netdev - Re: [PATCH net-next v7 5/5] net: phy: add Rust Asix PHY driver

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Message-ID: <363b810d-7d6c-48bd-879b-f97acffa70b6@lunn.ch>
Date: Sun, 19 Nov 2023 17:03:30 +0100
From: Andrew Lunn <andrew@...n.ch>
To: FUJITA Tomonori <fujita.tomonori@...il.com>
Cc: aliceryhl@...gle.com, benno.lossin@...ton.me,
	miguel.ojeda.sandonis@...il.com, netdev@...r.kernel.org,
	rust-for-linux@...r.kernel.org, tmgross@...ch.edu,
	wedsonaf@...il.com
Subject: Re: [PATCH net-next v7 5/5] net: phy: add Rust Asix PHY driver

> >> +            let _ = dev.init_hw();
> >> +            let _ = dev.start_aneg();
> > 
> > Just to confirm: You want to call `start_aneg` even if `init_hw` returns
> > failure? And you want to ignore both errors?
> 
> Yeah, I tried to implement the exact same behavior in the original C driver.

You probably could check the return values, and it would not make a
difference. Also, link_change_notify() is a void function, so you
cannot return the error anyway.

These low level functions basically only fail if the hardware is
`dead`. You get an -EIO or maybe -TIMEDOUT back. And there is no real
recovery. You tend to get such errors during probe and fail the
probe. Or maybe if power management is wrong and it has turned a
critical clock off. But that is unlikely in this case, we are calling
link_change_notify because the PHY has told us something changed
recently, so it probably is alive.

I would say part of not checking the return code is also that C does
not have the nice feature that Rust has of making very simple to check
the return code. That combined with it being mostly pointless for PHY
drivers.

    Andrew