[PATCH net-next v15 01/10] net: phy: phy_link_topology: Add a helper for opportunistic alloc

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

The phy_link_topology structure stores information about the PHY-related
components connected to a net_device. It is opportunistically allocated,
when we add the first item to the topology, as this is not relevant for
all kinds of net_devices.

In preparation for the addition of phy_port tracking in the topology,
let's make a dedicated helper for that allocation sequence.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---
 drivers/net/phy/phy_link_topology.c | 40 +++++++++++++++++++++++------
 1 file changed, 32 insertions(+), 8 deletions(-)

diff --git a/drivers/net/phy/phy_link_topology.c b/drivers/net/phy/phy_link_topology.c
index 4134de7ae313..dadeb8def7ea 100644
--- a/drivers/net/phy/phy_link_topology.c
+++ b/drivers/net/phy/phy_link_topology.c
@@ -28,11 +28,39 @@ static int netdev_alloc_phy_link_topology(struct net_device *dev)
 	return 0;
 }
 
+static struct phy_link_topology *phy_link_topo_get_or_alloc(struct net_device *dev)
+{
+	int ret;
+
+	if (dev->link_topo)
+		return dev->link_topo;
+
+	/* The topology is allocated the first time we add an object to it.
+	 * It is freed alongside the netdev. It can be called on multiple
+	 * contexts:
+	 *  - It can be called from .probe() : No rtnl, no netdev_lock
+	 *  - .ndo_open() : rtnl and possibly netdev_lock
+	 *  - SFP state machine : rtnl held or not
+	 *
+	 *  However, we can't really have races :
+	 *  - If we have a PHY, phy_link_topo_add_phy() will always run first
+	 *    and trigger the alloc. Only then the ports can be added through
+	 *    phylib of sfp.
+	 *  - If we don't, the SFP port for the cage is registered first, and
+	 *    only then other ports/PHYs can be registered.
+	 */
+	ret = netdev_alloc_phy_link_topology(dev);
+	if (ret)
+		return ERR_PTR(ret);
+
+	return dev->link_topo;
+}
+
 int phy_link_topo_add_phy(struct net_device *dev,
 			  struct phy_device *phy,
 			  enum phy_upstream upt, void *upstream)
 {
-	struct phy_link_topology *topo = dev->link_topo;
+	struct phy_link_topology *topo;
 	struct phy_device_node *pdn;
 	int ret;
 
@@ -45,13 +73,9 @@ int phy_link_topo_add_phy(struct net_device *dev,
 	if (WARN_ON_ONCE(netdev_need_ops_lock(dev)))
 		return -EOPNOTSUPP;
 
-	if (!topo) {
-		ret = netdev_alloc_phy_link_topology(dev);
-		if (ret)
-			return ret;
-
-		topo = dev->link_topo;
-	}
+	topo = phy_link_topo_get_or_alloc(dev);
+	if (IS_ERR(topo))
+		return PTR_ERR(topo);
 
 	pdn = kzalloc_obj(*pdn);
 	if (!pdn)
-- 
2.55.0