From fbb9a9d263a68f60a16c8ba5a51d6198d67171cd Mon Sep 17 00:00:00 2001
From: "Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>
Date: Fri, 3 Jan 2025 11:16:31 +0000
Subject: [PATCH] net: phylink: add support for PCS supported_interfaces bitmap

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>
Link: https://patch.msgid.link/E1tTffL-007RoD-1Y@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 drivers/net/phy/phylink.c | 11 +++++++++++
 include/linux/phylink.h   |  3 +++
 2 files changed, 14 insertions(+)

--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -701,6 +701,17 @@ static int phylink_validate_mac_and_pcs(
 			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);
--- 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;
