netdev - Re: [net-next PATCH v2 5/6] i40e: Add TX and RX support in switchdev mode.

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Date:   Fri, 6 Jan 2017 11:08:58 -0800
From:   Jakub Kicinski <kubakici@...pl>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     "Samudrala, Sridhar" <sridhar.samudrala@...el.com>,
        alexander.h.duyck@...el.com, john.r.fastabend@...el.com,
        anjali.singhai@...el.com, jakub.kicinski@...ronome.com,
        davem@...emloft.net, intel-wired-lan@...ts.osuosl.org,
        netdev@...r.kernel.org
Subject: Re: [net-next PATCH v2 5/6] i40e: Add TX and RX support in
 switchdev mode.

On Fri, 6 Jan 2017 18:30:35 +0100, Jiri Pirko wrote:
> >> > +	skb_dst_drop(skb);
> >> > +	dst_hold(&priv->vfpr_dst->dst);
> >> > +	skb_dst_set(skb, &priv->vfpr_dst->dst);
> >> > +	skb->dev = vsi->netdev;  
> >> This dst dance seems a bit odd to me. Why don't you just call
> >> i40e_xmit_frame_ring with an extra arg holding the needed metadata?  
> >
> >We don't have TX/RX queues associated with VFPR netdevs, so we need to set
> >the dev to PF netdev and requeue the skb.  
> 
> Still, you eventually call a function within same .c file. Using dst
> does not look right to me.

Do you mean you don't like reusing the dst_metadata to store the
representative id?  The missing patch provided the reasoning behind
this design [1].  It's mostly about being able to comfortably use the
queuing infrastructure.  Trying to push data from multiple netdevs into
single ring at driver layer is even less pretty.

[1] http://patchwork.ozlabs.org/patch/710563/