Re: [tip:perf/core] tracing/events: Add 'signed' field to format files

[Tom Zanussi <tzanussi@gmail.com>]

On Tue, 2009-10-06 at 17:05 +0200, Frederic Weisbecker wrote:
> On Tue, Oct 06, 2009 at 01:06:39PM +0000, tip-bot for Tom Zanussi wrote:
> > Commit-ID:  26a50744b21fff65bd754874072857bee8967f4d
> > Gitweb:     http://git.kernel.org/tip/26a50744b21fff65bd754874072857bee8967f4d
> > Author:     Tom Zanussi <tzanussi@gmail.com>
> > AuthorDate: Tue, 6 Oct 2009 01:09:50 -0500
> > Committer:  Ingo Molnar <mingo@elte.hu>
> > CommitDate: Tue, 6 Oct 2009 15:04:45 +0200
> > 
> > tracing/events: Add 'signed' field to format files
> > 
> > The sign info used for filters in the kernel is also useful to
> > applications that process the trace stream.  Add it to the format
> > files and make it available to userspace.
> 
> 
> 
> This is something we could already find using the type of
> the field.
> 

Hmm, yeah, we do have the field type but in the form of a string, which
I guess we'd need some kind of type map to get the sign out of.  Since
we already have the sign info, though, it made sense to me to stick it
in the format file, other than the fact that it might break some
existing tools.  I didn't think the final format was nailed down yet so
thought that might not be so important at this point...

Tom

> Also I wonder if that breaks the format definition ABI. I mean:
> event formats are not ABI, except for the TRACE_EVENT_ABI.
> But concerning how we describe the format description, I
> have doubts.
> 
> As an example, I don't know if this patch would break 2.6.32-rc1
> (and then 2.6.32) based perf tools running on a future 2.6.33
> kernel.
>