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Date:   Mon, 21 Oct 2019 17:49:00 +0200
From:   Andrew Lunn <andrew@lunn.ch>
To:     Oleksij Rempel <o.rempel@pengutronix.de>
Cc:     Chris Snook <chris.snook@gmail.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        James Hogan <jhogan@kernel.org>,
        Jay Cliburn <jcliburn@gmail.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Paul Burton <paul.burton@mips.com>,
        Ralf Baechle <ralf@linux-mips.org>,
        Rob Herring <robh+dt@kernel.org>,
        Vivien Didelot <vivien.didelot@gmail.com>,
        Pengutronix Kernel Team <kernel@pengutronix.de>,
        "David S. Miller" <davem@davemloft.net>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, devicetree@vger.kernel.org,
        linux-mips@vger.kernel.org, Russell King <linux@armlinux.org.uk>
Subject: Re: [PATCH v3 4/5] net: dsa: add support for Atheros AR9331 TAG
 format
Message-ID: <20191021154900.GF17002@lunn.ch>
References: <20191021053811.19818-1-o.rempel@pengutronix.de>
 <20191021053811.19818-5-o.rempel@pengutronix.de>
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> +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