From 0d22d4b626a4eaa3196019092eb6c1919e9f8caa Mon Sep 17 00:00:00 2001
From: "Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>
Date: Wed, 15 Dec 2021 15:34:20 +0000
Subject: [PATCH] net: phylink: add pcs_validate() method

Add a hook for PCS to validate the link parameters. This avoids MAC
drivers having to have knowledge of their PCS in their validate()
method, thereby allowing several MAC drivers to be simplfied.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
 drivers/net/phy/phylink.c | 31 +++++++++++++++++++++++++++++++
 include/linux/phylink.h   | 20 ++++++++++++++++++++
 2 files changed, 51 insertions(+)

--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -160,13 +160,44 @@ static int phylink_validate_mac_and_pcs(
 					struct phylink_link_state *state)
 {
 	struct phylink_pcs *pcs;
+	int ret;
 
+	/* Get the PCS for this interface mode */
 	if (pl->mac_ops->mac_select_pcs) {
 		pcs = pl->mac_ops->mac_select_pcs(pl->config, state->interface);
 		if (IS_ERR(pcs))
 			return PTR_ERR(pcs);
+	} else {
+		pcs = pl->pcs;
 	}
 
+	if (pcs) {
+		/* The PCS, if present, must be setup before phylink_create()
+		 * has been called. If the ops is not initialised, print an
+		 * error and backtrace rather than oopsing the kernel.
+		 */
+		if (!pcs->ops) {
+			phylink_err(pl, "interface %s: uninitialised PCS\n",
+				    phy_modes(state->interface));
+			dump_stack();
+			return -EINVAL;
+		}
+
+		/* Validate the link parameters with the PCS */
+		if (pcs->ops->pcs_validate) {
+			ret = pcs->ops->pcs_validate(pcs, supported, state);
+			if (ret < 0 || phylink_is_empty_linkmode(supported))
+				return -EINVAL;
+
+			/* Ensure the advertising mask is a subset of the
+			 * supported mask.
+			 */
+			linkmode_and(state->advertising, state->advertising,
+				     supported);
+		}
+	}
+
+	/* Then validate the link parameters with the MAC */
 	pl->mac_ops->validate(pl->config, supported, state);
 
 	return phylink_is_empty_linkmode(supported) ? -EINVAL : 0;
--- a/include/linux/phylink.h
+++ b/include/linux/phylink.h
@@ -396,6 +396,7 @@ struct phylink_pcs {
 
 /**
  * struct phylink_pcs_ops - MAC PCS operations structure.
+ * @pcs_validate: validate the link configuration.
  * @pcs_get_state: read the current MAC PCS link state from the hardware.
  * @pcs_config: configure the MAC PCS for the selected mode and state.
  * @pcs_an_restart: restart 802.3z BaseX autonegotiation.
@@ -403,6 +404,8 @@ struct phylink_pcs {
  *               (where necessary).
  */
 struct phylink_pcs_ops {
+	int (*pcs_validate)(struct phylink_pcs *pcs, unsigned long *supported,
+			    const struct phylink_link_state *state);
 	void (*pcs_get_state)(struct phylink_pcs *pcs,
 			      struct phylink_link_state *state);
 	int (*pcs_config)(struct phylink_pcs *pcs, unsigned int mode,
@@ -416,6 +419,23 @@ struct phylink_pcs_ops {
 
 #if 0 /* For kernel-doc purposes only. */
 /**
+ * pcs_validate() - validate the link configuration.
+ * @pcs: a pointer to a &struct phylink_pcs.
+ * @supported: ethtool bitmask for supported link modes.
+ * @state: a const pointer to a &struct phylink_link_state.
+ *
+ * Validate the interface mode, and advertising's autoneg bit, removing any
+ * media ethtool link modes that would not be supportable from the supported
+ * mask. Phylink will propagate the changes to the advertising mask. See the
+ * &struct phylink_mac_ops validate() method.
+ *
+ * Returns -EINVAL if the interface mode/autoneg mode is not supported.
+ * Returns non-zero positive if the link state can be supported.
+ */
+int pcs_validate(struct phylink_pcs *pcs, unsigned long *supported,
+		 const struct phylink_link_state *state);
+
+/**
  * pcs_get_state() - Read the current inband link state from the hardware
  * @pcs: a pointer to a &struct phylink_pcs.
  * @state: a pointer to a &struct phylink_link_state.
