linux-kernel - Re: [PATCH v4 4/8] bits: introduce fixed-type BIT

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Message-ID: <Z8hgqOB5Ym-GGykS@smile.fi.intel.com>
Date: Wed, 5 Mar 2025 16:33:12 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: mailhol.vincent@...adoo.fr
Cc: Yury Norov <yury.norov@...il.com>,
	Lucas De Marchi <lucas.demarchi@...el.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
	Rodrigo Vivi <rodrigo.vivi@...el.com>,
	Tvrtko Ursulin <tursulin@...ulin.net>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, intel-gfx@...ts.freedesktop.org,
	dri-devel@...ts.freedesktop.org,
	Andi Shyti <andi.shyti@...ux.intel.com>,
	David Laight <David.Laight@...lab.com>,
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
	Jani Nikula <jani.nikula@...el.com>
Subject: Re: [PATCH v4 4/8] bits: introduce fixed-type BIT

On Wed, Mar 05, 2025 at 10:00:16PM +0900, Vincent Mailhol via B4 Relay wrote:
> From: Lucas De Marchi <lucas.demarchi@...el.com>
> 
> Implement fixed-type BIT to help drivers add stricter checks, like was

Here and in the Subject I would use BIT_Uxx().

> done for GENMASK().

...

> +/*
> + * Fixed-type variants of BIT(), with additional checks like GENMASK_t(). The

GENMASK_t() is not a well named macro.

> + * following examples generate compiler warnings due to shift-count-overflow:
> + *
> + * - BIT_U8(8)
> + * - BIT_U32(-1)
> + * - BIT_U32(40)
> + */
> +#define BIT_INPUT_CHECK(type, b) \
> +	BUILD_BUG_ON_ZERO(const_true((b) >= BITS_PER_TYPE(type)))
> +
> +#define BIT_U8(b) (BIT_INPUT_CHECK(u8, b) + (unsigned int)BIT(b))
> +#define BIT_U16(b) (BIT_INPUT_CHECK(u16, b) + (unsigned int)BIT(b))

Why not u8 and u16? This inconsistency needs to be well justified.

> +#define BIT_U32(b) (BIT_INPUT_CHECK(u32, b) + (u32)BIT(b))
> +#define BIT_U64(b) (BIT_INPUT_CHECK(u64, b) + (u64)BIT_ULL(b))

Can you also use a TAB between the parentheses for better readability?
E.g.,

#define BIT_U64(b)r	(BIT_INPUT_CHECK(u64, b) + (u64)BIT_ULL(b))

-- 
With Best Regards,
Andy Shevchenko