netdev - Re: [PATCH 1/1] add ethtool loopback support

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Date:	Fri, 9 Apr 2010 09:43:59 -0700
From:	Laurent Chavey <chavey@...gle.com>
To:	Jeff Garzik <jeff@...zik.org>
Cc:	Ben Hutchings <bhutchings@...arflare.com>, davem@...emloft.net,
	netdev@...r.kernel.org, therbert@...gle.com
Subject: Re: [PATCH 1/1] add ethtool loopback support

isn't the existing ETHTOOL_TEST ioctl use for something like self test ?

the intent of this patch is to enable a mode whereby one could run
netperf / iperf and other application  and have the packets sent and
received by the driver.


On Thu, Apr 8, 2010 at 5:46 PM, Jeff Garzik <jeff@...zik.org> wrote:
> On 04/08/2010 06:43 PM, Laurent Chavey wrote:
>>
>> On Thu, Apr 8, 2010 at 12:35 PM, Ben Hutchings
>> <bhutchings@...arflare.com>  wrote:
>>>
>>> On Thu, 2010-04-08 at 12:17 -0700, Laurent Chavey wrote:
>>>>
>>>> On Thu, Apr 8, 2010 at 11:29 AM, Ben Hutchings
>>>> <bhutchings@...arflare.com>  wrote:
>>>>>
>>>>> On Thu, 2010-04-08 at 10:35 -0700, chavey@...gle.com wrote:
>>>
>>> [...]
>>>>>>
>>>>>> +enum ethtool_loopback_type {
>>>>>> +     ETH_MAC                 = 0x00000001,
>>>>>> +     ETH_PHY_INT             = 0x00000002,
>>>>>> +     ETH_PHY_EXT             = 0x00000004
>>>>>> +};
>>>>>
>>>>> [...]
>>>>>
>>>>> There are many different places you can loop back within a MAC or PHY,
>>>>> not to mention bypassing the MAC altogether.  See
>>>>> drivers/net/sfc/mcdi_pcol.h, starting from the line
>>>>> '#define MC_CMD_LOOPBACK_NONE 0'.  I believe we implement all of those
>>>>> loopback modes on at least one board.
>>>>>
>>>>> Also are these supposed to be an enumeration or flags?  In theory you
>>>>
>>>> those are enums that can be or together.
>>>
>>> I.e. they are flags.  So how do you answer this:
>>>
>>>>> could use wire-side and host-side loopback at the same time if they
>>>>> don't overlap, but it's probably too much trouble to bother with.  Any
>>>>> other combination is meaningless.
>>
>> since the intent is to enable the sending and receiving of packets at
>> the hw/driver interfaces, a simple loopback mode on/off is sufficient
>> and the ethtool_loopback_type are not necessary. the implementor can
>> choose
>> how to implement the loopback. From drivers/net/sfc/mcdi_pcol.h it is
>> clear
>> that unless ethtool_loopback_type as defined are meaningless.
>
> If an off/on switch is sufficient, the existing ethtool flags interface
> should work just fine.
>
>        Jeff
>
>
>
>
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