linux-kernel - Re: [PATCH v8 12/14] rust: hrtimer: add `HrTimerMode`

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Message-ID: <a87ef54e-9a09-4cf6-bfe8-4bb98850cdda@proton.me>
Date: Thu, 20 Feb 2025 23:23:55 +0000
From: Benno Lossin <benno.lossin@...ton.me>
To: Andreas Hindborg <a.hindborg@...nel.org>, Miguel Ojeda <ojeda@...nel.org>, Anna-Maria Behnsen <anna-maria@...utronix.de>, Frederic Weisbecker <frederic@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Danilo Krummrich <dakr@...nel.org>
Cc: Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, Björn Roy Baron <bjorn3_gh@...tonmail.com>, Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>, Lyude Paul <lyude@...hat.com>, Guangbo Cui <2407018371@...com>, Dirk Behme <dirk.behme@...il.com>, Daniel Almeida <daniel.almeida@...labora.com>, Tamir Duberstein <tamird@...il.com>, rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 12/14] rust: hrtimer: add `HrTimerMode`

On 18.02.25 14:27, Andreas Hindborg wrote:
> +/// Operational mode of [`HrTimer`].
> +#[derive(Clone, Copy)]
> +pub enum HrTimerMode {
> +    /// Timer expires at the given expiration time.
> +    Absolute,
> +    /// Timer expires after the given expiration time interpreted as a duration from now.
> +    Relative,
> +    /// Timer does not move between CPU cores.
> +    Pinned,
> +    /// Timer handler is executed in soft irq context.
> +    Soft,
> +    /// Timer handler is executed in hard irq context.
> +    Hard,
> +    /// Timer expires at the given expiration time.
> +    /// Timer does not move between CPU cores.
> +    AbsolutePinned,
> +    /// Timer expires after the given expiration time interpreted as a duration from now.
> +    /// Timer does not move between CPU cores.
> +    RelativePinned,
> +    /// Timer expires at the given expiration time.
> +    /// Timer handler is executed in soft irq context.
> +    AbsoluteSoft,
> +    /// Timer expires after the given expiration time interpreted as a duration from now.
> +    /// Timer handler is executed in soft irq context.
> +    RelativeSoft,
> +    /// Timer expires at the given expiration time.
> +    /// Timer does not move between CPU cores.
> +    /// Timer handler is executed in soft irq context.
> +    AbsolutePinnedSoft,
> +    /// Timer expires after the given expiration time interpreted as a duration from now.
> +    /// Timer does not move between CPU cores.
> +    /// Timer handler is executed in soft irq context.
> +    RelativePinnedSoft,
> +    /// Timer expires at the given expiration time.
> +    /// Timer handler is executed in hard irq context.
> +    AbsoluteHard,
> +    /// Timer expires after the given expiration time interpreted as a duration from now.
> +    /// Timer handler is executed in hard irq context.
> +    RelativeHard,
> +    /// Timer expires at the given expiration time.
> +    /// Timer does not move between CPU cores.
> +    /// Timer handler is executed in hard irq context.
> +    AbsolutePinnedHard,
> +    /// Timer expires after the given expiration time interpreted as a duration from now.
> +    /// Timer does not move between CPU cores.
> +    /// Timer handler is executed in hard irq context.
> +    RelativePinnedHard,
> +}

At some point we probably want to move this to bitfields, or do you
think it's better to keep it like this?

> +
> +impl From<HrTimerMode> for bindings::hrtimer_mode {
> +    fn from(value: HrTimerMode) -> Self {
> +        use bindings::*;
> +        match value {
> +            HrTimerMode::Absolute => hrtimer_mode_HRTIMER_MODE_ABS,
> +            HrTimerMode::Relative => hrtimer_mode_HRTIMER_MODE_REL,
> +            HrTimerMode::Pinned => hrtimer_mode_HRTIMER_MODE_PINNED,
> +            HrTimerMode::Soft => hrtimer_mode_HRTIMER_MODE_SOFT,
> +            HrTimerMode::Hard => hrtimer_mode_HRTIMER_MODE_HARD,
> +            HrTimerMode::AbsolutePinned => hrtimer_mode_HRTIMER_MODE_ABS_PINNED,
> +            HrTimerMode::RelativePinned => hrtimer_mode_HRTIMER_MODE_REL_PINNED,
> +            HrTimerMode::AbsoluteSoft => hrtimer_mode_HRTIMER_MODE_ABS_SOFT,
> +            HrTimerMode::RelativeSoft => hrtimer_mode_HRTIMER_MODE_REL_SOFT,
> +            HrTimerMode::AbsolutePinnedSoft => hrtimer_mode_HRTIMER_MODE_ABS_PINNED_SOFT,
> +            HrTimerMode::RelativePinnedSoft => hrtimer_mode_HRTIMER_MODE_REL_PINNED_SOFT,
> +            HrTimerMode::AbsoluteHard => hrtimer_mode_HRTIMER_MODE_ABS_HARD,
> +            HrTimerMode::RelativeHard => hrtimer_mode_HRTIMER_MODE_REL_HARD,
> +            HrTimerMode::AbsolutePinnedHard => hrtimer_mode_HRTIMER_MODE_ABS_PINNED_HARD,
> +            HrTimerMode::RelativePinnedHard => hrtimer_mode_HRTIMER_MODE_REL_PINNED_HARD,
> +        }
> +    }
> +}
> +
> +impl From<HrTimerMode> for u64 {
> +    fn from(value: HrTimerMode) -> Self {
> +        Into::<bindings::hrtimer_mode>::into(value) as u64
> +    }
> +}

Hmm do drivers really need these impls? If not, then you could also just
have a private function that does the conversion and use it only in the
abstraction layer.

---
Cheers,
Benno

> +
>  /// Use to implement the [`HasHrTimer<T>`] trait.
>  ///
>  /// See [`module`] documentation for an example.
> 
> --
> 2.47.0
> 
>