netdev - Re: [PATCH v3 bpf-next 1/2] net: xdp: introduce xdp_init

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Date:   Wed, 16 Dec 2020 09:35:43 +0100
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Lorenzo Bianconi <lorenzo@...nel.org>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org, davem@...emloft.net,
        kuba@...nel.org, ast@...nel.org, daniel@...earbox.net,
        lorenzo.bianconi@...hat.com, alexander.duyck@...il.com,
        maciej.fijalkowski@...el.com, saeed@...nel.org, brouer@...hat.com
Subject: Re: [PATCH v3 bpf-next 1/2] net: xdp: introduce xdp_init_buff
 utility routine

On Sat, 12 Dec 2020 18:41:48 +0100
Lorenzo Bianconi <lorenzo@...nel.org> wrote:

> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c
> index fcc262064766..b7942c3440c0 100644
> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c
> @@ -133,12 +133,11 @@ bool bnxt_rx_xdp(struct bnxt *bp, struct bnxt_rx_ring_info *rxr, u16 cons,
>  	dma_sync_single_for_cpu(&pdev->dev, mapping + offset, *len, bp->rx_dir);
>  
>  	txr = rxr->bnapi->tx_ring;
> +	xdp_init_buff(&xdp, PAGE_SIZE, &rxr->xdp_rxq);
>  	xdp.data_hard_start = *data_ptr - offset;
>  	xdp.data = *data_ptr;
>  	xdp_set_data_meta_invalid(&xdp);
>  	xdp.data_end = *data_ptr + *len;
> -	xdp.rxq = &rxr->xdp_rxq;
> -	xdp.frame_sz = PAGE_SIZE; /* BNXT_RX_PAGE_MODE(bp) when XDP enabled */
>  	orig_data = xdp.data;

I don't like loosing the comment here.  Other developers reading this
code might assume that size is always PAGE_SIZE, which is only the case
when XDP is enabled.  Lets save them from making this mistake.

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer