Re: [PATCH v5 2/7] bits: introduce fixed-type genmasks

Andy Shevchenko
2025-03-06T13:09:00Z

On Thu, Mar 06, 2025 at 08:29:53PM +0900, Vincent Mailhol via B4 Relay wrote:
> From: Yury Norov <yury.norov@gmail.com>
>
> Add GENMASK_TYPE() which generalizes __GENMASK() to support different
> types, and implement fixed-types versions of GENMASK() based on it.
> The fixed-type version allows more strict checks to the min/max values
> accepted, which is useful for defining registers like implemented by
> i915 and xe drivers with their REG_GENMASK*() macros.
>
> The strict checks rely on shift-count-overflow compiler check to fail
> the build if a number outside of the range allowed is passed.
> Example:
>
> #define FOO_MASK GENMASK_U32(33, 4)
>
> will generate a warning like:
>
> include/linux/bits.h:51:27: error: right shift count >= width of type [-Werror=shift-count-overflow]
> 51 | type_max(t) >> (BITS_PER_TYPE(t) - 1 - (h)))))
> | ^~

Code LGTM, but just to be sure: you prepared your series using histogram
diff algo, right?

--
With Best Regards,
Andy Shevchenko