[PATCH v3 2/3] bits: Introduce fixed-type BIT

[Lucas De Marchi]

On Fri, Feb 09, 2024 at 08:53:25AM -0800, Yury Norov wrote:
>On Wed, Feb 07, 2024 at 11:45:20PM -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 at intel.com>
>> Acked-by: Jani Nikula <jani.nikula at intel.com>
>
>So I get v1 from Jan.23 in my mailbox, and this one is v3. Did I miss
>a v2? Anyways, please bear my reviewed-by from v1 for this patch.

Jan 23 was actually the v2 and I missed the subject prefix.

My understanding was that you were going to apply this through some
bitmap tree, but checking MAINTAINERS now it seems there's no git tree
associated.  So I will just add your r-b and merge this through
drm-xe.

thanks
Lucas De Marchi

>
>Thanks,
>Yury
>
>> ---
>>  include/linux/bits.h | 17 +++++++++++++++++
>>  1 file changed, 17 insertions(+)
>>
>> diff --git a/include/linux/bits.h b/include/linux/bits.h
>> index bd56f32de44e..811846ce110e 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
>>
>>  /*
>> @@ -54,4 +58,17 @@
>>  #define GENMASK_U32(h, l)	__GENMASK(u32, h, l)
>>  #define GENMASK_U64(h, l)	__GENMASK(u64, h, l)
>>
>> +/*
>> + * Fixed-type variants of BIT(), with additional checks like __GENMASK().  The
>> + * following examples generate compiler warnings due to shift-count-overflow:
>> + *
>> + * - BIT_U8(8)
>> + * - BIT_U32(-1)
>> + * - BIT_U32(40)
>> + */
>> +#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