Date: Thu, 16 Jan 2014 12:13:10 -0500 (EST)
From: Vince Weaver <vincent.weaver@maine.edu>
To: Peter Zijlstra <peterz@infradead.org>
cc: Vince Weaver <vincent.weaver@maine.edu>, Will Deacon <will.deacon@arm.com>,
        Chad Paradis <chad.paradis@umit.maine.edu>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Paul Mackerras <paulus@samba.org>, Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
        Stephane Eranian <eranian@gmail.com>
Subject: Re: [patch/rfc] perf on raspberry-pi without overflow interrupt
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On Tue, 14 Jan 2014, Peter Zijlstra wrote:

> On Mon, Jan 13, 2014 at 11:55:17PM -0500, Vince Weaver wrote:

> > I don't see an existing pmu capabilities struct... or do you mean
> > coming up with one?
> 
> Yeah, adding one.

So would it be a struct, or just an integer with flags?

> > Would it only hold an "overflow_interrupt_available" flag, or are
> > there other generic capabilities it would be handy to know about?
> 
> Possible (other) flags could be:
> 
>   PMU_HAS_INT      -- would allow sampling events
>   PMU_HAS_PRECISE  -- would allow any ::precise value
>   PMU_HAS_FILTER   -- would allow all os/user/etc. flags

should we export these to userspace somehow?

It would be handy to be able to tell you're getting EOPNOTSUP because
PMU_HAS_INT is not set for your pmu, rather than trying to guess why 
things are failing.

Vince
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