netdev - Re: [PATCH net-next v2 00/10] net: dsa: add generic debugfs interface

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Message-ID: <9dd804f2-8d40-2a76-e692-a60b10182834@gmail.com>
Date:   Tue, 29 Aug 2017 12:19:08 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Arkadi Sharshevsky <arkadis@...lanox.com>,
        Andrew Lunn <andrew@...n.ch>, Jiri Pirko <jiri@...nulli.us>
Cc:     Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel@...oirfairelinux.com,
        "David S. Miller" <davem@...emloft.net>,
        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>, mlxsw@...lanox.com
Subject: Re: [PATCH net-next v2 00/10] net: dsa: add generic debugfs interface

On 08/29/2017 12:05 PM, Arkadi Sharshevsky wrote:
> 
> 
> On 08/29/2017 03:50 PM, Andrew Lunn wrote:
>> On Tue, Aug 29, 2017 at 08:25:23AM +0200, Jiri Pirko wrote:
>>> Mon, Aug 28, 2017 at 10:08:34PM CEST, andrew@...n.ch wrote:
>>>>> I see this overlaps a lot with DPIPE. Why won't you use that to expose
>>>>> your hw state?
>>>>
>>>> We took a look at dpipe and i talked to you about using it for this
>>>> sort of thing at netconf/netdev. But dpipe has issues displaying the
>>>> sort of information we have. I never figured out how to do two
>>>> dimensional tables. The output of the dpipe command is pretty
>>>> unreadable. A lot of the information being dumped here is not about
>>>> the data pipe, etc.
>>>
>>> So improve it. No problem. Also, we extend it to support what you neede.
>>
>> Will i did try to do this back in March. And i failed.
>>
>> Lets start with stats. Vivien gives an example on the cover letter:
>>
>>     # pr -mt switch0/port{5,6}/stats
>>     in_good_octets      : 0             in_good_octets      : 13824
>>     in_bad_octets       : 0             in_bad_octets       : 0
>>     in_unicast          : 0             in_unicast          : 0
>>     in_broadcasts       : 0             in_broadcasts       : 216
>>     in_multicasts       : 0             in_multicasts       : 0
>>     in_pause            : 0             in_pause            : 0
>>     in_undersize        : 0             in_undersize        : 0
>>
>> This is what i tried to implement using dpipe. It is a simple two
>> dimensional table. First column is a string, second a u64. In debugfs
>> we have such a table per port. That fits with the hierarchy that each
>> port is a directory in debugfs. But it could also be implemented as
>> one table with N+1 columns, for N switch ports.
>>
> 
> Hi Andrew,
> 
> This looks to me like basic L2 statistics that are obtained via
> ethtool, I remember you had this problem with the DSA and CPU port.
> Is this still the case?

Yes, there are no net_device representors for CPU and DSA ports because
if we did that, it would be confusing as we would be creating two
network devices for both ends of the pipe. For DSA (inter-switch)
interfaces you would have one "dsa" netdev for each adjacent switch so
two DSA interface represent the inter switch link.

For the "CPU" port, you have the master network device (e.g: eth0) and
the "cpu" network device, this is confusing. "cpu" is not usable, since
it does not make sense for the "cpu" to send traffic via this interface,
the model is to terminate user-facing ports and use a tag to deliver
packets to the right interfaces. For "dsa" it's pretty much the same story.

> 
> I remembered we wanted to use dpipe for the DSA routing table
> and IP priority table.
> 
> I think both those processes really look like match/action table
> , thus they can be modeled successfully by dpipe.
> 
>> How about you, or one of your team, implement that. It should be able
>> to use the dsa_loop driver, which is a simple dummy switch. But it
>> does have statistics counters for all ports. Florian or I can help you
>> get it running if needed.
>>
>> This branch contains some of the basic plumbing code from my previous
>> attempt:
>>
>> https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Flunn%2Flinux.git&data=02%7C01%7Carkadis%40mellanox.com%7Cb3cac139af204f79259c08d4eedc8410%7Ca652971c7d2e4d9ba6a4d149256f461b%7C0%7C0%7C636396078291326351&sdata=K5D3TAb2spckuF5k88oOaVt0dmtHj0AwE8bEEGPPdGI%3D&reserved=0 v4.11-rc4-net-next-dpipe
>>
>> 	 Andrew
>>


-- 
Florian