Linux Ethernet Bridging - Feb 2023 - [Bridge] [PATCH net-next 5/5] net: dsa: mv88e6xxx: implementation of dynamic ATU entries

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.

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.

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.