linux-kernel - Re: [PATCH net-next v2 01/10] net: dsa: add debugfs interface

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Date:   Fri, 15 Sep 2017 07:51:07 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Alexander Duyck <alexander.duyck@...il.com>,
        Maxim Uvarov <muvarov@...il.com>,
        Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        netdev <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        kernel@...oirfairelinux.com,
        "David S. Miller" <davem@...emloft.net>,
        Florian Fainelli <f.fainelli@...il.com>,
        Egil Hjelmeland <privat@...l-hjelmeland.no>,
        John Crispin <john@...ozen.org>,
        Woojung Huh <Woojung.Huh@...rochip.com>,
        Sean Wang <sean.wang@...iatek.com>,
        Nikita Yushchenko <nikita.yoush@...entembedded.com>,
        Chris Healy <cphealy@...il.com>
Subject: Re: [PATCH net-next v2 01/10] net: dsa: add debugfs interface

Thu, Sep 14, 2017 at 11:01:32PM CEST, andrew@...n.ch wrote:
>> Can you clarify what type of registers it is you are wanting to read?
>> We already have ethtool which is meant to allow reading the device
>> registers for a given netdev. As long as the port has a netdev
>> associated it then there is no need to be getting into debugfs since
>> we should probably just be using ethtool.
>
>Not all ports of a DSA switch have a netdev. This is by design. The
>presentation we gave to Netdev 2.1 gives some of the background.
>
>Plus a switch has a lot of registers not associated to port. Often a
>switch has more global registers than port registers.
> 
>> Also as Jiri pointed out there is already devlink which would probably
>> be a better way to get the associated information for those pieces
>> that don't have a netdev associated with them.
>
>We have looked at the devlink a few times. The current dpipe code is
>not generic enough. It makes assumptions about the architecture of the
>switch, that it is all match/action based. The niche of top of rack
>switches might be like that, but average switches are not.
>
>If dpipe was to support simple generic two dimensional tables, we
>probably would use it.
>
>David suggested making a class device for DSA. It is not ideal, but we
>are probably going to go that way.

I believe that is also big mistake.

Could you put together your requirements so we can work it out to extend
devlink to support them?

Thanks.