netdev - Re: [RFC net-next 3/6] ethernet: prestera: use eth_hw_addr_set

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Date:   Mon, 18 Oct 2021 10:01:41 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     "Taras Chornyi [C]" <tchornyi@...vell.com>
Cc:     Vladimir Oltean <olteanv@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "andrew@...n.ch" <andrew@...n.ch>,
        "idosch@...sch.org" <idosch@...sch.org>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "Vadym Kochan [C]" <vkochan@...vell.com>
Subject: Re: [RFC net-next 3/6] ethernet: prestera: use
 eth_hw_addr_set_port()

On Mon, 18 Oct 2021 16:54:00 +0000 Taras Chornyi [C] wrote:
> > @@ -341,8 +342,8 @@ static int prestera_port_create(struct prestera_switch *sw, u32 id)
> >       /* firmware requires that port's MAC address consist of the first
> >        * 5 bytes of the base MAC address
> >        */
> > -     memcpy(dev->dev_addr, sw->base_mac, dev->addr_len - 1);
> > -     dev->dev_addr[dev->addr_len - 1] = port->fp_id;
> > +     memcpy(addr, sw->base_mac, dev->addr_len - 1);  
> 
> This code is a bit buggy.  We do care about the last byte of the base mac address.
> For example if base mac is xx:xx:xx:xx:xx:10 first port mac should be  xx:xx:xx:xx:xx:11

Thanks for the reply, does it mean we can assume base_mac will be valid
or should we add a check like below?

diff --git a/drivers/net/ethernet/marvell/prestera/prestera_main.c b/drivers/net/ethernet/marvell/prestera/prestera_main.c
index b667f560b931..966f94c6c7a6 100644
--- a/drivers/net/ethernet/marvell/prestera/prestera_main.c
+++ b/drivers/net/ethernet/marvell/prestera/prestera_main.c
@@ -338,11 +338,14 @@ static int prestera_port_create(struct prestera_switch *sw, u32 id)
                goto err_port_init;
        }
 
-       /* firmware requires that port's MAC address consist of the first
-        * 5 bytes of the base MAC address
-        */
-       memcpy(dev->dev_addr, sw->base_mac, dev->addr_len - 1);
-       dev->dev_addr[dev->addr_len - 1] = port->fp_id;
+       eth_hw_addr_set_port(dev, sw->base_mac, port->fp_id);
+       if (memcmp(dev->dev_addr, sw->base_mac, ETH_ALEN - 1)) {
+               /* firmware requires that port's MAC address consists
+                * of the first 5 bytes of the base MAC address
+                */
+               dev_warn(prestera_dev(sw), "Port MAC address overflows the base for port(%u)\n", id);
+               dev_addr_mod(dev, 0, sw->base_mac, ETH_ALEN - 1);
+       }
 
        err = prestera_hw_port_mac_set(port, dev->dev_addr);
        if (err) {