Subject: [PATCH net-next 01/10] net: phylink: add phylink_limit_mac_speed()

From: "Russell King (Oracle)" <[email-masked]>
Date: Thu, 24 Aug 2023 14:37:53 +0100

Add a function which can be used to limit the phylink MAC capabilities
to an upper speed limit.

Signed-off-by: Russell King (Oracle) <[email-masked]>
---
 drivers/net/phy/phylink.c | 18 ++++++++++++++++++
 include/linux/phylink.h   |  2 ++
 2 files changed, 20 insertions(+)

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index 160bce608c34..0d7354955d62 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -426,6 +426,24 @@ static struct {
 	{ MAC_10HD,     SPEED_10,     DUPLEX_HALF },
 };
 
+/**
+ * phylink_limit_mac_speed - limit the phylink_config to a maximum speed
+ * @config: pointer to a &struct phylink_config
+ * @max_speed: maximum speed
+ *
+ * Mask off MAC capabilities for speeds higher than the @max_speed parameter.
+ * Any further motifications of config.mac_capabilities will override this.
+ */
+void phylink_limit_mac_speed(struct phylink_config *config, u32 max_speed)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(phylink_caps_params) &&
+		    phylink_caps_params[i].speed > max_speed; i++)
+		config->mac_capabilities &= ~phylink_caps_params[i].mask;
+}
+EXPORT_SYMBOL_GPL(phylink_limit_mac_speed);
+
 /**
  * phylink_cap_from_speed_duplex - Get mac capability from speed/duplex
  * @speed: the speed to search for
diff --git a/include/linux/phylink.h b/include/linux/phylink.h
index 789c516c6b4a..7d07f8736431 100644
--- a/include/linux/phylink.h
+++ b/include/linux/phylink.h
@@ -223,6 +223,8 @@ struct phylink_config {
 	unsigned long mac_capabilities;
 };
 
+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.
-- 
2.30.2