Re: [RFC][PATCH 09/11] perf: Default PMU ops

Frederic Weisbecker
2010-06-29T18:07:39Z

On Tue, Jun 29, 2010 at 06:34:10PM +0200, Peter Zijlstra wrote:
> On Tue, 2010-06-29 at 17:03 +0200, Frederic Weisbecker wrote:
> > > You mean, if (!pmu->start_txn && pmu->pmu_enable) { /* install defaults
> > > */ } ?
> >
> >
> > Not really. pmu_*able and txn are there for different purposes.
> > A pmu implementation may want to provide enable/disable things
> > but not require any txn. Or one may just not need any of those,
> > like software events.
> >
> > It should simply map to a nop if nothing is provided.
>
> Thing is, using at least the pmu_enable/disable fallback when no txn
> methods are provided can save bunch of hardware writes. So this trivial
> fallback makes sense.

In this case, archs should handle that by implementing their txn.

neglected pmu implementations shouldn't impact software pmus.