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Subject: Re: [PATCH 05/19] perf tools: Introduce new 'ftrace' tool
From: Namhyung Kim <namhyung@kernel.org>
To: David Ahern <dsahern@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Paul Mackerras <paulus@samba.org>, Ingo Molnar <mingo@kernel.org>,
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Date: Thu, 27 Jun 2013 23:22:50 +0900
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2013-06-27 (목), 07:51 -0600, David Ahern:
> On 6/26/13 11:04 PM, Namhyung Kim wrote:
> > Hi David,
> >
> > On Wed, 26 Jun 2013 11:10:34 -0600, David Ahern wrote:
> >> On 6/26/13 1:14 AM, Namhyung Kim wrote:
> >>> +	const char * const ftrace_usage[] = {
> >>> +		"perf ftrace [<options>] [<command>]",
> >>> +		"perf ftrace [<options>] -- <command> [<options>]",
> >>> +		NULL
> >>> +	};
> >>> +	const struct option ftrace_options[] = {
> >>> +	OPT_STRING('t', "tracer", &ftrace.tracer, "tracer",
> >>> +		   "tracer to use"),
> >>
> >> How does a user know what is a valid tracer string?
> >
> > The helpline should look like (at least):
> >
> >    "tracer to use: function_graph or function"
> 
> exactly. I would suggest making that OPT_CALLBACK as well to validate 
> the string content when options are parsed.

Did you mean it by checking /sys/kernel/debug/tracing/available_tracers?

Yes, I can do that.  But current code does not support other tracers and
it'd anyway emit warning on an invalid tracer argument.

Thanks,
Namhyung