ethtool: Extend link modes settings uAPI with lanes

Currently, when auto negotiation is on, the user can advertise all the
linkmodes which correspond to a specific speed, but does not have a
similar selector for the number of lanes. This is significant when a
specific speed can be achieved using different number of lanes.  For
example, 2x50 or 4x25.

Add 'ETHTOOL_A_LINKMODES_LANES' attribute and expand 'struct
ethtool_link_settings' with lanes field in order to implement a new
lanes-selector that will enable the user to advertise a specific number
of lanes as well.

When auto negotiation is off, lanes parameter can be forced only if the
driver supports it. Add a capability bit in 'struct ethtool_ops' that
allows ethtool know if the driver can handle the lanes parameter when
auto negotiation is off, so if it does not, an error message will be
returned when trying to set lanes.

Example:

$ ethtool -s swp1 lanes 4
$ ethtool swp1
  Settings for swp1:
	Supported ports: [ FIBRE ]
        Supported link modes:   1000baseKX/Full
                                10000baseKR/Full
                                40000baseCR4/Full
				40000baseSR4/Full
				40000baseLR4/Full
                                25000baseCR/Full
                                25000baseSR/Full
				50000baseCR2/Full
                                100000baseSR4/Full
				100000baseCR4/Full
        Supported pause frame use: Symmetric Receive-only
        Supports auto-negotiation: Yes
        Supported FEC modes: Not reported
        Advertised link modes:  40000baseCR4/Full
				40000baseSR4/Full
				40000baseLR4/Full
                                100000baseSR4/Full
				100000baseCR4/Full
        Advertised pause frame use: No
        Advertised auto-negotiation: Yes
        Advertised FEC modes: Not reported
        Speed: Unknown!
        Duplex: Unknown! (255)
        Auto-negotiation: on
        Port: Direct Attach Copper
        PHYAD: 0
        Transceiver: internal
        Link detected: no

Signed-off-by: Danielle Ratson <danieller@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
index e3da25b51ae4..1ab13c5dfb2f 100644
--- a/include/linux/ethtool.h
+++ b/include/linux/ethtool.h
@@ -128,6 +128,7 @@ struct ethtool_link_ksettings {
 		__ETHTOOL_DECLARE_LINK_MODE_MASK(advertising);
 		__ETHTOOL_DECLARE_LINK_MODE_MASK(lp_advertising);
 	} link_modes;
+	u32	lanes;
 };
 
 /**
@@ -265,6 +266,8 @@ struct ethtool_pause_stats {
 
 /**
  * struct ethtool_ops - optional netdev operations
+ * @cap_link_lanes_supported: indicates if the driver supports lanes
+ *	parameter.
  * @supported_coalesce_params: supported types of interrupt coalescing.
  * @get_drvinfo: Report driver/device information.  Should only set the
  *	@driver, @version, @fw_version and @bus_info fields.  If not
@@ -420,6 +423,7 @@ struct ethtool_pause_stats {
  * of the generic netdev features interface.
  */
 struct ethtool_ops {
+	u32     cap_link_lanes_supported:1;
 	u32	supported_coalesce_params;
 	void	(*get_drvinfo)(struct net_device *, struct ethtool_drvinfo *);
 	int	(*get_regs_len)(struct net_device *);