Subject: Re: [PATCH net-next 1/2 RESEND v3] net: use NETIF_F_ALL_TSO for vlan features

From: Dimitris Michailidis <[email-masked]>
Date: Thu, 12 May 2011 10:05:54 -0700

On 05/12/2011 02:54 AM, Shan Wei wrote:
> Dimitris Michailidis wrote, at 2011年05月12日 00:35:
>> On 05/10/2011 11:24 PM, Shan Wei wrote:
>>> As Dimitris Michailidis suggested, use NETIF_F_ALL_TSO for vlan_features,
>>> which is a mask, but not hw_features.
>>>
>>> Signed-off-by: Shan Wei <[email-masked]>
>> While these changes aren't wrong I don't see a good reason to make them.  I am also curious why you're changing only these three drivers.
> 
> A personal reason to quickly know what device supports ALL TSO,
> not to search one by one. :;)

But vlan_features doesn't indicate by itself what the device supports, and it 
is because of this that you can use NETIF_F_ALL_TSO in vlan_features without 
much future breakage risk.  There's still the potential that in the future some 
additional TSO variant will be added that some of the drivers you're changing 
support, but not over VLANs, and then they'll need to undo you change.

If you want to know which drivers support all TSOs you really need to look at 
their features and hw_features.  One could set NETIF_F_ALL_TSO in vlan_features 
of a driver that doesn't support any form of TSO.  The way you're checking 
you'd be misled into thinking that driver supports all TSO.