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

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Message-ID: <j2r97949e3e1004081543h6258125dm60083556ff28fa88@mail.gmail.com>
Date:	Thu, 8 Apr 2010 15:43:34 -0700
From:	Laurent Chavey <chavey@...gle.com>
To:	Ben Hutchings <bhutchings@...arflare.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org, therbert@...gle.com
Subject: Re: [PATCH 1/1] add ethtool loopback support

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.

> Ben.
>
> --
> Ben Hutchings, Senior Software Engineer, Solarflare Communications
> Not speaking for my employer; that's the marketing department's job.
> They asked us to note that Solarflare product names are trademarked.
>
>
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