netdev - Re: [PATCH net-next v3 2/7] ethtool: Get link mode in use instead of speed and duplex parameters

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Message-ID: <CAKOOJTx_JHcaL9Wh2ROkpXVSF3jZVsnGHTSndB42xp61PzP9Vg@mail.gmail.com>
Date:   Mon, 25 Jan 2021 10:03:57 -0800
From:   Edwin Peer <edwin.peer@...adcom.com>
To:     Danielle Ratson <danieller@...dia.com>
Cc:     netdev <netdev@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, Jiri Pirko <jiri@...dia.com>,
        Andrew Lunn <andrew@...n.ch>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        Michal Kubecek <mkubecek@...e.cz>, mlxsw <mlxsw@...dia.com>,
        Ido Schimmel <idosch@...dia.com>
Subject: Re: [PATCH net-next v3 2/7] ethtool: Get link mode in use instead of
 speed and duplex parameters

On Sun, Jan 24, 2021 at 12:36 AM Danielle Ratson <danieller@...dia.com> wrote:

> > Why isn't this also handled using a capability bit as is done for
> > lanes? Is link_mode read-only? Should it / will it always be? If not,
> > can drivers also derive the other fields if asked to set link_mode?
>
> The link_mode param is only for deriving all the speed, lanes and duplex params in ethtool instead of deriving in driver and then > passing each individual, as Michal asked.

I understand the benefit of deriving the dependent fields in core code
rather than in each driver, I just don't think this is necessarily
mutually exclusive with being able to force a particular link mode at
the driver API, making link_mode R/W (and even extend this interface
to user space). For a driver that works internally in terms of the
link_mode it's returning, this would be more natural.

> > That would be easy enough. Why don't we simply allow user space to set
> > link mode directly too (in addition to being able to constrain lanes
> > for autoneg or forced speeds)?
>
> It is already possible to do using 'advertise' parameter.

That's not the same thing. If it were, you wouldn't need the lanes
parameter in the first place.

Regards,
Edwin Peer

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