netdev - Re: HW communication debugging interface

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Date:	Tue, 6 Oct 2015 17:02:26 +0200
From:	Jiri Pirko <jiri@...nulli.us>
To:	John Fastabend <john.fastabend@...il.com>
Cc:	Andrew Lunn <andrew@...n.ch>, "Rosen, Rami" <rami.rosen@...el.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"eladr@...lanox.com" <eladr@...lanox.com>,
	"idosch@...lanox.com" <idosch@...lanox.com>
Subject: Re: HW communication debugging interface - ideas?

Tue, Oct 06, 2015 at 04:54:09PM CEST, john.fastabend@...il.com wrote:
>On 15-10-06 01:14 AM, Jiri Pirko wrote:
>> Mon, Oct 05, 2015 at 05:47:09PM CEST, john.fastabend@...il.com wrote:
>>> On 15-10-05 08:35 AM, Jiri Pirko wrote:
>>>> Mon, Oct 05, 2015 at 05:29:09PM CEST, john.fastabend@...il.com wrote:
>>>>> On 15-10-05 08:18 AM, Jiri Pirko wrote:
>>>>>> Mon, Oct 05, 2015 at 04:58:42PM CEST, andrew@...n.ch wrote:
>>>>>>> On Mon, Oct 05, 2015 at 04:55:42PM +0200, Jiri Pirko wrote:
>>>>>>>> Mon, Oct 05, 2015 at 04:49:41PM CEST, andrew@...n.ch wrote:
>>>>>>>>>>> Are you referring here to messages of the EMAD protocol ?
>>>>>>>>>
>>>>>>>>> I know nothing about this protocol.....
>>>>>>>>>
>>>>>>>>> Does it at least use standard Ethernet framing? Source and Destination
>>>>>>>>> header and an EtherType which mean EMAD?
>>>>>>>>
>>>>>>>> Yep, but that does not really matter. I believe we should find debugging
>>>>>>>> interface which is protocol agnostic. Just arbitrary messages
>>>>>>>> monitoring.
>>>>>>>
>>>>>>> Hi Jiri
>>>>>>>
>>>>>>> O.K, it is just that you mentioned wireshark. Passing the frames to
>>>>>>> network interface taps would make this trivial.
>>>>>>
>>>>>> That is true. But using netlink+nlmon would do the same.
>>>>>
>>>>> Also I guess if you go this direction you want to make it generic
>>>>> enough for any drivers to use it to snoop software/firmware msgs. This
>>>>> is common across many devices.
>>>>
>>>> Yes, definitelly, this should be something generic to be usable for
>>>> every device type.
>>>>
>>>>
>>>>>
>>>>> In the past though I've just used ethtool dump commands and some
>>>>> "scripts" on top of this to debug devices. And when it got really
>>>>> bad wrote some throw away code to debug my issue. I guess it might
>>>>> be nice to have something in the kernel to improve this but have
>>>>> you considered using the tracing features that already exist?
>>>>
>>>> Which ones do you have in mind?
>>>>
>>>
>>> I was thinking something like kprobes+bpf to dump a trace and
>>> then a lua script in wireshark to parse the input and pretty
>>> print it for users. This might get you good-enough support without
>>> having to carry it around in the kernel just so we can debug
>>> the devices. We could build some libs/pkgs around it in userspace
>>> and get it published somewhere so we can all work on it together.
>> 
>> Well, I was thinking rather about some standard interface, not dependent
>> on actual kernel internals.
>> 
>
>
>Sure just throwing out an idea. I suspect whatever interface you have
>will include the vendor-id or some other identifier and a set of
>parsers in user space to pretty print the msg.

Yes, that is the plan.
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