Re: powerpc64-linux-ld: drivers/i2c/busses/i2c-pasemi-core.o:undefined reference to `__this_module'

[Arnd Bergmann <arnd@arndb.de>]

On Mon, Dec 6, 2021 at 6:02 PM Sven Peter <sven@svenpeter.dev> wrote:
> On Mon, Dec 6, 2021, at 11:10, kernel test robot wrote:

> > If you fix the issue, kindly add following tag as appropriate
> > Reported-by: kernel test robot <lkp@intel.com>
> >
> > All error/warnings (new ones prefixed by >>):
> >
> >>> powerpc64-linux-ld: warning: orphan section `.stubs' from `drivers/i2c/busses/i2c-pasemi-core.o' being placed in section `.stubs'
> >>> powerpc64-linux-ld: drivers/i2c/busses/i2c-pasemi-core.o:(.toc+0x0): undefined reference to `__this_module'
>
> This seems to be triggered by compiling one of {pci,platform} as a module and the
> other one as built-in. That setup can only happen with COMPILE_TEST since -pci
> is otherwise only compiled for powerpc and -platform for arm64.
>
> -core.c is only built once with THIS_MODULE expanding to __this_module. That will
> fail when linking the built-in driver where THIS_MODULE should've been NULL instead.
>
> The most simple fix (that also has no chance of breaking anything) is probably to
> just move
>
>   smbus->adapter.owner = THIS_MODULE;
>
> from core to both apple.c and pci.c. I'll prepare a patch later this week.

I'd prefer fixing this in a better way, linking an object file into
both vmlinux and a loadable
module is not supported at all. Other options are:

- #include the common .c file from the individual drivers (not great)
- use Kconfig logic to prevent the broken configuration
- use Makefile tricks to make both drivers built-in when this happens
- make the common part a separate loadable module, exporting all the
  global symbols.

Out of these, I would prefer the last option.

       Arnd