linux-kernel - Re: [PATCH 2/3] bits: Introduce fixed-type BIT

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Date: Fri, 9 Feb 2024 08:48:31 -0800
From: Yury Norov <yury.norov@...il.com>
To: Lucas De Marchi <lucas.demarchi@...el.com>
Cc: linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	intel-xe@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org
Subject: Re: [PATCH 2/3] bits: Introduce fixed-type BIT

On Tue, Jan 23, 2024 at 09:02:04PM -0800, Lucas De Marchi wrote:
> Implement fixed-type BIT() to help drivers add stricter checks, like was
> done for GENMASK.
> 
> Signed-off-by: Lucas De Marchi <lucas.demarchi@...el.com>

Reviewed-by: Yury Norov <yury.norov@...il.com>

> ---
>  include/linux/bits.h | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/include/linux/bits.h b/include/linux/bits.h
> index cb94128171b2..5754a1251078 100644
> --- a/include/linux/bits.h
> +++ b/include/linux/bits.h
> @@ -24,12 +24,16 @@
>  #define GENMASK_INPUT_CHECK(h, l) \
>  	(BUILD_BUG_ON_ZERO(__builtin_choose_expr( \
>  		__is_constexpr((l) > (h)), (l) > (h), 0)))
> +#define BIT_INPUT_CHECK(type, b) \
> +	((BUILD_BUG_ON_ZERO(__builtin_choose_expr( \
> +		__is_constexpr(b), (b) >= BITS_PER_TYPE(type), 0))))
>  #else
>  /*
>   * BUILD_BUG_ON_ZERO is not available in h files included from asm files,
>   * disable the input check if that is the case.
>   */
>  #define GENMASK_INPUT_CHECK(h, l) 0
> +#define BIT_INPUT_CHECK(type, b) 0
>  #endif
>  
>  #define __GENMASK(t, h, l) \
> @@ -44,4 +48,9 @@
>  #define GENMASK_U32(h, l)	__GENMASK(u32, h, l)
>  #define GENMASK_U64(h, l)	__GENMASK(u64, h, l)
>  
> +#define BIT_U8(b)		((u8)(BIT_INPUT_CHECK(u8, b) + BIT(b)))
> +#define BIT_U16(b)		((u16)(BIT_INPUT_CHECK(u16, b) + BIT(b)))
> +#define BIT_U32(b)		((u32)(BIT_INPUT_CHECK(u32, b) + BIT(b)))
> +#define BIT_U64(b)		((u64)(BIT_INPUT_CHECK(u64, b) + BIT(b)))
> +
>  #endif	/* __LINUX_BITS_H */
> -- 
> 2.43.0