Re: [PATCH v7 1/5] bits: introduce fixed-type GENMASK_U*()

[Vincent Mailhol <mailhol.vincent@wanadoo.fr>]

On 24/03/2025 at 16:22, Andy Shevchenko wrote:
> On Sat, Mar 22, 2025 at 06:23:12PM +0900, Vincent Mailhol via B4 Relay wrote:
>>
>> 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)))))
>>         |                           ^~
>>
>> While GENMASK_TYPE() is crafted to cover all variants, including the
>> already existing GENMASK(), GENMASK_ULL() and GENMASK_U128(), for the
>> moment, only use it for the newly introduced GENMASK_U*(). The
>> consolidation will be done in a separate change.
> 
> ...
> 
>>  #if !defined(__ASSEMBLY__)
>> +
> 
>> -#else
> 
>> +#else /* defined(__ASSEMBLY__) */
> 
>> -#endif
>> +
>> +#endif /* !defined(__ASSEMBLY__) */
> 
> Up to you, but if new version is needed or maintainer require, I would move the
> above changes either to a separate patch (prerequisite) or dropped them at all.
> These are not big but unneeded churn,

I do not want to drop this. After all the changes, there is a lot of
scrolling between the #if, #else and #endif, and the comments helps to
keep track of which context we are in.

As for putting this into another patch, OK but only if there is a need
for new version for other reasons.


Yours sincerely,
Vincent Mailhol