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Subject: Re: [net-next RFC v3 4/7] net: ravb: Refactor GbEth RX code path
To: Paul Barker <paul.barker.ct@bp.renesas.com>, "David S. Miller"
	<davem@davemloft.net>, Eric Dumazet <edumazet@google.com>, Jakub Kicinski
	<kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>
CC: =?UTF-8?Q?Niklas_S=c3=b6derlund?= <niklas.soderlund+renesas@ragnatech.se>,
	Geert Uytterhoeven <geert+renesas@glider.be>, <netdev@vger.kernel.org>,
	<linux-renesas-soc@vger.kernel.org>, <linux-kernel@vger.kernel.org>
References: <20240415094804.8016-1-paul.barker.ct@bp.renesas.com>
 <20240415094804.8016-5-paul.barker.ct@bp.renesas.com>
From: Sergey Shtylyov <s.shtylyov@omp.ru>
Organization: Open Mobile Platform
Message-ID: <897c3e16-7ded-bdea-08c7-14bf497bfc05@omp.ru>
Date: Fri, 19 Apr 2024 23:03:52 +0300
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On 4/15/24 12:48 PM, Paul Barker wrote:

> We can reduce code duplication in ravb_rx_gbeth() and add comments to
> make the code flow easier to understand.
> 
> Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>
> ---
>  drivers/net/ethernet/renesas/ravb_main.c | 70 ++++++++++++------------
>  1 file changed, 35 insertions(+), 35 deletions(-)
> 
> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
> index baa01bd81f2d..12618171f6d5 100644
> --- a/drivers/net/ethernet/renesas/ravb_main.c
> +++ b/drivers/net/ethernet/renesas/ravb_main.c
> @@ -818,47 +818,47 @@ static int ravb_rx_gbeth(struct net_device *ndev, int budget, int q)
>  				stats->rx_missed_errors++;
>  		} else {
>  			die_dt = desc->die_dt & 0xF0;
> -			switch (die_dt) {
> -			case DT_FSINGLE:
> -				skb = ravb_get_skb_gbeth(ndev, entry, desc);
> +			skb = ravb_get_skb_gbeth(ndev, entry, desc);
> +			if (die_dt == DT_FSINGLE || die_dt == DT_FSTART) {

   No, please keep using *switch* statement here...

> +				/* Start of packet:
> +				 * Set initial data length.
> +				 */
>  				skb_put(skb, desc_len);
> +
> +				/* Save this SKB if the packet spans multiple
> +				 * descriptors.
> +				 */
> +				if (die_dt == DT_FSTART)
> +					priv->rx_1st_skb = skb;

   Hm, looks like we can do that under *case* DT_FSTART: and do
a fallthru to *case* DT_FSINGLE: after that...

> +			} else {
> +				/* Continuing a packet:
> +				 * Move data into the saved SKB.
> +				 */
> +				skb_copy_to_linear_data_offset(priv->rx_1st_skb,
> +							       priv->rx_1st_skb->len,
> +							       skb->data,
> +							       desc_len);
> +				skb_put(priv->rx_1st_skb, desc_len);
> +				dev_kfree_skb(skb);
> +
> +				/* Set skb to point at the whole packet so that
> +				 * we only need one code path for finishing a
> +				 * packet.
> +				 */
> +				skb = priv->rx_1st_skb;
> +			}
> +
> +			if (die_dt == DT_FSINGLE || die_dt == DT_FEND) {

   Again, keep using *switch*, please...

> +				/* Finishing a packet:
> +				 * Determine protocol & checksum, hand off to
> +				 * NAPI and update our stats.
> +				 */
>  				skb->protocol = eth_type_trans(skb, ndev);
>  				if (ndev->features & NETIF_F_RXCSUM)
>  					ravb_rx_csum_gbeth(skb);
> +				stats->rx_bytes += skb->len;
>  				napi_gro_receive(&priv->napi[q], skb);
>  				rx_packets++;
[...]

MBR, Sergey