Re: [PATCH net-next 02/15] net: sparx5: add indirection layer to register macros

[Daniel Machon]

> > +/* Non-constant mask variant of FIELD_GET() and FIELD_PREP() */
> > +#define spx5_field_get(_mask, _reg) (((_reg) & (_mask)) >> (ffs(_mask) - 1))
> > +#define spx5_field_prep(_mask, _val) (((_val) << (ffs(_mask) - 1)) & (_mask))
> > +
> 
> FIELD_GET and FIELD_SET have restrictions in place to enforce constant
> mask, which enables strict checks to ensure things fit and determine the
> bit shifts at compile time without ffs.
> 
> Would it make sense for these to exist in <linux/bitfields.h>? I'm not
> sure how common it is to have non-const masks..

There was a patch for this some time ago [1], it got some push-back and
never got in, AFAICS. 

[1] https://patchwork.kernel.org/project/linux-pm/patch/3a54a6703879d10f08cf0275a2a69297ebd2b1d4.1637592133.git.geert+renesas@xxxxxxxxx/#24611465

/Daniel