linux-kernel - Re: [PATCH 2.6.38.4] mii: add support of pause frames in mii_get

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Date:	Thu, 28 Apr 2011 13:45:38 +0100
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	artpol <artpol84@...il.com>, linux-kernel@...r.kernel.org,
	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH 2.6.38.4] mii: add support of pause frames in mii_get_an

On Wed, 2011-04-27 at 21:49 -0700, Stephen Hemminger wrote:
> On Thu, 28 Apr 2011 10:49:14 +0700
> artpol <artpol84@...il.com> wrote:
> 
> > Add support of pause frames advertise in mii_get_an. This provides all drivers 
> > that use mii_ethtool_gset to represent their own and Link partner flow control
> > abilities in ethtool.
> > 
> > Signed-off-by: Artem Polyakov <artpol84@...il.com>
> > 
> > ---
> > 
> > --- linux-2.6.38.4/drivers/net/mii.c.orig	2011-04-28 08:46:13.000000000 +0700
> > +++ linux-2.6.38.4/drivers/net/mii.c	2011-04-25 23:04:20.694981968 +0700
> > @@ -49,6 +49,10 @@ static u32 mii_get_an(struct mii_if_info
> >  		result |= ADVERTISED_100baseT_Half;
> >  	if (advert & ADVERTISE_100FULL)
> >  		result |= ADVERTISED_100baseT_Full;
> > +	if (advert & ADVERTISE_PAUSE_CAP)
> > +		result |= ADVERTISED_Pause;
> > +	if (advert & ADVERTISE_PAUSE_ASYM)
> > +		result |= ADVERTISED_Asym_Pause;
> >  
> >  	return result;
> >  }
> 
> One common driver problem is that auto negotiation of pause
> is really a separate operation from negotiation of speed.
> It should be possible to force no flow-control but still negotiate
> speed and vice-versa.

If you want to force flow control then turn off pause autoneg.
If you want to force speed then turn off advertising of other speeds.

> The ethtool api breaks this into two operations
> but many drivers munge them together.

There is some interaction between set_pauseparam and set_settings if
pause autoneg is enabled, which is why we have the
mii_advertise_flowctrl() function.

Anyway, this patch covers reporting only.

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare
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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