Re: [PATCH v8 3/7] rust: time: Introduce Instant type

[FUJITA Tomonori]

On Thu, 16 Jan 2025 13:37:42 +0100
Miguel Ojeda <miguel.ojeda.sandonis@xxxxxxxxx> wrote:

> On Thu, Jan 16, 2025 at 5:42 AM FUJITA Tomonori
> <fujita.tomonori@xxxxxxxxx> wrote:
>>
>> -/// A Rust wrapper around a `ktime_t`.
>> +/// A specific point in time.
>>  #[repr(transparent)]
>>  #[derive(Copy, Clone, PartialEq, PartialOrd, Eq, Ord)]
>> -pub struct Ktime {
>> +pub struct Instant {
>> +    // Range from 0 to `KTIME_MAX`.
> 
> On top of what Tom mentioned: is this intended as an invariant? If
> yes, then please document it publicly in the `Instant` docs in a `#
> Invariants` section. Otherwise, I would clarify this comment somehow,
> since it seems ambiguous.

As I wrote to Tom, that's the kernel's assumption. Do we need to make
it an invariant too?

Or improving the above "Range from 0 to `KTIME_MAX.`" is enough?

The kernel assumes that the range of the ktime_t type is from 0 to
KTIME_MAX. The ktime APIs guarantees to give a valid ktime_t.