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

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Message-ID: <CAOgh=Fw634rgNCzx+mMEQayhGKgUiBYsqpF7rFOz+q4DS1_kag@mail.gmail.com>
Date:   Tue, 21 Feb 2023 07:25:35 +0000
From:   Eric Curtin <ecurtin@...hat.com>
To:     Asahi Lina <lina@...hilina.net>
Cc:     Miguel Ojeda <ojeda@...nel.org>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Wedson Almeida Filho <wedsonaf@...il.com>,
        Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
        Björn Roy Baron <bjorn3_gh@...tonmail.com>,
        John Stultz <jstultz@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        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 Tue, 21 Feb 2023 at 07:16, Asahi Lina <lina@...hilina.net> wrote:
>
> This module is intended to contain functions related to kernel
> timekeeping and time. Initially, this just wraps ktime_get() and
> ktime_get_boottime() and returns them as core::time::Duration instances.
> This is useful for drivers that need to implement simple retry loops and
> timeouts.
>
> Signed-off-by: Asahi Lina <lina@...hilina.net>
> ---

Nice and simple C interface to create Rust abstractions for.

Reviewed-by: Eric Curtin <ecurtin@...hat.com>

Is mise le meas/Regards,

Eric Curtin

>  rust/bindings/bindings_helper.h |  4 +++-
>  rust/kernel/lib.rs              |  1 +
>  rust/kernel/time.rs             | 25 +++++++++++++++++++++++++
>  3 files changed, 29 insertions(+), 1 deletion(-)
>
> diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
> index 75d85bd6c592..587f3d1c0c9f 100644
> --- a/rust/bindings/bindings_helper.h
> +++ b/rust/bindings/bindings_helper.h
> @@ -6,8 +6,10 @@
>   * Sorted alphabetically.
>   */
>
> -#include <linux/slab.h>
> +#include <linux/ktime.h>
>  #include <linux/refcount.h>
> +#include <linux/slab.h>
> +#include <linux/timekeeping.h>
>
>  /* `bindgen` gets confused at certain things. */
>  const gfp_t BINDINGS_GFP_KERNEL = GFP_KERNEL;
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index 223564f9f0cc..371b1b17570e 100644
> --- a/rust/kernel/lib.rs
> +++ b/rust/kernel/lib.rs
> @@ -37,6 +37,7 @@ mod static_assert;
>  pub mod std_vendor;
>  pub mod str;
>  pub mod sync;
> +pub mod time;
>  pub mod types;
>
>  #[doc(hidden)]
> diff --git a/rust/kernel/time.rs b/rust/kernel/time.rs
> new file mode 100644
> index 000000000000..02844db47d34
> --- /dev/null
> +++ b/rust/kernel/time.rs
> @@ -0,0 +1,25 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! Timekeeping functions.
> +//!
> +//! C header: [`include/linux/ktime.h`](../../../../include/linux/ktime.h)
> +//! C header: [`include/linux/timekeeping.h`](../../../../include/linux/timekeeping.h)
> +
> +use crate::bindings;
> +use core::time::Duration;
> +
> +/// Returns the kernel time elapsed since boot, excluding time spent sleeping, as a [`Duration`].
> +pub fn ktime_get() -> Duration {
> +    // SAFETY: Function has no side effects and no inputs.
> +    Duration::from_nanos(unsafe { bindings::ktime_get() }.try_into().unwrap())
> +}
> +
> +/// Returns the kernel time elapsed since boot, including time spent sleeping, as a [`Duration`].
> +pub fn ktime_get_boottime() -> Duration {
> +    Duration::from_nanos(
> +        // SAFETY: Function has no side effects and no variable inputs.
> +        unsafe { bindings::ktime_get_with_offset(bindings::tk_offsets_TK_OFFS_BOOT) }
> +            .try_into()
> +            .unwrap(),
> +    )
> +}
>
> ---
> base-commit: 89f5349e0673322857bd432fa23113af56673739
> change-id: 20230221-gpu-up-time-ea9412204c3b
>
> Thank you,
> ~~ Lina
>
>