diff options
| -rw-r--r-- | include/linux/tnum.h | 20 |
1 files changed, 18 insertions, 2 deletions
diff --git a/include/linux/tnum.h b/include/linux/tnum.h index 498dbcedb451..1c3948a1d6ad 100644 --- a/include/linux/tnum.h +++ b/include/linux/tnum.h @@ -21,7 +21,12 @@ struct tnum { struct tnum tnum_const(u64 value); /* A completely unknown value */ extern const struct tnum tnum_unknown; -/* A value that's unknown except that @min <= value <= @max */ +/* An unknown value that is a superset of @min <= value <= @max. + * + * Could include values outside the range of [@min, @max]. + * For example tnum_range(0, 2) is represented by {0, 1, 2, *3*}, + * rather than the intended set of {0, 1, 2}. + */ struct tnum tnum_range(u64 min, u64 max); /* Arithmetic and logical ops */ @@ -73,7 +78,18 @@ static inline bool tnum_is_unknown(struct tnum a) */ bool tnum_is_aligned(struct tnum a, u64 size); -/* Returns true if @b represents a subset of @a. */ +/* Returns true if @b represents a subset of @a. + * + * Note that using tnum_range() as @a requires extra cautions as tnum_in() may + * return true unexpectedly due to tnum limited ability to represent tight + * range, e.g. + * + * tnum_in(tnum_range(0, 2), tnum_const(3)) == true + * + * As a rule of thumb, if @a is explicitly coded rather than coming from + * reg->var_off, it should be in form of tnum_const(), tnum_range(0, 2**n - 1), + * or tnum_range(2**n, 2**(n+1) - 1). + */ bool tnum_in(struct tnum a, struct tnum b); /* Formatting functions. These have snprintf-like semantics: they will write |