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Date: Mon,  9 Oct 2023 10:39:10 +0900
From: FUJITA Tomonori <fujita.tomonori@...il.com>
To: netdev@...r.kernel.org
Cc: rust-for-linux@...r.kernel.org,
	andrew@...n.ch,
	miguel.ojeda.sandonis@...il.com,
	greg@...ah.com,
	tmgross@...ch.edu
Subject: [PATCH net-next v3 1/3] rust: core abstractions for network PHY drivers

This patch adds abstractions to implement network PHY drivers; the
driver registration and bindings for some of callback functions in
struct phy_driver and many genphy_ functions.

This feature is enabled with CONFIG_RUST_PHYLIB_BINDINGS.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@...il.com>
---
 init/Kconfig                    |   8 +
 rust/Makefile                   |   1 +
 rust/bindings/bindings_helper.h |   3 +
 rust/kernel/lib.rs              |   3 +
 rust/kernel/net.rs              |   6 +
 rust/kernel/net/phy.rs          | 733 ++++++++++++++++++++++++++++++++
 6 files changed, 754 insertions(+)
 create mode 100644 rust/kernel/net.rs
 create mode 100644 rust/kernel/net/phy.rs

diff --git a/init/Kconfig b/init/Kconfig
index 6d35728b94b2..7ea415c9b144 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1903,6 +1903,14 @@ config RUST
 
 	  If unsure, say N.
 
+config RUST_PHYLIB_BINDINGS
+        bool "PHYLIB bindings support"
+        depends on RUST
+        depends on PHYLIB=y
+        help
+          Adds support needed for PHY drivers written in Rust. It provides
+          a wrapper around the C phlib core.
+
 config RUSTC_VERSION_TEXT
 	string
 	depends on RUST
diff --git a/rust/Makefile b/rust/Makefile
index 87958e864be0..f67e55945b36 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -331,6 +331,7 @@ quiet_cmd_bindgen = BINDGEN $@
       cmd_bindgen = \
 	$(BINDGEN) $< $(bindgen_target_flags) \
 		--use-core --with-derive-default --ctypes-prefix core::ffi --no-layout-tests \
+		--rustified-enum phy_state\
 		--no-debug '.*' \
 		-o $@ -- $(bindgen_c_flags_final) -DMODULE \
 		$(bindgen_target_cflags) $(bindgen_target_extra)
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index c91a3c24f607..ec4ee09a34ad 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -8,6 +8,9 @@
 
 #include <kunit/test.h>
 #include <linux/errname.h>
+#include <linux/ethtool.h>
+#include <linux/mdio.h>
+#include <linux/phy.h>
 #include <linux/slab.h>
 #include <linux/refcount.h>
 #include <linux/wait.h>
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index e8811700239a..0588422e273c 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -14,6 +14,7 @@
 #![no_std]
 #![feature(allocator_api)]
 #![feature(coerce_unsized)]
+#![feature(const_maybe_uninit_zeroed)]
 #![feature(dispatch_from_dyn)]
 #![feature(new_uninit)]
 #![feature(receiver_trait)]
@@ -36,6 +37,8 @@
 pub mod ioctl;
 #[cfg(CONFIG_KUNIT)]
 pub mod kunit;
+#[cfg(CONFIG_NET)]
+pub mod net;
 pub mod prelude;
 pub mod print;
 mod static_assert;
diff --git a/rust/kernel/net.rs b/rust/kernel/net.rs
new file mode 100644
index 000000000000..cc1de17cd5fa
--- /dev/null
+++ b/rust/kernel/net.rs
@@ -0,0 +1,6 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Networking.
+
+#[cfg(CONFIG_RUST_PHYLIB_BINDINGS)]
+pub mod phy;
diff --git a/rust/kernel/net/phy.rs b/rust/kernel/net/phy.rs
new file mode 100644
index 000000000000..f31983bf0460
--- /dev/null
+++ b/rust/kernel/net/phy.rs
@@ -0,0 +1,733 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2023 FUJITA Tomonori <fujita.tomonori@...il.com>
+
+//! Network PHY device.
+//!
+//! C headers: [`include/linux/phy.h`](../../../../include/linux/phy.h).
+
+use crate::{bindings, error::*, prelude::vtable, str::CStr, types::Opaque};
+use core::marker::PhantomData;
+
+/// 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,
+}
+
+/// Represents duplex mode.
+pub enum DuplexMode {
+    /// Full-duplex mode
+    Half,
+    /// Half-duplex mode
+    Full,
+    /// Unknown
+    Unknown,
+}
+
+/// An instance of a PHY device.
+/// 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 phy_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 }
+    }
+
+    /// Gets the state of the PHY.
+    pub fn state(&mut self) -> DeviceState {
+        let phydev = self.0.get();
+        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Self`.
+        let state = unsafe { (*phydev).state };
+        // FIXME: enum-cast
+        match state {
+            bindings::phy_state::PHY_DOWN => DeviceState::Down,
+            bindings::phy_state::PHY_READY => DeviceState::Ready,
+            bindings::phy_state::PHY_HALTED => DeviceState::Halted,
+            bindings::phy_state::PHY_ERROR => DeviceState::Error,
+            bindings::phy_state::PHY_UP => DeviceState::Up,
+            bindings::phy_state::PHY_RUNNING => DeviceState::Running,
+            bindings::phy_state::PHY_NOLINK => DeviceState::NoLink,
+            bindings::phy_state::PHY_CABLETEST => DeviceState::CableTest,
+        }
+    }
+
+    /// 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 }
+    }
+
+    /// Returns true if auto-negotiation is enabled.
+    pub fn is_autoneg_enabled(&mut self) -> bool {
+        let phydev = self.0.get();
+        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Self`.
+        unsafe { (*phydev).autoneg() == bindings::AUTONEG_ENABLE }
+    }
+
+    /// Returns true if auto-negotiation is completed.
+    pub fn is_autoneg_completed(&mut self) -> bool {
+        const AUTONEG_COMPLETED: u32 = 1;
+        let phydev = self.0.get();
+        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Self`.
+        unsafe { (*phydev).autoneg_complete() == AUTONEG_COMPLETED }
+    }
+
+    /// Sets the speed of the PHY.
+    pub fn set_speed(&mut self, speed: u32) {
+        let phydev = self.0.get();
+        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Self`.
+        unsafe { (*phydev).speed = speed as i32 };
+    }
+
+    /// Sets duplex mode.
+    pub fn set_duplex(&mut self, mode: DuplexMode) {
+        let phydev = self.0.get();
+        let v = match mode {
+            DuplexMode::Full => bindings::DUPLEX_FULL as i32,
+            DuplexMode::Half => bindings::DUPLEX_HALF as i32,
+            DuplexMode::Unknown => bindings::DUPLEX_UNKNOWN as i32,
+        };
+        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Self`.
+        unsafe { (*phydev).duplex = v };
+    }
+
+    /// Reads a given C22 PHY register.
+    pub fn read(&mut self, regnum: u16) -> Result<u16> {
+        let phydev = self.0.get();
+        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Self`.
+        // So an FFI call with a valid pointer.
+        let ret = unsafe {
+            bindings::mdiobus_read((*phydev).mdio.bus, (*phydev).mdio.addr, regnum.into())
+        };
+        if ret < 0 {
+            Err(Error::from_errno(ret))
+        } else {
+            Ok(ret as u16)
+        }
+    }
+
+    /// Writes a given C22 PHY register.
+    pub fn write(&mut self, regnum: u16, val: u16) -> Result {
+        let phydev = self.0.get();
+        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Self`.
+        // So an FFI call with a valid pointer.
+        to_result(unsafe {
+            bindings::mdiobus_write((*phydev).mdio.bus, (*phydev).mdio.addr, regnum.into(), val)
+        })
+    }
+
+    /// Reads a paged register.
+    pub fn read_paged(&mut self, page: u16, regnum: u16) -> Result<u16> {
+        let phydev = self.0.get();
+        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Self`.
+        // So an FFI call with a valid pointer.
+        let ret = unsafe { bindings::phy_read_paged(phydev, page.into(), regnum.into()) };
+        if ret < 0 {
+            Err(Error::from_errno(ret))
+        } else {
+            Ok(ret as u16)
+        }
+    }
+
+    /// Resolves the advertisements into PHY settings.
+    pub fn resolve_aneg_linkmode(&mut self) {
+        let phydev = self.0.get();
+        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Self`.
+        // So an FFI call with a valid pointer.
+        unsafe { bindings::phy_resolve_aneg_linkmode(phydev) };
+    }
+
+    /// Executes software reset the PHY via BMCR_RESET bit.
+    pub fn genphy_soft_reset(&mut self) -> Result {
+        let phydev = self.0.get();
+        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Self`.
+        // So an FFI call with a valid pointer.
+        to_result(unsafe { bindings::genphy_soft_reset(phydev) })
+    }
+
+    /// Initializes the PHY.
+    pub fn init_hw(&mut self) -> Result {
+        let phydev = self.0.get();
+        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Self`.
+        // so an FFI call with a valid pointer.
+        to_result(unsafe { bindings::phy_init_hw(phydev) })
+    }
+
+    /// Starts auto-negotiation.
+    pub fn start_aneg(&mut self) -> Result {
+        let phydev = self.0.get();
+        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Self`.
+        // So an FFI call with a valid pointer.
+        to_result(unsafe { bindings::phy_start_aneg(phydev) })
+    }
+
+    /// Resumes the PHY via BMCR_PDOWN bit.
+    pub fn genphy_resume(&mut self) -> Result {
+        let phydev = self.0.get();
+        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Self`.
+        // So an FFI call with a valid pointer.
+        to_result(unsafe { bindings::genphy_resume(phydev) })
+    }
+
+    /// Suspends the PHY via BMCR_PDOWN bit.
+    pub fn genphy_suspend(&mut self) -> Result {
+        let phydev = self.0.get();
+        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Self`.
+        // So an FFI call with a valid pointer.
+        to_result(unsafe { bindings::genphy_suspend(phydev) })
+    }
+
+    /// Checks the link status and updates current link state.
+    pub fn genphy_read_status(&mut self) -> Result<u16> {
+        let phydev = self.0.get();
+        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Self`.
+        // So an FFI call with a valid pointer.
+        let ret = unsafe { bindings::genphy_read_status(phydev) };
+        if ret < 0 {
+            Err(Error::from_errno(ret))
+        } else {
+            Ok(ret as u16)
+        }
+    }
+
+    /// Updates the link status.
+    pub fn genphy_update_link(&mut self) -> Result {
+        let phydev = self.0.get();
+        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Self`.
+        // So an FFI call with a valid pointer.
+        to_result(unsafe { bindings::genphy_update_link(phydev) })
+    }
+
+    /// Reads Link partner ability.
+    pub fn genphy_read_lpa(&mut self) -> Result {
+        let phydev = self.0.get();
+        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Self`.
+        // So an FFI call with a valid pointer.
+        to_result(unsafe { bindings::genphy_read_lpa(phydev) })
+    }
+
+    /// Reads PHY abilities.
+    pub fn genphy_read_abilities(&mut self) -> Result {
+        let phydev = self.0.get();
+        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Self`.
+        // So an FFI call with a valid pointer.
+        to_result(unsafe { bindings::genphy_read_abilities(phydev) })
+    }
+}
+
+/// Defines certain other features this PHY supports (like interrupts).
+pub mod flags {
+    /// PHY is internal.
+    pub const IS_INTERNAL: u32 = bindings::PHY_IS_INTERNAL;
+    /// PHY needs to be reset after the refclk is enabled.
+    pub const RST_AFTER_CLK_EN: u32 = bindings::PHY_RST_AFTER_CLK_EN;
+    /// Polling is used to detect PHY status changes.
+    pub const POLL_CABLE_TEST: u32 = bindings::PHY_POLL_CABLE_TEST;
+    /// Don't suspend.
+    pub const ALWAYS_CALL_SUSPEND: u32 = bindings::PHY_ALWAYS_CALL_SUSPEND;
+}
+
+/// An adapter for the registration of a PHY driver.
+struct Adapter<T: Driver> {
+    _p: PhantomData<T>,
+}
+
+impl<T: Driver> Adapter<T> {
+    /// # Safety
+    ///
+    /// `phydev` must be passed by the corresponding callback in `phy_driver`.
+    unsafe extern "C" fn soft_reset_callback(
+        phydev: *mut bindings::phy_device,
+    ) -> core::ffi::c_int {
+        from_result(|| {
+            // SAFETY: Preconditions ensure `phydev` is valid.
+            let dev = unsafe { Device::from_raw(phydev) };
+            T::soft_reset(dev)?;
+            Ok(0)
+        })
+    }
+
+    /// # Safety
+    ///
+    /// `phydev` must be passed by the corresponding callback in `phy_driver`.
+    unsafe extern "C" fn get_features_callback(
+        phydev: *mut bindings::phy_device,
+    ) -> core::ffi::c_int {
+        from_result(|| {
+            // SAFETY: Preconditions ensure `phydev` is valid.
+            let dev = unsafe { Device::from_raw(phydev) };
+            T::get_features(dev)?;
+            Ok(0)
+        })
+    }
+
+    /// # Safety
+    ///
+    /// `phydev` must be passed by the corresponding callback in `phy_driver`.
+    unsafe extern "C" fn suspend_callback(phydev: *mut bindings::phy_device) -> core::ffi::c_int {
+        from_result(|| {
+            // SAFETY: Preconditions ensure `phydev` is valid.
+            let dev = unsafe { Device::from_raw(phydev) };
+            T::suspend(dev)?;
+            Ok(0)
+        })
+    }
+
+    /// # Safety
+    ///
+    /// `phydev` must be passed by the corresponding callback in `phy_driver`.
+    unsafe extern "C" fn resume_callback(phydev: *mut bindings::phy_device) -> core::ffi::c_int {
+        from_result(|| {
+            // SAFETY: Preconditions ensure `phydev` is valid.
+            let dev = unsafe { Device::from_raw(phydev) };
+            T::resume(dev)?;
+            Ok(0)
+        })
+    }
+
+    /// # Safety
+    ///
+    /// `phydev` must be passed by the corresponding callback in `phy_driver`.
+    unsafe extern "C" fn config_aneg_callback(
+        phydev: *mut bindings::phy_device,
+    ) -> core::ffi::c_int {
+        from_result(|| {
+            // SAFETY: Preconditions ensure `phydev` is valid.
+            let dev = unsafe { Device::from_raw(phydev) };
+            T::config_aneg(dev)?;
+            Ok(0)
+        })
+    }
+
+    /// # Safety
+    ///
+    /// `phydev` must be passed by the corresponding callback in `phy_driver`.
+    unsafe extern "C" fn read_status_callback(
+        phydev: *mut bindings::phy_device,
+    ) -> core::ffi::c_int {
+        from_result(|| {
+            // SAFETY: Preconditions ensure `phydev` is valid.
+            let dev = unsafe { Device::from_raw(phydev) };
+            T::read_status(dev)?;
+            Ok(0)
+        })
+    }
+
+    /// # Safety
+    ///
+    /// `phydev` must be passed by the corresponding callback in `phy_driver`.
+    unsafe extern "C" fn match_phy_device_callback(
+        phydev: *mut bindings::phy_device,
+    ) -> core::ffi::c_int {
+        // SAFETY: Preconditions ensure `phydev` is valid.
+        let dev = unsafe { Device::from_raw(phydev) };
+        T::match_phy_device(dev) as i32
+    }
+
+    /// # Safety
+    ///
+    /// `phydev` must be passed by the corresponding callback in `phy_driver`.
+    unsafe extern "C" fn read_mmd_callback(
+        phydev: *mut bindings::phy_device,
+        devnum: i32,
+        regnum: u16,
+    ) -> i32 {
+        from_result(|| {
+            // SAFETY: Preconditions ensure `phydev` is valid.
+            let dev = unsafe { Device::from_raw(phydev) };
+            // CAST: the C side verifies devnum < 32.
+            let ret = T::read_mmd(dev, devnum as u8, regnum)?;
+            Ok(ret.into())
+        })
+    }
+
+    /// # Safety
+    ///
+    /// `phydev` must be passed by the corresponding callback in `phy_driver`.
+    unsafe extern "C" fn write_mmd_callback(
+        phydev: *mut bindings::phy_device,
+        devnum: i32,
+        regnum: u16,
+        val: u16,
+    ) -> i32 {
+        from_result(|| {
+            // SAFETY: Preconditions ensure `phydev` is valid.
+            let dev = unsafe { Device::from_raw(phydev) };
+            T::write_mmd(dev, devnum as u8, regnum, val)?;
+            Ok(0)
+        })
+    }
+
+    /// # Safety
+    ///
+    /// `phydev` must be passed by the corresponding callback in `phy_driver`.
+    unsafe extern "C" fn link_change_notify_callback(phydev: *mut bindings::phy_device) {
+        // SAFETY: Preconditions ensure `phydev` is valid.
+        let dev = unsafe { Device::from_raw(phydev) };
+        T::link_change_notify(dev);
+    }
+}
+
+/// Creates the kernel's `phy_driver` instance.
+///
+/// This is used by [`module_phy_driver`] macro to create a static array of phy_driver`.
+pub const fn create_phy_driver<T: Driver>() -> Opaque<bindings::phy_driver> {
+    Opaque::new(bindings::phy_driver {
+        name: T::NAME.as_char_ptr().cast_mut(),
+        flags: T::FLAGS,
+        phy_id: T::PHY_DEVICE_ID.id,
+        phy_id_mask: T::PHY_DEVICE_ID.mask_as_int(),
+        soft_reset: if T::HAS_SOFT_RESET {
+            Some(Adapter::<T>::soft_reset_callback)
+        } else {
+            None
+        },
+        get_features: if T::HAS_GET_FEATURES {
+            Some(Adapter::<T>::get_features_callback)
+        } else {
+            None
+        },
+        match_phy_device: if T::HAS_MATCH_PHY_DEVICE {
+            Some(Adapter::<T>::match_phy_device_callback)
+        } else {
+            None
+        },
+        suspend: if T::HAS_SUSPEND {
+            Some(Adapter::<T>::suspend_callback)
+        } else {
+            None
+        },
+        resume: if T::HAS_RESUME {
+            Some(Adapter::<T>::resume_callback)
+        } else {
+            None
+        },
+        config_aneg: if T::HAS_CONFIG_ANEG {
+            Some(Adapter::<T>::config_aneg_callback)
+        } else {
+            None
+        },
+        read_status: if T::HAS_READ_STATUS {
+            Some(Adapter::<T>::read_status_callback)
+        } else {
+            None
+        },
+        read_mmd: if T::HAS_READ_MMD {
+            Some(Adapter::<T>::read_mmd_callback)
+        } else {
+            None
+        },
+        write_mmd: if T::HAS_WRITE_MMD {
+            Some(Adapter::<T>::write_mmd_callback)
+        } else {
+            None
+        },
+        link_change_notify: if T::HAS_LINK_CHANGE_NOTIFY {
+            Some(Adapter::<T>::link_change_notify_callback)
+        } else {
+            None
+        },
+        // SAFETY: The rest is zeroed out to initialize `struct phy_driver`,
+        // sets `Option<&F>` to be `None`.
+        ..unsafe { core::mem::MaybeUninit::<bindings::phy_driver>::zeroed().assume_init() }
+    })
+}
+
+/// Corresponds to functions in `struct phy_driver`.
+///
+/// This is used to register a PHY driver.
+#[vtable]
+pub trait Driver {
+    /// Defines certain other features this PHY supports.
+    const FLAGS: u32 = 0;
+    /// The friendly name of this PHY type.
+    const NAME: &'static CStr;
+    /// This driver only works for PHYs with IDs which match this field.
+    const PHY_DEVICE_ID: DeviceId = DeviceId::new_with_custom_mask(0, 0);
+
+    /// Issues a PHY software reset.
+    fn soft_reset(_dev: &mut Device) -> Result {
+        Err(code::ENOTSUPP)
+    }
+
+    /// Probes the hardware to determine what abilities it has.
+    fn get_features(_dev: &mut Device) -> Result {
+        Err(code::ENOTSUPP)
+    }
+
+    /// Returns true if this is a suitable driver for the given phydev.
+    /// If not implemented, matching is based on [`PHY_DEVICE_ID`].
+    fn match_phy_device(_dev: &mut Device) -> bool {
+        false
+    }
+
+    /// Configures the advertisement and resets auto-negotiation
+    /// if auto-negotiation is enabled.
+    fn config_aneg(_dev: &mut Device) -> Result {
+        Err(code::ENOTSUPP)
+    }
+
+    /// Determines the negotiated speed and duplex.
+    fn read_status(_dev: &mut Device) -> Result<u16> {
+        Err(code::ENOTSUPP)
+    }
+
+    /// Suspends the hardware, saving state if needed.
+    fn suspend(_dev: &mut Device) -> Result {
+        Err(code::ENOTSUPP)
+    }
+
+    /// Resumes the hardware, restoring state if needed.
+    fn resume(_dev: &mut Device) -> Result {
+        Err(code::ENOTSUPP)
+    }
+
+    /// Overrides the default MMD read function for reading a MMD register.
+    fn read_mmd(_dev: &mut Device, _devnum: u8, _regnum: u16) -> Result<u16> {
+        Err(code::ENOTSUPP)
+    }
+
+    /// Overrides the default MMD write function for writing a MMD register.
+    fn write_mmd(_dev: &mut Device, _devnum: u8, _regnum: u16, _val: u16) -> Result {
+        Err(code::ENOTSUPP)
+    }
+
+    /// Callback for notification of link change.
+    fn link_change_notify(_dev: &mut Device) {}
+}
+
+/// Registration structure for a PHY driver.
+///
+/// # Invariants
+///
+/// The `drivers` points to an array of `struct phy_driver`, which is
+/// registered to the kernel via `phy_drivers_register`.
+pub struct Registration {
+    drivers: Option<&'static [Opaque<bindings::phy_driver>]>,
+}
+
+impl Registration {
+    /// Registers a PHY driver.
+    #[must_use]
+    pub fn register(
+        module: &'static crate::ThisModule,
+        drivers: &'static [Opaque<bindings::phy_driver>],
+    ) -> Result<Self> {
+        if drivers.len() == 0 {
+            return Err(code::EINVAL);
+        }
+        // SAFETY: `drivers` has static lifetime and used only in the C side.
+        to_result(unsafe {
+            bindings::phy_drivers_register(drivers[0].get(), drivers.len() as i32, module.0)
+        })?;
+        Ok(Registration {
+            drivers: Some(drivers),
+        })
+    }
+}
+
+impl Drop for Registration {
+    fn drop(&mut self) {
+        if let Some(drv) = self.drivers.take() {
+            // SAFETY: The type invariants guarantee that self.drivers is valid.
+            unsafe { bindings::phy_drivers_unregister(drv[0].get(), drv.len() as i32) };
+        }
+    }
+}
+
+// SAFETY: `Registration` does not expose any of its state across threads.
+unsafe impl Send for Registration {}
+
+// SAFETY: `Registration` does not expose any of its state across threads.
+unsafe impl Sync for Registration {}
+
+/// Represents the kernel's `struct mdio_device_id`.
+pub struct DeviceId {
+    /// Corresponds to `phy_id` in `struct mdio_device_id`.
+    pub id: u32,
+    mask: DeviceMask,
+}
+
+impl DeviceId {
+    /// Creates a new instance with the exact match mask.
+    pub const fn new_with_exact_mask(id: u32) -> Self {
+        DeviceId {
+            id,
+            mask: DeviceMask::Exact,
+        }
+    }
+
+    /// Creates a new instance with the model match mask.
+    pub const fn new_with_model_mask(id: u32) -> Self {
+        DeviceId {
+            id,
+            mask: DeviceMask::Model,
+        }
+    }
+
+    /// Creates a new instance with the vendor match mask.
+    pub const fn new_with_vendor_mask(id: u32) -> Self {
+        DeviceId {
+            id,
+            mask: DeviceMask::Vendor,
+        }
+    }
+
+    /// Creates a new instance with a custom match mask.
+    pub const fn new_with_custom_mask(id: u32, mask: u32) -> Self {
+        DeviceId {
+            id,
+            mask: DeviceMask::Custom(mask),
+        }
+    }
+
+    /// Creates a new instance from [`Driver`].
+    pub const fn new_with_driver<T: Driver>() -> Self {
+        T::PHY_DEVICE_ID
+    }
+
+    /// Get a mask as u32.
+    pub const fn mask_as_int(self) -> u32 {
+        self.mask.as_int()
+    }
+}
+
+enum DeviceMask {
+    Exact,
+    Model,
+    Vendor,
+    Custom(u32),
+}
+
+impl DeviceMask {
+    const MASK_EXACT: u32 = !0;
+    const MASK_MODEL: u32 = !0 << 4;
+    const MASK_VENDOR: u32 = !0 << 10;
+
+    const fn as_int(self) -> u32 {
+        match self {
+            DeviceMask::Exact => Self::MASK_EXACT,
+            DeviceMask::Model => Self::MASK_MODEL,
+            DeviceMask::Vendor => Self::MASK_VENDOR,
+            DeviceMask::Custom(mask) => mask,
+        }
+    }
+}
+
+/// Declares a kernel module for PHYs drivers.
+///
+/// This creates a static array of `struct phy_driver` and registers it.
+/// This also corresponds to the kernel's MODULE_DEVICE_TABLE macro, which embeds the information
+/// for module loading into the module binary file. Every driver needs an entry in device_table.
+///
+/// # Examples
+///
+/// ```ignore
+///
+/// use kernel::net::phy::{self, DeviceId, Driver};
+/// use kernel::prelude::*;
+///
+/// kernel::module_phy_driver! {
+///     drivers: [PhyAX88772A, PhyAX88772C, PhyAX88796B],
+///     device_table: [
+///         DeviceId::new_with_driver::<PhyAX88772A>(),
+///         DeviceId::new_with_driver::<PhyAX88772C>(),
+///         DeviceId::new_with_driver::<PhyAX88796B>()
+///     ],
+///     name: "rust_asix_phy",
+///     author: "Rust for Linux Contributors",
+///     description: "Rust Asix PHYs driver",
+///     license: "GPL",
+/// }
+/// ```
+#[macro_export]
+macro_rules! module_phy_driver {
+    (@replace_expr $_t:tt $sub:expr) => {$sub};
+
+    (@count_devices $($x:expr),*) => {
+        0usize $(+ $crate::module_phy_driver!(@replace_expr $x 1usize))*
+    };
+
+    (@device_table [$($dev:expr),+]) => {
+        #[no_mangle]
+        static __mod_mdio__phydev_device_table: [
+            kernel::bindings::mdio_device_id;
+            $crate::module_phy_driver!(@count_devices $($dev),+) + 1
+        ] = [
+            $(kernel::bindings::mdio_device_id {
+                phy_id: $dev.id,
+                phy_id_mask: $dev.mask_as_int()
+            }),+,
+            kernel::bindings::mdio_device_id {
+                phy_id: 0,
+                phy_id_mask: 0
+            }
+        ];
+    };
+
+    (drivers: [$($driver:ident),+], device_table: [$($dev:expr),+], $($f:tt)*) => {
+        struct Module {
+            _reg: kernel::net::phy::Registration,
+        }
+
+        $crate::prelude::module! {
+             type: Module,
+             $($f)*
+        }
+
+        static mut DRIVERS: [
+            kernel::types::Opaque<kernel::bindings::phy_driver>;
+            $crate::module_phy_driver!(@count_devices $($driver),+)
+        ] = [
+            $(kernel::net::phy::create_phy_driver::<$driver>()),+
+        ];
+
+        impl kernel::Module for Module {
+            fn init(module: &'static ThisModule) -> Result<Self> {
+                // SAFETY: static `DRIVERS` array is used only in the C side.
+                let mut reg = unsafe { kernel::net::phy::Registration::register(module, &DRIVERS) }?;
+
+                Ok(Module {
+                    _reg: reg,
+                })
+            }
+        }
+
+        $crate::module_phy_driver!(@device_table [$($dev),+]);
+    }
+}
-- 
2.34.1


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