Re: [dpdk-stable] [PATCH 20.11 v2 00/18] Backport the new VLAN design for Intel ice PMD

[Thomas Monjalon <thomas@monjalon.net>]

18/06/2021 05:22, Wang, Haiyue:
> From: Kevin Traynor <ktraynor@redhat.com>
> > On 17/06/2021 09:53, Xueming(Steven) Li wrote:
> > > From: Wang, Haiyue <haiyue.wang@intel.com>
> > >> From: Luca Boccassi <bluca@debian.org>
> > >>> On Fri, 2021-06-11 at 15:15 +0800, Haiyue Wang wrote:
> > >>>> When LTS 20.11 was released, the Intel ice PMD has a basic VLAN
> > >>>> offload, which can only handle single VLAN mode for firmware
> > >>>> limitation. Now the firmware is updated to support double VLAN mode
> > >>>> and single VLAN mode at the same time.
> > >>>> It depends on the driver to do selection at the boot time.
> > >>>>
> > >>>> As VLAN protocol handling like strip, filter, flow is very common
> > >>>> use, we request to support the ice PMD can run on the latest
> > >>>> firmware for enabling the new design. This is compatible backport as the main tree.
[...]
> > >>>>  19 files changed, 1545 insertions(+), 363 deletions(-)  create mode
[...]
> > >>> At 1.9k diffstat, this series is quite large. Given it's a new
> > >>> feature, rather than a series of bug fixes, this would seem a bit risky to me.
> > >>> Final word of course belongs to Xueming, since he's managing this one.

[...]
> > >> 06. Is it obvious that the feature will not impact existing functionality?
> > >>
> > >> Yes.
> > 
> > No. It is 1.9KLOC change. The key part of the question is "obvious". It
> > was meant so the maintainer could use their judgement and review that
> > for example, a few lines of code adding a PCI ID or adding a case in a
> > switch statement, is obviously not going to impact existing functionality.
> > On the other hand, for a more complex code change to existing code, it
> > is not immediately obvious that there would be no risk to existing
> > functionality.

[...]
> > >> 11. Is there a community consensus about the backport?
> > >>
> > >> ...
> > >
> > > Kevin happens to updated the documents on new feature backport 4 months ago, thanks for checking
> > them
> > > one by one. Luca's only concern is size of the series, driver vendor is on it's own risk to backport
> > a big patch set.
> > > The series supports new fw and QinQ, is it easy to split?
> > >
> > > Kevin, is this the first case of feature backport? How do you think?
> > >
> > 
> > Like Luca, main concern would be the size and intrusiveness of the
> > changes, and if it's ok to change 1.9KLOC in this driver now, then why
> > not 20KLOC in next release to multiple drivers. I had pushed against a
> 
> TBH, we won't want to change the stable i40e, ixgbe PMDs, but ice is a fresh
> one, current VLAN has a limited usage, customer is hard to use. That's why we
> try to request to backport the new VLAN design.

Yes ice is quite recent.
If a required feature is not working, it should motivate to upgrade.
Because ice is "fresh", I don't understand why sticking to 20.11.
My concern is that backporting this big feature would create a precedent,
so all users will require to stick on the last LTS when getting
all the new reworked features.
I think it would be a bad situation for all of us.