[PATCH net-next V4 1/5] net: phylink: Add phylink_set_fixed_link() to configure fixed link state in phylink

[Raju Lakkaraju <Raju.Lakkaraju@microchip.com>]

From: Russell King <linux@armlinux.org.uk>

The function allows for the configuration of a fixed link state for a given
phylink instance. This addition is particularly useful for network devices that
operate with a fixed link configuration, where the link parameters do not change
dynamically. By using `phylink_set_fixed_link()`, drivers can easily set up
the fixed link state during initialization or configuration changes.

Signed-off-by: Russell King <linux@armlinux.org.uk>
Signed-off-by: Raju Lakkaraju <Raju.Lakkaraju@microchip.com>
---
Change List:
============
V0 -> V1:
  - Change phylink fixed-link function header's string from "Returns" to        
    "Returns:" 
  - Add fixed-link patch along with this series.                                
    Note: Note: This code was developed by Mr.Russell King                      
    Ref:                                                                        
    https://lore.kernel.org/netdev/LV8PR11MB8700C786F5F1C274C73036CC9F8E2@LV8PR11MB8700.namprd11.prod.outlook.com/T/#me943adf54f1ea082edf294aba448fa003a116815

 drivers/net/phy/phylink.c | 42 +++++++++++++++++++++++++++++++++++++++
 include/linux/phylink.h   |  2 ++
 2 files changed, 44 insertions(+)

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index ab4e9fc03017..4309317de3d1 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -1635,6 +1635,48 @@ static int phylink_register_sfp(struct phylink *pl,
 	return ret;
 }
 
+/**
+ * phylink_set_fixed_link() - set the fixed link
+ * @pl: a pointer to a &struct phylink returned from phylink_create()
+ * @state: a pointer to a struct phylink_link_state.
+ *
+ * This function is used when the link parameters are known and do not change,
+ * making it suitable for certain types of network connections.
+ *
+ * Returns: zero on success or negative error code.
+ */
+int phylink_set_fixed_link(struct phylink *pl,
+			   const struct phylink_link_state *state)
+{
+	const struct phy_setting *s;
+	unsigned long *adv;
+
+	if (pl->cfg_link_an_mode != MLO_AN_PHY || !state ||
+	    !test_bit(PHYLINK_DISABLE_STOPPED, &pl->phylink_disable_state))
+		return -EINVAL;
+
+	s = phy_lookup_setting(state->speed, state->duplex,
+			       pl->supported, true);
+	if (!s)
+		return -EINVAL;
+
+	adv = pl->link_config.advertising;
+	linkmode_zero(adv);
+	linkmode_set_bit(s->bit, adv);
+	linkmode_set_bit(ETHTOOL_LINK_MODE_Autoneg_BIT, adv);
+
+	pl->link_config.speed = state->speed;
+	pl->link_config.duplex = state->duplex;
+	pl->link_config.link = 1;
+	pl->link_config.an_complete = 1;
+
+	pl->cfg_link_an_mode = MLO_AN_FIXED;
+	pl->cur_link_an_mode = pl->cfg_link_an_mode;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(phylink_set_fixed_link);
+
 /**
  * phylink_create() - create a phylink instance
  * @config: a pointer to the target &struct phylink_config
diff --git a/include/linux/phylink.h b/include/linux/phylink.h
index 2381e07429a2..5c01048860c4 100644
--- a/include/linux/phylink.h
+++ b/include/linux/phylink.h
@@ -598,6 +598,8 @@ int phylink_fwnode_phy_connect(struct phylink *pl,
 			       const struct fwnode_handle *fwnode,
 			       u32 flags);
 void phylink_disconnect_phy(struct phylink *);
+int phylink_set_fixed_link(struct phylink *,
+			   const struct phylink_link_state *);
 
 void phylink_mac_change(struct phylink *, bool up);
 void phylink_pcs_change(struct phylink_pcs *, bool up);
-- 
2.34.1