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Date:   Thu, 14 Jul 2022 09:07:13 -0700
From:   Jakub Kicinski <kuba@kernel.org>
To:     Jiri Pirko <jiri@nvidia.com>
Cc:     Jiri Pirko <jiri@resnulli.us>, Dima Chumak <dchumak@nvidia.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Paolo Abeni <pabeni@redhat.com>, netdev@vger.kernel.org,
        Simon Horman <horms@verge.net.au>,
        Michal Wilczynski <michal.wilczynski@intel.com>
Subject: Re: [PATCH net-next 0/5] devlink rate police limiter
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On Thu, 14 Jul 2022 06:55:05 +0200 Jiri Pirko wrote:
> Wed, Jul 13, 2022 at 07:52:55PM CEST, kuba@kernel.org wrote:
> >On Wed, 13 Jul 2022 07:04:04 +0200 Jiri Pirko wrote:  
> >> Even if there is no netdevice to hook it to, because it does not exist?
> >> I have to be missing something, sorry :/  
> >
> >What I'm saying is that we can treat the devlink rate API as a "lower
> >layer interface". A layer under the netdevs. That seems sensible and
> >removes the API duplication which otherwise annoys me.
> >
> >We want drivers to only have to implement one API.
> >
> >So when user calls the legacy NDO API it should check if the device has
> >devlink rate support, first, and try to translate the legacy request
> >into devlink rate.
> >
> >Same for TC police as installed by the OvS offload feature that Simon
> >knows far more about than I do. IIRC we use a combination of matchall
> >and police to do shaping.
> >
> >That way drivers don't have to implement all three APIs, only devlink
> >rate (four APIs if we count TC qdisc but I think only NFP uses that
> >one and it has RED etc so that's too much).
> >
> >Does this help or am I still not making sense?  
> 
> I think I got it now. But in our case, there is no change for the user,
> as the netdev does not exist. So user still uses devlink rate uapi as
> proposed by this patchset. Only internal kernel changes requested.
> Correct?

Right. If the user wants to use devlink-rate directly they can.
For legacy users the kernel will translate to devlink-rate.
The point is for drivers to only have to implement devlink-rate.