[PATCH v4 02/10] coresight: core: add a new API to retrieve the helper device

[Jie Gan <jie.gan@oss.qualcomm.com>]

Retrieving the helper device of the specific coresight device based on
its helper_subtype because a single coresight device may has multiple types
of the helper devices.

Signed-off-by: Jie Gan <jie.gan@oss.qualcomm.com>
---
 drivers/hwtracing/coresight/coresight-core.c | 35 ++++++++++++++++++++
 drivers/hwtracing/coresight/coresight-priv.h |  2 ++
 2 files changed, 37 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index 042c4fa39e55..018b1119c48a 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -580,6 +580,41 @@ struct coresight_device *coresight_get_sink(struct coresight_path *path)
 }
 EXPORT_SYMBOL_GPL(coresight_get_sink);
 
+/**
+ * coresight_get_helper: find the helper device of the assigned csdev.
+ *
+ * @csdev: The csdev the helper device is conntected to.
+ * @type:  helper_subtype of the expected helper device.
+ *
+ * Retrieve the helper device for the specific csdev based on its
+ * helper_subtype.
+ *
+ * Return: the helper's csdev upon success or NULL for fail.
+ */
+struct coresight_device *coresight_get_helper(struct coresight_device *csdev,
+					      int type)
+{
+	int i;
+	struct coresight_device *helper;
+
+	/* protect the connections */
+	mutex_lock(&coresight_mutex);
+	for (i = 0; i < csdev->pdata->nr_outconns; ++i) {
+		helper = csdev->pdata->out_conns[i]->dest_dev;
+		if (!helper || !coresight_is_helper(helper))
+			continue;
+
+		if (helper->subtype.helper_subtype == type) {
+			mutex_unlock(&coresight_mutex);
+			return helper;
+		}
+	}
+	mutex_unlock(&coresight_mutex);
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(coresight_get_helper);
+
 /**
  * coresight_get_in_port_dest: get the in-port number of the dest device
  * that is connected to the src device.
diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
index e51b22b8ebde..f80122827934 100644
--- a/drivers/hwtracing/coresight/coresight-priv.h
+++ b/drivers/hwtracing/coresight/coresight-priv.h
@@ -158,6 +158,8 @@ void coresight_path_assign_trace_id(struct coresight_path *path,
 				   enum cs_mode mode);
 int coresight_get_in_port_dest(struct coresight_device *src,
 			       struct coresight_device *dest);
+struct coresight_device *coresight_get_helper(struct coresight_device *csdev,
+					      int type);
 
 #if IS_ENABLED(CONFIG_CORESIGHT_SOURCE_ETM3X)
 int etm_readl_cp14(u32 off, unsigned int *val);
-- 
2.34.1