linux-kernel - Re: [PATCH net-next 3/3] net: hns3: add support for link diagnosis info in debugfs

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Date:   Sun, 4 Jul 2021 21:57:52 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     "huangguangbin (A)" <huangguangbin2@...wei.com>
Cc:     Jakub Kicinski <kuba@...nel.org>, davem@...emloft.net,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        salil.mehta@...wei.com, lipeng321@...wei.com
Subject: Re: [PATCH net-next 3/3] net: hns3: add support for link diagnosis
 info in debugfs

> > > Hi Jakub, I have a question to consult you.
> > > Some fault information in our patch are not existed in current ethtool extended
> > > link states, for examples:
> > > "Serdes reference clock lost"
> > > "Serdes analog loss of signal"
> > > "SFP tx is disabled"
> > > "PHY power down"
> > 
> > Why would the PHY be powered down if user requested port to be up?
> > 
> In the case of other user may use MDIO tool to write PHY register directly to make
> PHY power down, if link state can display this information, I think it is helpful.

If the user directly writes to PHY registers, they should expect bad
things to happen. They can do a lot more than power the PHY down. They
could configure it into loopback mode, turn off autoneg and force a
mode which is compatible with the peer, etc.

I don't think you need to tell the user they have pointed a foot gun
at their feet and pulled the trigger.

   Andrew