net: phylink: provide mac_get_caps() method

Provide a new method, mac_get_caps() to get the MAC capabilities for
the specified interface mode. This is for MACs which have special
requirements, such as not supporting half-duplex in certain interface
modes, and will replace the validate() method.
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://lore.kernel.org/r/E1qsPk5-009wiX-G5@rmk-PC.armlinux.org.ukSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/networking/sfp-phylink.rst

@@ -200,6 +200,13 @@ this documentation.
    when the in-band link state changes - otherwise the link will never
    come up.
 
+   The :c:func:`mac_get_caps` method is optional, and if provided should
+   return the phylink MAC capabilities that are supported for the passed
+   ``interface`` mode. In general, there is no need to implement this method.
+   Phylink will use these capabilities in combination with permissible
+   capabilities for ``interface`` to determine the allowable ethtool link
+   modes.
+
    The :c:func:`validate` method should mask the supplied supported mask,
    and ``state->advertising`` with the supported ethtool link modes.
    These are the new ethtool link modes, so bitmask operations must be

drivers/net/phy/phylink.c

@@ -657,6 +657,7 @@ static int phylink_validate_mac_and_pcs(struct phylink *pl,
 					unsigned long *supported,
 					struct phylink_link_state *state)
 {
+	unsigned long capabilities;
 	struct phylink_pcs *pcs;
 	int ret;
 
@@ -696,10 +697,17 @@ static int phylink_validate_mac_and_pcs(struct phylink *pl,
 	}
 
 	/* Then validate the link parameters with the MAC */
-	if (pl->mac_ops->validate)
+	if (pl->mac_ops->validate) {
 		pl->mac_ops->validate(pl->config, supported, state);
-	else
-		phylink_generic_validate(pl->config, supported, state);
+	} else {
+		if (pl->mac_ops->mac_get_caps)
+			capabilities = pl->mac_ops->mac_get_caps(pl->config,
+							state->interface);
+		else
+			capabilities = pl->config->mac_capabilities;
+
+		phylink_validate_mask_caps(supported, state, capabilities);
+	}
 
 	return phylink_is_empty_linkmode(supported) ? -EINVAL : 0;
 }

include/linux/phylink.h

@@ -228,6 +228,7 @@ void phylink_limit_mac_speed(struct phylink_config *config, u32 max_speed);
 /**
  * struct phylink_mac_ops - MAC operations structure.
  * @validate: Validate and update the link configuration.
+ * @mac_get_caps: Get MAC capabilities for interface mode.
  * @mac_select_pcs: Select a PCS for the interface mode.
  * @mac_prepare: prepare for a major reconfiguration of the interface.
  * @mac_config: configure the MAC for the selected mode and state.
@@ -241,6 +242,8 @@ struct phylink_mac_ops {
 	void (*validate)(struct phylink_config *config,
 			 unsigned long *supported,
 			 struct phylink_link_state *state);
+	unsigned long (*mac_get_caps)(struct phylink_config *config,
+				      phy_interface_t interface);
 	struct phylink_pcs *(*mac_select_pcs)(struct phylink_config *config,
 					      phy_interface_t interface);
 	int (*mac_prepare)(struct phylink_config *config, unsigned int mode,
@@ -292,6 +295,18 @@ struct phylink_mac_ops {
  */
 void validate(struct phylink_config *config, unsigned long *supported,
 	      struct phylink_link_state *state);
+/**
+ * mac_get_caps: Get MAC capabilities for interface mode.
+ * @config: a pointer to a &struct phylink_config.
+ * @interface: PHY interface mode.
+ *
+ * Optional method. When not provided, config->mac_capabilities will be used.
+ * When implemented, this returns the MAC capabilities for the specified
+ * interface mode where there is some special handling required by the MAC
+ * driver (e.g. not supporting half-duplex in certain interface modes.)
+ */
+unsigned long mac_get_caps(struct phylink_config *config,
+			   phy_interface_t interface);
 /**
  * mac_select_pcs: Select a PCS for the interface mode.
  * @config: a pointer to a &struct phylink_config.