Re: [RFC PATCH net-next 1/2] net: dsa: allow setting port-based QoS priority using tc matchall skbedit

On Wed, Jan 13, 2021 at 05:41:38PM +0200, Vladimir Oltean wrote:

From: Vladimir Oltean <vladimir.oltean@nxp.com>

In Time Sensitive Networking it is a common and simple use case to
configure switches to give all traffic from an attached station the same
priority, without requiring those stations to use VLAN PCP or IP DSCP to
signal the priority that they want. Many pieces of hardware support this
feature via a port-based default priority. We can model this in Linux
through a matchall action on the ingress qdisc of the port, plus a
skbedit priority action with the desired priority.

The mv88e6xxx has something similar. There is a bit to enable this
feature, as well as the priority the feature should have. I think that
then takes a value in the range of 0 to 4, but i could be remembering
it wrongly.

+	int	(*port_priority_set)(struct dsa_switch *ds, int port,
+				     struct dsa_mall_skbedit_tc_entry *skbedit);

The fact we can turn this on/off suggests there should be a way to
disable this in the hardware, when the matchall is removed. I don't
see any such remove support in this patch.

    Andrew