netdev - Re: [PATCH net-next v2 5/5] net: dsa: bcm

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Date:	Tue, 07 Jun 2016 13:33:18 -0400
From:	Vivien Didelot <vivien.didelot@...oirfairelinux.com>
To:	Andrew Lunn <andrew@...n.ch>
Cc:	Florian Fainelli <f.fainelli@...il.com>, netdev@...r.kernel.org,
	davem@...emlof.net
Subject: Re: [PATCH net-next v2 5/5] net: dsa: bcm_sf2: Register our slave MDIO bus

Andrew Lunn <andrew@...n.ch> writes:

> On Tue, Jun 07, 2016 at 12:48:37PM -0400, Vivien Didelot wrote:
>> Hi Florian, Andrew,
>> 
>> Vivien Didelot <vivien.didelot@...oirfairelinux.com> writes:
>> 
>> > Hum reviewing that again, I see that if one of the 2 subsequent calls to
>> > request_irq fails, you end up with an unregistered MDIO bus.
>> >
>> > We have the same issue in the mv88e6xxx legacy probe code if dsa.c fails
>> > to allocate the dsa_switch structure. I'm moving the MDIO register code
>> > to the setup function like you are doing here (good idea!) to fix that.
>> 
>> In fact it doesn't fix the issue because dsa_switch_driver doesn't
>> provide any remove/teardown function, in which mv88e6xxx and sf2 could
>> unregister their MDIO bus on switch removal.
>> 
>> Would it be worth it to add such optional function to DSA drivers?
>
> It is not needed with DSA2 binding. The driver is always in control,
> and it performs the unregister from the core. So it knows when to
> unregister the mdio bus, either because probe has failed for some
> reason, or it is being unloaded. That is also why i register the mdio
> bus in probe, and unregister it in remove. Normal practice for a
> driver.

Yes I know, I was still talking about the legacy code.

> With the legacy interface it is tricky. When would you call such a
> remove/tairdown function when using the old binding?

That'd go in dsa_switch_destroy I guess, but it just covers the case
where the whole DSA code is unloaded...

        Vivien