On Mon, Jul 16, 2018 at 02:21:19PM +0200, Martijn Coenen wrote: > As of Linux 4.17, there are more than 30000 exported symbols > in the kernel. There seems to be some consensus amongst > kernel devs that the export surface is too large, and hard > to reason about. > > Generally, these symbols fall in one of these categories: > 1) Symbols actually meant for drivers > 2) Symbols that are only exported because functionality is > split over multiple modules, yet they really shouldn't > be used by modules outside of their own subsystem > 3) Symbols really only meant for in-tree use > > When module developers try to upstream their code, it > regularly turns out that they are using exported symbols > that they really shouldn't be using. This problem is even > bigger for drivers that are currently out-of-tree, which > may be using many symbols that they shouldn't be using, > and that break when those symbols are removed or modified. > > This patch allows subsystem maintainers to partition their > exported symbols into separate namespaces, and module > authors to import such namespaces only when needed. > > This allows subsystem maintainers to more easily limit > availability of these namespaced symbols to other parts of > the kernel. It can also be used to partition the set of > exported symbols for documentation purposes; for example, > a set of symbols that is really only used for debugging > could be in a "SUBSYSTEM_DEBUG" namespace. To give people a bit more background here, this is something that both Andi Kleen and I talked about over a decade ago. Martijn based his work on Andi's original patches and made them all work well, something that I was unable to do :) His addition of using the build system to automatically generate a patch for a subsystem based on the symbol namespace changes is frickin amazing. Great work here, this is something that I have wanted for the kernel for a long time. greg k-h
