netdev - Re: [PATCH net-next v1 1/1] net: phy: add remote fault support

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Date:   Thu, 16 Jun 2022 11:34:51 +0200
From:   Oleksij Rempel <o.rempel@...gutronix.de>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        Michal Kubecek <mkubecek@...e.cz>,
        Jonathan Corbet <corbet@....net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
        kernel@...gutronix.de, Paolo Abeni <pabeni@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Heiner Kallweit <hkallweit1@...il.com>
Subject: Re: [PATCH net-next v1 1/1] net: phy: add remote fault support

On Wed, Jun 15, 2022 at 10:07:34PM +0200, Andrew Lunn wrote:
> On Tue, Jun 14, 2022 at 10:09:48PM -0700, Jakub Kicinski wrote:
> > On Wed, 15 Jun 2022 05:37:46 +0200 Andrew Lunn wrote:
> > > > Does this dovetail well with ETHTOOL_A_LINKSTATE_EXT_STATE /
> > > > ETHTOOL_A_LINKSTATE_EXT_SUBSTATE ?
> > > > 
> > > > That's where people who read extended link state out of FW put it
> > > > (and therefore it's read only now).  
> > > 
> > > I did wonder about that. But this is to do with autoneg which is part
> > > of ksetting. Firmware hindered MAC drivers also support ksetting
> > > set/get.  This patchset is also opening the door to more information
> > > which is passed via autoneg. It can also contain the ID the link peer
> > > PHY, etc. This is all part of 802.3, where as
> > > ETHTOOL_A_LINKSTATE_EXT_STATE tends to be whatever the firmware
> > > offers, not something covered by a standard.
> > 
> > I see, yeah, I think you're right.
> > 
> > But I'm missing the bigger picture. I'm unclear on who is supposed 
> > to be setting the fault user space or kernel / device?
> 
> It is also a bit unclear, but at the moment, i think user
> space. However, i can see the kernel making use of maybe RF TEST to
> ask the link peer to go quiet in order to perform a cable test.
> 
> Oleksij, what are your use cases?

Currently I was thinking only about diagnostic:
- request transmit pause for cable testing
- request remote loopback for selftest. In this case I will need to use
  vendor specific NextPage to request something like this.

> Maybe add something to patch 0/X indicating how you plan to make use of this?

I can move it from first patch if needed.

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