Re: [PATCH net-next v3 4/8] rust: time: Implement addition of Ktime and Delta

[Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>]

On Thu, Oct 17, 2024 at 7:03 PM Boqun Feng <boqun.feng@gmail.com> wrote:
>
> but one thing I'm not sure is since it looks like saturating to
> KTIME_SEC_MAX is the current C choice, if we want to do the same, should
> we use the name `add_safe()` instead of `saturating_add()`? FWIW, it
> seems harmless to saturate at KTIME_MAX to me. So personally, I like

Wait -- `ktime_add_safe()` calls `ktime_set(KTIME_SEC_MAX, 0)` which
goes into the conditional that returns `KTIME_MAX`, not `KTIME_SEC_MAX
* NSEC_PER_SEC` (which is what I guess you were saying).

So I am confused -- it doesn't saturate to `KTIME_SEC_MAX` (scaled)
anyway. Which is confusing in itself.

In fact, it means that `ktime_add_safe()` allows you to get any value
whatsoever as long as you don't overflow, but `ktime_set` does not
allow you to -- unless you use enough nanoseconds to get you there
(i.e. over a second in nanoseconds).

Cheers,
Miguel