[RFC PATCH v2 1/3] rust: core abstractions for network PHY drivers

[FUJITA Tomonori <fujita.tomonori@gmail.com>]

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.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
---
 rust/Makefile                   |   1 +
 rust/bindings/bindings_helper.h |   3 +
 rust/kernel/lib.rs              |   3 +
 rust/kernel/net.rs              |   6 +
 rust/kernel/net/phy.rs          | 760 ++++++++++++++++++++++++++++++++
 5 files changed, 773 insertions(+)
 create mode 100644 rust/kernel/net.rs
 create mode 100644 rust/kernel/net/phy.rs

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..b49b052969e5
--- /dev/null
+++ b/rust/kernel/net.rs
@@ -0,0 +1,6 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Networking.
+
+#[cfg(CONFIG_PHYLIB)]
+pub mod phy;
diff --git a/rust/kernel/net/phy.rs b/rust/kernel/net/phy.rs
new file mode 100644
index 000000000000..3b96b1e0f9ef
--- /dev/null
+++ b/rust/kernel/net/phy.rs
@@ -0,0 +1,760 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! 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,
+}
+
+/// Wraps the kernel's `struct phy_device`.
+#[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 as *mut Self) }
+    }
+
+    /// Gets the id of the PHY.
+    pub fn id(&mut self) -> u32 {
+        let phydev = Opaque::get(&self.0);
+        // SAFETY: This object is initialized by the `from_raw` constructor, so it's valid.
+        unsafe { (*phydev).phy_id }
+    }
+
+    /// Gets the state of the PHY.
+    pub fn state(&mut self) -> DeviceState {
+        let phydev = Opaque::get(&self.0);
+        // SAFETY: This object is initialized by the `from_raw` constructor, so it's valid.
+        let state = unsafe { (*phydev).state };
+        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 PHY has no link.
+    pub fn get_link(&mut self) -> bool {
+        let phydev = Opaque::get(&self.0);
+        // SAFETY: This object is initialized by the `from_raw` constructor, so it's valid.
+        unsafe { (*phydev).link() != 0 }
+    }
+
+    /// Returns true if auto-negotiation is enabled.
+    pub fn is_autoneg_enabled(&mut self) -> bool {
+        let phydev = Opaque::get(&self.0);
+        // SAFETY: This object is initialized by the `from_raw` constructor, so it's valid.
+        unsafe { (*phydev).autoneg() == bindings::AUTONEG_ENABLE }
+    }
+
+    /// Returns true if auto-negotiation is completed.
+    pub fn is_autoneg_completed(&mut self) -> bool {
+        let phydev = Opaque::get(&self.0);
+        // SAFETY: This object is initialized by the `from_raw` constructor, so it's valid.
+        unsafe { (*phydev).autoneg_complete() != 0 }
+    }
+
+    /// Sets the speed of the PHY.
+    pub fn set_speed(&mut self, speed: i32) {
+        let phydev = Opaque::get(&self.0);
+        // SAFETY: This object is initialized by the `from_raw` constructor, so it's valid.
+        unsafe {
+            (*phydev).speed = speed;
+        }
+    }
+
+    /// Sets duplex mode.
+    pub fn set_duplex(&mut self, mode: DuplexMode) {
+        let phydev = Opaque::get(&self.0);
+        // SAFETY: This object is initialized by the `from_raw` constructor, so it's valid.
+        unsafe {
+            match mode {
+                DuplexMode::Full => (*phydev).duplex = bindings::DUPLEX_FULL as i32,
+                DuplexMode::Half => (*phydev).duplex = bindings::DUPLEX_HALF as i32,
+                DuplexMode::Unknown => (*phydev).duplex = bindings::DUPLEX_UNKNOWN as i32,
+            }
+        }
+    }
+
+    /// Reads a given C22 PHY register.
+    pub fn read(&mut self, regnum: u16) -> Result<u16> {
+        let phydev = Opaque::get(&self.0);
+        // SAFETY: This object is initialized by the `from_raw` constructor,
+        // so an FFI call with a valid pointer.
+        let ret = unsafe {
+            bindings::mdiobus_read((*phydev).mdio.bus, (*phydev).mdio.addr, regnum as u32)
+        };
+        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 = Opaque::get(&self.0);
+        // SAFETY: This object is initialized by the `from_raw` constructor,
+        // so an FFI call with a valid pointer.
+        let ret = unsafe {
+            bindings::mdiobus_write((*phydev).mdio.bus, (*phydev).mdio.addr, regnum as u32, val)
+        };
+        if ret < 0 {
+            Err(Error::from_errno(ret))
+        } else {
+            Ok(())
+        }
+    }
+
+    /// Reads a paged register.
+    pub fn read_paged(&mut self, page: u16, regnum: u16) -> Result<u16> {
+        let phydev = Opaque::get(&self.0);
+        // SAFETY: This object is initialized by the `from_raw` constructor,
+        // so an FFI call with a valid pointer.
+        let ret = unsafe { bindings::phy_read_paged(phydev, page as i32, regnum as u32) };
+        if ret < 0 {
+            return 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 = Opaque::get(&self.0);
+        // SAFETY: This object is initialized by the `from_raw` constructor,
+        // 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 = Opaque::get(&self.0);
+        // SAFETY: This object is initialized by the `from_raw` constructor,
+        // so an FFI call with a valid pointer.
+        let ret = unsafe { bindings::genphy_soft_reset(phydev) };
+        if ret < 0 {
+            Err(Error::from_errno(ret))
+        } else {
+            Ok(())
+        }
+    }
+
+    /// Initializes the PHY.
+    pub fn init_hw(&mut self) -> Result {
+        let phydev = Opaque::get(&self.0);
+        // SAFETY: This object is initialized by the `from_raw` constructor,
+        // so an FFI call with a valid pointer.
+        let ret = unsafe { bindings::phy_init_hw(phydev) };
+        if ret != 0 {
+            return Err(Error::from_errno(ret));
+        } else {
+            Ok(())
+        }
+    }
+
+    /// Starts auto-negotiation.
+    pub fn start_aneg(&mut self) -> Result {
+        let phydev = Opaque::get(&self.0);
+        // SAFETY: This object is initialized by the `from_raw` constructor,
+        // so an FFI call with a valid pointer.
+        let ret = unsafe { bindings::phy_start_aneg(phydev) };
+        if ret != 0 {
+            return Err(Error::from_errno(ret));
+        } else {
+            Ok(())
+        }
+    }
+
+    /// Resumes the PHY via BMCR_PDOWN bit.
+    pub fn genphy_resume(&mut self) -> Result {
+        let phydev = Opaque::get(&self.0);
+        // SAFETY: This object is initialized by the `from_raw` constructor,
+        // so an FFI call with a valid pointer.
+        let ret = unsafe { bindings::genphy_resume(phydev) };
+        if ret != 0 {
+            Err(Error::from_errno(ret))
+        } else {
+            Ok(())
+        }
+    }
+
+    /// Suspends the PHY via BMCR_PDOWN bit.
+    pub fn genphy_suspend(&mut self) -> Result {
+        let phydev = Opaque::get(&self.0);
+        // SAFETY: This object is initialized by the `from_raw` constructor,
+        // so an FFI call with a valid pointer.
+        let ret = unsafe { bindings::genphy_suspend(phydev) };
+        if ret != 0 {
+            Err(Error::from_errno(ret))
+        } else {
+            Ok(())
+        }
+    }
+
+    /// Checks the link status and updates current link state.
+    pub fn genphy_read_status(&mut self) -> Result<u16> {
+        let phydev = Opaque::get(&self.0);
+        // SAFETY: This object is initialized by the `from_raw` constructor,
+        // 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 = Opaque::get(&self.0);
+        // SAFETY: This object is initialized by the `from_raw` constructor,
+        // so an FFI call with a valid pointer.
+        let ret = unsafe { bindings::genphy_update_link(phydev) };
+        if ret < 0 {
+            return Err(Error::from_errno(ret));
+        } else {
+            Ok(())
+        }
+    }
+
+    /// Reads Link partner ability.
+    pub fn genphy_read_lpa(&mut self) -> Result {
+        let phydev = Opaque::get(&self.0);
+        // SAFETY: This object is initialized by the `from_raw` constructor,
+        // so an FFI call with a valid pointer.
+        let ret = unsafe { bindings::genphy_read_lpa(phydev) };
+        if ret < 0 {
+            return Err(Error::from_errno(ret));
+        } else {
+            Ok(())
+        }
+    }
+
+    /// Reads PHY abilities.
+    pub fn genphy_read_abilities(&mut self) -> Result {
+        let phydev = Opaque::get(&self.0);
+        // SAFETY: This object is initialized by the `from_raw` constructor,
+        // so an FFI call with a valid pointer.
+        let ret = unsafe { bindings::genphy_read_abilities(phydev) };
+        if ret != 0 {
+            return Err(Error::from_errno(ret));
+        } else {
+            Ok(())
+        }
+    }
+}
+
+// Will be replaced with the bitflags macro once it's merged in upstream.
+const fn bit(shift: u8) -> u32 {
+    1 << shift
+}
+/// PHY is internal.
+pub const PHY_IS_INTERNAL: u32 = bit(0);
+/// PHY needs to be reset after the refclk is enabled.
+pub const PHY_RST_AFTER_CLK_EN: u32 = bit(1);
+/// Polling is used to detect PHY status changes.
+pub const PHY_POLL_CABLE_TEST: u32 = bit(2);
+/// Don't suspend.
+pub const PHY_ALWAYS_CALL_SUSPEND: u32 = bit(3);
+
+/// An adapter for the registration of a PHY driver.
+pub struct Adapter<T: Driver> {
+    _p: PhantomData<T>,
+}
+
+impl<T: Driver> Adapter<T> {
+    /// Creates a new `Adapter` instance.
+    pub const fn new() -> Adapter<T> {
+        Self { _p: PhantomData }
+    }
+
+    unsafe extern "C" fn soft_reset_callback(
+        phydev: *mut bindings::phy_device,
+    ) -> core::ffi::c_int {
+        from_result(|| {
+            // SAFETY: The C API guarantees that `phydev` is valid while this function is running.
+            let dev = unsafe { Device::from_raw(phydev) };
+            T::soft_reset(dev)?;
+            Ok(0)
+        })
+    }
+
+    unsafe extern "C" fn get_features_callback(
+        phydev: *mut bindings::phy_device,
+    ) -> core::ffi::c_int {
+        from_result(|| {
+            // SAFETY: The C API guarantees that `phydev` is valid while this function is running.
+            let dev = unsafe { Device::from_raw(phydev) };
+            T::get_features(dev)?;
+            Ok(0)
+        })
+    }
+
+    unsafe extern "C" fn suspend_callback(phydev: *mut bindings::phy_device) -> core::ffi::c_int {
+        from_result(|| {
+            // SAFETY: The C API guarantees that `phydev` is valid while this function is running.
+            let dev = unsafe { Device::from_raw(phydev) };
+            T::suspend(dev)?;
+            Ok(0)
+        })
+    }
+
+    unsafe extern "C" fn resume_callback(phydev: *mut bindings::phy_device) -> core::ffi::c_int {
+        from_result(|| {
+            // SAFETY: The C API guarantees that `phydev` is valid while this function is running.
+            let dev = unsafe { Device::from_raw(phydev) };
+            T::resume(dev)?;
+            Ok(0)
+        })
+    }
+
+    unsafe extern "C" fn config_aneg_callback(
+        phydev: *mut bindings::phy_device,
+    ) -> core::ffi::c_int {
+        from_result(|| {
+            // SAFETY: The C API guarantees that `phydev` is valid while this function is running.
+            let dev = unsafe { Device::from_raw(phydev) };
+            T::config_aneg(dev)?;
+            Ok(0)
+        })
+    }
+
+    unsafe extern "C" fn read_status_callback(
+        phydev: *mut bindings::phy_device,
+    ) -> core::ffi::c_int {
+        from_result(|| {
+            // SAFETY: The C API guarantees that `phydev` is valid while this function is running.
+            let dev = unsafe { Device::from_raw(phydev) };
+            T::read_status(dev)?;
+            Ok(0)
+        })
+    }
+
+    unsafe extern "C" fn match_phy_device_callback(
+        phydev: *mut bindings::phy_device,
+    ) -> core::ffi::c_int {
+        // SAFETY: The C API guarantees that `phydev` is valid while this function is running.
+        let dev = unsafe { Device::from_raw(phydev) };
+        T::match_phy_device(dev) as i32
+    }
+
+    unsafe extern "C" fn read_mmd_callback(
+        phydev: *mut bindings::phy_device,
+        devnum: i32,
+        regnum: u16,
+    ) -> i32 {
+        from_result(|| {
+            // SAFETY: The C API guarantees that `phydev` is valid while this function is running.
+            let dev = unsafe { Device::from_raw(phydev) };
+            let ret = T::read_mmd(dev, devnum as u8, regnum)?;
+            Ok(ret.into())
+        })
+    }
+
+    unsafe extern "C" fn write_mmd_callback(
+        phydev: *mut bindings::phy_device,
+        devnum: i32,
+        regnum: u16,
+        val: u16,
+    ) -> i32 {
+        from_result(|| {
+            // SAFETY: The C API guarantees that `phydev` is valid while this function is running.
+            let dev = unsafe { Device::from_raw(phydev) };
+            T::write_mmd(dev, devnum as u8, regnum, val)?;
+            Ok(0)
+        })
+    }
+
+    unsafe extern "C" fn link_change_notify_callback(phydev: *mut bindings::phy_device) {
+        // SAFETY: The C API guarantees that `phydev` is valid while this function is running.
+        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() -> Opaque<bindings::phy_driver> {
+        Opaque::new(bindings::phy_driver {
+            name: T::NAME.as_char_ptr() as *mut i8,
+            flags: <T>::FLAGS,
+            phy_id: <T>::PHY_ID,
+            phy_id_mask: <T>::PHY_ID_MASK,
+            soft_reset: if <T>::HAS_SOFT_RESET {
+                Some(Self::soft_reset_callback)
+            } else {
+                None
+            },
+            get_features: if <T>::HAS_GET_FEATURES {
+                Some(Self::get_features_callback)
+            } else {
+                None
+            },
+            match_phy_device: if <T>::HAS_MATCH_PHY_DEVICE {
+                Some(Self::match_phy_device_callback)
+            } else {
+                None
+            },
+            suspend: if <T>::HAS_SUSPEND {
+                Some(Self::suspend_callback)
+            } else {
+                None
+            },
+            resume: if <T>::HAS_RESUME {
+                Some(Self::resume_callback)
+            } else {
+                None
+            },
+            config_aneg: if <T>::HAS_CONFIG_ANEG {
+                Some(Self::config_aneg_callback)
+            } else {
+                None
+            },
+            read_status: if <T>::HAS_READ_STATUS {
+                Some(Self::read_status_callback)
+            } else {
+                None
+            },
+            read_mmd: if <T>::HAS_READ_MMD {
+                Some(Self::read_mmd_callback)
+            } else {
+                None
+            },
+            write_mmd: if <T>::HAS_WRITE_MMD {
+                Some(Self::write_mmd_callback)
+            } else {
+                None
+            },
+            link_change_notify: if <T>::HAS_LINK_CHANGE_NOTIFY {
+                Some(Self::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`.
+#[vtable]
+pub trait Driver {
+    /// Corresponds to `flags` in `struct phy_driver`.
+    const FLAGS: u32 = 0;
+    /// Corresponds to `name` in `struct phy_driver`.
+    const NAME: &'static CStr;
+    /// Corresponds to `phy_id` in `struct phy_driver`.
+    const PHY_ID: u32 = 0;
+    /// Corresponds to `phy_id_mask` in `struct phy_driver`.
+    const PHY_ID_MASK: u32 = 0;
+
+    /// Corresponds to `soft_reset` in `struct phy_driver`.
+    fn soft_reset(_dev: &mut Device) -> Result {
+        Err(code::ENOTSUPP)
+    }
+
+    /// Corresponds to `get_features` in `struct phy_driver`.
+    fn get_features(_dev: &mut Device) -> Result {
+        Err(code::ENOTSUPP)
+    }
+
+    /// Corresponds to `match_phy_device` in `struct phy_driver`.
+    fn match_phy_device(_dev: &mut Device) -> bool {
+        false
+    }
+
+    /// Corresponds to `config_aneg` in `struct phy_driver`.
+    fn config_aneg(_dev: &mut Device) -> Result {
+        Err(code::ENOTSUPP)
+    }
+
+    /// Corresponds to `read_status` in `struct phy_driver`.
+    fn read_status(_dev: &mut Device) -> Result<u16> {
+        Err(code::ENOTSUPP)
+    }
+
+    /// Corresponds to `suspend` in `struct phy_driver`.
+    fn suspend(_dev: &mut Device) -> Result {
+        Err(code::ENOTSUPP)
+    }
+
+    /// Corresponds to `resume` in `struct phy_driver`.
+    fn resume(_dev: &mut Device) -> Result {
+        Err(code::ENOTSUPP)
+    }
+
+    /// Corresponds to `read_mmd` in `struct phy_driver`.
+    fn read_mmd(_dev: &mut Device, _devnum: u8, _regnum: u16) -> Result<u16> {
+        Err(code::ENOTSUPP)
+    }
+
+    /// Corresponds to `write_mmd` in `struct phy_driver`.
+    fn write_mmd(_dev: &mut Device, _devnum: u8, _regnum: u16, _val: u16) -> Result {
+        Err(code::ENOTSUPP)
+    }
+
+    /// Corresponds to `link_change_notify` in `struct phy_driver`.
+    fn link_change_notify(_dev: &mut Device) {}
+}
+
+/// Registration structure for a PHY driver.
+pub struct Registration {
+    module: &'static crate::ThisModule,
+    drivers: Option<&'static [Opaque<bindings::phy_driver>]>,
+}
+
+impl Registration {
+    /// Creates a new `Registration` instance.
+    pub fn new(module: &'static crate::ThisModule) -> Self {
+        Registration {
+            module,
+            drivers: None,
+        }
+    }
+
+    /// Registers a PHY driver.
+    pub fn register(&mut self, drivers: &'static [Opaque<bindings::phy_driver>]) -> Result {
+        if drivers.len() > 0 {
+            // SAFETY: Just an FFI call.
+            let ret = unsafe {
+                bindings::phy_drivers_register(
+                    drivers[0].get(),
+                    drivers.len() as i32,
+                    self.module.0,
+                )
+            };
+            if ret != 0 {
+                return Err(Error::from_errno(ret));
+            }
+            self.drivers = Some(drivers);
+            Ok(())
+        } else {
+            Err(code::EINVAL)
+        }
+    }
+}
+
+impl Drop for Registration {
+    fn drop(&mut self) {
+        if let Some(drv) = self.drivers.take() {
+            // SAFETY: Just an FFI call.
+            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 {}
+
+const DEVICE_MASK_EXACT: u32 = !0;
+const DEVICE_MASK_MODEL: u32 = !0 << 4;
+const DEVICE_MASK_VENDOR: u32 = !0 << 10;
+
+/// 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 {
+        DeviceId {
+            id: T::PHY_ID,
+            mask: DeviceMask::new(T::PHY_ID_MASK),
+        }
+    }
+
+    /// Get a mask as u32.
+    pub const fn mask_as_int(self) -> u32 {
+        match self.mask {
+            DeviceMask::Exact => DEVICE_MASK_EXACT,
+            DeviceMask::Model => DEVICE_MASK_MODEL,
+            DeviceMask::Vendor => DEVICE_MASK_VENDOR,
+            DeviceMask::Custom(mask) => mask,
+        }
+    }
+}
+
+enum DeviceMask {
+    Exact,
+    Model,
+    Vendor,
+    Custom(u32),
+}
+
+impl DeviceMask {
+    const fn new(mask: u32) -> Self {
+        match mask {
+            DEVICE_MASK_EXACT => DeviceMask::Exact,
+            DEVICE_MASK_MODEL => DeviceMask::Model,
+            DEVICE_MASK_VENDOR => DeviceMask::Vendor,
+            _ => DeviceMask::Custom(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.
+///
+/// # 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>()
+///     ],
+///     type: RustAsixPhy,
+///     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 $name:ident, [$($dev:expr),+]) => {
+        ::kernel::macros::paste! {
+            #[no_mangle]
+            static [<__mod_mdio__ $name _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),+], type: $modname:ident, $($f:tt)*) => {
+        struct Module<$modname> {
+            _reg: kernel::net::phy::Registration,
+            _p: core::marker::PhantomData<$modname>,
+        }
+
+        type ModuleType = Module<$modname>;
+
+        $crate::prelude::module! {
+             type: ModuleType,
+             $($f)*
+        }
+
+        static mut DRIVERS: [kernel::types::Opaque<kernel::bindings::phy_driver>; $crate::module_phy_driver!(@count_devices $($driver),+)] = [
+            $(kernel::net::phy::Adapter::<$driver>::create_phy_driver()),+,
+        ];
+
+        impl kernel::Module for Module<$modname> {
+            fn init(module: &'static ThisModule) -> Result<Self> {
+                let mut reg: kernel::net::phy::Registration = kernel::net::phy::Registration::new(module);
+                // SAFETY: static `DRIVERS` array is used only in the C side.
+                unsafe {
+                    reg.register(&DRIVERS)?;
+                }
+
+                Ok(Module {
+                    _reg: reg,
+                    _p: core::marker::PhantomData,
+                })
+            }
+        }
+
+        $crate::module_phy_driver!(@device_table $modname, [$($dev),+]);
+    }
+}
-- 
2.34.1