On Tue, 23 Nov 2021 09:36:22 +0100 Geert Uytterhoeven wrote:

quoted

quoted

Also, you're using __ffs(), which doesn't work for 64-bit on 32-bit
architectures (afaict), so that seems a bit awkward.

Maybe we can make {u32,...}_get_bits() be doing compile-time only checks
if it is indeed a constant? The __field_overflow() usage is already only
done if __builtin_constant_p(v), so I guess we can do the same with
__bad_mask()?  

Either that or add decomposition macros. Are compilers still really bad
at passing small structs by value?  

Sorry, I don't get what you mean by adding decomposition macros.
Can you please elaborate?

#define DECOMPOSE(_mask) \
  (struct bf){ .mask = _mask, .shf = __bf_shf(_mask), }

Then drivers can save or pass around the mask and shift params 
broken apart as a small struct.