Hi Geert,

I love your patch! Yet something to improve:

[auto build test ERROR on robh/for-next]
[also build test ERROR on staging/staging-testing linus/master v5.13-rc7 next-20210625]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Geert-Uytterhoeven/auxdisplay-ht16k33-Add-character-display-support/20210625-210014
base:   https://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git for-next
config: powerpc-allmodconfig (attached as .config)
compiler: powerpc64-linux-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/5505aedee505055e2fe16a718203e24fd8519e2a
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Geert-Uytterhoeven/auxdisplay-ht16k33-Add-character-display-support/20210625-210014
        git checkout 5505aedee505055e2fe16a718203e24fd8519e2a
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=powerpc 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <redacted>

All errors (new ones prefixed by >>, old ones prefixed by <<):

quoted

ERROR: modpost: ".kernfs_create_link" [drivers/auxdisplay/img-ascii-lcd.ko] undefined!

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0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org