RE: [PATCH net v4 3/7] net: stmmac: Rework S-VLAN handling

[Ovidiu Panait]

Hi Joseph,

> 
> Hi
> 
> On Tue, Sep 08, 2026 at 04:43:05PM +0000, Ovidiu Panait wrote:
> > The ESVL and DOVLTC bits control S-VLAN tag processing and have
> > nothing to do with the double VLAN feature, which only provides a way
> > to process an additional inner VLAN tag. However, the driver code
> > that handles them always refers to "double VLAN", which is unrelated
> > and makes the implementation confusing. The driver does not use any
> > of the inner VLAN tag features, and the networking core does not
> > support offloads for the inner tag anyway.
> >
> > To simplify the logic and to reduce the confusion regarding S-Tag vs
> > double VLAN handling, drop the is_double logic and add a hw_svlan_en
> > flag that is set when S-Tag hardware handling is enabled.
> 
> I believe I suggested to just change the "double" word to "svlan", and
> not to drop the respective logic completely. The number of S-VLAN tags
> added/removed must be still counted, otherwise any subsequent VLAN
> S-Tag removal will disable S-VLAN processing even if there are S-Tags
> left added.
> 

While working on this I realized we don't actually need to toggle the
S-VLAN bits on/off whenever a S-VLAN tag is added/removed. We can just
keep them always set as long as the NETIF_F_HW_VLAN_STAG_RX or
NETIF_F_HW_VLAN_STAG_FILTER features are advertised.

This simplified the S-VLAN logic quite a bit, by getting rid of the counting.

Ovidiu

> -Joseph
> 
> >