netdev - Re: [PATCH net-next v7 1/5] rust: core abstractions for network PHY drivers

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Message-ID: <ZTwWse0COE3w6_US@boqun-archlinux>
Date: Fri, 27 Oct 2023 12:59:45 -0700
From: Boqun Feng <boqun.feng@...il.com>
To: FUJITA Tomonori <fujita.tomonori@...il.com>
Cc: netdev@...r.kernel.org, rust-for-linux@...r.kernel.org, andrew@...n.ch,
	tmgross@...ch.edu, miguel.ojeda.sandonis@...il.com,
	benno.lossin@...ton.me, wedsonaf@...il.com
Subject: Re: [PATCH net-next v7 1/5] rust: core abstractions for network PHY
 drivers

On Thu, Oct 26, 2023 at 09:10:46AM +0900, FUJITA Tomonori wrote:
[...]
> +    /// Gets the current link state.
> +    ///
> +    /// It returns true if the link is up.
> +    pub fn is_link_up(&self) -> bool {
> +        const LINK_IS_UP: u32 = 1;
> +        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Self`.
> +        let phydev = unsafe { *self.0.get() };

Tomo, FWIW, the above line means *copying* the content pointed by
`self.0.get()` into `phydev`, i.e. `phydev` is the semantically a copy
of the `phy_device` instead of an alias. In C code, it means you did:

	struct phy_device phydev = *ptr;

Sure, both compilers can figure this out, therefore no extra copy is
done, but still it's better to avoid this copy semantics by doing:

	let phydev = unsafe { &*self.0.get() };

it's equal to C code:

	struct phy_device *phydev = ptr;

Ditto for is_autoneg_enabled() and is_autoneg_completed().

Regards,
Boqun

> +        phydev.link() == LINK_IS_UP
> +    }
> +
> +    /// Gets the current auto-negotiation configuration.
> +    ///
> +    /// It returns true if auto-negotiation is enabled.
> +    pub fn is_autoneg_enabled(&self) -> bool {
> +        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Self`.
> +        let phydev = unsafe { *self.0.get() };
> +        phydev.autoneg() == bindings::AUTONEG_ENABLE
> +    }
> +
> +    /// Gets the current auto-negotiation state.
> +    ///
> +    /// It returns true if auto-negotiation is completed.
> +    pub fn is_autoneg_completed(&self) -> bool {
> +        const AUTONEG_COMPLETED: u32 = 1;
> +        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Self`.
> +        let phydev = unsafe { *self.0.get() };
> +        phydev.autoneg_complete() == AUTONEG_COMPLETED
> +    }
[...]