[PATCH v2 3/5] perf/x86/rapl: flip logic on default events visibility

[Stephane Eranian <eranian@google.com>]

This patch modifies the default visibility of the attribute_group
for each RAPL event. By default if the grp.is_visible field is NULL,
then sysfs considers that it must display the attribute group.
If the field is not NULL (callback function), then the return value
of the callback determines the visibility (0 = not visible). The RAPL
attribute groups had the field set to NULL, meaning that unless they
failed the probing from perf_msr_probe(), they would be visible. We want
to avoid having to specify attribute groups that are not supported by hw
in the rapl_msrs[] array, they don't have MSR address to begin with.
Therefore, we intialize the visible field of all RAPL attribute groups
to a callback that returns 0. If the RAPL msr goes through probing
and succeeds the is_visible field will be set back to NULL (visible).
If the probing fails the field is set to a callback that return 0 (no visible).

Signed-off-by: Stephane Eranian <eranian@google.com>

---
 arch/x86/events/rapl.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/x86/events/rapl.c b/arch/x86/events/rapl.c
index 72990e9a4e71f..fcb21fbcfe0d0 100644
--- a/arch/x86/events/rapl.c
+++ b/arch/x86/events/rapl.c
@@ -460,9 +460,16 @@ static struct attribute *rapl_events_cores[] = {
 	NULL,
 };
 
+static umode_t
+rapl_not_visible(struct kobject *kobj, struct attribute *attr, int i)
+{
+	return 0;
+}
+
 static struct attribute_group rapl_events_cores_group = {
 	.name  = "events",
 	.attrs = rapl_events_cores,
+	.is_visible = rapl_not_visible,
 };
 
 static struct attribute *rapl_events_pkg[] = {
@@ -475,6 +482,7 @@ static struct attribute *rapl_events_pkg[] = {
 static struct attribute_group rapl_events_pkg_group = {
 	.name  = "events",
 	.attrs = rapl_events_pkg,
+	.is_visible = rapl_not_visible,
 };
 
 static struct attribute *rapl_events_ram[] = {
@@ -487,6 +495,7 @@ static struct attribute *rapl_events_ram[] = {
 static struct attribute_group rapl_events_ram_group = {
 	.name  = "events",
 	.attrs = rapl_events_ram,
+	.is_visible = rapl_not_visible,
 };
 
 static struct attribute *rapl_events_gpu[] = {
@@ -499,6 +508,7 @@ static struct attribute *rapl_events_gpu[] = {
 static struct attribute_group rapl_events_gpu_group = {
 	.name  = "events",
 	.attrs = rapl_events_gpu,
+	.is_visible = rapl_not_visible,
 };
 
 static struct attribute *rapl_events_psys[] = {
@@ -511,6 +521,7 @@ static struct attribute *rapl_events_psys[] = {
 static struct attribute_group rapl_events_psys_group = {
 	.name  = "events",
 	.attrs = rapl_events_psys,
+	.is_visible = rapl_not_visible,
 };
 
 static bool test_msr(int idx, void *data)
-- 
2.27.0.rc0.183.gde8f92d652-goog