On Thu, Mar 28, 2024 at 1:41 AM Daniel Walker (danielwa) <danielwa@xxxxxxxxx> wrote: > > On Thu, Mar 21, 2024 at 12:01:23AM +0900, Masahiro Yamada wrote: > > On Wed, Mar 20, 2024 at 8:20 AM Daniel Walker (danielwa) > > <danielwa@xxxxxxxxx> wrote: > > > > > > > > > Masahiro, > > > > > > I found this commit, > > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=23a0cb8e3225122496bfa79172005c587c2d64bf > > > > > > It had this note, > > > > > > [masahiro: I do not think "M=$(OUT_DIR) src=$(PWD)" is the official way, > > > but this patch is a nice clean up anyway.] > > > > > > Is there an official way or recommended way to build objects in a directory > > > outside the external modules source directory and outside the original kernel > > > source directory ? > > > > > > Daniel > > > > > > There is no official way. > > One known tip is to use a relative path for M=. > > > > For example, the relative path from your kernel source > > to your external module directory is ../path/to/module > > > > $ make O=path/to/output M=../path/to/module > > > > > > The module objects will be output into > > path/to/output/../path/to/module/. > > It seems that this does place objects into the output directory, but there is an > issue where the build system expects include files to exist inside the output > directory as well. For example if the modules includes linux/module.h this file > exists and is found, but module.h also includes asm/rwonce.h which is not found. > I think it's located in include/asm-generic/rwonce.h . I think these asm location > are linked or added as special -I additions during the build but using O= > results in these asm directories not appearing to exist correctly. > > Daniel To use this workaround, you need to build the kernel with O= first. asm/rwonce.h is a generated header, and exists in the output directory specified with O=. # configure and build the kernel $ make O=path/to/output defconfig $ make O=path/to/output # build the module $ make O=path/to/output M=../path/to/module -- Best Regards Masahiro Yamada
