netdev - Re: iopoll abstraction

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Message-Id: <20241003.134518.2205814402977569500.fujita.tomonori@gmail.com>
Date: Thu, 03 Oct 2024 13:45:18 +0000 (UTC)
From: FUJITA Tomonori <fujita.tomonori@...il.com>
To: boqun.feng@...il.com
Cc: fujita.tomonori@...il.com, dirk.behme@...bosch.com, andrew@...n.ch,
 aliceryhl@...gle.com, 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
Subject: Re: iopoll abstraction

On Thu, 3 Oct 2024 04:52:48 -0700
Boqun Feng <boqun.feng@...il.com> wrote:

> You could use closure as a parameter to avoid macro interface, something
> like:
> 
> 	fn read_poll_timeout<Op, Cond, T>(
> 	    op: Op,
> 	    cond: Cond,
> 	    sleep: Delta,
> 	    timeout: Delta,
> 	) -> Result<T> where
> 	    Op: Fn() -> T,
> 	    cond: Fn() -> bool {
> 
> 	    let __timeout = kernel::Ktime::ktime_get() + timeout;
> 
> 	    let val = loop {
> 		let val = op();
> 		if cond() {
> 		    break Some(val);
> 		}
> 		kernel::delay::sleep(sleep);
> 
> 		if __timeout.after(kernel::Ktime::ktime_get()) {
> 		    break None;
> 		}
> 	    };
> 
> 	    if cond() {
> 		val
> 	    } else {
> 		Err(kernel::error::code::ETIMEDOUT)
> 	    }
> 	}

Great! I changed couple of things.

1. Op typically reads a value from a register and could need mut objects. So I use FnMut.
2. reading from hardware could fail so Op had better to return an error [1].
3. Cond needs val; typically check the value from a register.

[1] https://lore.kernel.org/netdev/ec7267b5-ae77-4c4a-94f8-aa933c87a9a2@lunn.ch

Seems that the following works QT2025 driver. How does it look?

fn read_poll_timeout<Op, Cond, T: Copy>(
    mut op: Op,
    cond: Cond,
    sleep: Delta,
    timeout: Delta,
) -> Result<T>
where
    Op: FnMut() -> Result<T>,
    Cond: Fn(T) -> bool,
{
    let timeout = Ktime::ktime_get() + timeout;
    let ret = loop {
        let val = op()?;
        if cond(val) {
            break Ok(val);
        }
        kernel::delay::sleep(sleep);

        if Ktime::ktime_get() > timeout {
            break Err(code::ETIMEDOUT);
        }
    };

    ret
}