On Wed, 2018-10-10 at 18:16 +0100, John Garry wrote:
> (to: get_maintainers -f include/linux/bitfield.h)
>
> Hi,
>
> I would like to use FIELD_PREP() macro for assigning a static array,
> like this:
> function()
> {
> static u32 val[2] = {FIELD_PREP(GENMASK_ULL(10, 0), 5), 0};
>
> }
>
> However the compiler complains of non-const expression:
> ./include/linux/bitfield.h:88:2: error: initializer element is not constant
> ({ \
>
> Specifically it doesn't like the __BF_FIELD_CHECK() in FIELD_PREP().
>
> Any ideas on compiler trickery we could do with the FIELD_PREP()
> definition to avoid this issue (i.e. enforce the check but only use the
> constant value)?
Perhaps __bf_shf should not use __builtin_ffsll.
As mask is known constant, maybe expand the test
in-place with some switch/case.
