netdev - Re: [PATCH net-next 1/2] net: enetc: declare NETIF_F_IP

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Date:   Wed, 6 Oct 2021 17:24:18 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Ioana Ciornei <ioana.ciornei@....com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        claudiu.manoil@....com, vladimir.oltean@....com
Subject: Re: [PATCH net-next 1/2] net: enetc: declare NETIF_F_IP_CSUM and do
 it in software

On Wed,  6 Oct 2021 23:13:07 +0300 Ioana Ciornei wrote:
> This is just a preparation patch for software TSO in the enetc driver.
> Unfortunately, ENETC does not support Tx checksum offload which would
> normally render TSO, even software, impossible.
> 
> Declare NETIF_F_IP_CSUM as part of the feature set and do it at driver
> level using skb_csum_hwoffload_help() so that we can move forward and
> also add support for TSO in the next patch.
> 
> Signed-off-by: Ioana Ciornei <ioana.ciornei@....com>

Did you choose NETIF_F_IP_CSUM intentionally?
It'll only support IPv4, and since you always fall back to SW
I'd think NETIF_F_HW_CSUM makes more sense.

> diff --git a/drivers/net/ethernet/freescale/enetc/enetc.c b/drivers/net/ethernet/freescale/enetc/enetc.c
> index 3cbfa8b4e265..a92bfd660f22 100644
> --- a/drivers/net/ethernet/freescale/enetc/enetc.c
> +++ b/drivers/net/ethernet/freescale/enetc/enetc.c
> @@ -319,7 +319,7 @@ static netdev_tx_t enetc_start_xmit(struct sk_buff *skb,
>  {
>  	struct enetc_ndev_priv *priv = netdev_priv(ndev);
>  	struct enetc_bdr *tx_ring;
> -	int count;
> +	int count, err;
>  
>  	/* Queue one-step Sync packet if already locked */
>  	if (skb->cb[0] & ENETC_F_TX_ONESTEP_SYNC_TSTAMP) {
> @@ -342,6 +342,12 @@ static netdev_tx_t enetc_start_xmit(struct sk_buff *skb,
>  		return NETDEV_TX_BUSY;
>  	}
>  
> +	if (skb->ip_summed == CHECKSUM_PARTIAL) {
> +		err = skb_csum_hwoffload_help(skb, 0);
> +		if (err)
> +			goto drop_packet_err;
> +	}

Any reason no to call skb_checksum_help() directly?