On Tue, Nov 27, 2018 at 2:33 AM Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> wrote: > > On Tue, Nov 27, 2018 at 4:49 AM Ulf Magnusson <ulfalizer@xxxxxxxxx> wrote: > > > > On Mon, Nov 26, 2018 at 8:31 AM Masahiro Yamada > > <yamada.masahiro@xxxxxxxxxxxxx> wrote: > > > > > > Hi Randy, > > > > > > > > > On Tue, Nov 20, 2018 at 5:51 AM Randy Dunlap <rdunlap@xxxxxxxxxxxxx> wrote: > > > > > > > > Hi Yamada-san, > > > > > > > > There was recently a netfilter build error in linux-next for which > > > > a patch was posted by Taehee Yoo. The patch works (fixes the build > > > > error) but I don't see how or why. > > > > > > > > My build error report is here: > > > > https://lore.kernel.org/lkml/fa7a7824-44df-c058-dba2-ec29c5028361@xxxxxxxxxxxxx/T/#u > > > > > > > > > > > > Would you take a look at it and try to explain why the patch works? > > > > > > > > The patch's email thread begins here: > > > > https://www.spinics.net/lists/netfilter-devel/msg56985.html > > > > > > > > > I think this is a bug of Kconfig. > > > > > > I sent a patch. > > > https://patchwork.kernel.org/patch/10697637/ > > > > > > > > > -- > > > Best Regards > > > Masahiro Yamada > > > > I always understood this behavior as intentional. > > > > Say that a high-level arch symbol has 'select FOO_HELPERS if FOO' for > > example, where both FOO and FOO_HELPERS can be compiled as modules. > > > > The intention there is probably to make sure that FOO_HELPERS is > > available whenever FOO is (FOO_HELPERS must be >= FOO). If FOO is y, > > then FOO_HELPERS must be y. If FOO is m, then it's fine for > > FOO_HELPERS to be m (but not n), because it can be loaded as needed > > whenever FOO is. > > If we find such an example, it should be rewritten to: > > > config FOO > tristate "foo" > select FOO_HELPERS Yup, almost always cleaner ways to do it. > > > > > > Forcing FOO_HELPERS to y would remove the possibility to compile it as > > a module. > > This depends on the selector if you write like this: > > > config OTHER_OPTION > tristate "?" > select FOO_HELPERS if FOO > > > although "FOO_HELPERS >= FOO" is not met. Yeah, that's why I mentioned "high-level arch symbol", because it gets more confusing for other symbols. Think boards and the like too. If you think of 'config A ... select C if B' as "A needs C if B", then the current behavior still does the right thing in all cases: A B | C --------+----- n n/m/y | n(+) (A not enabled, irrelevant) m n | n(+) (B not enabled, irrelevant) m m | m(+) (Fine, C can be loaded if A and B are) m y | m(+) (Ditto) y n | n(+) (B not enabled, irrelevant) y m | m(+) (Fine, C can be loaded if B is) y y | y (Fine, C is available whenever B is) The big if there is whether you think of select that way. Just trying to show why I think it was designed that way. Cheers, Ulf
