netdev - Re: [PATCHv1] e1000e: Allow ethtool to enable/disable loopback.

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Message-ID: <BANLkTi=YbTgy0cNJRvcg1QkWCv9sNKkvUQ@mail.gmail.com>
Date:	Thu, 12 May 2011 07:50:28 +0200
From:	Michał Mirosław <mirqus@...il.com>
To:	Mahesh Bandewar <maheshb@...gle.com>
Cc:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	e1000-devel <e1000-devel@...ts.sourceforge.net>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Tom Herbert <therbert@...gle.com>
Subject: Re: [PATCHv1] e1000e: Allow ethtool to enable/disable loopback.

W dniu 12 maja 2011 01:11 użytkownik Mahesh Bandewar
<maheshb@...gle.com> napisał:
> On Wed, May 11, 2011 at 12:15 PM, Michał Mirosław <mirqus@...il.com> wrote:
>> 2011/5/11 Mahesh Bandewar <maheshb@...gle.com>:
>>> This patch adds e1000_set_features() to handle loopback mode. When loopback
>>> is enabled, it enables internal-MAC loopback.
>> Please wait for this driver's conversion to hw_features. One comment
>> below, though.
> This is not intrusive so should not create problems when that happens.

Fine by me then.

>> [...]
>>> --- a/drivers/net/e1000e/netdev.c
>>> +++ b/drivers/net/e1000e/netdev.c
>> [...]
>>> +static int e1000_set_features(struct net_device *dev, u32 features)
>>> +{
>>> +       u32 changed = dev->features ^ features;
>>> +
>>> +       if ((changed & NETIF_F_LOOPBACK) && netif_running(dev))
>>> +               e1000_set_loopback(dev, features);
>>> +
>>> +       return 0;
>>> +}
>> [...]
>>
>> If e1000_set_loopback() fails, this should set dev->features to passed
>> features (but keeping NETIF_F_LOOPBACK unchanged in dev->features) to
>> keep the state consistent.
> set_features() can return the return code of set_loopback() instead of
> 0; this way the consistency will be maintained.

Only as long as NETIF_F_LOOPBACK is the only bit set in hw_features.
netdev_update_features() can't really know which features were changed
and which failed when ndo_set_features callback returns non-zero.

Best Regards,
Michał Mirosław
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