Re: [dpdk-dev] [PATCH v2] i40e: modify the meaning of single VLAN type

[Bruce Richardson <bruce.richardson@intel.com>]

On Mon, Jun 13, 2016 at 04:03:32PM +0800, Beilei Xing wrote:
> In current i40e codebase, if single VLAN header is added in a packet,
> it's treated as inner VLAN. Generally, a single VLAN header is
> treated as the outer VLAN header. So change corresponding register
> for single VLAN.
> At the meanwhile, change the meanings of inner VLAN and outer VLAN.
> 
> Signed-off-by: Beilei Xing <beilei.xing@intel.com>

This patch changes the ABI, since an app written to the original API as specified
e.g. to set a single vlan header, would no longer work with this change.
Therefore, even though the original behaviour was inconsistent with other drivers
it may still need to be preserved.

I'm thinking that we may need to provide appropriately versioned copies of the
vlan_offload_set and vlan_tpid_set functions for backward compatibility with
the old ABI.

Any other comments or thoughts on this? 
Neil, Thomas, Panu - is this fix something that we need to provide backward
version-compatibility for, or given that the functions are being called through
a generic ethdev API mean that this can just go in as a straight bug-fix?

/Bruce