net: phy: phy_caps: Allow looking-up link caps based on speed and duplex

As the link_caps array is efficient for <speed,duplex> lookups,
implement a function for speed/duplex lookups that matches a given
mask. This replicates to some extent the phy_lookup_settings()
behaviour, matching full link_capabilities instead of a single linkmode.

phy.c's phy_santize_settings() and phylink's
phylink_ethtool_ksettings_set() performs such lookup using the
phy_settings table, but are only interested in the actual speed/duplex
that were matched, rathet than the individual linkmode.

Similar to phy_lookup_settings(), the newly introduced phy_caps_lookup()
will run through the link_caps[] array by descending speed/duplex order.

If the link_capabilities for a given <speed/duplex> tuple intersects the
passed linkmodes, we consider that a match.

Similar to phy_lookup_settings(), we also allow passing an 'exact'
boolean, allowing non-exact match. Here, we MUST always match the
linkmodes mask, but we allow matching on lower speed settings.

Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Link: https://patch.msgid.link/20250307173611.129125-8-maxime.chevallier@bootlin.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/phy/phy-caps.h

@@ -51,4 +51,8 @@ phy_caps_lookup_by_linkmode(const unsigned long *linkmodes);
 const struct link_capabilities *
 phy_caps_lookup_by_linkmode_rev(const unsigned long *linkmodes, bool fdx_only);
 
+const struct link_capabilities *
+phy_caps_lookup(int speed, unsigned int duplex, const unsigned long *supported,
+		bool exact);
+
 #endif /* __PHY_CAPS_H */

drivers/net/phy/phy.c

@@ -213,25 +213,6 @@ int phy_aneg_done(struct phy_device *phydev)
 }
 EXPORT_SYMBOL(phy_aneg_done);
 
-/**
- * phy_find_valid - find a PHY setting that matches the requested parameters
- * @speed: desired speed
- * @duplex: desired duplex
- * @supported: mask of supported link modes
- *
- * Locate a supported phy setting that is, in priority order:
- * - an exact match for the specified speed and duplex mode
- * - a match for the specified speed, or slower speed
- * - the slowest supported speed
- * Returns the matched phy_setting entry, or %NULL if no supported phy
- * settings were found.
- */
-static const struct phy_setting *
-phy_find_valid(int speed, int duplex, unsigned long *supported)
-{
-	return phy_lookup_setting(speed, duplex, supported, false);
-}
-
 /**
  * phy_supported_speeds - return all speeds currently supported by a phy device
  * @phy: The phy device to return supported speeds of.
@@ -274,13 +255,14 @@ EXPORT_SYMBOL(phy_check_valid);
  */
 static void phy_sanitize_settings(struct phy_device *phydev)
 {
-	const struct phy_setting *setting;
+	const struct link_capabilities *c;
 
-	setting = phy_find_valid(phydev->speed, phydev->duplex,
-				 phydev->supported);
-	if (setting) {
-		phydev->speed = setting->speed;
-		phydev->duplex = setting->duplex;
+	c = phy_caps_lookup(phydev->speed, phydev->duplex, phydev->supported,
+			    false);
+
+	if (c) {
+		phydev->speed = c->speed;
+		phydev->duplex = c->duplex;
 	} else {
 		/* We failed to find anything (no supported speeds?) */
 		phydev->speed = SPEED_UNKNOWN;

drivers/net/phy/phy_caps.c

@@ -170,6 +170,53 @@ phy_caps_lookup_by_linkmode_rev(const unsigned long *linkmodes, bool fdx_only)
 	return NULL;
 }
 
+/**
+ * phy_caps_lookup() - Lookup capabilities by speed/duplex that matches a mask
+ * @speed: Speed to match
+ * @duplex: Duplex to match
+ * @supported: Mask of linkmodes to match
+ * @exact: Perform an exact match or not.
+ *
+ * Lookup a link_capabilities entry that intersect the supported linkmodes mask,
+ * and that matches the passed speed and duplex.
+ *
+ * When @exact is set, an exact match is performed on speed and duplex, meaning
+ * that if the linkmodes for the given speed and duplex intersect the supported
+ * mask, this capability is returned, otherwise we don't have a match and return
+ * NULL.
+ *
+ * When @exact is not set, we return either an exact match, or matching capabilities
+ * at lower speed, or the lowest matching speed, or NULL.
+ *
+ * Returns: a matched link_capabilities according to the above process, NULL
+ *	    otherwise.
+ */
+const struct link_capabilities *
+phy_caps_lookup(int speed, unsigned int duplex, const unsigned long *supported,
+		bool exact)
+{
+	const struct link_capabilities *lcap, *last = NULL;
+
+	for_each_link_caps_desc_speed(lcap) {
+		if (linkmode_intersects(lcap->linkmodes, supported)) {
+			last = lcap;
+			/* exact match on speed and duplex*/
+			if (lcap->speed == speed && lcap->duplex == duplex) {
+				return lcap;
+			} else if (!exact) {
+				if (lcap->speed <= speed)
+					return lcap;
+			}
+		}
+	}
+
+	if (!exact)
+		return last;
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(phy_caps_lookup);
+
 /**
  * phy_caps_linkmode_max_speed() - Clamp a linkmodes set to a max speed
  * @max_speed: Speed limit for the linkmode set

drivers/net/phy/phylink.c

@@ -20,6 +20,7 @@
 #include <linux/timer.h>
 #include <linux/workqueue.h>
 
+#include "phy-caps.h"
 #include "sfp.h"
 #include "swphy.h"
 
@@ -2852,8 +2853,8 @@ int phylink_ethtool_ksettings_set(struct phylink *pl,
 				  const struct ethtool_link_ksettings *kset)
 {
 	__ETHTOOL_DECLARE_LINK_MODE_MASK(support);
+	const struct link_capabilities *c;
 	struct phylink_link_state config;
-	const struct phy_setting *s;
 
 	ASSERT_RTNL();
 
@@ -2896,23 +2897,23 @@ int phylink_ethtool_ksettings_set(struct phylink *pl,
 		/* Autonegotiation disabled, select a suitable speed and
 		 * duplex.
 		 */
-		s = phy_lookup_setting(kset->base.speed, kset->base.duplex,
-				       pl->supported, false);
-		if (!s)
+		c = phy_caps_lookup(kset->base.speed, kset->base.duplex,
+				    pl->supported, false);
+		if (!c)
 			return -EINVAL;
 
 		/* If we have a fixed link, refuse to change link parameters.
 		 * If the link parameters match, accept them but do nothing.
 		 */
 		if (pl->req_link_an_mode == MLO_AN_FIXED) {
-			if (s->speed != pl->link_config.speed ||
-			    s->duplex != pl->link_config.duplex)
+			if (c->speed != pl->link_config.speed ||
+			    c->duplex != pl->link_config.duplex)
 				return -EINVAL;
 			return 0;
 		}
 
-		config.speed = s->speed;
-		config.duplex = s->duplex;
+		config.speed = c->speed;
+		config.duplex = c->duplex;
 		break;
 
 	case AUTONEG_ENABLE: