[PATCH net-next v16 07/10] net: phy: phy_link_topology: Add a helper to retrieve ports

[Maxime Chevallier <maxime.chevallier@bootlin.com>]

In order to allow netlink access to phy_ports, let's add a helper to
retrieve them. When handling a port coming from phy_link_topology, the
caller must hold rtnl until it's done with it.

Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---
 drivers/net/phy/phy_link_topology.c |  8 ++++++++
 include/linux/phy_link_topology.h   | 26 ++++++++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/drivers/net/phy/phy_link_topology.c b/drivers/net/phy/phy_link_topology.c
index 91cf9c62c511..046c4c4bf815 100644
--- a/drivers/net/phy/phy_link_topology.c
+++ b/drivers/net/phy/phy_link_topology.c
@@ -65,6 +65,14 @@ int phy_link_topo_add_port(struct net_device *dev, struct phy_port *port)
 	struct phy_link_topology *topo;
 	int ret;
 
+	/* Ports can now be queried without rtnl for ops-locked devices, which
+	 * we don't support now as port retrieval is done under rtnl.
+	 * We don't have phy_port enabled devices yet, let's make sure
+	 * we are loudly warned about that when it happens.
+	 */
+	if (WARN_ON_ONCE(netdev_need_ops_lock(dev)))
+		return -EOPNOTSUPP;
+
 	topo = phy_link_topo_get_or_alloc(dev);
 	if (IS_ERR(topo))
 		return PTR_ERR(topo);
diff --git a/include/linux/phy_link_topology.h b/include/linux/phy_link_topology.h
index 296ee514ba46..9585282cae3f 100644
--- a/include/linux/phy_link_topology.h
+++ b/include/linux/phy_link_topology.h
@@ -13,6 +13,7 @@
 
 #include <linux/ethtool.h>
 #include <linux/netdevice.h>
+#include <linux/rtnetlink.h>
 
 struct xarray;
 struct phy_device;
@@ -71,6 +72,25 @@ phy_link_topo_get_phy(struct net_device *dev, u32 phyindex)
 	return NULL;
 }
 
+static inline struct phy_port *
+phy_link_topo_get_port(struct net_device *dev, u32 port_id)
+{
+	struct phy_link_topology *topo = dev->link_topo;
+
+	if (!topo)
+		return NULL;
+
+	/* ports in the topo are RTNL protected, but may be accessed under
+	 * netdev_lock for ops-locked devices. For now keep them under rtnl
+	 * protection, as no ops-locked devices have phy_port capabilities
+	 * yet.
+	 */
+	ASSERT_RTNL();
+
+	/* Caller must hold RTNL while handling the phy_port */
+	return xa_load(&topo->ports, port_id);
+}
+
 #else
 static inline int phy_link_topo_add_phy(struct net_device *dev,
 					struct phy_device *phy,
@@ -100,6 +120,12 @@ phy_link_topo_get_phy(struct net_device *dev, u32 phyindex)
 {
 	return NULL;
 }
+
+static inline struct phy_port *
+phy_link_topo_get_port(struct net_device *dev, u32 port_id)
+{
+	return NULL;
+}
 #endif
 
 #endif /* __PHY_LINK_TOPOLOGY_H */
-- 
2.55.0