On Mon, Aug 25, 2025 at 10:28:20AM +0200, Nicolas Frattaroli wrote:

This series was spawned by [1], where I was asked to move every instance
of HIWORD_UPDATE et al that I could find to a common macro in the same
series that I am introducing said common macro.

The first patch of the series introduces a new header file,
hw_bitfield.h, which contains two new macros: FIELD_PREP_WM16 and
FIELD_PREP_WM16_CONST. The latter can be used in initializers.

I've cheekily added the hw_bitfield.h header to the BITMAP API section
of the MAINTAINERS file.

This macro definition checks that the mask fits, and that the value fits
in the mask. Like FIELD_PREP, it also shifts the value up to the mask,
so turning off a bit does not require using the mask as a value. Masks
are also required to be contiguous, like with FIELD_PREP.

For each definition of such a macro, the driver(s) that used it were
evaluated for three different treatments:
 - full conversion to the new macro, for cases where replacing the
   implementation of the old macro wouldn't have worked, or where the
   conversion was trivial. These are the most complex patches in this
   series, as they sometimes have to pull apart definitions of masks
   and values due to the new semantics, which require a contiguous
   mask and shift the value for us.
 - replacing the implementation of the old macro with an instance of the
   new macro, done where I felt it made the patch much easier to review
   because I didn't want to drop a big diff on people.
 - skipping conversion entirely, usually because the mask is
   non-constant and it's not trivial to make it constant. Sometimes an
   added complication is that said non-constant mask is either used in a
   path where runtime overhead may not be desirable, or in an
   initializer.

Applied in bitmap-for-next for testing.

Thanks,
Yury