[PATCH 08/24] gtrace: add perf symlink support for gtrace components

[Zane Leung]

Implement gtrace_perf_symlink() to let RISC-V Trace encoder
link themselves to the gtrace PMU directory as "cpuX" based
on their bound CPU.
---
 drivers/hwtracing/gtrace/gtrace-perf.c        | 29 +++++++++++++++++--
 .../hwtracing/gtrace/rvtrace-encoder-core.c   | 10 +++++++
 include/linux/gtrace.h                        |  2 ++
 3 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/drivers/hwtracing/gtrace/gtrace-perf.c b/drivers/hwtracing/gtrace/gtrace-perf.c
index 2fcfbae9acf6..604b673a29d5 100644
--- a/drivers/hwtracing/gtrace/gtrace-perf.c
+++ b/drivers/hwtracing/gtrace/gtrace-perf.c
@@ -23,6 +23,7 @@
 #define GTRACE_PMU_NAME "gtrace"
 static struct pmu gtrace_pmu;
 static struct workqueue_struct *gtrace_wq;
+static bool gtrace_perf_up;
 
 /**
  * struct gtrace_event_data - generic hardware trace perf event data
@@ -351,6 +352,27 @@ static const struct attribute_group *gtrace_pmu_attr_groups[] = {
 	NULL,
 };
 
+int gtrace_perf_symlink(struct gtrace_component *comp, bool link)
+{
+	char entry[sizeof("cpu9999999")];
+	int ret = 0, cpu = comp->pdata->bound_cpu;
+	struct device *pmu_dev = gtrace_pmu.dev;
+	struct device *comp_dev = &comp->dev;
+
+	sprintf(entry, "cpu%d", cpu);
+
+	if (!gtrace_perf_up)
+		return -EPROBE_DEFER;
+
+	if (link)
+		ret = sysfs_create_link(&pmu_dev->kobj, &comp_dev->kobj, entry);
+	else
+		sysfs_remove_link(&pmu_dev->kobj, entry);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gtrace_perf_symlink);
+
 int __init gtrace_perf_init(void)
 {
 	int ret;
@@ -373,10 +395,13 @@ int __init gtrace_perf_init(void)
 		return -ENOMEM;
 
 	ret = perf_pmu_register(&gtrace_pmu, GTRACE_PMU_NAME, -1);
-	if (ret)
+	if (ret) {
 		destroy_workqueue(gtrace_wq);
+		return ret;
+	}
 
-	return ret;
+	gtrace_perf_up = true;
+	return 0;
 }
 
 void __exit gtrace_perf_exit(void)
diff --git a/drivers/hwtracing/gtrace/rvtrace-encoder-core.c b/drivers/hwtracing/gtrace/rvtrace-encoder-core.c
index 817535ff9558..17a3dde1314c 100644
--- a/drivers/hwtracing/gtrace/rvtrace-encoder-core.c
+++ b/drivers/hwtracing/gtrace/rvtrace-encoder-core.c
@@ -129,6 +129,10 @@ static int rvtrace_encoder_probe(struct gtrace_component *comp)
 	}
 	dev_set_drvdata(&comp->dev, priv);
 
+	ret = gtrace_perf_symlink(comp, true);
+	if (ret)
+		return ret;
+
 	if (boot_enable) {
 		ret = gtrace_enable_sysfs(comp);
 		if (ret) {
@@ -140,6 +144,11 @@ static int rvtrace_encoder_probe(struct gtrace_component *comp)
 	return 0;
 }
 
+static void rvtrace_encoder_remove(struct gtrace_component *comp)
+{
+	gtrace_perf_symlink(comp, false);
+}
+
 static void rvtrace_encoder_parse_event_config(struct rvtrace_encoder_priv *priv,
 					       struct perf_event *event)
 {
@@ -240,6 +249,7 @@ static const struct gtrace_component_id rvtrace_encoder_ids[] = {
 static struct gtrace_driver rvtrace_encoder_driver = {
 	.id_table = rvtrace_encoder_ids,
 	.probe = rvtrace_encoder_probe,
+	.remove = rvtrace_encoder_remove,
 	.start = rvtrace_encoder_start,
 	.stop = rvtrace_encoder_stop,
 	.driver = {
diff --git a/include/linux/gtrace.h b/include/linux/gtrace.h
index 3d769b405030..4bbe5ac835ec 100644
--- a/include/linux/gtrace.h
+++ b/include/linux/gtrace.h
@@ -437,4 +437,6 @@ int gtrace_disable_sysfs(struct gtrace_component *comp);
 int gtrace_sysfs_add(struct gtrace_component *comp);
 void gtrace_sysfs_remove(struct gtrace_component *comp);
 
+int gtrace_perf_symlink(struct gtrace_component *comp, bool link);
+
 #endif /* __LINUX_GTRACE_H__ */
-- 
2.34.1