cxl: Introduce parent_port_of() helper

Often a parent port must be determined. Introduce the parent_port_of()
helper function to avoid open coding of determination of a parent
port.

Signed-off-by: Robert Richter <[email protected]>
Reviewed-by: Gregory Price <[email protected]>
Reviewed-by: Jonathan Cameron <[email protected]>
Reviewed-by: Dave Jiang <[email protected]>
Reviewed-by: Alison Schofield <[email protected]>
Reviewed-by: "Fabio M. De Francesco" <[email protected]>
Tested-by: Gregory Price <[email protected]>
Acked-by: Dan Williams <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Dave Jiang <[email protected]>

Author: Robert Richter

drivers/cxl/core/port.c

@@ -602,17 +602,19 @@ struct cxl_port *to_cxl_port(const struct device *dev)
 }
 EXPORT_SYMBOL_NS_GPL(to_cxl_port, "CXL");
 
+struct cxl_port *parent_port_of(struct cxl_port *port)
+{
+	if (!port || !port->parent_dport)
+		return NULL;
+	return port->parent_dport->port;
+}
+
 static void unregister_port(void *_port)
 {
 	struct cxl_port *port = _port;
-	struct cxl_port *parent;
+	struct cxl_port *parent = parent_port_of(port);
 	struct device *lock_dev;
 
-	if (is_cxl_root(port))
-		parent = NULL;
-	else
-		parent = to_cxl_port(port->dev.parent);
-
 	/*
 	 * CXL root port's and the first level of ports are unregistered
 	 * under the platform firmware device lock, all other ports are

drivers/cxl/core/region.c

@@ -1747,13 +1747,6 @@ static int cmp_interleave_pos(const void *a, const void *b)
 	return cxled_a->pos - cxled_b->pos;
 }
 
-static struct cxl_port *next_port(struct cxl_port *port)
-{
-	if (!port->parent_dport)
-		return NULL;
-	return port->parent_dport->port;
-}
-
 static int match_switch_decoder_by_range(struct device *dev,
 					 const void *data)
 {
@@ -1780,7 +1773,7 @@ static int find_pos_and_ways(struct cxl_port *port, struct range *range,
 	struct device *dev;
 	int rc = -ENXIO;
 
-	parent = next_port(port);
+	parent = parent_port_of(port);
 	if (!parent)
 		return rc;
 
@@ -1860,7 +1853,7 @@ static int cxl_calc_interleave_pos(struct cxl_endpoint_decoder *cxled)
 	 */
 
 	/* Iterate from endpoint to root_port refining the position */
-	for (iter = port; iter; iter = next_port(iter)) {
+	for (iter = port; iter; iter = parent_port_of(iter)) {
 		if (is_cxl_root(iter))
 			break;
 

drivers/cxl/cxl.h

@@ -724,6 +724,7 @@ static inline bool is_cxl_root(struct cxl_port *port)
 int cxl_num_decoders_committed(struct cxl_port *port);
 bool is_cxl_port(const struct device *dev);
 struct cxl_port *to_cxl_port(const struct device *dev);
+struct cxl_port *parent_port_of(struct cxl_port *port);
 void cxl_port_commit_reap(struct cxl_decoder *cxld);
 struct pci_bus;
 int devm_cxl_register_pci_bus(struct device *host, struct device *uport_dev,