Subject: Re: [PATCH net-next 2/4] net: dsa: remove phy arg from port
 enable/disable
To: Vivien Didelot <vivien.didelot@savoirfairelinux.com>,
        netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel@savoirfairelinux.com,
        "David S. Miller" <davem@davemloft.net>, Andrew Lunn <andrew@lunn.ch>
References: <20170922161753.19563-1-vivien.didelot@savoirfairelinux.com>
 <20170922161753.19563-3-vivien.didelot@savoirfairelinux.com>
 <f8d74c3c-bd7f-8a84-2d57-c37250ff25f8@gmail.com>
 <87377eob5t.fsf@weeman.i-did-not-set--mail-host-address--so-tickle-me>
From: Florian Fainelli <f.fainelli@gmail.com>
Message-ID: <6d7799bb-2b33-0696-1805-63cea5e52667@gmail.com>
Date: Fri, 22 Sep 2017 11:23:57 -0700
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On 09/22/2017 11:12 AM, Vivien Didelot wrote:
> Hi Florian,
> 
> Florian Fainelli <f.fainelli@gmail.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