devlink: Add a new devlink port lanes attribute and pass to netlink

Add a new devlink port attribute that indicates the port's number of lanes.

Drivers are expected to set it via devlink_port_attrs_set(), before
registering the port.

The attribute is not passed to user space in case the number of lanes is
invalid (0).
Signed-off-by: Danielle Ratson <danieller@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/core.c

@@ -2134,6 +2134,7 @@ static int __mlxsw_core_port_init(struct mlxsw_core *mlxsw_core, u8 local_port,
 	int err;
 
 	attrs.split = split;
+	attrs.lanes = lanes;
 	attrs.flavour = flavour;
 	attrs.phys.port_number = port_number;
 	attrs.phys.split_subport_number = split_port_subnumber;

include/net/devlink.h

@@ -68,10 +68,12 @@ struct devlink_port_pci_vf_attrs {
  * struct devlink_port_attrs - devlink port object
  * @flavour: flavour of the port
  * @split: indicates if this is split port
+ * @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
  */
 struct devlink_port_attrs {
 	u8 split:1;
+	u32 lanes;
 	enum devlink_port_flavour flavour;
 	struct netdev_phys_item_id switch_id;
 	union {

include/uapi/linux/devlink.h

@@ -455,6 +455,8 @@ enum devlink_attr {
 
 	DEVLINK_ATTR_INFO_BOARD_SERIAL_NUMBER,	/* string */
 
+	DEVLINK_ATTR_PORT_LANES,			/* u32 */
+
 	/* add new attributes above here, update the policy in devlink.c */
 
 	__DEVLINK_ATTR_MAX,

net/core/devlink.c

@@ -530,6 +530,10 @@ static int devlink_nl_port_attrs_put(struct sk_buff *msg,
 
 	if (!devlink_port->attrs_set)
 		return 0;
+	if (attrs->lanes) {
+		if (nla_put_u32(msg, DEVLINK_ATTR_PORT_LANES, attrs->lanes))
+			return -EMSGSIZE;
+	}
 	if (nla_put_u16(msg, DEVLINK_ATTR_PORT_FLAVOUR, attrs->flavour))
 		return -EMSGSIZE;
 	switch (devlink_port->attrs.flavour) {