Hi Tom, On 17/01/17 22:05, Tom Herbert wrote: > There was some discussion about the problems of dealing with the > explosion of NIC features in the mlx directory restructuring proposal, > but I think the is a deeper issue here that should be discussed. > > It's hard not to notice that there has been quite a proliferation of > NIC features in several drivers. This trend had resulted in very > complex driver code that may or may not segment individual features. > One visible manifestation of this is number of ndo functions which is > somewhere around seventy-five now. > > I suspect the vast majority of these advances NIC features (e.g. > bridging, UDP offloads, tc offload, etc.) are only relevant to some of > the people some of the time. The problem we have, in this case those > of us that are attempting to deploy and maintain NICs at scale, is > when we have to deal with the ramifications of these features being > intertwined with core driver functionality that is relevant to > everyone. This becomes very obvious when we need to backport drivers > from later versions of kernel. > > I realize that backports of a driver is not a specific concern of the > Linux kernel, but nevertheless this is a real problem and a fact of > life for many users. Rebasing the full kernel is still a major effort > and it seems the best we could ever do is one rebase per year. In the > interim we need to occasionally backport drivers. Backporting drivers > is difficult precisely because of new features or API changes to > existing ones. These sort of changes tend to have a spiderweb of > dependencies in other parts of the stack so that the number of patches > we need to cherry-pick goes way beyond those that touch the driver we > are interested in.
For the sfc driver (Solarflare Adapters) we currently do backports internally for: - RedHat Enterprise Linux 5.10, 5.11 - RedHat Enterprise Linux 6.5, 6.6, 6.7, 6.8 - Redhat Messaging Realtime and Grid 2.5 - RedHat Enterprise Linux 7.0, 7.1, 7.2 - RedHat Enterprise Linux for Realtime 7.1, 7.2 - SuSE Linux Enterprise Server 11 sp3, sp4 - SuSE Linux Enterprise RealTime Extension 11 - SuSE Linux Enterprise Server 12 base release, sp1 - Canonical Ubuntu Server LTS 14.04, 16.04 - Canonical Ubuntu Server - - Debian 7 "Wheezy" 7.X - Debian 8 "Jessie" 8.X - Linux 2.6.18 to 4.9-rc1 We update this list as needed, and always try to support the latest kernel. I do not know if that would cover the kernel version you are using. Best regards, Martin > Currently we (FB) need to backport two NIC drivers. I've already gave > details of backporting mlx5 on the thread to restructure the driver > directories. The other driver being backporting seems to suffer from > the same type of feature complexity. > > In short, I would like to ask if driver maintainers to start to > modularize driver features. If something being added is obviously a > narrow feature that only a subset of users will need can we allow > config options to #ifdef those out somehow? Furthermore can the file > and directory structure of drivers reflect that; our lives would be > _so_ much simpler to maintain drivers in production if we have such > modularity and the ability to build drivers with the features of our > choosing. > > Thanks, > Tom
