Re: [PATCH v2 1/4] rust: time: add jiffies conversion helpers to Delta
FUJITA Tomonori <[email protected]>
| Newsgroups | org.kernel.vger.rust-for-linux |
|---|---|
| Message-ID | <[email protected]> |
On Wed, 15 Jul 2026 15:38:17 +0100 "Gary Guo" <[email protected]> wrote: > On Wed Jul 15, 2026 at 3:22 PM BST, Miguel Ojeda wrote: >> On Wed, Jul 15, 2026 at 3:34 PM Andreas Hindborg <[email protected]> wrote: >>> >>> I think widening to 128 bits is fine. My question is why `NSEC_PER_SEC >>> as u128` instead of `u128::from(NSEC_PER_SEC)`? >> >> Yes, please avoid casts if possible. >> >> Regarding `u128` -- please make sure it works in 32-bit architectures. >> It seems like you are doing a 128-bit multiplication there? > > This will also need a division when HZ is not a factor of NSEC_PER_SEC -- which > will be the case for HZ_300. > > This should just limit the precision by doing a multiplication with > (USEC_PER_SEC / HZ) like jiffies_to_usecs. Agreed. Device drivers use jiffies_to_usecs() rather than jiffies64_to_nsecs(), so the microsecond precision from a plain (USEC_PER_SEC / HZ) multiplication should be sufficient here. I'll implement it with that logic in v3.