> -----Original Message-----
> From: Jakub Kicinski <k...@kernel.org>
> Sent: Friday, January 8, 2021 2:35 AM
> To: Danielle Ratson <daniel...@mellanox.com>
> Cc: netdev@vger.kernel.org; da...@davemloft.net; Jiri Pirko
> <j...@nvidia.com>; and...@lunn.ch; f.faine...@gmail.com;
> mkube...@suse.cz; mlxsw <ml...@nvidia.com>; Ido Schimmel <ido...@nvidia.com>;
> Danielle Ratson <daniel...@nvidia.com>
> Subject: Re: [PATCH net-next repost v2 1/7] ethtool: Extend link modes
> settings uAPI with lanes
>
> On Wed, 6 Jan 2021 15:06:16 +0200 Danielle Ratson wrote:
> > From: Danielle Ratson <daniel...@nvidia.com>
> >
> > 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.
>
> > @@ -420,6 +423,7 @@ struct ethtool_pause_stats {
> > * of the generic netdev features interface.
> > */
> > struct ethtool_ops {
> > + u32 capabilities;
>
> An appropriately named bitfield seems better. Alternatively maybe let the
> driver specify which lane counts it can accept?
Not sure what did you mean, can you please explain?
Thanks!
>
> And please remember to add the kdoc.
>
> > u32 supported_coalesce_params;
> > void (*get_drvinfo)(struct net_device *, struct ethtool_drvinfo *);
> > int (*get_regs_len)(struct net_device *);
>
> > @@ -274,16 +277,17 @@ const struct nla_policy ethnl_linkmodes_set_policy[]
> > = {
> > [ETHTOOL_A_LINKMODES_SPEED] = { .type = NLA_U32 },
> > [ETHTOOL_A_LINKMODES_DUPLEX] = { .type = NLA_U8 },
> > [ETHTOOL_A_LINKMODES_MASTER_SLAVE_CFG] = { .type = NLA_U8 },
> > + [ETHTOOL_A_LINKMODES_LANES] = { .type = NLA_U32 },
>
> Please set the min and max for the policy, so userspace can at least see that
> part.
>
> > +static bool ethnl_validate_lanes_cfg(u32 cfg) {
> > + switch (cfg) {
> > + case 1:
> > + case 2:
> > + case 4:
> > + case 8:
> > + return true;
>
> And with the policy checking min and max this can be turned into a simple
> is_power_of_2() call.
>
> > + }
> > +
> > + return false;
> > +}
