Re: [PATCH 1/2] trace: document how to specify multiple --trace patterns

[Stefan Hajnoczi]

On Wed, Jan 13, 2021 at 01:51:17PM +0100, BALATON Zoltan wrote:
> On Wed, 13 Jan 2021, Stefan Hajnoczi wrote:
> > On Tue, Jan 12, 2021 at 09:44:03PM +0100, BALATON Zoltan wrote:
> > > On Tue, 12 Jan 2021, Stefan Hajnoczi wrote:
> > > > It is possible to repeat the --trace option to specify multiple
> > > > patterns. This may be preferrable to users who do not want to create a
> > > > file with a list of patterns.
> > > > 
> > > > Suggested-by: BALATON Zoltan <balaton@eik.bme.hu>
> > > > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> > > > ---
> > > > docs/devel/tracing.rst | 9 +++++++--
> > > > 1 file changed, 7 insertions(+), 2 deletions(-)
> > > > 
> > > > diff --git a/docs/devel/tracing.rst b/docs/devel/tracing.rst
> > > > index 4ebf8e38ea..8777c19d14 100644
> > > > --- a/docs/devel/tracing.rst
> > > > +++ b/docs/devel/tracing.rst
> > > > @@ -22,10 +22,15 @@ events::
> > > > This output comes from the "log" trace backend that is enabled by 
> > > > default when
> > > > ``./configure --enable-trace-backends=BACKENDS`` was not explicitly 
> > > > specified.
> > > > 
> > > > -More than one trace event pattern can be specified by providing a file
> > > > -instead::
> > > > +Multiple patterns can be specified by repeating the ``--trace`` 
> > > > option::
> > > > +
> > > > +    $ qemu --trace "kvm_*" --trace "virtio_*" ...
> > > 
> > > QEMU options are single dash with double dash accepted for compatibility 
> > > but
> > > help and other docs have single dash so these (and below) should be 
> > > -trace.
> > > (Also a bit less typing for otherwise already way too long command lines.)
> > 
> > Is this documented somewhere?
> 
> Maybe qemu-system-* -help ?

I mean developer documentation like CODING_STYLE.rst so we can point to
that when someone submits a patch that does not use the preferred
syntax.

> > I was under the impression that '-' is legacy syntax and '--' is the
> > preferred syntax. There are examples of '--' on the QEMU man page.
> 
> -- is also accepted but they are the same as single dash options. Some tools
> may have -- syntax preferred but not QEMU itself. If so that may be an
> inconsistency.
> 
> > Let's reach agreement, document it, and then make the documentation
> > consistent.
> 
> Since we don't have long and short arguments for the same options (like
> -m,--memory) I think -- does not make much sense. Also single dash is less
> typing and there are other programs using the same convention (e.g. whole X
> Window System) so I think the current one dash options are fine and should
> be kept consistent. As long as we can agree on this I can agree with that.
> :-)

I'm fine with either (or even using both interchangeably) but want to
make sure it's agreed for all of QEMU so we can really follow it and
don't need to spend time on it in the future.

Kevin: You used '--' in qemu-storage-daemon --help. Does this mean you
want QEMU to stop using '-'?

Stefan

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