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

[Florian Fainelli <f.fainelli@gmail.com>]

On 2/9/2021 5:02 PM, George McCollister wrote:
> 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]
> +	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?)
- should there be a notifier running to advertise NETDEV_FEAT_CHANGE?
-- 
Florian