netdev - Re: [PATCH v8 4/7] rust: time: Add wrapper for fsleep function

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Message-ID: <CANiq72nNsmuQz1mEx2ov8SXj_UAEURDZFtLotf4qP2pf+r97eQ@mail.gmail.com>
Date: Fri, 17 Jan 2025 19:59:15 +0100
From: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To: FUJITA Tomonori <fujita.tomonori@...il.com>
Cc: linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org, 
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Subject: Re: [PATCH v8 4/7] rust: time: Add wrapper for fsleep function

On Thu, Jan 16, 2025 at 5:42 AM FUJITA Tomonori
<fujita.tomonori@...il.com> wrote:
>
> +/// `delta` must be 0 or greater and no more than `u32::MAX / 2` microseconds.
> +/// If a value outside the range is given, the function will sleep
> +/// for `u32::MAX / 2` microseconds (= ~2147 seconds or ~36 minutes) at least.

I would emphasize with something like:

    `delta` must be within [0, `u32::MAX / 2`] microseconds;
otherwise, it is erroneous behavior. That is, it is considered a bug
to call this function with an out-of-range value, in which case the
function will sleep for at least the maximum value in the range and
may warn in the future.

In addition, I would add a new paragraph how the behavior differs
w.r.t. the C `fsleep()`, i.e. IIRC from the past discussions,
`fsleep()` would do an infinite sleep instead. So I think it is
important to highlight that.

> +    // The argument of fsleep is an unsigned long, 32-bit on 32-bit architectures.
> +    // Considering that fsleep rounds up the duration to the nearest millisecond,
> +    // set the maximum value to u32::MAX / 2 microseconds.

Nit: please use Markdown code spans in normal comments (no need for
intra-doc links there).

> +    let duration = if delta > MAX_DURATION || delta.is_negative() {
> +        // TODO: add WARN_ONCE() when it's supported.

Ditto (also "Add").

By the way, can this be written differently maybe? e.g. using a range
since it is `const`?

You can probably reuse `delta` as the new bindings name, since we
don't need the old one after this step.

Thanks!

Cheers,
Miguel