Subject: Re: [PATCH v2 08/16] bitfield: Simplify __BF_FIELD_CHECK_REG()

From: Jonathan Cameron <[email-masked]>
Date: Wed, 17 Dec 2025 10:26:18 +0000

On Fri, 12 Dec 2025 19:37:13 +0000
[email-masked] wrote:

> From: David Laight <[email-masked]>
> 
> Simplify the check for 'reg' being large enough to hold 'mask' using
> sizeof (reg) rather than a convoluted scheme to generate an unsigned
> type the same size as 'reg'.
> 
> Signed-off-by: David Laight <[email-masked]>
Hi David,

Just one really trivial comment inline. Feel free to ignore.

Jonathan

> ---
> @@ -75,8 +59,8 @@
>  	})
>  
>  #define __BF_FIELD_CHECK_REG(mask, reg, pfx)				\
> -	BUILD_BUG_ON_MSG(__bf_cast_unsigned(mask, mask) >		\
> -			 __bf_cast_unsigned(reg, ~0ull),		\
> +	BUILD_BUG_ON_MSG((mask) + 0U + 0UL + 0ULL >			\
> +			 ~0ULL >> (64 - 8 * sizeof (reg)),		\

Trivial.  sizeof(reg) is much more comment syntax in kernel code.

>  			 pfx "type of reg too small for mask")
>  
>  #define __BF_FIELD_CHECK(mask, reg, val, pfx)				\