Re: [PATCH 1/9] bitfield: add FIELD_GET_SIGNED()

Johannes Berg
2026-04-20T08:43:38Z

On Fri, 2026-04-17 at 13:36 -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);

That's indeed pretty awful...

> +#define FIELD_GET_SIGNED(mask, reg) \
>

[...]

I (personally) tend to prefer the "__MAKE_OP" versions (*_get_bits()
etc.), in particular because WiFi and firmware interfaces deal a lot
with fixed endian fields.

Any chance it'd be simple to generate u32_get_bits_signed() etc.? Could
be especially useful for le32_get_bits_signed() for example, to have the
endian conversion built-in unlike FIELD_GET_SIGNED().

johannes