13/03/2019 22:11, John Daley (johndale): > From: Thomas Monjalon <tho...@monjalon.net> > > 13/03/2019 19:32, Ferruh Yigit: > > > On 3/5/2019 7:11 AM, Hyong Youb Kim wrote: > > > > The driver currently has a devarg to set the rewrite mode during > > > > init. Some apps want to programatically set it after running > > > > rte_eal_init() and finding that ports are VIC. Add a private > > > > function to support such applications. > > > > > > It is not good idea to have PMD specific APIs (although we already have > > some). > > > > > > Specific to this case, as far as I can see it is to pass a config > > > value and do the action related to it, what would you think having a > > > generic key/value set/get API in ethdev for this? Similar to rawdev > > get_attr/set_attr [1]? > > > > > > My concern is it may turn into something like ioctl with many things > > > pushed to it, and cause possible duplication ... > > > > Yes, it is clearly ioctl style. > > > > Please could you explain more what is the rewrite mode? > > Does it apply to the port or the queue? > > > It applies to a port. By default the Cisco VIC VLAN tags every packet on > ingress even if they were untagged coming in on the wire. They are tagged > with VLAN 0 or a VLAN id programmed into the NIC depending on the > configuration. Its part of the original design, to maintain priority bits, > ancient history. > > Some apps don't like this (VPP) or take a slower path (OVS). Hyong added a > ig-vlan-rewrite=untag devarg to disable this (leave untagged/default vlan > packets untagged) during rte_eal_init and this is helpful for OVS, but VPP > likes to set the rewrite mode after rte_eal_init() and finding the ports are > VIC ports. So that is the reasoning behind the private API call.
It looks like an application will always set this flag or never. So I don't see the need for an API function. Why VPP prefers set this flag later? Would it be better to have some driver-specific flags, no matter the ports?
