Re: [PATCH] arm64/fpsimd: Avoid warning when sve_to_fpsimd() is unused

["Arnd Bergmann" <arnd@arndb.de>]

On Wed, Apr 30, 2025, at 19:32, Mark Rutland wrote:
>
> diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
> index b0874402f7ecc..422b9d43b1e64 100644
> --- a/arch/arm64/kernel/fpsimd.c
> +++ b/arch/arm64/kernel/fpsimd.c
> @@ -649,7 +649,7 @@ static void __fpsimd_to_sve(void *sst, struct 
> user_fpsimd_state const *fst,
>   * task->thread.uw.fpsimd_state must be up to date before calling this
>   * function.
>   */
> -static void fpsimd_to_sve(struct task_struct *task)
> +static inline void fpsimd_to_sve(struct task_struct *task)
>  {
>  	unsigned int vq;
>  	void *sst = task->thread.sve_state;

I just sent a different patch (adding an #ifdef) before I
saw this one is already applied.

Avoiding the #ifdef does make your version nicer, though this
may come back later, since I think this would still be a warning
at W=1 level, see this bit in linux/compiler.h:

/*
 * GCC does not warn about unused static inline functions for -Wunused-function.
 * Suppress the warning in clang as well by using __maybe_unused, but enable it
 * for W=1 build. This will allow clang to find unused functions. Remove the
 * __inline_maybe_unused entirely after fixing most of -Wunused-function warnings.
 */
#ifdef KBUILD_EXTRA_WARN1
#define __inline_maybe_unused
#else
#define __inline_maybe_unused __maybe_unused
#endif
#define inline inline __gnu_inline __inline_maybe_unused notrace

IIRC, gcc never warns for unused inline functions, but clang warns
about them when they are defined in a .c file rather than a header.

    Arnd