Hi Yangbo,

I love your patch! Yet something to improve:

[auto build test ERROR on 19938bafa7ae8fc0a4a2c1c1430abb1a04668da1]

url:    https://github.com/0day-ci/linux/commits/Yangbo-Lu/ptp-support-virtual-clocks-and-timestamping/20210625-172554
base:   19938bafa7ae8fc0a4a2c1c1430abb1a04668da1
config: x86_64-rhel-8.3-kselftests (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce:
        # apt-get install sparse
        # sparse version: v0.6.3-341-g8af24329-dirty
        # https://github.com/0day-ci/linux/commit/57d8340e44c72b7f0a11cfbcd6f9f4ce81b40c18
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Yangbo-Lu/ptp-support-virtual-clocks-and-timestamping/20210625-172554
        git checkout 57d8340e44c72b7f0a11cfbcd6f9f4ce81b40c18
        # save the attached .config to linux build tree
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' W=1 ARCH=x86_64 

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 >>):

>> timestamping.c:48:8: error: redefinition of 'struct so_timestamping'
      48 | struct so_timestamping {
         |        ^~~~~~~~~~~~~~~
   In file included from timestamping.c:33:
   usr/include/linux/net_tstamp.h:57:8: note: originally defined here
      57 | struct so_timestamping {
         |        ^~~~~~~~~~~~~~~

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