linux-kernel - Re: [PATCH 1/1] net: core: 'ethtool' issue with querying phy settings

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Message-ID: <1433102046.6319.103.camel@decadent.org.uk>
Date:	Sun, 31 May 2015 20:54:06 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	David Miller <davem@...emloft.net>
Cc:	aparames@...adcom.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	bcm-kernel-feedback-list@...adcom.com, rjui@...adcom.com,
	sbranden@...adcom.com, jdzheng@...adcom.com
Subject: Re: [PATCH 1/1] net: core: 'ethtool' issue with querying phy
 settings

On Fri, 2015-05-22 at 16:15 -0400, David Miller wrote:
> From: Arun Parameswaran <aparames@...adcom.com>
> Date: Wed, 20 May 2015 14:35:30 -0700
> 
> > When trying to configure the settings for PHY1, using commands
> > like 'ethtool -s eth0 phyad 1 speed 100', the 'ethtool' seems to
> > modify other settings apart from the speed of the PHY1, in the
> > above case.
> > 
> > The ethtool seems to query the settings for PHY0, and use this
> > as the base to apply the new settings to the PHY1. This is
> > causing the other settings of the PHY 1 to be wrongly
> > configured.
> > 
> > The issue is caused by the '_ethtool_get_settings()' API, which
> > gets called because of the 'ETHTOOL_GSET' command, is clearing
> > the 'cmd' pointer (of type 'struct ethtool_cmd') by calling
> > memset. This clears all the parameters (if any) passed for the
> > 'ETHTOOL_GSET' cmd. So the driver's callback is always invoked
> > with 'cmd->phy_address' as '0'.
> > 
> > The '_ethtool_get_settings()' is called from other files in the
> > 'net/core'. So the fix is applied to the 'ethtool_get_settings()'
> > which is only called in the context of the 'ethtool'.
> > 
> > Signed-off-by: Arun Parameswaran <aparames@...adcom.com>
> > Reviewed-by: Ray Jui <rjui@...adcom.com>
> > Reviewed-by: Scott Branden <sbranden@...adcom.com>
> 
> Applied and queued up for -stable, thanks.

Please revert this.  This is an incompatible API change, not a bug fix.
The established semantics are that 'phyad' is filled in by the driver;
it is not a parameter to the ETHTOOL_GSET command.

Ben.

-- 
Ben Hutchings
Reality is just a crutch for people who can't handle science fiction.

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