netdev - Re: [RFC PATCH net-next 8/9] net: dsa: Use PHYLINK for the CPU/DSA ports

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Date:   Wed, 22 May 2019 19:17:00 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Ioana Ciornei <ioana.ciornei@....com>,
        "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "andrew@...n.ch" <andrew@...n.ch>,
        "hkallweit1@...il.com" <hkallweit1@...il.com>,
        "maxime.chevallier@...tlin.com" <maxime.chevallier@...tlin.com>,
        "olteanv@...il.com" <olteanv@...il.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>
Subject: Re: [RFC PATCH net-next 8/9] net: dsa: Use PHYLINK for the CPU/DSA
 ports



On 5/22/2019 6:20 PM, Ioana Ciornei wrote:
> This completely removes the usage of PHYLIB from DSA, namely for the
> aforementioned switch ports which used to drive a software PHY manually
> using genphy operations.
> 
> For these ports, the newly introduced phylink_create_raw API must be
> used, and the callbacks are received through a notifier block registered
> per dsa_port, but otherwise the implementation is fairly
> straightforward, and the handling of the regular vs raw PHYLINK
> instances is common from the perspective of the driver.
> 
> What changes for drivers:
> 
> The .adjust_link callback is no longer called for the fixed-link CPU/DSA
> ports and drivers must migrate to standard PHYLINK operations (e.g.
> .phylink_mac_config).  The reason why we can't do anything for them is
> because PHYLINK does not wrap the fixed link state behind a phydev
> object, so we cannot wrap .phylink_mac_config into .adjust_link unless
> we fabricate a phy_device structure.

Can't we offer a slightly nicer transition period for DSA switch drivers:

- if adjust_link and phylink_mac_ops are both supported, prefer
phylink_mac_ops
- if phylink_mac_ops is defined alone use it, we're good
- if adjust_link alone is defined, keep using it with the existing code
but print a warning inviting to migrate?

The changes look fine but the transition path needs to be a little more
gentle IMHO.
-- 
Florian