netdev - Re: [patch 1/9] [PATCH] qeth: convert to hw

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Message-ID: <20110512115959.GA37368@tuxmaker.boeblingen.de.ibm.com>
Date:	Thu, 12 May 2011 13:59:59 +0200
From:	Frank Blaschka <blaschka@...ux.vnet.ibm.com>
To:	Michał Mirosław <mirqus@...il.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org,
	linux-s390@...r.kernel.org
Subject: Re: [patch 1/9] [PATCH] qeth: convert to hw_features part 2

On Thu, May 12, 2011 at 01:25:51PM +0200, Michał Mirosław wrote:
> W dniu 12 maja 2011 13:10 użytkownik Frank Blaschka
> <blaschka@...ux.vnet.ibm.com> napisał:
> > On Thu, May 12, 2011 at 10:12:51AM +0200, Michał Mirosław wrote:
> >> W dniu 12 maja 2011 09:21 użytkownik Frank Blaschka
> >> <blaschka@...ux.vnet.ibm.com> napisał:
> >> > On Thu, May 12, 2011 at 07:59:45AM +0200, Michał Mirosław wrote:
> >> >> 2011/5/12  <frank.blaschka@...ibm.com>:
> >> >> > Set rx csum default to hw checksumming again.
> >> >> > Remove sysfs interface for rx csum (checksumming) and TSO (large_send).
> >> >> > With the new hw_features it does not work to keep the old sysfs
> >> >> > interface in parallel. Convert options.checksum_type to new hw_features.
> >> >> [...]
> >> >> > +               /* hw may have changed during offline or recovery */
> >> >> > +               if (!qeth_is_supported(card, IPA_INBOUND_CHECKSUM)) {
> >> >> [...]
> >> >>
> >> >> This check should go to ndo_fix_features callback. If it fails then
> >> >> just return features &~NETIF_F_RXCSUM from there ...
> >> >>
> > Ok so all I have to do to complete this is to remove
> >  card->dev->hw_features &= ~NETIF_F_RXCSUM;
> > from here (ndo_fix_feature has already the check)?
> >
> > Since we might be in recovery it is smarter to keep the support check here so we
> > do not have to use try and error approach to see if capabilities have
> > changed. Do you aggree?
> 
> The key is that the driver should call netdev_update_features()
> whenever some conditions affecting available features might have
> changed. If you can keep the checks contained inside ndo_fix_features
> callback, you can avoid caring about the offloads in the recovery
> process.
Ok, we have this now.
> 
> There's also the question what happens when packets are queued while
> there's ongoing recovery? Simplest way would be to drop them all until
> recovery completes.
Since this is RX processing there is nothing queued during recovery. But
you are right for tx csum or TSO we have to think about this. For now
I would like to complete this patch.
> 
> Best Regards,
> Michał Mirosław
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