perf: provide sysfs_show for struct perf_pmu_events_attr

(struct perf_pmu_events_attr) is defined in include/linux/perf_event.h,
but the only "show" for it is in x86 and contains x86 specific stuff.

Make a generic one for those of us who are just using the event_str.
Signed-off-by: Cody P Schafer <cody@linux.vnet.ibm.com>
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

include/linux/perf_event.h

@@ -897,6 +897,9 @@ struct perf_pmu_events_attr {
 	const char *event_str;
 };
 
+ssize_t perf_event_sysfs_show(struct device *dev, struct device_attribute *attr,
+			      char *page);
+
 #define PMU_EVENT_ATTR(_name, _var, _id, _show)				\
 static struct perf_pmu_events_attr _var = {				\
 	.attr = __ATTR(_name, 0444, _show, NULL),			\

kernel/events/core.c

@@ -8276,6 +8276,18 @@ void __init perf_event_init(void)
 		     != 1024);
 }
 
+ssize_t perf_event_sysfs_show(struct device *dev, struct device_attribute *attr,
+			      char *page)
+{
+	struct perf_pmu_events_attr *pmu_attr =
+		container_of(attr, struct perf_pmu_events_attr, attr);
+
+	if (pmu_attr->event_str)
+		return sprintf(page, "%s\n", pmu_attr->event_str);
+
+	return 0;
+}
+
 static int __init perf_event_sysfs_init(void)
 {
 	struct pmu *pmu;