netdev - Re: Broken link partner advertised reporting in ethtool

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Message-ID: <871802ee-3b9a-87fb-4a16-db570828ef2d@intel.com>
Date:   Mon, 27 Jul 2020 12:19:13 -0700
From:   Jacob Keller <jacob.e.keller@...el.com>
To:     Jamie Gloudon <jamie.gloudon@....fr>, netdev@...r.kernel.org
Subject: Re: Broken link partner advertised reporting in ethtool

On 7/27/2020 8:47 AM, Jamie Gloudon wrote:
> Hey,
> 
> While having a discussion with Sasha from Intel. I noticed link partner
> advertised support is broken in ethtool 5.7. Sasha hinted to me, the
> new API that ethtool is using.
> 
> I see the actual cause in dump_peer_modes() in netlink/settings.c, that
> the mask parameter is set to false for dump_link_modes, dump_pause and
> bitset_get_bit.
> 
> Regards,
> Jamie Gloudon
> 

Hi,

Seems like more detail here would be useful. This is about the ethtool
application.

Answering the following questions would help:

 - what you wanted to achieve;

 - what you did (including what versions of software and the command
   sequence to reproduce the behavior);

 - what you saw happen;

 - what you expected to see; and

 - how the last two are different.

The mask parameter for dump_link_modes is used to select between
displaying the mask and the value for a bitset.

According to the source in filling the LINKMODES_PEER, we actually don't
send a mask at all with this setting, so using true for the mask in
dump_link_modes here seems like it would be wrong.

It appears that to get link partner settings your driver must fill in
lp_advertising. If you're referring to an Intel driver, a quick search
over drivers/net/ethernet/intel shows that only the ice driver currently
supports reporting this information.

Given this, I am not convinced there is a bug in ethtool.

Thanks,
Jake