Re: [PATCH net-next 0/2] net: dsa: mv88e6xxx: add support for dcb pcp app

[Luke Howard]

Hi Cedric,

> On 4 Jun 2026, at 10:01 pm, Cedric Jehasse <cedric.jehasse@xxxxxxxxx> wrote:
> 
> On Thu, Jun 04, 2026 at 08:37:17PM +1000, Luke Howard wrote:
>> I still need to find a similarly natural way to expose the switch’s AVB capabilities / 802.1Qat admission control. Perhaps there is none and it will need to remain a local patch.
> 
> There's a devlink port param command. I've been wondering if this could be used
> to set a port's AvbMode. However:
> * at the moment there are no drivers supporting this.
>  eg. devlink_nl_port_param_set_doit and other return this isn't supported
> * i don't know if AvbMode is a valid use for devlink port param, and if it
>  would get accepted

mv88e6xxx already exposes the ATU_hash driver-specific devlink parameter, so there is a precedent which augurs well.

A per-port AVB mode devlink could configure:

- AVB mode to enhanced
- iso ptrs to number of enabled ports * N (currently we use N=64)
- enabling interpreting AVB_NRL entries as AVB with G1_ATU_CTL_MAC_AVB

The leaves two issues:

- if at least one port has AVB mode set, we could install permanent MDB entries as AVB_NRL. But here we have the old problem, that AVB mode is on the ingress port, whereas MDB entries are on the egress port.
- also the AVB FPri and QPri values would need to be configured, either via another devlink parameter or MQPRIO

This approach would integrate well with your CBS and DCB patches. Having said that, AVB mode could likely be reimplemented with TCAM, and (assuming an SRP daemon that knew how to install those flower entries) that might be a more portable and idiomatic solution. I am not sure how it would perform compared to the native AVB admission control in the switch.

Luke