linux-kernel - Re: [PATCH] arm64: armv8_deprecated: fix unused-function error

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Message-ID: <Y3z9dEkMdCeWAWq0@FVFF77S0Q05N.cambridge.arm.com>
Date:   Tue, 22 Nov 2022 16:48:52 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Ren Zhijie <renzhijie2@...wei.com>
Cc:     catalin.marinas@....com, will@...nel.org, yusongping@...wei.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: armv8_deprecated: fix unused-function error

On Tue, Nov 22, 2022 at 03:20:10AM +0000, Ren Zhijie wrote:
> If CONFIG_SWP_EMULATION is not set and
> CONFIG_CP15_BARRIER_EMULATION is not set,
> aarch64-linux-gnu complained about unused-function :
> 
> arch/arm64/kernel/armv8_deprecated.c:67:21: error: ‘aarch32_check_condition’ defined but not used [-Werror=unused-function]
>  static unsigned int aarch32_check_condition(u32 opcode, u32 psr)
>                      ^~~~~~~~~~~~~~~~~~~~~~~
> cc1: all warnings being treated as errors
> 
> To fix this error, warp the definition of
> aarch32_check_condition() by defined(CONFIG_SWP_EMULATION) ||
> defined(CONFIG_CP15_BARRIER_EMULATION)
> 
> Fixes: 0c5f416219da ("arm64: armv8_deprecated: move aarch32 helper earlier")

This also depends on building with additional options to turn warnings into
errors, no?

> Signed-off-by: Ren Zhijie <renzhijie2@...wei.com>
> ---
>  arch/arm64/kernel/armv8_deprecated.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c
> index ed0788cf6bbb..3f29ceb6653a 100644
> --- a/arch/arm64/kernel/armv8_deprecated.c
> +++ b/arch/arm64/kernel/armv8_deprecated.c
> @@ -64,6 +64,7 @@ struct insn_emulation {
>  
>  #define	ARM_OPCODE_CONDITION_UNCOND	0xf
>  
> +#if defined(CONFIG_SWP_EMULATION) || defined(CONFIG_CP15_BARRIER_EMULATION)
>  static unsigned int aarch32_check_condition(u32 opcode, u32 psr)
>  {
>  	u32 cc_bits  = opcode >> 28;
> @@ -76,6 +77,7 @@ static unsigned int aarch32_check_condition(u32 opcode, u32 psr)
>  	}
>  	return ARM_OPCODE_CONDTEST_UNCOND;
>  }
> +#endif

Could we mark this as '__maybe_unused' or 'inline' instead? I think that's
preferable to the ifdeferry.

Thanks,
Mark.

>  
>  #ifdef CONFIG_SWP_EMULATION
>  /*
> -- 
> 2.17.1
>