perf python: Add evsel read method

Add the evsel read method to enable python to read counter data for the
given evsel.

Signed-off-by: Gautam Menghani <gautam@linux.ibm.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Howard Chu <howardchu95@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/linux-perf-users/20250512055748.479786-1-gautam@linux.ibm.com/
Link: https://lore.kernel.org/r/20250519195148.1708988-6-irogers@google.com
[ make the API take a CPU and thread then compute from these the appropriate indices. ]
Signed-off-by: Ian Rogers <irogers@google.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Author: Gautam Menghani

tools/perf/util/python.c

@@ -888,6 +888,37 @@ static PyObject *pyrf_evsel__threads(struct pyrf_evsel *pevsel)
 	return (PyObject *)pthread_map;
 }
 
+static PyObject *pyrf_evsel__read(struct pyrf_evsel *pevsel,
+				  PyObject *args, PyObject *kwargs)
+{
+	struct evsel *evsel = &pevsel->evsel;
+	int cpu = 0, cpu_idx, thread = 0, thread_idx;
+	struct perf_counts_values counts;
+	struct pyrf_counts_values *count_values = PyObject_New(struct pyrf_counts_values,
+							       &pyrf_counts_values__type);
+
+	if (!count_values)
+		return NULL;
+
+	if (!PyArg_ParseTuple(args, "ii", &cpu, &thread))
+		return NULL;
+
+	cpu_idx = perf_cpu_map__idx(evsel->core.cpus, (struct perf_cpu){.cpu = cpu});
+	if (cpu_idx < 0) {
+		PyErr_Format(PyExc_TypeError, "CPU %d is not part of evsel's CPUs", cpu);
+		return NULL;
+	}
+	thread_idx = perf_thread_map__idx(evsel->core.threads, thread);
+	if (cpu_idx < 0) {
+		PyErr_Format(PyExc_TypeError, "Thread %d is not part of evsel's threads",
+			     thread);
+		return NULL;
+	}
+	perf_evsel__read(&(evsel->core), cpu_idx, thread_idx, &counts);
+	count_values->values = counts;
+	return (PyObject *)count_values;
+}
+
 static PyObject *pyrf_evsel__str(PyObject *self)
 {
 	struct pyrf_evsel *pevsel = (void *)self;
@@ -918,6 +949,12 @@ static PyMethodDef pyrf_evsel__methods[] = {
 		.ml_flags = METH_NOARGS,
 		.ml_doc	  = PyDoc_STR("threads the event is to be used with.")
 	},
+	{
+		.ml_name  = "read",
+		.ml_meth  = (PyCFunction)pyrf_evsel__read,
+		.ml_flags = METH_VARARGS | METH_KEYWORDS,
+		.ml_doc	  = PyDoc_STR("read counters")
+	},
 	{ .ml_name = NULL, }
 };