[PATCH net-next 1/6] net: phylink: add support for PCS supported_interfaces bitmap

["Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>]

Add support for the PCS to specify which interfaces it supports, which
can be used by MAC drivers to build the main supported_interfaces
bitmap. Phylink also validates that the PCS returned by the MAC driver
supports the interface that the MAC was asked for.

An empty supported_interfaces bitmap from the PCS indicates that it
does not provide this information, and we handle that appropriately.

Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---
 drivers/net/phy/phylink.c | 11 +++++++++++
 include/linux/phylink.h   |  3 +++
 2 files changed, 14 insertions(+)

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index 6d50c2fdb190..31754d5fd659 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -691,6 +691,17 @@ static int phylink_validate_mac_and_pcs(struct phylink *pl,
 			return -EINVAL;
 		}
 
+		/* Ensure that this PCS supports the interface which the MAC
+		 * returned it for. It is an error for the MAC to return a PCS
+		 * that does not support the interface mode.
+		 */
+		if (!phy_interface_empty(pcs->supported_interfaces) &&
+		    !test_bit(state->interface, pcs->supported_interfaces)) {
+			phylink_err(pl, "MAC returned PCS which does not support %s\n",
+				    phy_modes(state->interface));
+			return -EINVAL;
+		}
+
 		/* Validate the link parameters with the PCS */
 		if (pcs->ops->pcs_validate) {
 			ret = pcs->ops->pcs_validate(pcs, supported, state);
diff --git a/include/linux/phylink.h b/include/linux/phylink.h
index 5462cc6a37dc..4b7a20620b49 100644
--- a/include/linux/phylink.h
+++ b/include/linux/phylink.h
@@ -393,6 +393,8 @@ struct phylink_pcs_ops;
 
 /**
  * struct phylink_pcs - PHYLINK PCS instance
+ * @supported_interfaces: describing which PHY_INTERFACE_MODE_xxx
+ *                        are supported by this PCS.
  * @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
@@ -409,6 +411,7 @@ struct phylink_pcs_ops;
  * the PCS driver.
  */
 struct phylink_pcs {
+	DECLARE_PHY_INTERFACE_MASK(supported_interfaces);
 	const struct phylink_pcs_ops *ops;
 	struct phylink *phylink;
 	bool neg_mode;
-- 
2.30.2