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    SubjectRe: [patch 1/1] [RFC] uml: add and use generic hw_controller_type->release
    Date
    On Friday 27 May 2005 04:11, Chris Wedgwood wrote:
    > On Fri, May 27, 2005 at 02:39:26AM +0200, blaisorblade@yahoo.it wrote:
    > > From: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>, Chris
    > > Wedgwood <cw@f00f.org> CC: Ingo Molnar <mingo@redhat.com>
    >
    > [...]
    >
    > > 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
    time).
    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
    http://www.user-mode-linux.org/~blaisorblade





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