perf/core: Add attr_groups_update into struct pmu

Adding attr_update attribute group into pmu, to allow
having multiple attribute groups for same group name.

This will allow us to update "events" or "format"
directories with attributes that depend on various
HW conditions.

For example having group_format_extra group that updates
"format" directory only if pmu version is 2 and higher:

  static umode_t
  exra_is_visible(struct kobject *kobj, struct attribute *attr, int i)
  {
         return x86_pmu.version >= 2 ? attr->mode : 0;
  }

  static struct attribute_group group_format_extra = {
         .name       = "format",
         .is_visible = exra_is_visible,
  };

Signed-off-by: Jiri Olsa <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

2 files changed, 7 insertions, 0 deletions

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 0ab99c7b652d..3dc01cf98e16 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -255,6 +255,7 @@ struct pmu {
 	struct module			*module;
 	struct device			*dev;
 	const struct attribute_group	**attr_groups;
+	const struct attribute_group	**attr_update;
 	const char			*name;
 	int				type;
 
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 3005c80f621d..118ad1aef6af 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -9874,6 +9874,12 @@ static int pmu_dev_alloc(struct pmu *pmu)
 	if (ret)
 		goto del_dev;
 
+	if (pmu->attr_update)
+		ret = sysfs_update_groups(&pmu->dev->kobj, pmu->attr_update);
+
+	if (ret)
+		goto del_dev;
+
 out:
 	return ret;