From: Johannes Berg <johannes.b...@intel.com> John Garry requested to be able to use FIELD_PREP() and friends in constant initializers, but we cannot completely switch all of the current assertions to BUILD_BUG_ON_ZERO().
So instead of this, add __FIELD_PREP() which is suitable in such contexts, and also add __{u,le,be}{16,32,64}encode_bits() like the existing versions without underscores, but again suitable in constant contexts. Requested-by: John Garry <john.ga...@huawei.com> Signed-off-by: Johannes Berg <johannes.b...@intel.com> --- include/linux/bitfield.h | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) diff --git a/include/linux/bitfield.h b/include/linux/bitfield.h index 3f1ef4450a7c..245dfb47d201 100644 --- a/include/linux/bitfield.h +++ b/include/linux/bitfield.h @@ -63,6 +63,14 @@ (1ULL << __bf_shf(_mask))); \ }) +#define __BF_CHECK_POW2(n) BUILD_BUG_ON_ZERO(((n) & ((n) - 1)) != 0) + +#define __BF_FIELD_CHECK_CONST(_mask, _reg, _val) \ + (BUILD_BUG_ON_ZERO((_mask) == 0) + \ + BUILD_BUG_ON_ZERO(~((_mask) >> __bf_shf(_mask)) & (_val)) + \ + BUILD_BUG_ON_ZERO((_mask) > (typeof(_reg))~0ull) + \ + __BF_CHECK_POW2((_mask) + (1ULL << __bf_shf(_mask)))) + /** * FIELD_FIT() - check if value fits in the field * @_mask: shifted mask defining the field's length and position @@ -90,6 +98,21 @@ ((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask); \ }) +/** + * __FIELD_PREP() - prepare a constant bitfield element + * @_mask: shifted mask defining the field's length and position + * @_val: value to put in the field + * + * __FIELD_PREP() masks and shifts up the value. The result should + * be combined with other fields of the bitfield using local OR. + * + * This version is suitable for use in a pure constant context, e.g. + * a constant initializer. + */ +#define __FIELD_PREP(_mask, _val) \ + ((typeof(_mask))__BF_FIELD_CHECK_CONST(_mask, 0ULL, _val) + \ + (((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask))) + /** * FIELD_GET() - extract a bitfield element * @_mask: shifted mask defining the field's length and position @@ -150,4 +173,15 @@ __MAKE_OP(64) #undef __MAKE_OP #undef ____MAKE_OP +#define __encode_bits(w, v, field) __FIELD_PREP((u##w)(field), v) +#define __u16_encode_bits(v, field) __encode_bits(16, v, field) +#define __le16_encode_bits(v, field) cpu_to_le16(__encode_bits(16, v, field)) +#define __be16_encode_bits(v, field) cpu_to_be16(__encode_bits(16, v, field)) +#define __u32_encode_bits(v, field) __encode_bits(32, v, field) +#define __le32_encode_bits(v, field) cpu_to_le32(__encode_bits(32, v, field)) +#define __be32_encode_bits(v, field) cpu_to_be32(__encode_bits(32, v, field)) +#define __u64_encode_bits(v, field) __encode_bits(64, v, field) +#define __le64_encode_bits(v, field) cpu_to_le64(__encode_bits(64, v, field)) +#define __be64_encode_bits(v, field) cpu_to_be64(__encode_bits(64, v, field)) + #endif -- 2.17.2