Re: [PATCH net-next 06/12] net: dsa: rzn1-a5psw: add Renesas RZ/N1 advanced 5 port switch driver

[Russell King (Oracle)]

On Fri, Apr 15, 2022 at 02:14:19PM +0300, Vladimir Oltean wrote:
> On Fri, Apr 15, 2022 at 12:02:14PM +0100, Russell King (Oracle) wrote:
> > On Fri, Apr 15, 2022 at 01:55:03PM +0300, Vladimir Oltean wrote:
> > > I meant that for a DSA switch driver is mandatory to call dsa_switch_shutdown()
> > > from your ->shutdown method, otherwise subtle things break, sorry for being unclear.
> > > 
> > > Please blindly copy-paste the odd pattern that all other DSA drivers use
> > > in ->shutdown and ->remove (with the platform_set_drvdata(dev, NULL) calls),
> > > like a normal person :)
> > 
> > Those platform_set_drvdata(, NULL) calls should be killed - the
> > driver model will set the driver data to NULL after ->remove has
> > been called - so having drivers also setting the driver data to
> > NULL is mere duplication.
> 
> I can see why you say that, but the reverse is not true.
> A driver can be removed from a device after said device has been shut
> down, and DSA does things in dsa_unregister_switch() and in
> dsa_switch_shutdown() that are incompatible with each other, so either
> one or the other should be called, but not both.

How would ->remove be called after ->shutdown has been called? Aren't
the two calls already exclusive - if ->remove has been called, the
device is no longer bound to the driver, so ->shutdown can't be called
for the device.  If ->shutdown has been called, the system is going
down, and userspace is probably already dead.

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