Hi Maxime,

kernel test robot noticed the following build warnings:

[auto build test WARNING on net-next/main]

url:    https://github.com/intel-lab-lkp/linux/commits/Maxime-Chevallier/net-phy-phy_port-Correctly-recompute-the-port-s-linkmodes/20260127-215318
base:   net-next/main
patch link:    https://lore.kernel.org/r/20260127134202.8208-11-maxime.chevallier%40bootlin.com
patch subject: [PATCH net-next 10/13] net: phy: phy_link_topology: Add a helper to retrieve ports
config: s390-randconfig-002-20260128 (https://download.01.org/0day-ci/archive/20260128/202601280624.F1IZ2yHm-lkp@intel.com/config)
compiler: s390-linux-gcc (GCC) 8.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260128/202601280624.F1IZ2yHm-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot [off-list ref]
| Closes: https://lore.kernel.org/oe-kbuild-all/202601280624.F1IZ2yHm-lkp@intel.com/ (local)

All warnings (new ones prefixed by >>):

   In file included from net/ethtool/tsinfo.c:5:
   include/linux/phy_link_topology.h:110:1: error: return type defaults to 'int' [-Werror=implicit-int]
    phy_link_topo_get_port(struct net_device *dev, u32 port_id)
    ^~~~~~~~~~~~~~~~~~~~~~
   include/linux/phy_link_topology.h:110:1: warning: no previous prototype for 'phy_link_topo_get_port' [-Wmissing-prototypes]
   In file included from include/uapi/linux/posix_types.h:5,
                    from include/uapi/linux/types.h:14,
                    from include/linux/types.h:6,
                    from include/uapi/linux/net_tstamp.h:13,
                    from include/linux/net_tstamp.h:6,
                    from net/ethtool/tsinfo.c:3:
   include/linux/phy_link_topology.h: In function 'phy_link_topo_get_port':

quoted

include/linux/stddef.h:8:14: warning: returning 'void *' from a function with return type 'int' makes integer from pointer without a cast [-Wint-conversion]

    #define NULL ((void *)0)
                 ^
   include/linux/phy_link_topology.h:112:9: note: in expansion of macro 'NULL'
     return NULL;
            ^~~~
   cc1: some warnings being treated as errors


vim +8 include/linux/stddef.h

^1da177e4c3f41 Linus Torvalds   2005-04-16  6  
^1da177e4c3f41 Linus Torvalds   2005-04-16  7  #undef NULL
^1da177e4c3f41 Linus Torvalds   2005-04-16 @8  #define NULL ((void *)0)
6e218287432472 Richard Knutsson 2006-09-30  9  

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