linux-kernel - Re: [PATCH net-next v2 07/10] net: fec: fec_enet_rx_queue(): replace manual VLAN header calculation with skb_vlan_eth

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Message-ID: <4877c76a-d0c1-41d7-95c6-553542e2d9b1@lunn.ch>
Date: Mon, 16 Jun 2025 15:12:37 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Wei Fang <wei.fang@....com>
Cc: Marc Kleine-Budde <mkl@...gutronix.de>,
	Shenwei Wang <shenwei.wang@....com>,
	Clark Wang <xiaoning.wang@....com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Richard Cochran <richardcochran@...il.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"imx@...ts.linux.dev" <imx@...ts.linux.dev>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kernel@...gutronix.de" <kernel@...gutronix.de>,
	Frank Li <frank.li@....com>
Subject: Re: [PATCH net-next v2 07/10] net: fec: fec_enet_rx_queue(): replace
 manual VLAN header calculation with skb_vlan_eth_hdr()

On Mon, Jun 16, 2025 at 01:42:08AM +0000, Wei Fang wrote:
> > >  drivers/net/ethernet/freescale/fec_main.c | 3 +--
> > >  1 file changed, 1 insertion(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/net/ethernet/freescale/fec_main.c
> > > b/drivers/net/ethernet/freescale/fec_main.c
> > > index 6b456372de9a..f238cb60aa65 100644
> > > --- a/drivers/net/ethernet/freescale/fec_main.c
> > > +++ b/drivers/net/ethernet/freescale/fec_main.c
> > > @@ -1860,8 +1860,7 @@ fec_enet_rx_queue(struct net_device *ndev, u16
> > queue_id, int budget)
> > >  		    fep->bufdesc_ex &&
> > >  		    (ebdp->cbd_esc & cpu_to_fec32(BD_ENET_RX_VLAN))) {
> > >  			/* Push and remove the vlan tag */
> > > -			struct vlan_hdr *vlan_header =
> > > -					(struct vlan_hdr *) (data + ETH_HLEN);
> > > +			struct vlan_ethhdr *vlan_header = skb_vlan_eth_hdr(skb);
> > 
> > This is not 'obviously correct', so probably the commit message needs expanding.
> > 
> > static inline struct vlan_ethhdr *skb_vlan_eth_hdr(const struct sk_buff *skb) {
> > 	return (struct vlan_ethhdr *)skb->data; }
> > 
> > I can see a few lines early:
> > 
> > 		data = skb->data;
> > 
> > but what about the + ETH_HLEN?
> > 
> 
> The type of vlan_header has been changed from "struct vlan_hdr *" to
> "struct vlan_ethhdr *", so it is correct to use skb->data directly.

Doh! I missed that, sorry. Maybe extend the commit message, you
mention skb_vlan_eth_hdr() but you could add something like

... and change the type of vlan_header to struct vlan_ethhdr to take
into account the ethernet header plus vlan header is returned.

With that, please add: Reviewed-by: Andrew Lunn <andrew@...n.ch>

    Andrew