linux-kernel - Re: arch/powerpc/platforms/83xx/suspend.c:210:3: error: call to undeclared function 'enable_kernel_fp'; ISO C99 and later do not support implicit function declarations

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Message-ID: <e53780ac-15cd-7aa9-8203-b62a20ae5629@csgroup.eu>
Date:   Mon, 20 Mar 2023 08:19:45 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Randy Dunlap <rdunlap@...radead.org>,
        kernel test robot <lkp@...el.com>,
        Arnd Bergmann <arnd@...db.de>
CC:     "llvm@...ts.linux.dev" <llvm@...ts.linux.dev>,
        "oe-kbuild-all@...ts.linux.dev" <oe-kbuild-all@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Alex Shi <alexs@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Miguel Ojeda <ojeda@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: Re: arch/powerpc/platforms/83xx/suspend.c:210:3: error: call to
 undeclared function 'enable_kernel_fp'; ISO C99 and later do not support
 implicit function declarations

Hi Randy,

Le 19/02/2023 à 08:13, Randy Dunlap a écrit :
> Hi Christophe,
> 
> On 2/17/23 22:21, kernel test robot wrote:
>> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
>> head:   38f8ccde04a3fa317b51b05e63c3cb57e1641931
>> commit: e8c07082a810fbb9db303a2b66b66b8d7e588b53 Kbuild: move to -std=gnu11
>> date:   11 months ago
>> config: powerpc-randconfig-r013-20230218 (https://download.01.org/0day-ci/archive/20230218/202302181414.nAdxC08J-lkp@intel.com/config)
>> compiler: clang version 17.0.0 (https://github.com/llvm/llvm-project db89896bbbd2251fff457699635acbbedeead27f)
>> 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 powerpc cross compiling tool for clang build
>>          # apt-get install binutils-powerpc-linux-gnu
>>          # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e8c07082a810fbb9db303a2b66b66b8d7e588b53
>>          git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>>          git fetch --no-tags linus master
>>          git checkout e8c07082a810fbb9db303a2b66b66b8d7e588b53
>>          # save the config file
>>          mkdir build_dir && cp config build_dir/.config
>>          COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=powerpc olddefconfig
>>          COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=powerpc SHELL=/bin/bash arch/powerpc/platforms/83xx/ drivers/android/
>>
>> If you fix the issue, kindly add following tag where applicable
>> | Reported-by: kernel test robot <lkp@...el.com>
>> | Link: https://lore.kernel.org/oe-kbuild-all/202302181414.nAdxC08J-lkp@intel.com/
>>
>> All errors (new ones prefixed by >>):
>>
>>>> arch/powerpc/platforms/83xx/suspend.c:210:3: error: call to undeclared function 'enable_kernel_fp'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
>>                     enable_kernel_fp();
>>                     ^
>>     arch/powerpc/platforms/83xx/suspend.c:210:3: note: did you mean 'enable_kernel_vsx'?
>>     arch/powerpc/include/asm/switch_to.h:75:20: note: 'enable_kernel_vsx' declared here
>>     static inline void enable_kernel_vsx(void)
>>                        ^
>>     1 error generated.
>>
> 
> When # CONFIG_PPC_FPU is not set, enable_kernel_fp() is not defined.
> Looks to me like it is caused by:
> 
> commit 7d68c8916950
> Author: Christophe Leroy <christophe.leroy@...roup.eu>
> Date:   Tue Aug 18 17:19:18 2020 +0000
> 
>      powerpc/32s: Allow deselecting CONFIG_PPC_FPU on mpc832x
> 
> Adding a stub for enable_kernel_fp() in include/asm/switch_to.h
> makes this problem disappear. (There is still a different build error.)
> 
> Ideas?
> 

I think it should be handled like ALTIVEC.

I will have a look at it.

Christophe