devlink: let driver opt out of automatic phys_port_name generation

JIRA: https://issues.redhat.com/browse/RHEL-109607

commit c5ec7f4
Author: Jedrzej Jagielski <[email protected]>
Date:   Fri Jul 4 13:17:47 2025 +0200

    devlink: let driver opt out of automatic phys_port_name generation

    Currently when adding devlink port, phys_port_name is automatically
    generated within devlink port initialization flow. As a result adding
    devlink port support to driver may result in forced changes of interface
    names, which breaks already existing network configs.

    This is an expected behavior but in some scenarios it would not be
    preferable to provide such limitation for legacy driver not being able to
    keep 'pre-devlink' interface name.

    Add flag no_phys_port_name to devlink_port_attrs struct which indicates
    if devlink should not alter name of interface.

    Suggested-by: Jiri Pirko <[email protected]>
    Link: https://lore.kernel.org/all/nbwrfnjhvrcduqzjl4a2jafnvvud6qsbxlvxaxilnryglf4j7r@btuqrimnfuly/
    Signed-off-by: Jedrzej Jagielski <[email protected]>
    Signed-off-by: Tony Nguyen <[email protected]>

Signed-off-by: CKI Backport Bot <[email protected]>
Signed-off-by: Michal Schmidt <[email protected]>

Author: CKI Backport Bot

include/net/devlink.h

@@ -80,6 +80,9 @@ struct devlink_port_pci_sf_attrs {
  * @flavour: flavour of the port
  * @split: indicates if this is split port
  * @splittable: indicates if the port can be split.
+ * @no_phys_port_name: skip automatic phys_port_name generation; for
+ *		       compatibility only, newly added driver/port instance
+ *		       should never set this.
  * @lanes: maximum number of lanes the port supports. 0 value is not passed to netlink.
  * @switch_id: if the port is part of switch, this is buffer with ID, otherwise this is NULL
  * @phys: physical port attributes
@@ -89,7 +92,8 @@ struct devlink_port_pci_sf_attrs {
  */
 struct devlink_port_attrs {
 	u8 split:1,
-	   splittable:1;
+	   splittable:1,
+	   no_phys_port_name:1;
 	u32 lanes;
 	enum devlink_port_flavour flavour;
 	struct netdev_phys_item_id switch_id;

net/devlink/port.c

@@ -1519,7 +1519,7 @@ static int __devlink_port_phys_port_name_get(struct devlink_port *devlink_port,
 	struct devlink_port_attrs *attrs = &devlink_port->attrs;
 	int n = 0;
 
-	if (!devlink_port->attrs_set)
+	if (!devlink_port->attrs_set || devlink_port->attrs.no_phys_port_name)
 		return -EOPNOTSUPP;
 
 	switch (attrs->flavour) {