linux-kernel - Re: [PATCH] rust: time: add Ktime

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Date: Fri, 22 Mar 2024 08:50:18 +0100
From: Alice Ryhl <aliceryhl@...gle.com>
To: Boqun Feng <boqun.feng@...il.com>
Cc: Miguel Ojeda <ojeda@...nel.org>, John Stultz <jstultz@...gle.com>, 
	Thomas Gleixner <tglx@...utronix.de>, Stephen Boyd <sboyd@...nel.org>, 
	Alex Gaynor <alex.gaynor@...il.com>, Wedson Almeida Filho <wedsonaf@...il.com>, Gary Guo <gary@...yguo.net>, 
	Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
	Benno Lossin <benno.lossin@...ton.me>, Andreas Hindborg <a.hindborg@...sung.com>, 
	rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rust: time: add Ktime

On Wed, Mar 20, 2024 at 4:30 PM Boqun Feng <boqun.feng@...il.com> wrote:
>
> Hi,
>
> On Wed, Mar 20, 2024 at 10:08:45AM +0000, Alice Ryhl wrote:
> > Introduce a wrapper around `ktime_t` with a few different useful
> > methods.
> >
> > Rust Binder will use these bindings to compute how many milliseconds a
> > transaction has been active for when dumping the current state of the
> > Binder driver. This replicates the logic in C Binder [1].
> >
>
> I wonder whether Lina's previous patch also works for your case?
>
>         https://lore.kernel.org/rust-for-linux/20230714-rust-time-v2-1-f5aed84218c4@asahilina.net/
>
> You don't need to implement all the `Clock`s since you only need
> MONOTONIC time. But maybe `Duration::as_nanos` and `Duration::as_millis`
> return `u128` is problematic?

It would work for me too, but adds more than what I need. As for
`u128`, I don't really know what the status on that is. I need to be
able to print it as a base-10 integer.

Adding an API with separate types that distinguish between Instant and
Duration and different clock sources so that you don't mix them up is
reasonable, but a bit overkill for my needs. I am spending enough API
design cycles on my uaccess, file, and linked list patchsets. Someone
else can submit patches to add a more well-typed time API in the
future.

Alice