[PATCH v14 02/18] bitfield: Add less-checking __FIELD_{GET, PREP}()

[Simon Glass]

Hi Mikhail,

On 2026-07-02T05:57:27, Mikhail Kshevetskiy
<mikhail.kshevetskiy at iopsys.eu> wrote:
> bitfield: Add less-checking __FIELD_{GET,PREP}()
>
> The BUILD_BUG_ON_MSG() check against '~0ull' works only with "unsigned
> (long) long" _mask types.  For constant masks, that condition is usually
> met, as GENMASK() yields an UL value.  The few places where the
> constant mask is stored in an intermediate variable were fixed by
> changing the variable type to u64 (see e.g. [1] and [2]).
>
> However, for non-constant masks, smaller unsigned types should be valid,
> too, but currently lead to "result of comparison of constant
> 18446744073709551615 with expression of type ... is always
> false"-warnings with clang and W=1.
>
> Hence refactor the __BF_FIELD_CHECK() helper, and factor out
> __FIELD_{GET,PREP}().  The later lack the single problematic check, but
> are otherwise identical to FIELD_{GET,PREP}(), and are intended to be
> used in the fully non-const variants later.
>
> [1] commit 5c667d5a5a3ec166 ("clk: sp7021: Adjust width of _m in
>     HWM_FIELD_PREP()")
> [...]
>
> include/linux/bitfield.h | 36 ++++++++++++++++++++++++++++--------
>  1 file changed, 28 insertions(+), 8 deletions(-)

> Signed-off-by: Geert Uytterhoeven <geert+renesas at glider.be>
> Link: https://git.kernel.org/torvalds/c/5c667d5a5a3ec166 [1]
> Signed-off-by: Yury Norov (NVIDIA) <yury.norov at gmail.com>
> Reviewed-by: David Lechner <dlechner at baylibre.com>

Reviewed-by: Simon Glass <sjg at chromium.org>

Please can you add your own Signed-off-by at the end of the chain?

It's a bit confusing that you seem to refer to Linux commit hashes in
the commit. So maybe this should have a Cherry-picked-from: line
indicating it came from Linux?

Regards,
Simon