[RFC PATCH 15/20] cxl: Add a routine to find cxl root decoder on cxl bus

[Neeraj Kumar <s.neeraj@samsung.com>]

Add cxl_find_root_decoder to find root decoder on cxl bus. It is used to
find root decoder during region creation

Signed-off-by: Neeraj Kumar <s.neeraj@samsung.com>
---
 drivers/cxl/core/port.c | 26 ++++++++++++++++++++++++++
 drivers/cxl/cxl.h       |  1 +
 2 files changed, 27 insertions(+)

diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index 2452f7c15b2d..94d9322b8e38 100644
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -513,6 +513,32 @@ struct cxl_switch_decoder *to_cxl_switch_decoder(struct device *dev)
 }
 EXPORT_SYMBOL_NS_GPL(to_cxl_switch_decoder, "CXL");
 
+static int match_root_decoder(struct device *dev, void *data)
+{
+	return is_root_decoder(dev);
+}
+
+/**
+ * cxl_find_root_decoder() - find a cxl root decoder on cxl bus
+ * @port: any descendant port in root-cxl-port topology
+ */
+struct cxl_root_decoder *cxl_find_root_decoder(struct cxl_port *port)
+{
+	struct cxl_root *cxl_root __free(put_cxl_root) = find_cxl_root(port);
+	struct device *dev;
+
+	if (!cxl_root)
+		return NULL;
+
+	dev = device_find_child(&cxl_root->port.dev, NULL, match_root_decoder);
+
+	if (!dev)
+		return NULL;
+
+	return to_cxl_root_decoder(dev);
+}
+EXPORT_SYMBOL_NS_GPL(cxl_find_root_decoder, "CXL");
+
 static void cxl_ep_release(struct cxl_ep *ep)
 {
 	put_device(ep->ep);
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 30c80e04cb27..2c6a782d0941 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -871,6 +871,7 @@ bool is_cxl_nvdimm_bridge(struct device *dev);
 int devm_cxl_add_nvdimm(struct cxl_port *parent_port, struct cxl_memdev *cxlmd);
 struct cxl_nvdimm_bridge *cxl_find_nvdimm_bridge(struct cxl_port *port);
 void cxl_region_discovery(struct cxl_port *port);
+struct cxl_root_decoder *cxl_find_root_decoder(struct cxl_port *port);
 
 #ifdef CONFIG_CXL_REGION
 bool is_cxl_pmem_region(struct device *dev);
-- 
2.34.1