[PATCH 2/8] perf: Add attr_groups_update into struct pmu

[Jiri Olsa <jolsa@kernel.org>]

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 <jolsa@kernel.org>
---
 include/linux/perf_event.h | 1 +
 kernel/events/core.c       | 6 ++++++
 2 files changed, 7 insertions(+)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index f3864e1c5569..cb5f07d50edb 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 abbd4b3b96c2..21ef9b843af0 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;
 
-- 
2.20.1