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

Hi Joseph,

Hi

On Tue, Sep 08, 2026 at 04:43:05PM +0000, Ovidiu Panait wrote:

quoted

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

quoted