Re: [PATCH net-next v1 2/8] net: ieee8021q: add pcp_to_tt()

On Fri, Oct 2, 2026 at 1:58 PM Oleksij Rempel [off-list ref] wrote:

Add a helper that maps an IEEE 802.1Q Priority Code Point (PCP) to the
corresponding 802.1Q traffic type, complementing the existing
ietf_dscp_to_ieee8021q_tt().

It is very nearly an identity map, except that PCP 0 (Best Effort) and
PCP 1 (Background) are swapped: per 802.1Q-2022 (Annex I, Table I-2)
Background is a lower priority than Best Effort even though it carries
the higher PCP value. PCP 2..7 map straight through to the matching
traffic type, and values above 7 are rejected with -EINVAL. This decodes
the 8P0D encoding (Table I-7), where every PCP value is a priority and
none carries drop eligibility.

Drivers that classify ingress traffic by PCP need this to map into a
priority-ordered internal space without misordering Best Effort and
Background. The first consumer, the realtek rtl8365mb DSA driver, lands
later in this series.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>

This looks very generally helpful.
Reviewed-by: Linus Walleij <linusw@kernel.org>

Yours,
Linus Walleij