net: phylink: add support for PCS link change notifications

Add a function, phylink_pcs_change() which can be used by PCs drivers
to notify phylink about changes to the PCS link state.

Signed-off-by: Russell King (Oracle) <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/phy/phylink.c

···
 	if (pcs_changed) {
 		phylink_pcs_disable(pl->pcs);
 
+		if (pl->pcs)
+			pl->pcs->phylink = NULL;
+
+		pcs->phylink = pl;
+
 		pl->pcs = pcs;
 	}
 
···
 }
 EXPORT_SYMBOL_GPL(phylink_disconnect_phy);
 
+static void phylink_link_changed(struct phylink *pl, bool up, const char *what)
+{
+	if (!up)
+		pl->mac_link_dropped = true;
+	phylink_run_resolve(pl);
+	phylink_dbg(pl, "%s link %s\n", what, up ? "up" : "down");
+}
+
 /**
  * phylink_mac_change() - notify phylink of a change in MAC state
  * @pl: a pointer to a &struct phylink returned from phylink_create()
···
  */
 void phylink_mac_change(struct phylink *pl, bool up)
 {
-	if (!up)
-		pl->mac_link_dropped = true;
-	phylink_run_resolve(pl);
-	phylink_dbg(pl, "mac link %s\n", up ? "up" : "down");
+	phylink_link_changed(pl, up, "mac");
 }
 EXPORT_SYMBOL_GPL(phylink_mac_change);
+
+/**
+ * phylink_pcs_change() - notify phylink of a change to PCS link state
+ * @pcs: pointer to &struct phylink_pcs
+ * @up: indicates whether the link is currently up.
+ *
+ * The PCS driver should call this when the state of its link changes
+ * (e.g. link failure, new negotiation results, etc.) Note: it should
+ * not determine "up" by reading the BMSR. If in doubt about the link
+ * state at interrupt time, then pass true if pcs_get_state() returns
+ * the latched link-down state, otherwise pass false.
+ */
+void phylink_pcs_change(struct phylink_pcs *pcs, bool up)
+{
+	struct phylink *pl = pcs->phylink;
+
+	if (pl)
+		phylink_link_changed(pl, up, "pcs");
+}
+EXPORT_SYMBOL_GPL(phylink_pcs_change);
 
 static irqreturn_t phylink_link_handler(int irq, void *data)
 {

include/linux/phylink.h

···
 struct ethtool_cmd;
 struct fwnode_handle;
 struct net_device;
+struct phylink;
 
 enum {
 	MLO_PAUSE_NONE,
···
 /**
  * struct phylink_pcs - PHYLINK PCS instance
  * @ops: a pointer to the &struct phylink_pcs_ops structure
+ * @phylink: pointer to &struct phylink_config
  * @neg_mode: provide PCS neg mode via "mode" argument
  * @poll: poll the PCS for link changes
  *
  * This structure is designed to be embedded within the PCS private data,
  * and will be passed between phylink and the PCS.
+ *
+ * The @phylink member is private to phylink and must not be touched by
+ * the PCS driver.
  */
 struct phylink_pcs {
 	const struct phylink_pcs_ops *ops;
+	struct phylink *phylink;
 	bool neg_mode;
 	bool poll;
 };
···
 void phylink_disconnect_phy(struct phylink *);
 
 void phylink_mac_change(struct phylink *, bool up);
+void phylink_pcs_change(struct phylink_pcs *, bool up);
 
 void phylink_start(struct phylink *);
 void phylink_stop(struct phylink *);