Subject: Re: [PATCH] Documentation: document the gianfar tx vlan offload issue

From: Claudiu Manoil <[email-masked]>
Date: Fri, 4 Apr 2014 10:07:05 +0300

On 4/4/2014 6:04 AM, [email-masked] wrote:
> From: Li RongQing <[email-masked]>
>
> The commit b852b72087[gianfar: fix bug caused by 87c288c6e9] and e2c53be223
> [gianfar: fix default tx vlan offload feature flag] disabled tx vlan offload
> from dev->feature, since enabling vlan tag insertion leads to unusable
> connections on some configurations.
>
> But this feature is in dev->hw_feature still, and a user can enable it by
> "ethtool", so document the tx vlan offload issue.
>
> Signed-off-by: Li RongQing <[email-masked]>
> Signed-off-by: Zhu Yanjun <[email-masked]>
> Cc: Claudiu Manoil <[email-masked]>
> ---
>   Documentation/networking/gianfar.txt |   12 ++++++++++++
>   1 file changed, 12 insertions(+)
>
> diff --git a/Documentation/networking/gianfar.txt b/Documentation/networking/gianfar.txt
> index ad474ea..2d3dbe6 100644
> --- a/Documentation/networking/gianfar.txt
> +++ b/Documentation/networking/gianfar.txt
> @@ -51,6 +51,18 @@ configuring VLANs.  The gianfar driver supports hardware insertion and
>   extraction of VLAN headers, but not filtering.  Filtering will be
>   done by the kernel.
>   
> +But if tx vlan tag hardware insertion is enabled, and a vlan-device is
> +created, the physical device which vlan device is on will be unable to
> +work, like:
> +
> +	$ethtool -K eth0 tx-vlan-stag-hw-insert on
> +	$ifconfig eth0 192.168.1.13/24 up
> +
> +	$vconfig add eth0 4091
> +	$ifconfig eth0.4091 10.1.1.13/24 up
> +eth0.4091 can work, but eth0 can not work, since eth0 sends the insane
> +packets out.
> +
I don't really like this, this is hardly a technical explanation. 
("insane packets"?)
Please have a look at the HW reference manual.  There you have the 
description
of the VLAN extraction feature (see VLEX).

Regards,
Claudiu