linux-kernel - Re: [PATCH] rust: time: New module for timekeeping functions

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Message-ID: <25f16677-8633-8c06-cf67-8024fae7854f@asahilina.net>
Date:   Wed, 22 Feb 2023 01:37:44 +0900
From:   Asahi Lina <lina@...hilina.net>
To:     Boqun Feng <boqun.feng@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Miguel Ojeda <ojeda@...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>,
        John Stultz <jstultz@...gle.com>,
        Stephen Boyd <sboyd@...nel.org>, linux-kernel@...r.kernel.org,
        rust-for-linux@...r.kernel.org, asahi@...ts.linux.dev
Subject: Re: [PATCH] rust: time: New module for timekeeping functions

On 22/02/2023 01.27, Asahi Lina wrote:
> I think that's the better approach, but I was hoping to leave that for a
> future patch, especially since right now I'm the only user of this API
> in the upcoming Apple GPU driver and it only uses it to implement some
> really simple timeouts for polled operations, which isn't much API
> coverage... I figured we might get a better idea for what to do once a
> second user comes along. For example, do we want straight methods like
> that or std::ops trait impls? And do we make everything fallible or
> panic on overflow or just wrap?

Also, it's probably worth mentioning that this kind of refactor can be
done without rewriting all the user code. For example, here is how I use
the APIs:

    let timeout = time::ktime_get() + Duration::from_millis(...);
    while time::ktime_get() < timeout {
        [...]
    }

Even if ktime_get() starts returning another type, as long as it can
interoperate with core::time::Duration the same way, it will continue to
compile (and if it only interoperates with a new kernel-specific
Duration, you'd only have to change the `use` statement at the top).

~~ Lina