Re: [PATCH v7 0/4] tracing: improve symbolic printing

[Steven Rostedt <rostedt@goodmis.org>]

On Thu, 05 Nov 2026 17:26:58 +0100
Johannes Berg <johannes@sipsolutions.net> wrote:

> On Thu, 2026-11-05 at 11:24 -0500, Steven Rostedt wrote:
> > > Any objection to simply converting the __print_symbolic() sample? It
> > > would look something like this:  
> > 
> > Actually, keeping them both would be very useful. That way one can see how
> > to do it the other way. We can say, the old way is being deprecated so
> > please use the new way.  
> 
> What's the point? But OK, sure.

I thought I mentioned the point? "That way one can see how to do it the
other way". Basically, seeing the equivalent way.

> 
> > > +/*
> > > + * Alternatively, you could define a function for the names:
> > > + *
> > > + * The _lookup() function returns the string for the given value.
> > > + *
> > > + * The _show() function must
> > > + *	seq_printf(m, ", { %u, \"%s\" }", value, name);
> > > + * for each value that userspace should be able to parse.
> > > + */
> > > +const char *sample_names2_lookup(unsigned long long value);
> > > +void sample_names2_show(struct seq_file *m);  
> > 
> > Are the above going to be defined somewhere?  
> 
> Well, it's a sample, and I wasn't even using "sample_names2" in the
> below, so I didn't actually define it. I can flesh that out even more,
> but I'm not sure it's worth it?

It is, otherwise it is confusing. If it is in the sample code, people will
think it's required.

> 
> I reckon most users won't even need the dynamic way, but obviously part
> of the reason I'm doing this is that I _do_ need the dynamic way for the
> drop reasons, which are registered/built at runtime.

Right, but if we want to deprecate the old way, we need to have the
simplest sample of it. That is, have one event that shows the simple way to
do this (one that simply replaces the old way), and then have another
example of how to do it in a more complex and featureful way.

Honestly, this is why I asked for this. Your updates use the complex
method, I wasn't sure from the code how to do it for the simple case. That
is, what wasn't needed for just replacing static __print_symbolic() lists.

-- Steve