Re: [PATCH net-next v3 4/4] net: dsa: xrs700x: add HSR offloading support

On Tue, Feb 09, 2021 at 08:11:15PM -0800, Florian Fainelli wrote:

On 2/9/2021 5:02 PM, George McCollister wrote:

quoted

Add offloading for HSR/PRP (IEC 62439-3) tag insertion, tag removal
forwarding and duplication supported by the xrs7000 series switches.

Only HSR v1 and PRP v1 are supported by the xrs7000 series switches (HSR
v0 is not).

Signed-off-by: George McCollister <george.mccollister@gmail.com>
---

[snip]

quoted

+	val &= ~BIT(dsa_upstream_port(ds, port));
+	regmap_write(priv->regmap, XRS_PORT_FWD_MASK(partner->index), val);
+	regmap_write(priv->regmap, XRS_PORT_FWD_MASK(port), val);
+
+	regmap_fields_write(priv->ps_forward, partner->index,
+			    XRS_PORT_FORWARDING);
+	regmap_fields_write(priv->ps_forward, port, XRS_PORT_FORWARDING);
+
+	hsr_pair[0] = port;
+	hsr_pair[1] = partner->index;
+	for (i = 0; i < ARRAY_SIZE(hsr_pair); i++) {
+		slave = dsa_to_port(ds, hsr_pair[i])->slave;
+		slave->features |= XRS7000X_SUPPORTED_HSR_FEATURES;

It's a bit weird to change the supported features while joining, usually
you set them ahead of time to indicate what you are capable of doing and
those can get toggled by user-space to enable/disable said feature, I
suppose the goal here is to influence the HSR data path's decisions to
insert or not tags so this may be okay. This does beg several questions:

- should slave->vlan_features also include that feature set somehow (can
I have a VLAN upper?)

hsr_check_dev_ok:
	if (is_vlan_dev(dev)) {
		NL_SET_ERR_MSG_MOD(extack, "HSR on top of VLAN is not yet supported in this driver.");
		return -EINVAL;
	}

- should there be a notifier running to advertise NETDEV_FEAT_CHANGE?

I felt it's a bit weird too to toggle the netdev flags just like that
instead of just enabling them at probe time or something (or have DSA
set them in dsa_slave_create(), just as it currently checks
ds->ops->port_vlan_add), but since there's no need for anyone to process
that notification, and there don't appear to be any strict guidelines, I
didn't say anything. I guess the current code is just fine for what is
needed at the moment.

Reviewed-by: Vladimir Oltean <olteanv@gmail.com>