that
way from a module.  Also, this limits the number of event channels to
NR_IRQS (minus the ones that are used in other ways).  Instead I have
the event channel subsystem register for a single IRQ and then
demultiplex internally (in the way that is already done by
evtchn_do_upcall).

Matt


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