netdev - RE: [PATCH net-next 07/11] net: fec: use switch statement to check the type of tx

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Message-ID:
 <PAXPR04MB8510292C43DE527926154759888FA@PAXPR04MB8510.eurprd04.prod.outlook.com>
Date: Wed, 14 Jan 2026 10:01:26 +0000
From: Wei Fang <wei.fang@....com>
To: Frank Li <frank.li@....com>
CC: Shenwei Wang <shenwei.wang@....com>, Clark Wang <xiaoning.wang@....com>,
	"andrew+netdev@...n.ch" <andrew+netdev@...n.ch>, "davem@...emloft.net"
	<davem@...emloft.net>, "edumazet@...gle.com" <edumazet@...gle.com>,
	"kuba@...nel.org" <kuba@...nel.org>, "pabeni@...hat.com" <pabeni@...hat.com>,
	"ast@...nel.org" <ast@...nel.org>, "daniel@...earbox.net"
	<daniel@...earbox.net>, "hawk@...nel.org" <hawk@...nel.org>,
	"john.fastabend@...il.com" <john.fastabend@...il.com>, "sdf@...ichev.me"
	<sdf@...ichev.me>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"imx@...ts.linux.dev" <imx@...ts.linux.dev>, "bpf@...r.kernel.org"
	<bpf@...r.kernel.org>
Subject: RE: [PATCH net-next 07/11] net: fec: use switch statement to check
 the type of tx_buf

> On Tue, Jan 13, 2026 at 11:29:35AM +0800, Wei Fang wrote:
> > The tx_buf has three types: FEC_TXBUF_T_SKB, FEC_TXBUF_T_XDP_NDO and
> > FEC_TXBUF_T_XDP_TX. Currently, the driver uses 'if...else...'
> > statements to check the type and perform the corresponding processing.
> > This is very detrimental to future expansion. For example, if new
> > types are added to support XDP zero copy in the future, continuing to use
> 'if...else...'
> > would be a very bad coding style. So the 'if...else...' statements in
> > the current driver are replaced with switch statements to support XDP
> > zero copy in the future.
> >
> > Signed-off-by: Wei Fang <wei.fang@....com>
> > ---
> >  drivers/net/ethernet/freescale/fec_main.c | 167
> > +++++++++++-----------
> >  1 file changed, 82 insertions(+), 85 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/freescale/fec_main.c
> > b/drivers/net/ethernet/freescale/fec_main.c
> > index f3e93598a27c..3bd89d7f105b 100644
> > --- a/drivers/net/ethernet/freescale/fec_main.c
> > +++ b/drivers/net/ethernet/freescale/fec_main.c
> > @@ -1023,33 +1023,33 @@ static void fec_enet_bd_init(struct net_device
> *dev)
> >  		txq->bd.cur = bdp;
> >
> >  		for (i = 0; i < txq->bd.ring_size; i++) {
> > +			dma_addr_t dma = fec32_to_cpu(bdp->cbd_bufaddr);
> > +			struct page *page;
> > +
> >  			/* Initialize the BD for every fragment in the page. */
> >  			bdp->cbd_sc = cpu_to_fec16(0);
> > -			if (txq->tx_buf[i].type == FEC_TXBUF_T_SKB) {
> > -				if (bdp->cbd_bufaddr &&
> > -				    !IS_TSO_HEADER(txq,
> fec32_to_cpu(bdp->cbd_bufaddr)))
> > -					dma_unmap_single(&fep->pdev->dev,
> > -							 fec32_to_cpu(bdp->cbd_bufaddr),
> > -							 fec16_to_cpu(bdp->cbd_datlen),
> > -							 DMA_TO_DEVICE);
> > -				if (txq->tx_buf[i].buf_p)
> > -					dev_kfree_skb_any(txq->tx_buf[i].buf_p);
> > -			} else if (txq->tx_buf[i].type == FEC_TXBUF_T_XDP_NDO) {
> > -				if (bdp->cbd_bufaddr)
> > -					dma_unmap_single(&fep->pdev->dev,
> > -							 fec32_to_cpu(bdp->cbd_bufaddr),
> > +			switch (txq->tx_buf[i].type) {
> > +			case FEC_TXBUF_T_SKB:
> > +				if (dma && !IS_TSO_HEADER(txq, dma))
> > +					dma_unmap_single(&fep->pdev->dev, dma,
> >  							 fec16_to_cpu(bdp->cbd_datlen),
> >  							 DMA_TO_DEVICE);
> >
> > -				if (txq->tx_buf[i].buf_p)
> > -					xdp_return_frame(txq->tx_buf[i].buf_p);
> > -			} else {
> > -				struct page *page = txq->tx_buf[i].buf_p;
> > -
> > -				if (page)
> > -					page_pool_put_page(pp_page_to_nmdesc(page)->pp,
> > -							   page, 0,
> > -							   false);
> > +				dev_kfree_skb_any(txq->tx_buf[i].buf_p);
> > +				break;
> > +			case FEC_TXBUF_T_XDP_NDO:
> > +				dma_unmap_single(&fep->pdev->dev, dma,
> > +						 fec16_to_cpu(bdp->cbd_datlen),
> > +						 DMA_TO_DEVICE);
> > +				xdp_return_frame(txq->tx_buf[i].buf_p);
> 
> look like logic is not exactly same as original one
> 
> if (txq->tx_buf[i].type == FEC_TXBUF_T_XDP_NDO) {
> 	if (bdp->cbd_bufaddr)
> 		...

Yes, I did some cleanup as well, because the case of NULL pointer is
always false.