Subject: Re: [PATCH v5 05/11] mfd: macsmc: Add new __SMC_KEY macro

From: Lee Jones <[email-masked]>
Date: Thu, 20 Nov 2025 13:44:45 +0000

On Wed, 12 Nov 2025, James Calligeros wrote:

> When using the _SMC_KEY macro in switch/case statements, GCC 15.2.1 errors
> out with 'case label does not reduce to an integer constant'. Introduce
> a new __SMC_KEY macro that can be used instead.
> 
> Signed-off-by: James Calligeros <[email-masked]>
> ---
>  include/linux/mfd/macsmc.h | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/include/linux/mfd/macsmc.h b/include/linux/mfd/macsmc.h
> index 6b13f01a8592..f6f80c33b5cf 100644
> --- a/include/linux/mfd/macsmc.h
> +++ b/include/linux/mfd/macsmc.h
> @@ -41,6 +41,7 @@ typedef u32 smc_key;
>   */
>  #define SMC_KEY(s) (smc_key)(_SMC_KEY(#s))
>  #define _SMC_KEY(s) (((s)[0] << 24) | ((s)[1] << 16) | ((s)[2] << 8) | (s)[3])
> +#define __SMC_KEY(a, b, c, d) (((u32)(a) << 24) | ((u32)(b) << 16) | ((u32)(c) << 8) | ((u32)(d)))

Are we expecting users/consumers to be able to tell the difference
between SMC_KEY and __SMC_KEY (assuming that _SMC_KEY is just an
internal)?

I have not tested this and it is just off the top of my head, but does
this work:

#define _SMC_KEY(s) __SMC_KEY((s)[0], (s)[1], (s)[2], (s)[3])

-- 
Lee Jones [李琼斯]