perf pmu: Add pmu_id()

Add a function to read the PMU id sysfs entry. This is only done for uncore
PMUs where this would possibly be relevant.
Signed-off-by: John Garry <john.garry@huawei.com>
Acked-by: Kajol Jain <kjain@linux.ibm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Joakim Zhang <qiangqing.zhang@nxp.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Kim Phillips <kim.phillips@amd.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Shaokun Zhang <zhangshaokun@hisilicon.com>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linuxarm@huawei.com
Link: http://lore.kernel.org/lkml/1607080216-36968-4-git-send-email-john.garry@huawei.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/pmu.c

@@ -597,6 +597,7 @@ static struct perf_cpu_map *__pmu_cpumask(const char *path)
  * Uncore PMUs have a "cpumask" file under sysfs. CPU PMUs (e.g. on arm/arm64)
  * may have a "cpus" file.
  */
+#define SYS_TEMPLATE_ID	"./bus/event_source/devices/%s/identifier"
 #define CPUS_TEMPLATE_UNCORE	"%s/bus/event_source/devices/%s/cpumask"
 #define CPUS_TEMPLATE_CPU	"%s/bus/event_source/devices/%s/cpus"
 
@@ -635,6 +636,21 @@ static bool pmu_is_uncore(const char *name)
 	return file_available(path);
 }
 
+static char *pmu_id(const char *name)
+{
+	char path[PATH_MAX], *str;
+	size_t len;
+
+	snprintf(path, PATH_MAX, SYS_TEMPLATE_ID, name);
+
+	if (sysfs__read_str(path, &str, &len) < 0)
+		return NULL;
+
+	str[len - 1] = 0; /* remove line feed */
+
+	return str;
+}
+
 /*
  *  PMU CORE devices have different name other than cpu in sysfs on some
  *  platforms.
@@ -847,6 +863,8 @@ static struct perf_pmu *pmu_lookup(const char *name)
 	pmu->name = strdup(name);
 	pmu->type = type;
 	pmu->is_uncore = pmu_is_uncore(name);
+	if (pmu->is_uncore)
+		pmu->id = pmu_id(name);
 	pmu->max_precise = pmu_max_precise(name);
 	pmu_add_cpu_aliases(&aliases, pmu);
 

tools/perf/util/pmu.h

@@ -30,6 +30,7 @@ struct perf_pmu_caps {
 
 struct perf_pmu {
 	char *name;
+	char *id;
 	__u32 type;
 	bool selectable;
 	bool is_uncore;