bitfield: Ensure the return values of helper functions are checked

As type##_replace_bits() has no side effects it is only useful if its
return value is checked. Add __must_check to enforce this usage. To have
the bits replaced in-place typep##_replace_bits() can be used instead.

Although, type_##_get_bits() and type_##_encode_bits() are harder to misuse
they are still only useful if the return value is checked. For
consistency, also add __must_check to these.

Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>

diff --git a/include/linux/bitfield.h b/include/linux/bitfield.h
index 6d9a53db54b66c0833973c880444bd289d9667b1..5355f8f806a97974fe0e94033e4d9db960e6ee4b 100644 (file)
--- a/include/linux/bitfield.h
+++ b/include/linux/bitfield.h
@@ -189,14 +189,14 @@ static __always_inline u64 field_mask(u64 field)
 }
 #define field_max(field)       ((typeof(field))field_mask(field))
 #define ____MAKE_OP(type,base,to,from)                                 \
-static __always_inline __##type type##_encode_bits(base v, base field) \
+static __always_inline __##type __must_check type##_encode_bits(base v, base field)    \
 {                                                                      \
        if (__builtin_constant_p(v) && (v & ~field_mask(field)))        \
                __field_overflow();                                     \
        return to((v & field_mask(field)) * field_multiplier(field));   \
 }                                                                      \
-static __always_inline __##type type##_replace_bits(__##type old,      \
-                                       base val, base field)           \
+static __always_inline __##type __must_check type##_replace_bits(__##type old, \
+                                                       base val, base field)   \
 {                                                                      \
        return (old & ~to(field)) | type##_encode_bits(val, field);     \
 }                                                                      \
@@ -205,7 +205,7 @@ static __always_inline void type##p_replace_bits(__##type *p,               \
 {                                                                      \
        *p = (*p & ~to(field)) | type##_encode_bits(val, field);        \
 }                                                                      \
-static __always_inline base type##_get_bits(__##type v, base field)    \
+static __always_inline base __must_check type##_get_bits(__##type v, base field)       \
 {                                                                      \
        return (from(v) & field)/field_multiplier(field);               \
 }