On 05/10/2014 10:02 PM, George Spelvin wrote: > I had to ask on the mailing list, so save developers the bother of > answering the question again. (Wanna-be kernel developers might also > be helped, but who cares about them?) > > Signed-off-by: George Spelvin <linux@xxxxxxxxxxx> > --- > As with most documentation patches, this is also an exercise in eliciting > corrections by proposing a wrong answer which will be jumped on. Hi Michal, Any comments on this patch? Thanks. > > Documentation/kbuild/makefiles.txt | 23 +++++++++++++++++++++-- > 1 file changed, 21 insertions(+), 2 deletions(-) > > diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt > index d567a7cc55..f6cc266163 100644 > --- a/Documentation/kbuild/makefiles.txt > +++ b/Documentation/kbuild/makefiles.txt > @@ -237,10 +237,29 @@ more details, with real examples. > be included in a library, lib.a. > All objects listed with lib-y are combined in a single > library for that directory. > + > + The entire kernel is then linked against these libraries, > + so the linker will include the code in the final kernel only > + if it is referenced somewhere. Thus, lib-* goals may be > + designed with false positives. > + > Objects that are listed in obj-y and additionally listed in > lib-y will not be included in the library, since they will > be accessible anyway. > - For consistency, objects listed in lib-m will be included in lib.a. > + > + For consistency, objects listed in lib-m will be included > + in lib.a, but this will probably not do what you want. If a > + function in lib.a is referenced only from a module, and not from > + the main kernel image, the linker will not incorporate it into > + the kernel image and later attempts to load the module will fail. > + > + One solution to this issue are to declare the object boolean > + and link it into the kernel with obj-y if it's depended on by > + a module. The object's code will be included in the main kernel > + but unused until the module is loaded. > + > + The other is to make the object a module itself, and use an > + obj-m goal. Many helper modules in lib are used this way. > > Note that the same kbuild makefile may list files to be built-in > and to be part of a library. Therefore the same directory > @@ -252,7 +271,7 @@ more details, with real examples. > > This will create a library lib.a based on delay.o. For kbuild to > actually recognize that there is a lib.a being built, the directory > - shall be listed in libs-y. > + must be listed in libs-y in its parent makefile. > See also "6.4 List directories to visit when descending". > > Use of lib-y is normally restricted to lib/ and arch/*/lib. > -- ~Randy -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
