netdev - Re: [PATCH net-next v1 1/2] rust: add delay abstraction

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Message-ID: <b47f8509-97c6-4513-8d22-fb4e43735213@lunn.ch>
Date: Tue, 1 Oct 2024 14:31:39 +0200
From: Andrew Lunn <andrew@...n.ch>
To: FUJITA Tomonori <fujita.tomonori@...il.com>
Cc: netdev@...r.kernel.org, rust-for-linux@...r.kernel.org,
	hkallweit1@...il.com, tmgross@...ch.edu, ojeda@...nel.org,
	alex.gaynor@...il.com, gary@...yguo.net, bjorn3_gh@...tonmail.com,
	benno.lossin@...ton.me, a.hindborg@...sung.com,
	aliceryhl@...gle.com
Subject: Re: [PATCH net-next v1 1/2] rust: add delay abstraction

On Tue, Oct 01, 2024 at 11:25:11AM +0000, FUJITA Tomonori wrote:
> Add an abstraction for sleep functions in `include/linux/delay.h` for
> dealing with hardware delays.
> 
> The kernel supports several `sleep` functions for handles various

s/for/which

> lengths of delay. This adds fsleep helper function, internally calls
> an appropriate sleep function.
> 
> This is used by QT2025 PHY driver to wait until a PHY becomes ready.
> 
> Signed-off-by: FUJITA Tomonori <fujita.tomonori@...il.com>
> ---
>  rust/bindings/bindings_helper.h |  1 +
>  rust/helpers/delay.c            |  8 ++++++++
>  rust/helpers/helpers.c          |  1 +
>  rust/kernel/delay.rs            | 18 ++++++++++++++++++
>  rust/kernel/lib.rs              |  1 +
>  5 files changed, 29 insertions(+)
>  create mode 100644 rust/helpers/delay.c
>  create mode 100644 rust/kernel/delay.rs
> 
> diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
> index ae82e9c941af..29a2f59294ba 100644
> --- a/rust/bindings/bindings_helper.h
> +++ b/rust/bindings/bindings_helper.h
> @@ -10,6 +10,7 @@
>  #include <linux/blk-mq.h>
>  #include <linux/blk_types.h>
>  #include <linux/blkdev.h>
> +#include <linux/delay.h>
>  #include <linux/errname.h>
>  #include <linux/ethtool.h>
>  #include <linux/firmware.h>
> diff --git a/rust/helpers/delay.c b/rust/helpers/delay.c
> new file mode 100644
> index 000000000000..7ae64ad8141d
> --- /dev/null
> +++ b/rust/helpers/delay.c
> @@ -0,0 +1,8 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/delay.h>
> +
> +void rust_helper_fsleep(unsigned long usecs)
> +{
> +	fsleep(usecs);
> +}
> diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
> index 30f40149f3a9..279ea662ee3b 100644
> --- a/rust/helpers/helpers.c
> +++ b/rust/helpers/helpers.c
> @@ -12,6 +12,7 @@
>  #include "build_assert.c"
>  #include "build_bug.c"
>  #include "err.c"
> +#include "delay.c"
>  #include "kunit.c"
>  #include "mutex.c"
>  #include "page.c"
> diff --git a/rust/kernel/delay.rs b/rust/kernel/delay.rs
> new file mode 100644
> index 000000000000..79f51a9608b5
> --- /dev/null
> +++ b/rust/kernel/delay.rs
> @@ -0,0 +1,18 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! Delay and sleep routines.
> +//!
> +//! C headers: [`include/linux/delay.h`](srctree/include/linux/delay.h).
> +
> +use core::{ffi::c_ulong, time::Duration};
> +
> +/// Sleeps for a given duration.
> +///
> +/// Equivalent to the kernel's [`fsleep`] function, internally calls `udelay`,
> +/// `usleep_range`, or `msleep`.

Is it possible to cross reference
Documentation/timers/timers-howto.rst ?  fsleep() points to it, so it
would e good if the Rust version also did.

I would also document the units for the parameter. Is it picoseconds
or centuries?

	Andrew