Subject: Re: [RFC PATCH 07/12] vlan: convert VLAN devices to use ndo_fix_features()

From: Ben Hutchings <[email-masked]>
Date: Thu, 16 Dec 2010 23:36:58 +0000

On Wed, 2010-12-15 at 23:24 +0100, Michał Mirosław wrote:
> Note: get_flags was actually broken, because it should return the
> flags capped with vlan_features. This is now done implicitly by
> limiting netdev->hw_features.
> 
> RX checksumming offload control is (and was) broken, as there was no way
> before to say whether it's done for tagged packets.
> 
> Signed-off-by: Michał Mirosław <[email-masked]>
> ---
>  net/8021q/vlan.c     |    3 +-
>  net/8021q/vlan_dev.c |   51 ++++++++++++++-----------------------------------
>  2 files changed, 16 insertions(+), 38 deletions(-)
> 
> diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c
> index 6e64f7c..583d47b 100644
> --- a/net/8021q/vlan.c
> +++ b/net/8021q/vlan.c
> @@ -329,8 +329,7 @@ static void vlan_transfer_features(struct net_device *dev,
>  {
>  	unsigned long old_features = vlandev->features;
>  
> -	vlandev->features &= ~dev->vlan_features;
> -	vlandev->features |= dev->features & dev->vlan_features;
> +	netdev_update_features(vlandev);
>  	vlandev->gso_max_size = dev->gso_max_size;
>  
>  	if (dev->features & NETIF_F_HW_VLAN_TX)
> diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
> index be73753..468c899 100644
> --- a/net/8021q/vlan_dev.c
> +++ b/net/8021q/vlan_dev.c
> @@ -691,8 +691,8 @@ static int vlan_dev_init(struct net_device *dev)
>  					  (1<<__LINK_STATE_DORMANT))) |
>  		      (1<<__LINK_STATE_PRESENT);
>  
> -	dev->features |= real_dev->features & real_dev->vlan_features;
> -	dev->features |= NETIF_F_LLTX;
> +	dev->hw_features = real_dev->vlan_features;
[...]

net_device::hw_features is supposed to represent features that can be
toggled, but the inclusion of a flag in net_device::vlan_features does
not mean the feature can be toggled.

If this is to be a straight conversion, that line should be:

	dev->hw_features = real_dev->vlan_features & NETIF_F_TSO;

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.