Re: [PATCH v2 03/10] e1000e: Support RXFCS feature flag.

[Ben Greear <greearb@xxxxxxxxxxxxxxx>]

On 02/10/2012 03:09 PM, Michał Mirosław wrote:
> W dniu 10 lutego 2012 23:57 użytkownik Ben Greear
> <greearb@xxxxxxxxxxxxxxx>  napisał:
> > On 02/10/2012 02:46 PM, Michał Mirosław wrote:
> > > 2012/2/8<greearb@xxxxxxxxxxxxxxx>:
> > > > From: Ben Greear<greearb@xxxxxxxxxxxxxxx>
> > > >
> > > > This enables enabling/disabling reception of the Ethernet
> > > > FCS.  This can be useful when sniffing packets.
> > > >
> > > > For e1000e, enabling RXFCS can change the default
> > > > behaviour for how the NIC handles CRC.  Disabling RXFCS
> > > > will take the NIC back to defaults, which can be configured
> > > > as part of the module options.
> > >
> > > [...]
> > >
> > > This is not how I would expect the features to behave. Default value
> > > should be set on probe() time, and when you disable RXFCS it should
> > > just get disabled.
> > The NIC itself may still receive the FCS, but it will be removed
> > before the pkt is sent up the stack once you disable the 'rx-fcs' flag.
> >
> > My goal was to make sure that if you enabled and then disabled the
> > new rx-fcs flag, then you would be back at the original behaviour.
> >
> > I think that if the "rx-fcs off" logic is to change the default
> > behaviour, then the Intel folks probably need to make those changes:
> > It seems that there are some tricky work-arounds regarding fcs and
> > segmented packets for at least some versions of the e1000e chipsets.
>
> That makes sense. The flag FLAG2_DFLT_CRC_STRIPPING should be called
> FLAG2_FORCE_CRC_STRIPPING_OFF or something if that's the case.
> "Default" doesn't tell if that's a strong preference or just because.

The new flag is just to store the original crc-stripping preference
configured by the module options.  It's not really forcing anything,
it is just the 'default' value.

So, I don't think it should be changed.  However, I will defer to the
driver maintainers...if they think I should change it, then I will,
otherwise, I'm going to leave it as is.

Thanks,
Ben

--
Ben Greear <greearb@xxxxxxxxxxxxxxx>
Candela Technologies Inc  http://www.candelatech.com

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