Re: [PATCH v3 3/4] perf cs-etm: Synthesize missing HW_ID mappings for raw trace

[James Clark]

On 02/10/2026 18:14, Leo Yan wrote:
> On Fri, Oct 02, 2026 at 12:15:13PM +0100, James Clark wrote:
>
> [...]
>
> >   static struct cs_etm_queue *cs_etm__get_queue(struct cs_etm_auxtrace *etm, int cpu)
> > @@ -314,12 +317,11 @@ static int cs_etm__map_trace_id_v0(struct cs_etm_auxtrace *etm, u8 trace_chan_id
> >   		return -EINVAL;
> >   
> >   	/*
> > -	 * If the queue is unformatted then only save one mapping in the
> > -	 * queue associated with that CPU so only one decoder is made.
> > +	 * Ignore HW_IDs for unformatted, a decoder will be made
> > +	 * unconditionally later.
> >   	 */
> >   	if (etmq->format == UNFORMATTED)
> > -		return cs_etm__insert_trace_id_node(etmq, trace_chan_id,
> > -						    cpu_metadata);
> > +		return 0;
>
> Nitpick: It seems to me that we can move the
> etmq->format == UNFORMATTED check into cs_etm__process_aux_output_hw_id().
>
> This avoids duplicating the check in both cs_etm__map_trace_id_v0()
> and cs_etm__process_trace_id_v0_1(), and makes it more apparent that
> the unformatted case does not use HW_ID at all.
>
> It's up to you whether to keep it as is or update it. Either way:

I might leave it for now. It's also called by 
cs_etm__map_trace_ids_metadata() which doesn't have a reference to the 
queue, and neither does cs_etm__process_aux_output_hw_id(). Probably not 
worth another refactor at this point.

> Reviewed-by: Leo Yan leo.yan@xxxxxxx
>
> P.S. Although I contributed the initial idea, the change is now quite
> different from the original patch I shared. Please feel free to drop my
> name if you prefer.

Will do if I send another one, but it looks like it can be applied now 
so it might have to stay.