netdev - Re: [RFC net-next 9/9] net: dsa: mv88e6xxx: setup RMU bus

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Date:   Tue, 21 May 2019 22:42:02 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Vivien Didelot <vivien.didelot@...il.com>
Cc:     netdev@...r.kernel.org, cphealy@...il.com,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [RFC net-next 9/9] net: dsa: mv88e6xxx: setup RMU bus

> +	ether_addr_copy(eth_dest_addr, dest_addr); /* Marvell broadcast or switch MAC */
> +	ether_addr_copy(eth_src_addr, dev->dev_addr);
> +	dsa_tag[0] = 0x40 | (chip->ds->index & 0x1f); /* From_CPU */
> +	dsa_tag[1] = 0xfa;
> +	dsa_tag[2] = 0xf;
> +	dsa_tag[3] = ++chip->rmu_sequence_num;
> +	*eth_ethertype = htons(ETH_P_EDSA); /* User defined, useless really */
> +
> +	req = skb_put(skb, sizeof(*req));
> +	req->format = htons(MV88E6XXX_RMU_REQUEST_FORMAT_SOHO);
> +	req->pad = 0x0000;
> +	req->code = htons(code);

Hi Vivien

When i looked at this before, i had a different idea how to do this.

The EthType you put into this header is also used in the reply. So we
could define an ETH_P_RMU. It is then possible to get the stack to
pass all frames for an ether type to a handler. e.g the batman code:

int batadv_hardif_enable_interface(struct batadv_hard_iface *hard_iface,
                                   struct net *net, const char *iface_name)
{
        struct batadv_priv *bat_priv;
        struct net_device *soft_iface, *master;
        __be16 ethertype = htons(ETH_P_BATMAN);

        hard_iface->batman_adv_ptype.type = ethertype;
        hard_iface->batman_adv_ptype.func = batadv_batman_skb_recv;
        hard_iface->batman_adv_ptype.dev = hard_iface->net_dev;
        dev_add_pack(&hard_iface->batman_adv_ptype);

So i would let the tag driver take off the {E}DSA header and pass the
frame to the stack, and the stack can then identify the frame and pass
it to the switch driver. I think it makes the split between tag code
and switch code cleaner.

       Andrew