[RFC PATCH net 3/5] net: dsa: hellcreek: be compatible with masters which unregister on shutdown

[Kurt Kanzenbach]

On Sun Sep 12 2021, Vladimir Oltean wrote:
> Since commit 2f1e8ea726e9 ("net: dsa: link interfaces with the DSA
> master to get rid of lockdep warnings"), DSA gained a requirement which
> it did not fulfill, which is to unlink itself from the DSA master at
> shutdown time.
>
> Since the hellcreek driver was introduced after the bad commit, it has
> never worked with DSA masters which decide to unregister their
> net_device on shutdown, effectively hanging the reboot process.
>
> Hellcreek is a platform device driver, so we probably cannot have the
> oddities of ->shutdown and ->remove getting both called for the exact
> same struct device. But to be in line with the pattern from the other
> device drivers which are on slow buses, implement the same "if this then
> not that" pattern of either running the ->shutdown or the ->remove hook.
> The driver's current ->remove implementation makes that very easy
> because it already zeroes out its device_drvdata on ->remove.
>
> Fixes: e4b27ebc780f ("net: dsa: Add DSA driver for Hirschmann Hellcreek switches")
> Link: https://lore.kernel.org/netdev/20210909095324.12978-1-LinoSanfilippo@gmx.de/
> Reported-by: Lino Sanfilippo <LinoSanfilippo at gmx.de>
> Signed-off-by: Vladimir Oltean <vladimir.oltean at nxp.com>

Acked-by: Kurt Kanzenbach <kurt at linutronix.de>
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