Re: [PATCH net-next v6 5/5] net: dsa: yt921x: Add DCB/QoS support

[David Yang]

On Mon, Feb 2, 2026 at 9:10 PM Vladimir Oltean <olteanv@xxxxxxxxx> wrote:
>
> On Sat, Jan 31, 2026 at 10:18:51AM +0800, David Yang wrote:
> > @@ -1774,8 +1778,11 @@ yt921x_vlan_aware_set(struct yt921x_priv *priv, int port, bool vlan_aware)
> >  {
> >       u32 ctrl;
> >
> > +     /* Abuse SVLAN for PCP parsing without polluting the FDB - it just works
> > +      * despite YT921X_VLAN_CTRL_SVLAN_EN never being set
> > +      */
>
> Why "abuse" - what else does this setting affect? Does the port not
> remain VLAN-unaware w.r.t. filtering/forwarding destinations?
>

It does. Recognizing SVLAN without enabling SVLAN bit makes it ignore
VLAN tag, but somehow except for PCP. I guess the manufacturer never
expected such usage.

> How is the unused YT921X_VLAN_CTRL_PRIO_EN field from VLAN table entries
> related to VLAN PCP parsing?
>

It's another appsel APP_SEL_VID, using priority in PRIO_M instead.