rust: net::phy unified read/write API for C22 and C45 registers

Add the unified read/write API for C22 and C45 registers. The
abstractions support access to only C22 registers now. Instead of
adding read/write_c45 methods specifically for C45, a new reg module
supports the unified API to access C22 and C45 registers with trait,
by calling an appropriate phylib functions.

Reviewed-by: Trevor Gross <tmgross@umich.edu>
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

MAINTAINERS

@@ -8357,6 +8357,7 @@ L:	netdev@vger.kernel.org
 L:	rust-for-linux@vger.kernel.org
 S:	Maintained
 F:	rust/kernel/net/phy.rs
+F:	rust/kernel/net/phy/reg.rs
 
 EXEC & BINFMT API, ELF
 R:	Eric Biederman <ebiederm@xmission.com>

drivers/net/phy/ax88796b_rust.rs

@@ -6,7 +6,7 @@
 //! C version of this driver: [`drivers/net/phy/ax88796b.c`](./ax88796b.c)
 use kernel::{
     c_str,
-    net::phy::{self, DeviceId, Driver},
+    net::phy::{self, reg::C22, DeviceId, Driver},
     prelude::*,
     uapi,
 };
@@ -24,7 +24,6 @@ kernel::module_phy_driver! {
     license: "GPL",
 }
 
-const MII_BMCR: u16 = uapi::MII_BMCR as u16;
 const BMCR_SPEED100: u16 = uapi::BMCR_SPEED100 as u16;
 const BMCR_FULLDPLX: u16 = uapi::BMCR_FULLDPLX as u16;
 
@@ -33,7 +32,7 @@ const BMCR_FULLDPLX: u16 = uapi::BMCR_FULLDPLX as u16;
 // Toggle BMCR_RESET bit off to accommodate broken AX8796B PHY implementation
 // such as used on the Individual Computers' X-Surf 100 Zorro card.
 fn asix_soft_reset(dev: &mut phy::Device) -> Result {
-    dev.write(uapi::MII_BMCR as u16, 0)?;
+    dev.write(C22::BMCR, 0)?;
     dev.genphy_soft_reset()
 }
 
@@ -55,7 +54,7 @@ impl Driver for PhyAX88772A {
         }
         // If MII_LPA is 0, phy_resolve_aneg_linkmode() will fail to resolve
         // linkmode so use MII_BMCR as default values.
-        let ret = dev.read(MII_BMCR)?;
+        let ret = dev.read(C22::BMCR)?;
 
         if ret & BMCR_SPEED100 != 0 {
             dev.set_speed(uapi::SPEED_100);

rust/kernel/net/phy.rs

@@ -9,6 +9,8 @@
 use crate::{error::*, prelude::*, types::Opaque};
 use core::{marker::PhantomData, ptr::addr_of_mut};
 
+pub mod reg;
+
 /// PHY state machine states.
 ///
 /// Corresponds to the kernel's [`enum phy_state`].
@@ -177,32 +179,15 @@ impl Device {
         unsafe { (*phydev).duplex = v };
     }
 
-    /// Reads a given C22 PHY register.
+    /// Reads a PHY register.
     // This function reads a hardware register and updates the stats so takes `&mut self`.
-    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 it's just an FFI call, open code of `phy_read()` with a valid `phy_device` pointer
-        // `phydev`.
-        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)
-        }
+    pub fn read<R: reg::Register>(&mut self, reg: R) -> Result<u16> {
+        reg.read(self)
     }
 
-    /// 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 it's just an FFI call, open code of `phy_write()` with a valid `phy_device` pointer
-        // `phydev`.
-        to_result(unsafe {
-            bindings::mdiobus_write((*phydev).mdio.bus, (*phydev).mdio.addr, regnum.into(), val)
-        })
+    /// Writes a PHY register.
+    pub fn write<R: reg::Register>(&mut self, reg: R, val: u16) -> Result {
+        reg.write(self, val)
     }
 
     /// Reads a paged register.

rust/kernel/net/phy/reg.rs

@@ -0,0 +1,196 @@
+// SPDX-License-Identifier: GPL-2.0
+
+// Copyright (C) 2024 FUJITA Tomonori <fujita.tomonori@gmail.com>
+
+//! PHY register interfaces.
+//!
+//! This module provides support for accessing PHY registers in the
+//! Ethernet management interface clauses 22 and 45 register namespaces, as
+//! defined in IEEE 802.3.
+
+use super::Device;
+use crate::build_assert;
+use crate::error::*;
+use crate::uapi;
+
+mod private {
+    /// Marker that a trait cannot be implemented outside of this crate
+    pub trait Sealed {}
+}
+
+/// Accesses PHY registers.
+///
+/// This trait is used to implement the unified interface to access
+/// C22 and C45 PHY registers.
+///
+/// # Examples
+///
+/// ```ignore
+/// fn link_change_notify(dev: &mut Device) {
+///     // read C22 BMCR register
+///     dev.read(C22::BMCR);
+///     // read C45 PMA/PMD control 1 register
+///     dev.read(C45::new(Mmd::PMAPMD, 0));
+/// }
+/// ```
+pub trait Register: private::Sealed {
+    /// Reads a PHY register.
+    fn read(&self, dev: &mut Device) -> Result<u16>;
+
+    /// Writes a PHY register.
+    fn write(&self, dev: &mut Device, val: u16) -> Result;
+}
+
+/// A single MDIO clause 22 register address (5 bits).
+#[derive(Copy, Clone, Debug)]
+pub struct C22(u8);
+
+impl C22 {
+    /// Basic mode control.
+    pub const BMCR: Self = C22(0x00);
+    /// Basic mode status.
+    pub const BMSR: Self = C22(0x01);
+    /// PHY identifier 1.
+    pub const PHYSID1: Self = C22(0x02);
+    /// PHY identifier 2.
+    pub const PHYSID2: Self = C22(0x03);
+    /// Auto-negotiation advertisement.
+    pub const ADVERTISE: Self = C22(0x04);
+    /// Auto-negotiation link partner base page ability.
+    pub const LPA: Self = C22(0x05);
+    /// Auto-negotiation expansion.
+    pub const EXPANSION: Self = C22(0x06);
+    /// Auto-negotiation next page transmit.
+    pub const NEXT_PAGE_TRANSMIT: Self = C22(0x07);
+    /// Auto-negotiation link partner received next page.
+    pub const LP_RECEIVED_NEXT_PAGE: Self = C22(0x08);
+    /// Master-slave control.
+    pub const MASTER_SLAVE_CONTROL: Self = C22(0x09);
+    /// Master-slave status.
+    pub const MASTER_SLAVE_STATUS: Self = C22(0x0a);
+    /// PSE Control.
+    pub const PSE_CONTROL: Self = C22(0x0b);
+    /// PSE Status.
+    pub const PSE_STATUS: Self = C22(0x0c);
+    /// MMD Register control.
+    pub const MMD_CONTROL: Self = C22(0x0d);
+    /// MMD Register address data.
+    pub const MMD_DATA: Self = C22(0x0e);
+    /// Extended status.
+    pub const EXTENDED_STATUS: Self = C22(0x0f);
+
+    /// Creates a new instance of `C22` with a vendor specific register.
+    pub const fn vendor_specific<const N: u8>() -> Self {
+        build_assert!(
+            N > 0x0f && N < 0x20,
+            "Vendor-specific register address must be between 16 and 31"
+        );
+        C22(N)
+    }
+}
+
+impl private::Sealed for C22 {}
+
+impl Register for C22 {
+    fn read(&self, dev: &mut Device) -> Result<u16> {
+        let phydev = dev.0.get();
+        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Device`.
+        // So it's just an FFI call, open code of `phy_read()` with a valid `phy_device` pointer
+        // `phydev`.
+        let ret = unsafe {
+            bindings::mdiobus_read((*phydev).mdio.bus, (*phydev).mdio.addr, self.0.into())
+        };
+        to_result(ret)?;
+        Ok(ret as u16)
+    }
+
+    fn write(&self, dev: &mut Device, val: u16) -> Result {
+        let phydev = dev.0.get();
+        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Device`.
+        // So it's just an FFI call, open code of `phy_write()` with a valid `phy_device` pointer
+        // `phydev`.
+        to_result(unsafe {
+            bindings::mdiobus_write((*phydev).mdio.bus, (*phydev).mdio.addr, self.0.into(), val)
+        })
+    }
+}
+
+/// A single MDIO clause 45 register device and address.
+#[derive(Copy, Clone, Debug)]
+pub struct Mmd(u8);
+
+impl Mmd {
+    /// Physical Medium Attachment/Dependent.
+    pub const PMAPMD: Self = Mmd(uapi::MDIO_MMD_PMAPMD as u8);
+    /// WAN interface sublayer.
+    pub const WIS: Self = Mmd(uapi::MDIO_MMD_WIS as u8);
+    /// Physical coding sublayer.
+    pub const PCS: Self = Mmd(uapi::MDIO_MMD_PCS as u8);
+    /// PHY Extender sublayer.
+    pub const PHYXS: Self = Mmd(uapi::MDIO_MMD_PHYXS as u8);
+    /// DTE Extender sublayer.
+    pub const DTEXS: Self = Mmd(uapi::MDIO_MMD_DTEXS as u8);
+    /// Transmission convergence.
+    pub const TC: Self = Mmd(uapi::MDIO_MMD_TC as u8);
+    /// Auto negotiation.
+    pub const AN: Self = Mmd(uapi::MDIO_MMD_AN as u8);
+    /// Separated PMA (1).
+    pub const SEPARATED_PMA1: Self = Mmd(8);
+    /// Separated PMA (2).
+    pub const SEPARATED_PMA2: Self = Mmd(9);
+    /// Separated PMA (3).
+    pub const SEPARATED_PMA3: Self = Mmd(10);
+    /// Separated PMA (4).
+    pub const SEPARATED_PMA4: Self = Mmd(11);
+    /// OFDM PMA/PMD.
+    pub const OFDM_PMAPMD: Self = Mmd(12);
+    /// Power unit.
+    pub const POWER_UNIT: Self = Mmd(13);
+    /// Clause 22 extension.
+    pub const C22_EXT: Self = Mmd(uapi::MDIO_MMD_C22EXT as u8);
+    /// Vendor specific 1.
+    pub const VEND1: Self = Mmd(uapi::MDIO_MMD_VEND1 as u8);
+    /// Vendor specific 2.
+    pub const VEND2: Self = Mmd(uapi::MDIO_MMD_VEND2 as u8);
+}
+
+/// A single MDIO clause 45 register device and address.
+///
+/// Clause 45 uses a 5-bit device address to access a specific MMD within
+/// a port, then a 16-bit register address to access a location within
+/// that device. `C45` represents this by storing a [`Mmd`] and
+/// a register number.
+pub struct C45 {
+    devad: Mmd,
+    regnum: u16,
+}
+
+impl C45 {
+    /// Creates a new instance of `C45`.
+    pub fn new(devad: Mmd, regnum: u16) -> Self {
+        Self { devad, regnum }
+    }
+}
+
+impl private::Sealed for C45 {}
+
+impl Register for C45 {
+    fn read(&self, dev: &mut Device) -> Result<u16> {
+        let phydev = dev.0.get();
+        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Device`.
+        // So it's just an FFI call.
+        let ret =
+            unsafe { bindings::phy_read_mmd(phydev, self.devad.0.into(), self.regnum.into()) };
+        to_result(ret)?;
+        Ok(ret as u16)
+    }
+
+    fn write(&self, dev: &mut Device, val: u16) -> Result {
+        let phydev = dev.0.get();
+        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Device`.
+        // So it's just an FFI call.
+        to_result(unsafe {
+            bindings::phy_write_mmd(phydev, self.devad.0.into(), self.regnum.into(), val)
+        })
+    }
+}

rust/uapi/uapi_helper.h

@@ -7,5 +7,6 @@
  */
 
 #include <uapi/asm-generic/ioctl.h>
+#include <uapi/linux/mdio.h>
 #include <uapi/linux/mii.h>
 #include <uapi/linux/ethtool.h>