Hi Joe, Steven,

On Tue, Sep 10, 2019 at 12:44:03PM -0700, Joe Perches wrote:

On Tue, 2019-09-10 at 15:03 -0400, Steven Rostedt wrote:

quoted

On Tue, 10 Sep 2019 11:42:06 -0700

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quoted

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btw:

Is there kernel version information available in
trace output files?

Not really. This is just a library that parses the trace event formats,
there's not kernel versions passed in, but we do use variations in
formats and such to determine what is supported.

quoted

If so, it might be reasonable to change the tooling
there instead.

Actually, I think we could just look to see if "%pfw" is used and fall
to that, otherwise consider it an older kernel and do it the original
way.

Well, if you think that works, OK great.

But could that work?
How would an individual trace record know if
another trace record used %pfw?

Perhaps not reusing %pf, marking it reserved
for a period of years, and using another unused
prefix %p<type> like %pnfw may be simpler.

%p[Ff]w does not exist (I grepped for it) in older kernels since v3.0. So
kernel support for %p[fF] and %pfw are mutually exclusive. If you're ok
with that, I could change the patch to check %pf isn't followed by 'w',
in order to support %pf on older kernels.

Although that still does not address using older tooling on newer kernels
with support for %pfw.

If you think that's an issue, I'll opt for another extension than %pfw,
which I chose originally since it's memorable --- fw for fwnode (names,
paths, and probably more in the future).

-- 
Regards,

Sakari Ailus
sakari.ailus@linux.intel.com