netdev - Re: [net-next-2.6 PATCH] ethtool: update get_rx_ntuple to correctly interpret string count

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Date:	Wed, 05 Jan 2011 15:26:56 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Alexander Duyck <alexander.h.duyck@...el.com>
Cc:	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [net-next-2.6 PATCH] ethtool: update get_rx_ntuple to
 correctly interpret string count

On Tue, 2011-01-04 at 17:06 -0800, Alexander Duyck wrote:
> On 1/4/2011 4:01 PM, Ben Hutchings wrote:
> > On Tue, 2011-01-04 at 15:29 -0800, Alexander Duyck wrote:
> >> Currently any strings returned via the get_rx_ntuple call will just be
> >> dropped because the num_strings will be zero.  In order to correct this I
> >> am updating things so that the return value of get_rx_ntuple is the number
> >> of strings that were written, or a negative value if there was an error.
> > [...]
> >
> > Nothing implements ethtool_ops::get_rx_ntuple, anyway.
> >
> > The fallback implementation is totally bogus, too.  Maximum of 1024
> > filters?  Erm, sfc can handle more than that.  And doing complex string
> > formatting in the kernel, even though all the parsing is in ethtool?
> >
> > Please, let's write off ETHTOOL_GRXNTUPLE as a failed experiment and
> > replace it with a command that behaves more like ETHTOOL_GRXCLSRLALL.
> >
> > Ben.
> 
> In order to address several different issues in the perfect filters 
> provided by 82599 I found it necessary to implement get_rx_ntuple so 
> that the driver could maintain the filter list inside of the driver 
> instead of having it maintained by the stack.  In doing so though I 
> found the bug.
> 
> I agree the fallback implementation has a limitation on the number and 
> format of filters it supports.  However declaring the function a "failed 
> experiment" and just dropping it isn't exactly constructive since we 
> have customers that are making use of the feature.
[...]

We can at least drop that fallback implementation since it apparently
doesn't work properly for either of the drivers that currently use it.

In the medium term, I do want to replace it with a binary interface and
move that formatting to ethtool.  ETHTOOL_GRXNTUPLE could be kept around
for a while for ixgbe only, while your customers have a chance to get
the updated ethtool.

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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