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

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Date:	Thu, 08 Apr 2010 19:29:33 +0100
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	chavey@...gle.com
Cc:	davem@...emloft.net, netdev@...r.kernel.org, therbert@...gle.com
Subject: Re: [PATCH 1/1] add ethtool loopback support

On Thu, 2010-04-08 at 10:35 -0700, chavey@...gle.com wrote:
> From: Ranjit Manomohan <ranjitm@...gle.com>
> Date: Wed, 7 Apr 2010 15:19:48 -0700
> 
> Add an ethtool option to use internal loopback mode for testing. 
> This feature is used for component and driver test coverage by putting
> the device in hardware loopback mode and sending / receiving network
> traffic from a user application to test the hardware and driver
> transmit / receive paths. 
> 
> Signed-off-by: laurent chavey <chavey@...gle.com>
> ---
>  include/linux/ethtool.h |   16 ++++++++++++++++
>  net/core/ethtool.c      |   40 ++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 56 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
> index b33f316..df1dcc7 100644
> --- a/include/linux/ethtool.h
> +++ b/include/linux/ethtool.h
> @@ -292,6 +292,18 @@ struct ethtool_stats {
>  	__u64	data[0];
>  };
>  
> +/* for setting the NIC into loopback mode */
> +struct ethtool_loopback {
> +	u32 cmd;		/* ETHTOOL_SLOOPBACK */
> +	u32 type;		/* ethtool_loopback_type */
> +};
> +
> +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
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.

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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