netdev - Re: [net-2.6 PATCH 1/2] net: dcbnl: remove redundant DCB_CAP_DCBX

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Message-ID: <4D3D123F.40700@intel.com>
Date:	Sun, 23 Jan 2011 21:46:39 -0800
From:	John Fastabend <john.r.fastabend@...el.com>
To:	Shmulik Ravid <shmulikr@...adcom.com>
CC:	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [net-2.6 PATCH 1/2] net: dcbnl: remove redundant DCB_CAP_DCBX_STATIC
 bit

On 1/23/2011 8:53 AM, Shmulik Ravid wrote:
> 
> On Fri, 2011-01-21 at 18:52 -0800, John Fastabend wrote:
>> On 1/21/2011 6:35 PM, John Fastabend wrote:
>>> Remove redundant DCB_CAP_DCBX_STATIC bit in DCB capabilities
>>>
>>> Setting this bit indicates that no embedded DCBx engine is
>>> present and the hardware can not be configured. This is the
>>> same as having none of the DCB capability flags set or simply
>>> not implementing the dcbnl ops at all.
>>>
>>> This patch removes this bit. The bit has not made a stable
>>> release yet so removing it should not be an issue with
>>> existing apps.
>>>
>>> Signed-off-by: John Fastabend <john.r.fastabend@...el.com>
>>> CC: Shmulik Ravid <shmulikr@...adcom.com>
>>> ---
>>>
>>
>> Shmulik, could you ACK this because you added these bits? But
>> I was adding support for this in lldpad and I see no reason that
>> we need these?
>>
> DCB_CAP_DCBX_STATIC means that the embedded engine will turn the user
> configuration into the operational configuration without performing the
> actual negotiation, so it is not equivalent to not having an embedded
> DCBx engine. This is mostly a debug and integration option as it allows
> you to do DCB related or dependent testing and development without
> having a proper DCBx peer.
> 
> On second thought, I'm not sure this option is justified although we
> found it useful during our development. If you think it's not useful
> enough (or not at all) then by all means remove it.

We have an advertise bit in userspace that can be set and cleared to
do something similar for host based agents. I think for pg and application
data you can get the same behavior by setting the device to not willing.

However for PFC it could potentially be useful. But how would the
user set this mode? This is a capabilities bit indicating the device
supports this. Is there a way to subsequently put the device in this
mode?

--John  


> 
> Thanks,
> Shmulik
> 
> 
> 

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