Re: [PATCH next 08/14] bits: simplify GENMASK_TYPE()

[Yury Norov]

On Wed, Jan 21, 2026 at 02:57:25PM +0000, david.laight.linux@xxxxxxxxx wrote:
> From: David Laight <david.laight.linux@xxxxxxxxx>
> 
> Since the type is always unsigned (T)-1 is always the correct value
> so there is no need to use type_max().
> 
> Signed-off-by: David Laight <david.laight.linux@xxxxxxxxx>

Here you implicitly add a new restriction that all types passed in
GENMASK_TYPE() must be unsigned. Can you enforce it with
is_signed_type(), or at lease with a corresponding comment?

> ---
>  include/linux/bits.h | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/include/linux/bits.h b/include/linux/bits.h
> index a40cc861b3a7..697318f2a47d 100644
> --- a/include/linux/bits.h
> +++ b/include/linux/bits.h
> @@ -45,8 +45,7 @@
>   */
>  #define GENMASK_TYPE(t, h, l)					\
>  	((t)(GENMASK_INPUT_CHECK(h, l) +			\
> -	     (type_max(t) << (l) &				\
> -	      type_max(t) >> (BITS_PER_TYPE(t) - 1 - (h)))))
> +	     ((t)-1 << (l) & (t)-1 >> (BITS_PER_TYPE(t) - 1 - (h)))))
>  
>  #define GENMASK(h, l)		GENMASK_TYPE(unsigned long, h, l)
>  #define GENMASK_ULL(h, l)	GENMASK_TYPE(unsigned long long, h, l)
> -- 
> 2.39.5