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SubjectRe: drivers/soc/litex/litex_soc_ctrl.c:143:34: warning: unused variable 'litex_soc_ctrl_of_match'
On Mon, Jan 11, 2021 at 09:43:34AM -0700, Nathan Chancellor wrote:
> 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 <lkp@intel.com>
> > >
> > > 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!

That helps, I noticed it was only used in those macros so that was fishy. I
forgot to add W=1.

We will need to surround the definition in:

#if defined(CONFIG_OF)
#endif /* CONFIG_OF */

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