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Mon, 11 Jan 2021 08:43:35 -0800 (PST) Date: Mon, 11 Jan 2021 09:43:34 -0700 From: Nathan Chancellor To: Stafford Horne Cc: kernel test robot , Pawel Czarnecki , kbuild-all@lists.01.org, clang-built-linux@googlegroups.com, linux-kernel@vger.kernel.org, Mateusz Holenko Subject: Re: drivers/soc/litex/litex_soc_ctrl.c:143:34: warning: unused variable 'litex_soc_ctrl_of_match' Message-ID: <20210111164334.GA1322395@ubuntu-m3-large-x86> References: <202101070445.8Kz6oJcS-lkp@intel.com> <20210111123055.GA2002709@lianli.shorne-pla.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20210111123055.GA2002709@lianli.shorne-pla.net> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 11, 2021 at 09:30:55PM +0900, Stafford Horne wrote: > On Thu, Jan 07, 2021 at 04:04:47AM +0800, kernel test robot wrote: > > Hi Pawel, > > > > FYI, the error/warning still remains. > > > > tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master > > head: e71ba9452f0b5b2e8dc8aa5445198cd9214a6a62 > > commit: 22447a99c97e353bde8f90c2353873f27681d57c drivers/soc/litex: add LiteX SoC Controller driver > > date: 8 weeks ago > > config: x86_64-randconfig-a001-20210107 (attached as .config) > > compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project 5c951623bc8965fa1e89660f2f5f4a2944e4981a) > > 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 x86_64 cross compiling tool for clang build > > # apt-get install binutils-x86-64-linux-gnu > > # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=22447a99c97e353bde8f90c2353873f27681d57c > > git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git > > git fetch --no-tags linus master > > git checkout 22447a99c97e353bde8f90c2353873f27681d57c > > # save the attached .config to linux build tree > > COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 > > > > If you fix the issue, kindly add following tag as appropriate > > Reported-by: kernel test robot > > > > All warnings (new ones prefixed by >>): > > > > >> drivers/soc/litex/litex_soc_ctrl.c:143:34: warning: unused variable 'litex_soc_ctrl_of_match' [-Wunused-const-variable] > > static const struct of_device_id litex_soc_ctrl_of_match[] = { > > ^ > > 1 warning generated. > > > > > > vim +/litex_soc_ctrl_of_match +143 drivers/soc/litex/litex_soc_ctrl.c > > > > 142 > > > 143 static const struct of_device_id litex_soc_ctrl_of_match[] = { > > 144 {.compatible = "litex,soc-controller"}, > > 145 {}, > > 146 }; > > 147 > > > > I don't use clang but GCC, and I cannot reproduce this warning. > > $ make drivers/soc/litex/litex_soc_ctrl.o > CALL scripts/checksyscalls.sh > CALL scripts/atomic/check-atomics.sh > DESCEND objtool > CC drivers/soc/litex/litex_soc_ctrl.o > > Also, I can see litex_soc_ctrl_of_match is used. I am not sure what is going on > here. > > -Stafford > You need W=1 $ make -skj"$(nproc)" W=1 olddefconfig drivers/soc/litex/litex_soc_ctrl.o drivers/soc/litex/litex_soc_ctrl.c:143:34: warning: ‘litex_soc_ctrl_of_match’ defined but not used [-Wunused-const-variable=] 143 | static const struct of_device_id litex_soc_ctrl_of_match[] = { | ^~~~~~~~~~~~~~~~~~~~~~~ $ rg "CONFIG_OF|CONFIG_LITEX_SOC_CONTROLLER" .config 1124:# CONFIG_OF is not set 4673:CONFIG_LITEX_SOC_CONTROLLER=y This variable is used in two places in that file, in the MODULE_DEVICE_TABLE macro and the of_match_ptr macro. When CONFIG_OF is disabled, of_match_ptr evaluates to NULL. When the file is built into the kernel image, MODULE_DEVICE_TABLE evaluates to nothing, leaving this variable defined but unused in the final preprocessed source. Hope that helps! Cheers, Nathan