Re: [RFC PATCH net-next] net: dsa: replace NETDEV_PRE_CHANGE_HWTSTAMP notifier with a stub

[kernel test robot <lkp@intel.com>]

Hi Vladimir,

[This is a private test report for your RFC patch.]
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/Vladimir-Oltean/net-dsa-replace-NETDEV_PRE_CHANGE_HWTSTAMP-notifier-with-a-stub/20230406-005302
patch link:    https://lore.kernel.org/r/20230405165115.3744445-1-vladimir.oltean%40nxp.com
patch subject: [RFC PATCH net-next] net: dsa: replace NETDEV_PRE_CHANGE_HWTSTAMP notifier with a stub
config: arm-randconfig-r023-20230403 (https://download.01.org/0day-ci/archive/20230406/202304061058.ZYSqgL8r-lkp@intel.com/config)
compiler: clang version 17.0.0 (https://github.com/llvm/llvm-project 67409911353323ca5edf2049ef0df54132fa1ca7)
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
        # install arm cross compiling tool for clang build
        # apt-get install binutils-arm-linux-gnueabi
        # https://github.com/intel-lab-lkp/linux/commit/4788a6c004ab7f7210b1d27777e733eab85db17e
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Vladimir-Oltean/net-dsa-replace-NETDEV_PRE_CHANGE_HWTSTAMP-notifier-with-a-stub/20230406-005302
        git checkout 4788a6c004ab7f7210b1d27777e733eab85db17e
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm SHELL=/bin/bash net/dsa/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202304061058.ZYSqgL8r-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from net/dsa/stubs.c:7:
>> include/net/dsa_stubs.h:33:2: warning: variable 'err' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
           if (dsa_stubs)
           ^~~~~~~~~~~~~~
   include/linux/compiler.h:56:28: note: expanded from macro 'if'
   #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
                              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/compiler.h:58:30: note: expanded from macro '__trace_if_var'
   #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond))
                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/net/dsa_stubs.h:38:9: note: uninitialized use occurs here
           return err;
                  ^~~
   include/net/dsa_stubs.h:33:2: note: remove the 'if' if its condition is always true
           if (dsa_stubs)
           ^~~~~~~~~~~~~~
   include/linux/compiler.h:56:23: note: expanded from macro 'if'
   #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
                         ^
   include/net/dsa_stubs.h:26:9: note: initialize the variable 'err' to silence this warning
           int err;
                  ^
                   = 0
   1 warning generated.


vim +33 include/net/dsa_stubs.h

    21	
    22	static inline int dsa_master_hwtstamp_validate(struct net_device *dev,
    23						       const struct kernel_hwtstamp_config *config,
    24						       struct netlink_ext_ack *extack)
    25	{
    26		int err;
    27	
    28		if (!netdev_uses_dsa(dev))
    29			return 0;
    30	
    31		mutex_lock(&dsa_stubs_lock);
    32	
  > 33		if (dsa_stubs)
    34			err = dsa_stubs->master_hwtstamp_validate(dev, config, extack);
    35	
    36		mutex_unlock(&dsa_stubs_lock);
    37	
    38		return err;
    39	}
    40	

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https://github.com/intel/lkp-tests