net: phy: Introduce generic SFP handling for PHY drivers

There are currently 4 PHY drivers that can drive downstream SFPs:
marvell.c, marvell10g.c, at803x.c and marvell-88x2222.c. Most of the
logic is boilerplate, either calling into generic phylib helpers (for
SFP PHY attach, bus attach, etc.) or performing the same tasks with a
bit of validation :
 - Getting the module's expected interface mode
 - Making sure the PHY supports it
 - Optionaly perform some configuration to make sure the PHY outputs
   the right mode

This can be made more generic by leveraging the phy_port, and its
configure_mii() callback which allows setting a port's interfaces when
the port is a serdes.

Introduce a generic PHY SFP support. If a driver doesn't probe the SFP
bus itself, but an SFP phandle is found in devicetree/firmware, then the
generic PHY SFP support will be used, relying on port ops.

PHY driver need to :
 - Register a .attach_port() callback
 - When a serdes port is registered to the PHY, drivers must set
   port->interfaces to the set of PHY_INTERFACE_MODE the port can output
 - If the port has limitations regarding speed, duplex and aneg, the
   port can also fine-tune the final linkmodes that can be supported
 - The port may register a set of ops, including .configure_mii(), that
   will be called at module_insert time to adjust the interface based on
   the module detected.

Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Link: https://patch.msgid.link/20260108080041.553250-8-maxime.chevallier@bootlin.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

2 files changed, 4 insertions, 0 deletions

diff --git a/include/linux/phy.h b/include/linux/phy.h
index b7e769b52e6c..eb7fd533b0e4 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -2455,6 +2455,8 @@ int __phy_hwtstamp_set(struct phy_device *phydev,
 		       struct kernel_hwtstamp_config *config,
 		       struct netlink_ext_ack *extack);
 
+struct phy_port *phy_get_sfp_port(struct phy_device *phydev);
+
 extern const struct bus_type mdio_bus_type;
 extern const struct class mdio_bus_class;
 
diff --git a/include/linux/phy_port.h b/include/linux/phy_port.h
index ce0208fbccf7..550c3f4ab19f 100644
--- a/include/linux/phy_port.h
+++ b/include/linux/phy_port.h
@@ -49,6 +49,7 @@ struct phy_port_ops {
  * @active: Indicates if the port is currently part of the active link.
  * @is_mii: Indicates if this port is MII (Media Independent Interface),
  *          or MDI (Media Dependent Interface).
+ * @is_sfp: Indicates if this port drives an SFP cage.
  */
 struct phy_port {
 	struct list_head head;
@@ -67,6 +68,7 @@ struct phy_port {
 	unsigned int not_described:1;
 	unsigned int active:1;
 	unsigned int is_mii:1;
+	unsigned int is_sfp:1;
 };
 
 struct phy_port *phy_port_alloc(void);