Date: Mon, 3 Nov 2014 17:50:19 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Vince Weaver <vince@deater.net>, Stephane Eranian <eranian@google.com>,
        Ingo Molnar <mingo@kernel.org>, Jiri Olsa <jolsa@redhat.com>,
        Andy Lutomirski <luto@amacapital.net>,
        Thomas Gleixner <tglx@linutronix.de>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFD] perf syscall error handling
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On Mon, Nov 03, 2014 at 02:25:48PM -0200, Arnaldo Carvalho de Melo wrote:

> The way that peterz suggested, i.e. returning information about which
> perf_event_attr and which of the parameters was invalid/had issues could
> help with fallbacking/capability querying, i.e. tooling may want to use
> some features if available automagically, fallbacking to something else
> when that fails.
> 
> We already do that to some degree in various cases, but for some if the
> only way that becomes available to disambiguate some EINVAL return is a
> string, code will start having strcmps :-\

OK, so how about we do both, the offset+mask for the tools and the
string for the humans?
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