Re: [PATCH net-next 5/5] net: dsa: mv88e6xxx: implementation of dynamic ATU entries

[netdev]

On 2023-02-04 09:12, Simon Horman wrote:
> On Fri, Feb 03, 2023 at 10:44:22PM +0200, Vladimir Oltean wrote:
> > On Fri, Feb 03, 2023 at 09:20:22AM +0100, Simon Horman wrote:
> > > > else if (someflag)
> > > >         dosomething();
> > > >
> > > > For now only one flag will actually be set and they are mutually exclusive,
> > > > as they will not make sense together with the potential flags I know, but
> > > > that can change at some time of course.
> > >
> > > Yes, I see that is workable. I do feel that checking for other flags would
> > > be a bit more robust. But as you say, there are none. So whichever
> > > approach you prefer is fine by me.
> >
> > The model we have for unsupported bits in the 
> > SWITCHDEV_ATTR_ID_PORT_PRE_BRIDGE_FLAGS
> > and SWITCHDEV_ATTR_ID_PORT_BRIDGE_FLAGS handlers is essentially this:
> >
> > 	if (flags & ~(supported_flag_mask))
> > 		return -EOPNOTSUPP;
> >
> > 	if (flags & supported_flag_1)
> > 		...
> >
> > 	if (flags & supported_flag_2)
> > 		...
> >
> > I suppose applying this model here would address Simon's extensibility 
> > concern.
>
> Yes, that is the model I had in mind.

The only thing is that we actually need to return both 0 and -EOPNOTSUPP 
for unsupported flags. The dynamic flag requires 0 when not supported 
(and supported) AFAICS.
Setting a mask as 'supported' for a feature that is not really supported 
defeats the notion of 'supported' IMHO.