Subject: Re: [PATCH v3 4/5] net: dsa: add support for Atheros AR9331 TAG format

From: Andrew Lunn <[email-masked]>
Date: Mon, 21 Oct 2019 17:49:00 +0200

> +static struct sk_buff *ar9331_tag_rcv(struct sk_buff *skb,
> +				      struct net_device *ndev,
> +				      struct packet_type *pt)
> +{
> +	u8 ver, port;
> +	u16 hdr;
> +
> +	if (unlikely(!pskb_may_pull(skb, AR9331_HDR_LEN)))
> +		return NULL;
> +
> +	hdr = le16_to_cpu(*(__le16 *)skb_mac_header(skb));
> +
> +	ver = FIELD_GET(AR9331_HDR_VERSION_MASK, hdr);
> +	if (unlikely(ver != AR9331_HDR_VERSION)) {
> +		netdev_warn_once(ndev, "%s:%i wrong header version 0x%2x\n",
> +				 __func__, __LINE__, hdr);
> +		return NULL;
> +	}
> +
> +	if (unlikely(hdr & AR9331_HDR_FROM_CPU)) {
> +		netdev_warn_once(ndev, "%s:%i packet should not be from cpu 0x%2x\n",
> +				 __func__, __LINE__, hdr);
> +		return NULL;
> +	}
> +
> +	skb_pull(skb, AR9331_HDR_LEN);
> +	skb_set_mac_header(skb, -ETH_HLEN);

No other tag driver calls skb_set_mac_header().  Also, the -ETH_HLEN
looks odd, give you have just pulled off AR9331_HDR_LEN?

What other tag drivers use is skb_pull_rcsum().

     Andrew