netdev - Re: [PATCH v1 1/3] rust: core abstractions for network PHY drivers

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Date: Mon, 2 Oct 2023 11:14:36 +0200
From: Greg KH <greg@...ah.com>
To: FUJITA Tomonori <fujita.tomonori@...il.com>
Cc: netdev@...r.kernel.org, rust-for-linux@...r.kernel.org, andrew@...n.ch,
	miguel.ojeda.sandonis@...il.com
Subject: Re: [PATCH v1 1/3] rust: core abstractions for network PHY drivers

On Mon, Oct 02, 2023 at 05:53:00PM +0900, FUJITA Tomonori wrote:
> +/// Corresponds to the kernel's `enum phy_state`.
> +#[derive(PartialEq)]
> +pub enum DeviceState {
> +    /// PHY device and driver are not ready for anything.
> +    Down,
> +    /// PHY is ready to send and receive packets.
> +    Ready,
> +    /// PHY is up, but no polling or interrupts are done.
> +    Halted,
> +    /// PHY is up, but is in an error state.
> +    Error,
> +    /// PHY and attached device are ready to do work.
> +    Up,
> +    /// PHY is currently running.
> +    Running,
> +    /// PHY is up, but not currently plugged in.
> +    NoLink,
> +    /// PHY is performing a cable test.
> +    CableTest,
> +}

I still think these should come straight from the C code, and that
moving them to an enum makes sense to make this possible, but hey, it's
not my subsystem to maintain!  :)

> +/// Wraps the kernel's `struct phy_device`.
> +///
> +/// # Invariants
> +///
> +/// `self.0` is always in a valid state.
> +#[repr(transparent)]
> +pub struct Device(Opaque<bindings::phy_device>);
> +
> +impl Device {
> +    /// Creates a new [`Device`] instance from a raw pointer.
> +    ///
> +    /// # Safety
> +    ///
> +    /// For the duration of the lifetime 'a, the pointer must be valid for writing and nobody else
> +    /// may read or write to the `phy_device` object.
> +    pub unsafe fn from_raw<'a>(ptr: *mut bindings::phy_device) -> &'a mut Self {
> +        unsafe { &mut *ptr.cast() }
> +    }
> +
> +    /// Gets the id of the PHY.
> +    pub fn id(&mut self) -> u32 {
> +        let phydev = self.0.get();
> +        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Self`.
> +        unsafe { (*phydev).phy_id }
> +    }

Naming question, why are you making this "id" instead of "phy_id"
like the C code has?  Same for many of these bindings.

> +    /// Returns true if the link is up.
> +    pub fn get_link(&mut self) -> bool {
> +        const LINK_IS_UP: u32 = 1;
> +        let phydev = self.0.get();
> +        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Self`.
> +        unsafe { (*phydev).link() == LINK_IS_UP }
> +    }

"get_" normally means to grab a reference, if this isn't matching a C
call, why not just call it link_is_up or to match your other state
checks "is_link_up"?

but hey, I'm just bikeshedding at this point in time, if they maintainer
likes these as-is, keep them :)

thanks,

greg k-h