perf auxtrace: Allow number of queues to be specified

Currently it's only possible to initialize with the default number of
queues and then use auxtrace_queues__add_event() to grow the array.

But that's problematic if you don't have a real event to pass into that
function yet.

The queues hold a void *priv member to store custom state, and for
Coresight we want to create decoders upfront before receiving data, so
add a new function that allows pre-allocating queues.

One reason to do this is because we might need to store metadata (HW_ID
events) that effects other queues, but never actually receive auxtrace
data on that queue.

Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: James Clark <james.clark@arm.com>
Tested-by: Ganapatrao Kulkarni <gankulkarni@os.amperecomputing.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Leo Yan <leo.yan@linux.dev>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steve Clevenger <scclevenger@os.amperecomputing.com>
Cc: Suzuki Poulouse <suzuki.poulose@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20240429152207.479221-3-james.clark@arm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/auxtrace.c

@@ -218,15 +218,20 @@ static struct auxtrace_queue *auxtrace_alloc_queue_array(unsigned int nr_queues)
 	return queue_array;
 }
 
-int auxtrace_queues__init(struct auxtrace_queues *queues)
+int auxtrace_queues__init_nr(struct auxtrace_queues *queues, int nr_queues)
 {
-	queues->nr_queues = AUXTRACE_INIT_NR_QUEUES;
+	queues->nr_queues = nr_queues;
 	queues->queue_array = auxtrace_alloc_queue_array(queues->nr_queues);
 	if (!queues->queue_array)
 		return -ENOMEM;
 	return 0;
 }
 
+int auxtrace_queues__init(struct auxtrace_queues *queues)
+{
+	return auxtrace_queues__init_nr(queues, AUXTRACE_INIT_NR_QUEUES);
+}
+
 static int auxtrace_queues__grow(struct auxtrace_queues *queues,
 				 unsigned int new_nr_queues)
 {

tools/perf/util/auxtrace.h

@@ -521,6 +521,7 @@ int auxtrace_mmap__read_snapshot(struct mmap *map,
 				 struct perf_tool *tool, process_auxtrace_t fn,
 				 size_t snapshot_size);
 
+int auxtrace_queues__init_nr(struct auxtrace_queues *queues, int nr_queues);
 int auxtrace_queues__init(struct auxtrace_queues *queues);
 int auxtrace_queues__add_event(struct auxtrace_queues *queues,
 			       struct perf_session *session,