netdev - Re: [PATCH net-next 1/6] ethtool: Extend link modes settings uAPI with lanes

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Message-ID: <20201123094026.GF3055@nanopsycho.orion>
Date:   Mon, 23 Nov 2020 10:40:26 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     Edwin Peer <edwin.peer@...adcom.com>
Cc:     Ido Schimmel <idosch@...sch.org>, netdev <netdev@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, jiri@...dia.com,
        danieller@...dia.com, andrew@...n.ch, f.fainelli@...il.com,
        mkubecek@...e.cz, mlxsw@...dia.com,
        Ido Schimmel <idosch@...dia.com>
Subject: Re: [PATCH net-next 1/6] ethtool: Extend link modes settings uAPI
 with lanes

Thu, Nov 19, 2020 at 09:38:34PM CET, edwin.peer@...adcom.com wrote:
>On Sat, Oct 10, 2020 at 3:54 PM Ido Schimmel <idosch@...sch.org> wrote:
>
>> 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.
>
>Why can't this be implied by port break-out configuration? For higher
>speed signalling modes like PAM4, what's the difference between a
>port with unused lanes vs the same port split into multiple logical
>ports? In essence, the driver could then always choose the slowest

There is a crucial difference. Split port is configured alwasy by user.
Each split port has a devlink instace, netdevice associated with it.
It is one level above the lanes.


>signalling mode that utilizes all the available lanes.
>
>Regards,
>Edwin Peer