[net-next RFC PATCH v5 03/10] net: phylink: add phylink_release_pcs() to externally release a PCS

[Christian Marangi <ansuelsmth@gmail.com>]

Add phylink_release_pcs() to externally release a PCS from a phylink
instance. This can be used to handle case when a single PCS needs to be
removed and the phylink instance needs to be refreshed.

On calling phylink_release_pcs(), the PCS will be removed from the
phylink internal PCS list and the phylink supported_interfaces value is
reparsed with the remaining PCS interfaces.

Also a phylink resolve is triggered to handle the PCS removal.

The flag force_major_config is set to make phylink resolve reconfigure
the interface (even if it didn't change) is also added.
This is needed to handle the special case when the current PCS used
by phylink is removed and a major_config is needed to propagae the
configuration change. With this option enabled we also force mac_config
even if the PHY link is not up for the in-band case.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
---
 drivers/net/phy/phylink.c | 49 +++++++++++++++++++++++++++++++++++++++
 include/linux/phylink.h   |  2 ++
 2 files changed, 51 insertions(+)

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index 1a261060d78e..ca4f4f655a31 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -923,6 +923,55 @@ static void phylink_resolve_an_pause(struct phylink_link_state *state)
 	}
 }
 
+/**
+ * phylink_release_pcs - Removes a PCS from the phylink PCS available list
+ * @pcs: a pointer to the phylink_pcs struct to be released
+ *
+ * This function release a PCS from the phylink PCS available list if
+ * actually in use. It also refreshes the supported interfaces of the
+ * phylink instance by copying the supported interfaces from the phylink
+ * conf and merging the supported interfaces of the remaining available PCS
+ * in the list and trigger a resolve.
+ */
+void phylink_release_pcs(struct phylink_pcs *pcs)
+{
+	struct phylink *pl;
+
+	ASSERT_RTNL();
+
+	pl = pcs->phylink;
+	if (!pl)
+		return;
+
+	list_del(&pcs->list);
+	pcs->phylink = NULL;
+
+	/* Check if we are removing the PCS currently
+	 * in use by phylink. If this is the case,
+	 * force phylink resolve to reconfigure the interface
+	 * mode and set the phylink PCS to NULL.
+	 */
+	if (pl->pcs == pcs) {
+		mutex_lock(&pl->state_mutex);
+
+		pl->force_major_config = true;
+		pl->pcs = NULL;
+
+		mutex_unlock(&pl->state_mutex);
+	}
+
+	/* Refresh supported interfaces */
+	phy_interface_copy(pl->supported_interfaces,
+			   pl->config->supported_interfaces);
+	list_for_each_entry(pcs, &pl->pcs_list, list)
+		phy_interface_or(pl->supported_interfaces,
+				 pl->supported_interfaces,
+				 pcs->supported_interfaces);
+
+	phylink_run_resolve(pl);
+}
+EXPORT_SYMBOL_GPL(phylink_release_pcs);
+
 static unsigned int phylink_pcs_inband_caps(struct phylink_pcs *pcs,
 				    phy_interface_t interface)
 {
diff --git a/include/linux/phylink.h b/include/linux/phylink.h
index 9c5a43febde1..aef4a4fcf6e5 100644
--- a/include/linux/phylink.h
+++ b/include/linux/phylink.h
@@ -746,6 +746,8 @@ void phylink_disconnect_phy(struct phylink *);
 int phylink_set_fixed_link(struct phylink *,
 			   const struct phylink_link_state *);
 
+void phylink_release_pcs(struct phylink_pcs *pcs);
+
 void phylink_mac_change(struct phylink *, bool up);
 void phylink_pcs_change(struct phylink_pcs *, bool up);
 
-- 
2.53.0