Re: [PATCH net] net: dsa: Keep a reference count on ethernet_dev

From: Florian Fainelli
Date: Tue Jan 24 2017 - 12:56:51 EST

On 01/24/2017 09:39 AM, David Miller wrote:
> From: Florian Fainelli <f.fainelli@xxxxxxxxx>
> Date: Sat, 21 Jan 2017 09:40:54 -0800
>> of_find_net_device_by_node() just returns a reference to a net_device but does
>> not increment its reference count, which means that the master network device
>> can just vanish under our feet.
>> Fixes: 83c0afaec7b7 ("net: dsa: Add new binding implementation")
>> Signed-off-by: Florian Fainelli <f.fainelli@xxxxxxxxx>
> This is fine, except now this netdev is completely locked into place with
> no way to dynamically unload it.
> If someone tries to modunload the driver for this ethernet device,
> their screen will fill up with warning messages indicating that the
> reference taken here in the DSA code is not going away.
> You need to implement a netdev notifier that tears down this DSA
> instance during an unregister event and releases the ethernet_dev.
> Similar to how we handle protocol addresses bound to a netdev, etc.

OK, that was actually my original approach, and then while detaching the
switch from the network device seemed easy enough, re-attaching it could
be a little challenging. Let's try again.