Re: [dpdk-dev] [PATCH v3 1/3] fm10k: enable FTAG based forwarding

[Thomas Monjalon <thomas.monjalon@6wind.com>]

2016-02-26 04:31, Wang, Xiao W:
> From: Richardson, Bruce
> > On Thu, Feb 25, 2016 at 03:45:45PM +0000, Chen, Jing D wrote:
> > > From: Richardson, Bruce
> > > > On Thu, Feb 25, 2016 at 10:04:02AM +0000, Chen, Jing D wrote:
> > > > > This feature is trying to use FTAG (a unique tech in fm10k)
> > > > > instead of mac/vlan to forward packets. App need a way to tell PMD
> > > > > driver that which forwarding style it would like to use.
> > > >
> > > > Why not just specify this in the port configuration at setup time?
> > > >
> > >
> > > Please educate me. I think the port configuration flags are also
> > > common to all PMD Drivers. Is it possible to add a flag like "RTE_USE_FTAG"
> > and pass to PMD driver?
> > >
> > They are.
> > For something PMD specific, like FTAG, it's always a challenge, and I don't
> > know off the top of my head if there is a simple option. However, given the
> > choice between an mbuf flag and a port config flag, I'd always choose the
> > former.
> > Other alternatives would be to have a fm10k specific API in the fm10k driver
> > alone.
> > 
> > I'll let Thomas as ethdev maintainer comment if he has other suggestions as to
> > how to handle this case. I suspect this won't be the first device-specific piece of
> > functionality we need to deal with.
> > 
> > /Bruce
> 
> Whatever method we choose, we have to find a way for the user to express his need
> for FTAG, it maybe a build time config option, or a port config flag (no such flag now),
> or a fast path flag in mbuf (no such flag now) etc. For the customer Topsec's use case,
> they use FTAG for all the TX packets, so all the above methods (per build config, per
> port config, per mbuf config) can meet their need. Since the pmd frame work is for
> common, it's hard to add new fields only for one specific NIC, so I add a build time
> config and make an introduction in the doc.
> 
> Thanks for the discussion, Thomas, do you have any suggestions?

I don't understand why you say this feature is specific to fm10k. Can we
imagine another NIC having this capability?
I think it must be an port configuration, as Bruce suggested.
What about a field in struct rte_eth_conf?