netdev - Re: [PATCH net-next 2/4] net: dsa: remove phy arg from port enable/disable

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Date:   Fri, 22 Sep 2017 11:23:57 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
        netdev@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel@...oirfairelinux.com,
        "David S. Miller" <davem@...emloft.net>,
        Andrew Lunn <andrew@...n.ch>
Subject: Re: [PATCH net-next 2/4] net: dsa: remove phy arg from port
 enable/disable

On 09/22/2017 11:12 AM, Vivien Didelot wrote:
> Hi Florian,
> 
> Florian Fainelli <f.fainelli@...il.com> writes:
> 
>> On 09/22/2017 09:17 AM, Vivien Didelot wrote:
>>> The .port_enable and .port_disable functions are meant to deal with the
>>> switch ports only, and no driver is using the phy argument anyway.
>>> Remove it.
>>
>> I don't think this makes sense, there are perfectly legit reasons why a
>> switch driver may have something to do with the PHY device attached to
>> its per-port network interface, we should definitively keep that around,
>> unless you think we should be accessing the PHY within the switch
>> drivers by doing:
>>
>> struct phy_device *phydev = ds->ports[port].netdev->phydev?
> 
> bcm_sf2 is the only user for this phy argument right now. The reason I'm
> doing this is because I prefer to discourage switch drivers to dig into
> the phy device themselves while as you said there must be a cleaner
> solution. This must be handled somehow elsewhere in the stack.

The current approach of passing the phy_device reference as an argument
is certainly a cleaner way then. The port_enable caller can provide the
correct phy_device and that lifts the switch driver from having to dig
it itself from its per-port netdev.

> 
> In the meantime, moving the PHY device up to the dsa_port structure is a
> good solution, in order not to expose it in switch ops, but still make
> it available to more complex drivers.
> 
> Do you know if netdev->phydev is usable? Why do DSA has its own copy in
> dsa_slave_priv then?

Historical reasons mostly. Considering the complexity of
dsa_slave_phy_setup(), I would certainly be extremely careful in
changing any of this, the potential for breakage is pretty big. At first
glance, I would say that this is a safe conversion to do, and I can test
this on the HW I have here anyway.
-- 
Florian