Hi Arnaud,

I love your patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v5.11-rc6 next-20210125]
[cannot apply to rpmsg/for-next]
[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/Arnaud-Pouliquen/introduce-a-generic-IOCTL-interface-for-RPMsg-channels-management/20210204-165337
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 61556703b610a104de324e4f061dc6cf7b218b46
config: arm-randconfig-s032-20210204 (attached as .config)
compiler: arm-linux-gnueabi-gcc (GCC) 9.3.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # apt-get install sparse
        # sparse version: v0.6.3-215-g0fb77bb6-dirty
        # https://github.com/0day-ci/linux/commit/4033f1be7a04b2b78a2a0946a5b6544afa8b77c7
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Arnaud-Pouliquen/introduce-a-generic-IOCTL-interface-for-RPMsg-channels-management/20210204-165337
        git checkout 4033f1be7a04b2b78a2a0946a5b6544afa8b77c7
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' ARCH=arm 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

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

>> ERROR: modpost: "rpmsg_ctrl_register_device" [drivers/rpmsg/virtio_rpmsg_bus.ko] undefined!

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