Re: [PATCH v3 net-next] net: ethernet: mtk_ppe_offload: Allow QinQ

[Simon Horman]

On Wed, Feb 12, 2025 at 08:33:52PM +0100, Eric Woudstra wrote:
> 
> 
> On 2/12/25 1:51 AM, Jakub Kicinski wrote:
> > On Sun,  9 Feb 2025 12:09:36 +0100 Eric Woudstra wrote:
> >> This patch adds QinQ support to mtk_flow_offload_replace().
> >>
> >> Only PPPoE-in-Q (as before) and Q-in-Q are allowed. A combination
> >> of PPPoE and Q-in-Q is not allowed.
> > 
> > AFAIU the standard asks for outer tag in Q-in-Q to be ETH_P_8021AD,
> > but you still check:
> > 
> >> 			    act->vlan.proto != htons(ETH_P_8021Q))
> >> 				return -EOPNOTSUPP;
> > 
> > If this is a HW limitation I think you should document that more
> > clearly in the commit message. If you can fix it, I think you should..
> 
> It will be the first case. mtk_foe_entry_set_vlan() is limited to using
> only 1 fixed protocol. I'll drop the reviewed-by, amend the commit
> message and send v4.

I agree with Jakub's comment regarding the spec, and his suggested actions.
But, FWIIW, I also think that situations such as this are not uncommon in
the wild.