Re: [PATCH 0/9] bitfield: add FIELD_GET_SIGNED()

Andy Shevchenko
2026-04-17T18:23:13Z

On Fri, Apr 17, 2026 at 01:36:11PM -0400, Yury Norov wrote:
> The bitfields are designed in assumption that fields contain unsigned
> integer values, thus extracting the values from the field implies
> zero-extending.
>
> Some drivers need to sign-extend their fields, and currently do it like:
>
> dc_re += sign_extend32(FIELD_GET(0xfff000, tmp), 11);
> dc_im += sign_extend32(FIELD_GET(0xfff, tmp), 11);
>
> It's error-prone because it relies on user to provide the correct
> index of the most significant bit.
>
> This series adds a signed version of FIELD_GET(), which is the more
> convenient and compiles (on x86_64) to just a couple instructions:
> shl and sar.
>
> Patch #1 adds FIELD_GET_SIGNED(), and the rest of the series applies it
> tree-wide.

Here the example is missing.

Nevertheless, I looked at the implementation a bit and wondering how would it
work for 64-bit mask of say GENMASK_ULL(63, 60)? Wouldn't it give an overflow?

--
With Best Regards,
Andy Shevchenko