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

On 01/24/2017 09:39 AM, David Miller wrote:

From: Florian Fainelli <f.fainelli@gmail.com>
Date: Sat, 21 Jan 2017 09:40:54 -0800

quoted

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@gmail.com>

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.

Thanks!
-- 
Florian