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From:   Vince Weaver <vincent.weaver@maine.edu>
Date:   Tue, 28 Aug 2018 13:51:29 -0400 (EDT)
To:     Peter Zijlstra <peterz@infradead.org>
cc:     Vince Weaver <vincent.weaver@maine.edu>,
        linux-kernel@vger.kernel.org, Josh Poimboeuf <jpoimboe@redhat.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Andy Lutomirski <luto@kernel.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Stephane Eranian <eranian@google.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@kernel.org>
Subject: Re: [perf] perf_event.h ABI visibility question
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On Mon, 27 Aug 2018, Peter Zijlstra wrote:

> Something like so then?
> 
> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
> index eeb787b1c53c..f35eb72739c0 100644
> --- a/include/uapi/linux/perf_event.h
> +++ b/include/uapi/linux/perf_event.h
> @@ -144,7 +144,7 @@ enum perf_event_sample_format {
>  
>  	PERF_SAMPLE_MAX = 1U << 20,		/* non-ABI */
>  
> -	__PERF_SAMPLE_CALLCHAIN_EARLY		= 1ULL << 63,
> +	__PERF_SAMPLE_CALLCHAIN_EARLY		= 1ULL << 63, /* non-ABI; internal use */
>  };

yes, something like that would be fine.

I am being difficult about this, but from experience when trying to keep 
the manpage updated, what seems obvious now will not be so obvious 6 
months from now and trying to dig through the git logs / mailing list 
archives to verify the purpose of an addition can be a lot of work 
sometimes.

Vince