netdev - Re: [PATCH v2 net-next 3/9] net: dsa: tag_ksz: add tag handling for Microchip LAN937x

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Message-ID: <YIaxpsBFDiEiiRj4@lunn.ch>
Date:   Mon, 26 Apr 2021 14:27:18 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Prasanna Vengateshan <prasanna.vengateshan@...rochip.com>
Cc:     Vladimir Oltean <olteanv@...il.com>, netdev@...r.kernel.org,
        robh+dt@...nel.org, UNGLinuxDriver@...rochip.com,
        hkallweit1@...il.com, linux@...linux.org.uk, davem@...emloft.net,
        kuba@...nel.org, linux-kernel@...r.kernel.org,
        vivien.didelot@...il.com, f.fainelli@...il.com,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v2 net-next 3/9] net: dsa: tag_ksz: add tag handling for
 Microchip LAN937x

> > > +#define LAN937X_TAIL_TAG_LOOKUP              BIT(12)
> > > +#define LAN937X_TAIL_TAG_VALID               BIT(13)
> > > +#define LAN937X_TAIL_TAG_PORT_MASK   7
> > > +
> > > +static struct sk_buff *lan937x_xmit(struct sk_buff *skb,
> > > +                                 struct net_device *dev)
> > > +{
> > > +     struct dsa_port *dp = dsa_slave_to_port(dev);
> > > +     __be16 *tag;
> > > +     u8 *addr;
> > > +     u16 val;
> > > +r
> > > +     tag = skb_put(skb, LAN937X_INGRESS_TAG_LEN);
> > 
> > Here we go again.. why is it called INGRESS_TAG_LEN if it is used during
> > xmit, and only during xmit?

> Definition is ingress to the LAN937x since it has different tag length for
> ingress and egress of LAN937x. Do you think should it be changed? 

tag drivers run on Linux, not the switch. So all ingress/egress should
be relative to linux, not the switch. You are writing a linux driver
here, not firmware running on the switch.

      Andrew