netdev - Re: [PATCH V2 net-next 2/3] lan78xx: add ethtool set & get pause functions

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Message-ID: <1456185827.15241.77.camel@decadent.org.uk>
Date:	Tue, 23 Feb 2016 00:03:47 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Woojung.Huh@...rochip.com, davem@...emloft.net
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH V2 net-next 2/3] lan78xx: add ethtool set & get pause
 functions

On Mon, 2016-02-22 at 20:28 +0000, Woojung.Huh@...rochip.com wrote:
> > -----Original Message-----
> > From: Ben Hutchings [mailto:ben@...adent.org.uk]
> > Sent: Monday, February 22, 2016 3:05 PM
> > To: David Miller; Woojung Huh - C21699
> > Cc: netdev@...r.kernel.org
> > Subject: Re: [PATCH V2 net-next 2/3] lan78xx: add ethtool set & get pause
> > functions
> > 
> > On Mon, 2016-02-22 at 14:10 -0500, David Miller wrote:
> > > From: <Woojung.Huh@...rochip.com>
> > > Date: Mon, 22 Feb 2016 18:28:18 +0000
> > > 
> > > > > This is incorrect; you should always return the manual settings
> > > > > (fc_request_control flags) here.  If autonegotiation is enabled then
> > > > > your get_settings function will return the actual pause flags.
> > > > > 
> > > > What do you mean "return actual pause flags" when autoneg is enabled?
> > > > Pause flags set by (or default) advertise flag?
> > > 
> > > It means what was negotiated by autonegotiation, and is actually in use.
> > > 
> > > Otherwise, how can the user find out what was negotiated?
> > 
> > Well, actually we don't *directly* report the autonegotiation flow
> > control mode at present.  We report which pause flags were advertised
> > and what the link partner advertised, from which you can work it out.
> 
> NIC advertises pause flags via advertise register (phy reg 0x4) based on Rx & Tx flags,
> and get_pauseparam() returns Rx & Tx flags set by set_pauseparm() if autonegotiation is enabled?

Yes.

> > Perhaps ethtool (the utility) should explicitly show what the result
> > is.
> Ethtool -a reports Rx/Tx flags and Rx/Tx negotiated flag based on advertising and lp_advertising value.

It would probably make sense to include the result of pause frame
autonegotiation in both the 'ethtool -a' and 'ethtool' (no option)
output.

Ben.

-- 
Ben Hutchings
The generation of random numbers is too important to be left to chance.
                                                            - Robert Coveyou
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