Re: [PATCH v2 08/16] bitfield: Simplify __BF_FIELD_CHECK_REG()

Jonathan Cameron
2025-12-17T10:26:24Z

On Fri, 12 Dec 2025 19:37:13 +0000
david.laight.linux@gmail.com wrote:

> From: David Laight <david.laight.linux@gmail.com>
>
> Simplify the check for 'reg' being large enough to hold 'mask' using
> sizeof (reg) rather than a convoluted scheme to generate an unsigned
> type the same size as 'reg'.
>
> Signed-off-by: David Laight <david.laight.linux@gmail.com>
Hi David,

Just one really trivial comment inline. Feel free to ignore.

Jonathan

> ---
> @@ -75,8 +59,8 @@
> })
>
> #define __BF_FIELD_CHECK_REG(mask, reg, pfx) \
> - BUILD_BUG_ON_MSG(__bf_cast_unsigned(mask, mask) > \
> - __bf_cast_unsigned(reg, ~0ull), \
> + BUILD_BUG_ON_MSG((mask) + 0U + 0UL + 0ULL > \
> + ~0ULL >> (64 - 8 * sizeof (reg)), \

Trivial. sizeof(reg) is much more comment syntax in kernel code.

> pfx "type of reg too small for mask")
>
> #define __BF_FIELD_CHECK(mask, reg, val, pfx) \