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SubjectRe: [patch 1/1] [RFC] uml: add and use generic hw_controller_type->release
On Friday 27 May 2005 04:11, Chris Wedgwood wrote:
> On Fri, May 27, 2005 at 02:39:26AM +0200, wrote:
> > From: Paolo 'Blaisorblade' Giarrusso <>, Chris
> > Wedgwood <> CC: Ingo Molnar <>
> [...]
> > This is heavily based on some work by Chris Wedgwood, which however
> > didn't get the patch merged for something I'd call a
> > "misunderstanding" (the need for this patch wasn't cleanly
> > explained, thus adding the generic hook was felt as undesirable).

> Looks very reasonable to me and your explaination is much better than
> mine was :-)
Yes, it took some time to me to go working on this and getting the time to
explain it clearly.
> > diff -puN kernel/irq/manage.c~uml-gen-irq-release kernel/irq/manage.c
> > --- linux-2.6.git/kernel/irq/manage.c~uml-gen-irq-release 2005-05-25
> > 01:15:46.000000000 +0200 +++
> > linux-2.6.git-paolo/kernel/irq/manage.c 2005-05-25 01:15:46.000000000
> > +0200 @@ -255,6 +255,10 @@ void free_irq(unsigned int irq, void *de
> >
> > /* Found it - now remove it from the list of entries */
> > *pp = action->next;
> > +
> > + if (desc->handler->release)
> > + desc->handler->release(irq, dev_id);
> > +
> Because right now we know the *only* port that needs a release method
> is UML I wonder if we could do save a couple of bytes & cycles for
> everyone else by doing something like #ifdef CONFIG_IRQ_HAS_RELEASE,
> #endif around that and then letting the Kconfig magic set
> CONFIG_IRQ_HAS_RELEASE as required? If other arches need it thay can
> do the same and if eventually almost everyone does we can kill the
> #ifdef crud?
Well, that's a point, even because a conditional jump needs to flush the
pipeline when mispredicted (which won't happen on other ARCHs after the
initial period, if this jump stays in the Branch Target Buffers).
> Longer term I wonder if some of the irq mechanics in UML couldn't end
> up being a bit more like the s390 stuff too?
Christoph Hellwig too suggested this, however anything such *must* be longer
term (while this was earlier pointed as a reason to drop this patch, last
Beyond that, I've not a clear understanding of S390, so I cannot for now help
(including any merit discussion) on this point... Bodo Stroesser is porting
UML on S390 so probably he might help more on this point.
Paolo Giarrusso, aka Blaisorblade
Skype user "PaoloGiarrusso"
Linux registered user n. 292729

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